Merging upstream version 1.62.1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

74 files changed, 3720 insertions, 4386 deletions

diff --git a/src/HtmlParser.cc b/src/HtmlParser.cc
index 591c4c7..a420c93 100644
--- a/src/HtmlParser.cc
+++ b/src/HtmlParser.cc
@@ -58,11 +58,11 @@ StringRef get_attr(const xmlChar **attrs, const StringRef &name) {
 namespace {
 ResourceType
 get_resource_type_for_preload_as(const StringRef &attribute_value) {
-  if (util::strieq_l("image", attribute_value)) {
+  if (util::strieq("image"_sr, attribute_value)) {
     return REQ_IMG;
-  } else if (util::strieq_l("style", attribute_value)) {
+  } else if (util::strieq("style"_sr, attribute_value)) {
     return REQ_CSS;
-  } else if (util::strieq_l("script", attribute_value)) {
+  } else if (util::strieq("script"_sr, attribute_value)) {
     return REQ_UNBLOCK_JS;
   } else {
     return REQ_OTHERS;
@@ -74,7 +74,7 @@ namespace {
 void add_link(ParserData *parser_data, const StringRef &uri,
               ResourceType res_type) {
   auto u = xmlBuildURI(
-      reinterpret_cast<const xmlChar *>(uri.c_str()),
+      reinterpret_cast<const xmlChar *>(uri.data()),
       reinterpret_cast<const xmlChar *>(parser_data->base_uri.c_str()));
   if (u) {
     parser_data->links.push_back(
@@ -90,35 +90,35 @@ void start_element_func(void *user_data, const xmlChar *src_name,
   auto parser_data = static_cast<ParserData *>(user_data);
   auto name =
       StringRef{src_name, strlen(reinterpret_cast<const char *>(src_name))};
-  if (util::strieq_l("head", name)) {
+  if (util::strieq("head"_sr, name)) {
     ++parser_data->inside_head;
   }
-  if (util::strieq_l("link", name)) {
-    auto rel_attr = get_attr(attrs, StringRef::from_lit("rel"));
-    auto href_attr = get_attr(attrs, StringRef::from_lit("href"));
+  if (util::strieq("link"_sr, name)) {
+    auto rel_attr = get_attr(attrs, "rel"_sr);
+    auto href_attr = get_attr(attrs, "href"_sr);
     if (rel_attr.empty() || href_attr.empty()) {
       return;
     }
-    if (util::strieq_l("shortcut icon", rel_attr)) {
+    if (util::strieq("shortcut icon"_sr, rel_attr)) {
       add_link(parser_data, href_attr, REQ_OTHERS);
-    } else if (util::strieq_l("stylesheet", rel_attr)) {
+    } else if (util::strieq("stylesheet"_sr, rel_attr)) {
       add_link(parser_data, href_attr, REQ_CSS);
-    } else if (util::strieq_l("preload", rel_attr)) {
-      auto as_attr = get_attr(attrs, StringRef::from_lit("as"));
+    } else if (util::strieq("preload"_sr, rel_attr)) {
+      auto as_attr = get_attr(attrs, "as"_sr);
       if (as_attr.empty()) {
         return;
       }
       add_link(parser_data, href_attr,
                get_resource_type_for_preload_as(as_attr));
     }
-  } else if (util::strieq_l("img", name)) {
-    auto src_attr = get_attr(attrs, StringRef::from_lit("src"));
+  } else if (util::strieq("img"_sr, name)) {
+    auto src_attr = get_attr(attrs, "src"_sr);
     if (src_attr.empty()) {
       return;
     }
     add_link(parser_data, src_attr, REQ_IMG);
-  } else if (util::strieq_l("script", name)) {
-    auto src_attr = get_attr(attrs, StringRef::from_lit("src"));
+  } else if (util::strieq("script"_sr, name)) {
+    auto src_attr = get_attr(attrs, "src"_sr);
     if (src_attr.empty()) {
       return;
     }
@@ -134,8 +134,8 @@ void start_element_func(void *user_data, const xmlChar *src_name,
 namespace {
 void end_element_func(void *user_data, const xmlChar *name) {
   auto parser_data = static_cast<ParserData *>(user_data);
-  if (util::strieq_l(
-          "head",
+  if (util::strieq(
+          "head"_sr,
           StringRef{name, strlen(reinterpret_cast<const char *>(name))})) {
     --parser_data->inside_head;
   }
diff --git a/src/HttpServer.cc b/src/HttpServer.cc
index 6b28d1b..fb7b1db 100644
--- a/src/HttpServer.cc
+++ b/src/HttpServer.cc
@@ -78,9 +78,8 @@ namespace nghttp2 {
 
 namespace {
 // TODO could be constexpr
-constexpr auto DEFAULT_HTML = StringRef::from_lit("index.html");
-constexpr auto NGHTTPD_SERVER =
-    StringRef::from_lit("nghttpd nghttp2/" NGHTTP2_VERSION);
+constexpr auto DEFAULT_HTML = "index.html"_sr;
+constexpr auto NGHTTPD_SERVER = "nghttpd nghttp2/" NGHTTP2_VERSION ""_sr;
 } // namespace
 
 namespace {
@@ -925,28 +924,32 @@ int Http2Handler::submit_file_response(const StringRef &status, Stream *stream,
                                        const std::string *content_type,
                                        nghttp2_data_provider2 *data_prd) {
   std::string last_modified_str;
-  auto nva = make_array(http2::make_nv_ls_nocopy(":status", status),
-                        http2::make_nv_ls_nocopy("server", NGHTTPD_SERVER),
-                        http2::make_nv_ll("cache-control", "max-age=3600"),
-                        http2::make_nv_ls("date", sessions_->get_cached_date()),
-                        http2::make_nv_ll("", ""), http2::make_nv_ll("", ""),
-                        http2::make_nv_ll("", ""), http2::make_nv_ll("", ""));
+  auto nva = std::to_array({
+      http2::make_field(":status"_sr, status),
+      http2::make_field("server"_sr, NGHTTPD_SERVER),
+      http2::make_field("cache-control"_sr, "max-age=3600"_sr),
+      http2::make_field_v("date"_sr, sessions_->get_cached_date()),
+      {},
+      {},
+      {},
+      {},
+  });
   size_t nvlen = 4;
   if (!get_config()->no_content_length) {
-    nva[nvlen++] = http2::make_nv_ls_nocopy(
-        "content-length",
+    nva[nvlen++] = http2::make_field(
+        "content-length"_sr,
         util::make_string_ref_uint(stream->balloc, file_length));
   }
   if (last_modified != 0) {
     last_modified_str = util::http_date(last_modified);
-    nva[nvlen++] = http2::make_nv_ls("last-modified", last_modified_str);
+    nva[nvlen++] = http2::make_field_v("last-modified"_sr, last_modified_str);
   }
   if (content_type) {
-    nva[nvlen++] = http2::make_nv_ls("content-type", *content_type);
+    nva[nvlen++] = http2::make_field_v("content-type"_sr, *content_type);
   }
   auto &trailer_names = get_config()->trailer_names;
   if (!trailer_names.empty()) {
-    nva[nvlen++] = http2::make_nv_ls_nocopy("trailer", trailer_names);
+    nva[nvlen++] = http2::make_field("trailer"_sr, trailer_names);
   }
   return nghttp2_submit_response2(session_, stream->stream_id, nva.data(),
                                   nvlen, data_prd);
@@ -957,19 +960,20 @@ int Http2Handler::submit_response(const StringRef &status, int32_t stream_id,
                                   nghttp2_data_provider2 *data_prd) {
   auto nva = std::vector<nghttp2_nv>();
   nva.reserve(4 + headers.size());
-  nva.push_back(http2::make_nv_ls_nocopy(":status", status));
-  nva.push_back(http2::make_nv_ls_nocopy("server", NGHTTPD_SERVER));
-  nva.push_back(http2::make_nv_ls("date", sessions_->get_cached_date()));
+  nva.push_back(http2::make_field(":status"_sr, status));
+  nva.push_back(http2::make_field("server"_sr, NGHTTPD_SERVER));
+  nva.push_back(http2::make_field_v("date"_sr, sessions_->get_cached_date()));
 
   if (data_prd) {
     auto &trailer_names = get_config()->trailer_names;
     if (!trailer_names.empty()) {
-      nva.push_back(http2::make_nv_ls_nocopy("trailer", trailer_names));
+      nva.push_back(http2::make_field("trailer"_sr, trailer_names));
     }
   }
 
   for (auto &nv : headers) {
-    nva.push_back(http2::make_nv_nocopy(nv.name, nv.value, nv.no_index));
+    nva.push_back(
+        http2::make_field(nv.name, nv.value, http2::no_index(nv.no_index)));
   }
   int r = nghttp2_submit_response2(session_, stream_id, nva.data(), nva.size(),
                                    data_prd);
@@ -978,16 +982,18 @@ int Http2Handler::submit_response(const StringRef &status, int32_t stream_id,
 
 int Http2Handler::submit_response(const StringRef &status, int32_t stream_id,
                                   nghttp2_data_provider2 *data_prd) {
-  auto nva = make_array(http2::make_nv_ls_nocopy(":status", status),
-                        http2::make_nv_ls_nocopy("server", NGHTTPD_SERVER),
-                        http2::make_nv_ls("date", sessions_->get_cached_date()),
-                        http2::make_nv_ll("", ""));
+  auto nva = std::to_array({
+      http2::make_field(":status"_sr, status),
+      http2::make_field("server"_sr, NGHTTPD_SERVER),
+      http2::make_field_v("date"_sr, sessions_->get_cached_date()),
+      {},
+  });
   size_t nvlen = 3;
 
   if (data_prd) {
     auto &trailer_names = get_config()->trailer_names;
     if (!trailer_names.empty()) {
-      nva[nvlen++] = http2::make_nv_ls_nocopy("trailer", trailer_names);
+      nva[nvlen++] = http2::make_field("trailer"_sr, trailer_names);
     }
   }
 
@@ -997,7 +1003,7 @@ int Http2Handler::submit_response(const StringRef &status, int32_t stream_id,
 
 int Http2Handler::submit_non_final_response(const std::string &status,
                                             int32_t stream_id) {
-  auto nva = make_array(http2::make_nv_ls(":status", status));
+  auto nva = std::to_array({http2::make_field_v(":status"_sr, status)});
   return nghttp2_submit_headers(session_, NGHTTP2_FLAG_NONE, stream_id, nullptr,
                                 nva.data(), nva.size(), nullptr);
 }
@@ -1010,13 +1016,12 @@ int Http2Handler::submit_push_promise(Stream *stream,
     authority = stream->header.host;
   }
 
-  auto scheme = get_config()->no_tls ? StringRef::from_lit("http")
-                                     : StringRef::from_lit("https");
+  auto scheme = get_config()->no_tls ? "http"_sr : "https"_sr;
 
-  auto nva = make_array(http2::make_nv_ll(":method", "GET"),
-                        http2::make_nv_ls_nocopy(":path", push_path),
-                        http2::make_nv_ls_nocopy(":scheme", scheme),
-                        http2::make_nv_ls_nocopy(":authority", authority));
+  auto nva = std::to_array({http2::make_field(":method"_sr, "GET"_sr),
+                            http2::make_field(":path"_sr, push_path),
+                            http2::make_field(":scheme"_sr, scheme),
+                            http2::make_field(":authority"_sr, authority)});
 
   auto promised_stream_id = nghttp2_submit_push_promise(
       session_, NGHTTP2_FLAG_END_HEADERS, stream->stream_id, nva.data(),
@@ -1029,7 +1034,7 @@ int Http2Handler::submit_push_promise(Stream *stream,
   auto promised_stream = std::make_unique<Stream>(this, promised_stream_id);
 
   auto &promised_header = promised_stream->header;
-  promised_header.method = StringRef::from_lit("GET");
+  promised_header.method = "GET"_sr;
   promised_header.path = push_path;
   promised_header.scheme = scheme;
   promised_header.authority =
@@ -1103,7 +1108,8 @@ nghttp2_ssize file_read_callback(nghttp2_session *session, int32_t stream_id,
       std::vector<nghttp2_nv> nva;
       nva.reserve(config->trailer.size());
       for (auto &kv : config->trailer) {
-        nva.push_back(http2::make_nv(kv.name, kv.value, kv.no_index));
+        nva.push_back(http2::make_field_nv(kv.name, kv.value,
+                                           http2::no_index(kv.no_index)));
       }
       rv = nghttp2_submit_trailer(session, stream_id, nva.data(), nva.size());
       if (rv != 0) {
@@ -1140,10 +1146,9 @@ void prepare_status_response(Stream *stream, Http2Handler *hd, int status) {
 
   HeaderRefs headers;
   headers.reserve(2);
-  headers.emplace_back(StringRef::from_lit("content-type"),
-                       StringRef::from_lit("text/html; charset=UTF-8"));
+  headers.emplace_back("content-type"_sr, "text/html; charset=UTF-8"_sr);
   headers.emplace_back(
-      StringRef::from_lit("content-length"),
+      "content-length"_sr,
       util::make_string_ref_uint(stream->balloc, file_ent->length));
   hd->submit_response(StringRef{status_page->status}, stream->stream_id,
                       headers, &data_prd);
@@ -1167,15 +1172,13 @@ void prepare_echo_response(Stream *stream, Http2Handler *hd) {
   data_prd.read_callback = file_read_callback;
 
   HeaderRefs headers;
-  headers.emplace_back(StringRef::from_lit("nghttpd-response"),
-                       StringRef::from_lit("echo"));
+  headers.emplace_back("nghttpd-response"_sr, "echo"_sr);
   if (!hd->get_config()->no_content_length) {
-    headers.emplace_back(StringRef::from_lit("content-length"),
+    headers.emplace_back("content-length"_sr,
                          util::make_string_ref_uint(stream->balloc, length));
   }
 
-  hd->submit_response(StringRef::from_lit("200"), stream->stream_id, headers,
-                      &data_prd);
+  hd->submit_response("200"_sr, stream->stream_id, headers, &data_prd);
 }
 } // namespace
 
@@ -1209,10 +1212,10 @@ void prepare_redirect_response(Stream *stream, Http2Handler *hd,
     authority = stream->header.host;
   }
 
-  auto location = concat_string_ref(
-      stream->balloc, scheme, StringRef::from_lit("://"), authority, path);
+  auto location =
+      concat_string_ref(stream->balloc, scheme, "://"_sr, authority, path);
 
-  auto headers = HeaderRefs{{StringRef::from_lit("location"), location}};
+  auto headers = HeaderRefs{{"location"_sr, location}};
 
   auto sessions = hd->get_sessions();
   auto status_page = sessions->get_server()->get_status_page(status);
@@ -1245,8 +1248,8 @@ void prepare_response(Stream *stream, Http2Handler *hd,
   auto query_pos = std::find(std::begin(reqpath), std::end(reqpath), '?');
   if (query_pos != std::end(reqpath)) {
     // Do not response to this request to allow clients to test timeouts.
-    if (util::streq_l("nghttpd_do_not_respond_to_req=yes",
-                      StringRef{query_pos, std::end(reqpath)})) {
+    if ("nghttpd_do_not_respond_to_req=yes"_sr ==
+        StringRef{query_pos, std::end(reqpath)}) {
       return;
     }
     raw_path = StringRef{std::begin(reqpath), query_pos};
@@ -1278,7 +1281,7 @@ void prepare_response(Stream *stream, Http2Handler *hd,
   }
 
   if (!hd->get_config()->push.empty()) {
-    auto push_itr = hd->get_config()->push.find(path.str());
+    auto push_itr = hd->get_config()->push.find(std::string{path});
     if (allow_push && push_itr != std::end(hd->get_config()->push)) {
       for (auto &push_path : (*push_itr).second) {
         rv = hd->submit_push_promise(stream, StringRef{push_path});
@@ -1339,8 +1342,8 @@ void prepare_response(Stream *stream, Http2Handler *hd,
     if (buf.st_mode & S_IFDIR) {
       close(file);
 
-      auto reqpath = concat_string_ref(stream->balloc, raw_path,
-                                       StringRef::from_lit("/"), raw_query);
+      auto reqpath =
+          concat_string_ref(stream->balloc, raw_path, "/"_sr, raw_query);
 
       prepare_redirect_response(stream, hd, reqpath, 301);
 
@@ -1370,16 +1373,15 @@ void prepare_response(Stream *stream, Http2Handler *hd,
   stream->file_ent = file_ent;
 
   if (last_mod_found && file_ent->mtime <= last_mod) {
-    hd->submit_response(StringRef::from_lit("304"), stream->stream_id, nullptr);
+    hd->submit_response("304"_sr, stream->stream_id, nullptr);
 
     return;
   }
 
   auto method = stream->header.method;
-  if (method == StringRef::from_lit("HEAD")) {
-    hd->submit_file_response(StringRef::from_lit("200"), stream,
-                             file_ent->mtime, file_ent->length,
-                             file_ent->content_type, nullptr);
+  if (method == "HEAD"_sr) {
+    hd->submit_file_response("200"_sr, stream, file_ent->mtime,
+                             file_ent->length, file_ent->content_type, nullptr);
     return;
   }
 
@@ -1390,8 +1392,8 @@ void prepare_response(Stream *stream, Http2Handler *hd,
   data_prd.source.fd = file_ent->fd;
   data_prd.read_callback = file_read_callback;
 
-  hd->submit_file_response(StringRef::from_lit("200"), stream, file_ent->mtime,
-                           file_ent->length, file_ent->content_type, &data_prd);
+  hd->submit_file_response("200"_sr, stream, file_ent->mtime, file_ent->length,
+                           file_ent->content_type, &data_prd);
 }
 } // namespace
 
@@ -1425,7 +1427,7 @@ int on_header_callback2(nghttp2_session *session, const nghttp2_frame *frame,
 
   stream->header_buffer_size += namebuf.len + valuebuf.len;
 
-  auto token = http2::lookup_token(namebuf.base, namebuf.len);
+  auto token = http2::lookup_token(StringRef{namebuf.base, namebuf.len});
 
   auto &header = stream->header;
 
@@ -1528,14 +1530,13 @@ int hd_on_frame_recv_callback(nghttp2_session *session,
 
       auto expect100 = stream->header.expect;
 
-      if (util::strieq_l("100-continue", expect100)) {
+      if (util::strieq("100-continue"_sr, expect100)) {
         hd->submit_non_final_response("100", frame->hd.stream_id);
       }
 
       auto method = stream->header.method;
       if (hd->get_config()->echo_upload &&
-          (method == StringRef::from_lit("POST") ||
-           method == StringRef::from_lit("PUT"))) {
+          (method == "POST"_sr || method == "PUT"_sr)) {
         if (!prepare_upload_temp_store(stream, hd)) {
           hd->submit_rst_stream(stream, NGHTTP2_INTERNAL_ERROR);
           return 0;
@@ -2129,7 +2130,8 @@ int HttpServer::run() {
       return -1;
     }
 
-    if (SSL_CTX_set_cipher_list(ssl_ctx, tls::DEFAULT_CIPHER_LIST) == 0) {
+    if (SSL_CTX_set_cipher_list(ssl_ctx, tls::DEFAULT_CIPHER_LIST.data()) ==
+        0) {
       std::cerr << ERR_error_string(ERR_get_error(), nullptr) << std::endl;
       return -1;
     }
diff --git a/src/HttpServer.h b/src/HttpServer.h
index 00fd6bf..348f85a 100644
--- a/src/HttpServer.h
+++ b/src/HttpServer.h
@@ -245,9 +245,10 @@ private:
   const Config *config_;
 };
 
-ssize_t file_read_callback(nghttp2_session *session, int32_t stream_id,
-                           uint8_t *buf, size_t length, uint32_t *data_flags,
-                           nghttp2_data_source *source, void *user_data);
+nghttp2_ssize file_read_callback(nghttp2_session *session, int32_t stream_id,
+                                 uint8_t *buf, size_t length,
+                                 uint32_t *data_flags,
+                                 nghttp2_data_source *source, void *user_data);
 
 } // namespace nghttp2
 
diff --git a/src/allocator.h b/src/allocator.h
index 363ee91..b4dee5a 100644
--- a/src/allocator.h
+++ b/src/allocator.h
@@ -33,6 +33,7 @@
 
 #include <cassert>
 #include <utility>
+#include <span>
 
 #include "template.h"
 
@@ -48,6 +49,18 @@ struct MemBlock {
   uint8_t *begin, *last, *end;
 };
 
+static_assert((sizeof(MemBlock) & 0xf) == 0);
+
+struct ChunkHead {
+  union {
+    size_t size;
+    uint64_t pad1;
+  };
+  uint64_t pad2;
+};
+
+static_assert(sizeof(ChunkHead) == 16);
+
 // BlockAllocator allocates memory block with given size at once, and
 // cuts the region from it when allocation is requested.  If the
 // requested size is larger than given threshold (plus small internal
@@ -88,7 +101,7 @@ struct BlockAllocator {
   void reset() {
     for (auto mb = retain; mb;) {
       auto next = mb->next;
-      delete[] reinterpret_cast<uint8_t *>(mb);
+      operator delete[](reinterpret_cast<uint8_t *>(mb), std::align_val_t(16));
       mb = next;
     }
 
@@ -97,36 +110,40 @@ struct BlockAllocator {
   }
 
   MemBlock *alloc_mem_block(size_t size) {
-    auto block = new uint8_t[sizeof(MemBlock) + size];
+    auto block = new (std::align_val_t(16)) uint8_t[sizeof(MemBlock) + size];
     auto mb = reinterpret_cast<MemBlock *>(block);
 
     mb->next = retain;
-    mb->begin = mb->last = block + sizeof(MemBlock);
+    mb->begin = mb->last = reinterpret_cast<uint8_t *>(
+        (reinterpret_cast<intptr_t>(block + sizeof(MemBlock)) + 0xf) & ~0xf);
     mb->end = mb->begin + size;
     retain = mb;
     return mb;
   }
 
+  constexpr size_t alloc_unit(size_t size) { return sizeof(ChunkHead) + size; }
+
   void *alloc(size_t size) {
-    if (size + sizeof(size_t) >= isolation_threshold) {
-      auto len = std::max(static_cast<size_t>(16), size);
+    auto au = alloc_unit(size);
+
+    if (au >= isolation_threshold) {
+      size = std::max(static_cast<size_t>(16), size);
       // We will store the allocated size in size_t field.
-      auto mb = alloc_mem_block(len + sizeof(size_t));
-      auto sp = reinterpret_cast<size_t *>(mb->begin);
-      *sp = len;
+      auto mb = alloc_mem_block(alloc_unit(size));
+      auto ch = reinterpret_cast<ChunkHead *>(mb->begin);
+      ch->size = size;
       mb->last = mb->end;
-      return mb->begin + sizeof(size_t);
+      return mb->begin + sizeof(ChunkHead);
     }
 
-    if (!head ||
-        static_cast<size_t>(head->end - head->last) < size + sizeof(size_t)) {
+    if (!head || static_cast<size_t>(head->end - head->last) < au) {
       head = alloc_mem_block(block_size);
     }
 
     // We will store the allocated size in size_t field.
-    auto res = head->last + sizeof(size_t);
-    auto sp = reinterpret_cast<size_t *>(head->last);
-    *sp = size;
+    auto res = head->last + sizeof(ChunkHead);
+    auto ch = reinterpret_cast<ChunkHead *>(head->last);
+    ch->size = size;
 
     head->last = reinterpret_cast<uint8_t *>(
         (reinterpret_cast<intptr_t>(res + size) + 0xf) & ~0xf);
@@ -137,8 +154,9 @@ struct BlockAllocator {
   // Returns allocated size for memory pointed by |ptr|.  We assume
   // that |ptr| was returned from alloc() or realloc().
   size_t get_alloc_length(void *ptr) {
-    return *reinterpret_cast<size_t *>(static_cast<uint8_t *>(ptr) -
-                                       sizeof(size_t));
+    return reinterpret_cast<ChunkHead *>(static_cast<uint8_t *>(ptr) -
+                                         sizeof(ChunkHead))
+        ->size;
   }
 
   // Allocates memory of at least |size| bytes.  If |ptr| is nullptr,
@@ -253,19 +271,10 @@ StringRef realloc_concat_string_ref(BlockAllocator &alloc,
   return StringRef{dst, len};
 }
 
-struct ByteRef {
-  // The pointer to the beginning of the buffer.
-  uint8_t *base;
-  // The length of the buffer.
-  size_t len;
-};
-
-// Makes a buffer with given size.  The resulting byte string might
-// not be NULL-terminated.
+// Makes an uninitialized buffer with given size.
 template <typename BlockAllocator>
-ByteRef make_byte_ref(BlockAllocator &alloc, size_t size) {
-  auto dst = static_cast<uint8_t *>(alloc.alloc(size));
-  return {dst, size};
+std::span<uint8_t> make_byte_ref(BlockAllocator &alloc, size_t size) {
+  return {static_cast<uint8_t *>(alloc.alloc(size)), size};
 }
 
 } // namespace nghttp2
diff --git a/src/app_helper.cc b/src/app_helper.cc
index 666d16c..2ccecbe 100644
--- a/src/app_helper.cc
+++ b/src/app_helper.cc
@@ -115,7 +115,7 @@ std::string strframetype(uint8_t type) {
   }
 
   std::string s = "extension(0x";
-  s += util::format_hex(&type, 1);
+  s += util::format_hex(std::span{&type, 1});
   s += ')';
 
   return s;
@@ -329,7 +329,7 @@ void print_frame(print_type ptype, const nghttp2_frame *frame) {
   case NGHTTP2_PING:
     print_frame_attr_indent();
     fprintf(outfile, "(opaque_data=%s)\n",
-            util::format_hex(frame->ping.opaque_data, 8).c_str());
+            util::format_hex(frame->ping.opaque_data).c_str());
     break;
   case NGHTTP2_GOAWAY:
     print_frame_attr_indent();
diff --git a/src/base64.h b/src/base64.h
index 1bd51af..8789427 100644
--- a/src/base64.h
+++ b/src/base64.h
@@ -204,18 +204,19 @@ template <typename InputIt> std::string decode(InputIt first, InputIt last) {
 }
 
 template <typename InputIt>
-StringRef decode(BlockAllocator &balloc, InputIt first, InputIt last) {
+std::span<const uint8_t> decode(BlockAllocator &balloc, InputIt first,
+                                InputIt last) {
   auto len = std::distance(first, last);
   if (len % 4 != 0) {
-    return StringRef::from_lit("");
+    return {};
   }
   auto iov = make_byte_ref(balloc, len / 4 * 3 + 1);
-  auto p = iov.base;
+  auto p = std::begin(iov);
 
   p = decode(first, last, p);
   *p = '\0';
 
-  return StringRef{iov.base, p};
+  return {std::begin(iov), p};
 }
 
 } // namespace base64
diff --git a/src/base64_test.cc b/src/base64_test.cc
index 9ab770f..0aeadf7 100644
--- a/src/base64_test.cc
+++ b/src/base64_test.cc
@@ -33,6 +33,8 @@
 
 #include "base64.h"
 
+using namespace std::literals;
+
 namespace nghttp2 {
 
 namespace {
@@ -73,67 +75,68 @@ void test_base64_encode(void) {
 void test_base64_decode(void) {
   BlockAllocator balloc(4096, 4096);
   {
-    std::string in = "/w==";
+    auto in = "/w=="sv;
     auto out = base64::decode(std::begin(in), std::end(in));
-    assert_stdstring_equal("\xff", out);
-    assert_stdstring_equal(
-        "\xff", base64::decode(balloc, std::begin(in), std::end(in)).str());
+    assert_stdsv_equal("\xff"sv, out);
+    assert_stdsv_equal("\xff"sv, StringRef{base64::decode(
+                                     balloc, std::begin(in), std::end(in))});
   }
   {
-    std::string in = "//4=";
+    auto in = "//4="sv;
     auto out = base64::decode(std::begin(in), std::end(in));
-    assert_stdstring_equal("\xff\xfe", out);
-    assert_stdstring_equal(
-        "\xff\xfe", base64::decode(balloc, std::begin(in), std::end(in)).str());
+    assert_stdsv_equal("\xff\xfe"sv, out);
+    assert_stdsv_equal(
+        "\xff\xfe"sv,
+        StringRef{base64::decode(balloc, std::begin(in), std::end(in))});
   }
   {
-    std::string in = "//79";
+    auto in = "//79"sv;
     auto out = base64::decode(std::begin(in), std::end(in));
-    assert_stdstring_equal("\xff\xfe\xfd", out);
-    assert_stdstring_equal(
-        "\xff\xfe\xfd",
-        base64::decode(balloc, std::begin(in), std::end(in)).str());
+    assert_stdsv_equal("\xff\xfe\xfd"sv, out);
+    assert_stdsv_equal(
+        "\xff\xfe\xfd"sv,
+        StringRef{base64::decode(balloc, std::begin(in), std::end(in))});
   }
   {
-    std::string in = "//79/A==";
+    auto in = "//79/A=="sv;
     auto out = base64::decode(std::begin(in), std::end(in));
-    assert_stdstring_equal("\xff\xfe\xfd\xfc", out);
-    assert_stdstring_equal(
-        "\xff\xfe\xfd\xfc",
-        base64::decode(balloc, std::begin(in), std::end(in)).str());
+    assert_stdsv_equal("\xff\xfe\xfd\xfc"sv, out);
+    assert_stdsv_equal(
+        "\xff\xfe\xfd\xfc"sv,
+        StringRef{base64::decode(balloc, std::begin(in), std::end(in))});
   }
   {
     // we check the number of valid input must be multiples of 4
-    std::string in = "//79=";
+    auto in = "//79="sv;
     auto out = base64::decode(std::begin(in), std::end(in));
-    assert_stdstring_equal("", out);
-    assert_stdstring_equal(
-        "", base64::decode(balloc, std::begin(in), std::end(in)).str());
+    assert_stdsv_equal(""sv, out);
+    assert_stdsv_equal(
+        ""sv, StringRef{base64::decode(balloc, std::begin(in), std::end(in))});
   }
   {
     // ending invalid character at the boundary of multiples of 4 is
     // bad
-    std::string in = "bmdodHRw\n";
+    auto in = "bmdodHRw\n"sv;
     auto out = base64::decode(std::begin(in), std::end(in));
-    assert_stdstring_equal("", out);
-    assert_stdstring_equal(
-        "", base64::decode(balloc, std::begin(in), std::end(in)).str());
+    assert_stdsv_equal("", out);
+    assert_stdsv_equal(
+        ""sv, StringRef{base64::decode(balloc, std::begin(in), std::end(in))});
   }
   {
     // after seeing '=', subsequent input must be also '='.
-    std::string in = "//79/A=A";
+    auto in = "//79/A=A"sv;
     auto out = base64::decode(std::begin(in), std::end(in));
-    assert_stdstring_equal("", out);
-    assert_stdstring_equal(
-        "", base64::decode(balloc, std::begin(in), std::end(in)).str());
+    assert_stdsv_equal(""sv, out);
+    assert_stdsv_equal(
+        ""sv, StringRef{base64::decode(balloc, std::begin(in), std::end(in))});
   }
   {
     // additional '=' at the end is bad
-    std::string in = "//79/A======";
+    auto in = "//79/A======"sv;
     auto out = base64::decode(std::begin(in), std::end(in));
-    assert_stdstring_equal("", out);
-    assert_stdstring_equal(
-        "", base64::decode(balloc, std::begin(in), std::end(in)).str());
+    assert_stdsv_equal(""sv, out);
+    assert_stdsv_equal(
+        ""sv, StringRef{base64::decode(balloc, std::begin(in), std::end(in))});
   }
 }
 
diff --git a/src/deflatehd.cc b/src/deflatehd.cc
index ad472de..e51bab1 100644
--- a/src/deflatehd.cc
+++ b/src/deflatehd.cc
@@ -403,21 +403,21 @@ int main(int argc, char **argv) {
     case 's': {
       // --table-size
       auto n = util::parse_uint(optarg);
-      if (n == -1) {
+      if (!n) {
         fprintf(stderr, "-s: Bad option value\n");
         exit(EXIT_FAILURE);
       }
-      config.table_size = n;
+      config.table_size = *n;
       break;
     }
     case 'S': {
       // --deflate-table-size
       auto n = util::parse_uint(optarg);
-      if (n == -1) {
+      if (!n) {
         fprintf(stderr, "-S: Bad option value\n");
         exit(EXIT_FAILURE);
       }
-      config.deflate_table_size = n;
+      config.deflate_table_size = *n;
       break;
     }
     case 'd':
diff --git a/src/h2load.cc b/src/h2load.cc
index 4f9f00e..43931f9 100644
--- a/src/h2load.cc
+++ b/src/h2load.cc
@@ -47,6 +47,7 @@
 #include <thread>
 #include <future>
 #include <random>
+#include <string_view>
 
 #include <openssl/err.h>
 
@@ -826,6 +827,7 @@ void Client::process_request_failure() {
             << std::endl;
 }
 
+#ifndef NGHTTP2_OPENSSL_IS_BORINGSSL
 namespace {
 void print_server_tmp_key(SSL *ssl) {
   EVP_PKEY *key;
@@ -847,7 +849,7 @@ void print_server_tmp_key(SSL *ssl) {
     std::cout << "DH " << EVP_PKEY_bits(key) << " bits" << std::endl;
     break;
   case EVP_PKEY_EC: {
-#if OPENSSL_3_0_0_API
+#  if OPENSSL_3_0_0_API
     std::array<char, 64> curve_name;
     const char *cname;
     if (!EVP_PKEY_get_utf8_string_param(key, "group", curve_name.data(),
@@ -856,7 +858,7 @@ void print_server_tmp_key(SSL *ssl) {
     } else {
       cname = curve_name.data();
     }
-#else  // !OPENSSL_3_0_0_API
+#  else  // !OPENSSL_3_0_0_API
     auto ec = EVP_PKEY_get1_EC_KEY(key);
     auto ec_del = defer(EC_KEY_free, ec);
     auto nid = EC_GROUP_get_curve_name(EC_KEY_get0_group(ec));
@@ -864,7 +866,7 @@ void print_server_tmp_key(SSL *ssl) {
     if (!cname) {
       cname = OBJ_nid2sn(nid);
     }
-#endif // !OPENSSL_3_0_0_API
+#  endif // !OPENSSL_3_0_0_API
 
     std::cout << "ECDH " << cname << " " << EVP_PKEY_bits(key) << " bits"
               << std::endl;
@@ -877,6 +879,7 @@ void print_server_tmp_key(SSL *ssl) {
   }
 }
 } // namespace
+#endif // !NGHTTP2_OPENSSL_IS_BORINGSSL
 
 void Client::report_tls_info() {
   if (worker->id == 0 && !worker->tls_info_report_done) {
@@ -884,7 +887,9 @@ void Client::report_tls_info() {
     auto cipher = SSL_get_current_cipher(ssl);
     std::cout << "TLS Protocol: " << tls::get_tls_protocol(ssl) << "\n"
               << "Cipher: " << SSL_CIPHER_get_name(cipher) << std::endl;
+#ifndef NGHTTP2_OPENSSL_IS_BORINGSSL
     print_server_tmp_key(ssl);
+#endif // !NGHTTP2_OPENSSL_IS_BORINGSSL
   }
 }
 
@@ -927,7 +932,7 @@ void Client::on_header(int32_t stream_id, const uint8_t *name, size_t namelen,
   }
 
   if (stream.status_success == -1 && namelen == 7 &&
-      util::streq_l(":status", name, namelen)) {
+      ":status"_sr == StringRef{name, namelen}) {
     int status = 0;
     for (size_t i = 0; i < valuelen; ++i) {
       if ('0' <= value[i] && value[i] <= '9') {
@@ -1101,20 +1106,19 @@ int Client::connection_made() {
       if (config.is_quic()) {
 #ifdef ENABLE_HTTP3
         assert(session);
-        if (!util::streq(StringRef{&NGHTTP3_ALPN_H3[1]}, proto) &&
-            !util::streq_l("h3-29", proto)) {
+        if ("h3"_sr != proto && "h3-29"_sr != proto) {
           return -1;
         }
 #endif // ENABLE_HTTP3
       } else if (util::check_h2_is_selected(proto)) {
         session = std::make_unique<Http2Session>(this);
-      } else if (util::streq(NGHTTP2_H1_1, proto)) {
+      } else if (NGHTTP2_H1_1 == proto) {
         session = std::make_unique<Http1Session>(this);
       }
 
       // Just assign next_proto to selected_proto anyway to show the
       // negotiation result.
-      selected_proto = proto.str();
+      selected_proto = proto;
     } else if (config.is_quic()) {
       std::cerr << "QUIC requires ALPN negotiation" << std::endl;
       return -1;
@@ -1123,11 +1127,11 @@ int Client::connection_made() {
                 << std::endl;
 
       for (const auto &proto : config.alpn_list) {
-        if (util::streq(NGHTTP2_H1_1_ALPN, StringRef{proto})) {
+        if (NGHTTP2_H1_1_ALPN == proto) {
           std::cout << "Server does not support ALPN. Falling back to HTTP/1.1."
                     << std::endl;
           session = std::make_unique<Http1Session>(this);
-          selected_proto = NGHTTP2_H1_1.str();
+          selected_proto = NGHTTP2_H1_1;
           break;
         }
       }
@@ -1155,7 +1159,7 @@ int Client::connection_made() {
       break;
     case Config::PROTO_HTTP1_1:
       session = std::make_unique<Http1Session>(this);
-      selected_proto = NGHTTP2_H1_1.str();
+      selected_proto = NGHTTP2_H1_1;
       break;
     default:
       // unreachable
@@ -1861,7 +1865,7 @@ std::string get_reqline(const char *uri, const http_parser_url &u) {
   std::string reqline;
 
   if (util::has_uri_field(u, UF_PATH)) {
-    reqline = util::get_uri_field(uri, u, UF_PATH).str();
+    reqline = util::get_uri_field(uri, u, UF_PATH);
   } else {
     reqline = "/";
   }
@@ -1876,20 +1880,20 @@ std::string get_reqline(const char *uri, const http_parser_url &u) {
 } // namespace
 
 namespace {
-constexpr char UNIX_PATH_PREFIX[] = "unix:";
+constexpr auto UNIX_PATH_PREFIX = "unix:"_sr;
 } // namespace
 
 namespace {
 bool parse_base_uri(const StringRef &base_uri) {
   http_parser_url u{};
-  if (http_parser_parse_url(base_uri.c_str(), base_uri.size(), 0, &u) != 0 ||
+  if (http_parser_parse_url(base_uri.data(), base_uri.size(), 0, &u) != 0 ||
       !util::has_uri_field(u, UF_SCHEMA) || !util::has_uri_field(u, UF_HOST)) {
     return false;
   }
 
-  config.scheme = util::get_uri_field(base_uri.c_str(), u, UF_SCHEMA).str();
-  config.host = util::get_uri_field(base_uri.c_str(), u, UF_HOST).str();
-  config.default_port = util::get_default_port(base_uri.c_str(), u);
+  config.scheme = util::get_uri_field(base_uri.data(), u, UF_SCHEMA);
+  config.host = util::get_uri_field(base_uri.data(), u, UF_HOST);
+  config.default_port = util::get_default_port(base_uri.data(), u);
   if (util::has_uri_field(u, UF_PORT)) {
     config.port = u.port;
   } else {
@@ -2033,7 +2037,7 @@ namespace {
 int parse_header_table_size(uint32_t &dst, const char *opt,
                             const char *optarg) {
   auto n = util::parse_uint_with_unit(optarg);
-  if (n == -1) {
+  if (!n) {
     std::cerr << "--" << opt << ": Bad option value: " << optarg << std::endl;
     return -1;
   }
@@ -2044,7 +2048,7 @@ int parse_header_table_size(uint32_t &dst, const char *opt,
     return -1;
   }
 
-  dst = n;
+  dst = *n;
 
   return 0;
 }
@@ -2086,7 +2090,7 @@ benchmarking tool for HTTP/2 server)"
 } // namespace
 
 namespace {
-constexpr char DEFAULT_ALPN_LIST[] = "h2,h2-16,h2-14,http/1.1";
+constexpr auto DEFAULT_ALPN_LIST = "h2,h2-16,h2-14,http/1.1"_sr;
 } // namespace
 
 namespace {
@@ -2373,21 +2377,21 @@ int main(int argc, char **argv) {
     switch (c) {
     case 'n': {
       auto n = util::parse_uint(optarg);
-      if (n == -1) {
+      if (!n) {
         std::cerr << "-n: bad option value: " << optarg << std::endl;
         exit(EXIT_FAILURE);
       }
-      config.nreqs = n;
+      config.nreqs = *n;
       nreqs_set_manually = true;
       break;
     }
     case 'c': {
       auto n = util::parse_uint(optarg);
-      if (n == -1) {
+      if (!n) {
         std::cerr << "-c: bad option value: " << optarg << std::endl;
         exit(EXIT_FAILURE);
       }
-      config.nclients = n;
+      config.nclients = *n;
       break;
     }
     case 'd':
@@ -2399,55 +2403,55 @@ int main(int argc, char **argv) {
                 << "no threads created." << std::endl;
 #else
       auto n = util::parse_uint(optarg);
-      if (n == -1) {
+      if (!n) {
         std::cerr << "-t: bad option value: " << optarg << std::endl;
         exit(EXIT_FAILURE);
       }
-      config.nthreads = n;
+      config.nthreads = *n;
 #endif // NOTHREADS
       break;
     }
     case 'm': {
       auto n = util::parse_uint(optarg);
-      if (n == -1) {
+      if (!n) {
         std::cerr << "-m: bad option value: " << optarg << std::endl;
         exit(EXIT_FAILURE);
       }
-      config.max_concurrent_streams = n;
+      config.max_concurrent_streams = *n;
       break;
     }
     case 'w':
     case 'W': {
       auto n = util::parse_uint(optarg);
-      if (n == -1 || n > 30) {
+      if (!n || n > 30) {
         std::cerr << "-" << static_cast<char>(c)
                   << ": specify the integer in the range [0, 30], inclusive"
                   << std::endl;
         exit(EXIT_FAILURE);
       }
       if (c == 'w') {
-        config.window_bits = n;
+        config.window_bits = *n;
       } else {
-        config.connection_window_bits = n;
+        config.connection_window_bits = *n;
       }
       break;
     }
     case 'f': {
       auto n = util::parse_uint_with_unit(optarg);
-      if (n == -1) {
+      if (!n) {
         std::cerr << "--max-frame-size: bad option value: " << optarg
                   << std::endl;
         exit(EXIT_FAILURE);
       }
-      if (static_cast<uint64_t>(n) < 16_k) {
+      if (static_cast<uint64_t>(*n) < 16_k) {
         std::cerr << "--max-frame-size: minimum 16384" << std::endl;
         exit(EXIT_FAILURE);
       }
-      if (static_cast<uint64_t>(n) > 16_m - 1) {
+      if (static_cast<uint64_t>(*n) > 16_m - 1) {
         std::cerr << "--max-frame-size: maximum 16777215" << std::endl;
         exit(EXIT_FAILURE);
       }
-      config.max_frame_size = n;
+      config.max_frame_size = *n;
       break;
     }
     case 'H': {
@@ -2481,8 +2485,7 @@ int main(int argc, char **argv) {
       break;
     case 'p': {
       auto proto = StringRef{optarg};
-      if (util::strieq(StringRef::from_lit(NGHTTP2_CLEARTEXT_PROTO_VERSION_ID),
-                       proto)) {
+      if (util::strieq(NGHTTP2_CLEARTEXT_PROTO_VERSION_ID ""_sr, proto)) {
         config.no_tls_proto = Config::PROTO_HTTP2;
       } else if (util::strieq(NGHTTP2_H1_1, proto)) {
         config.no_tls_proto = Config::PROTO_HTTP1_1;
@@ -2494,7 +2497,7 @@ int main(int argc, char **argv) {
     }
     case 'r': {
       auto n = util::parse_uint(optarg);
-      if (n == -1) {
+      if (!n) {
         std::cerr << "-r: bad option value: " << optarg << std::endl;
         exit(EXIT_FAILURE);
       }
@@ -2503,36 +2506,40 @@ int main(int argc, char **argv) {
                   << "must be positive." << std::endl;
         exit(EXIT_FAILURE);
       }
-      config.rate = n;
+      config.rate = *n;
       break;
     }
-    case 'T':
-      config.conn_active_timeout = util::parse_duration_with_unit(optarg);
-      if (!std::isfinite(config.conn_active_timeout)) {
+    case 'T': {
+      auto d = util::parse_duration_with_unit(optarg);
+      if (!d) {
         std::cerr << "-T: bad value for the conn_active_timeout wait time: "
                   << optarg << std::endl;
         exit(EXIT_FAILURE);
       }
+      config.conn_active_timeout = *d;
       break;
-    case 'N':
-      config.conn_inactivity_timeout = util::parse_duration_with_unit(optarg);
-      if (!std::isfinite(config.conn_inactivity_timeout)) {
+    }
+    case 'N': {
+      auto d = util::parse_duration_with_unit(optarg);
+      if (!d) {
         std::cerr << "-N: bad value for the conn_inactivity_timeout wait time: "
                   << optarg << std::endl;
         exit(EXIT_FAILURE);
       }
+      config.conn_inactivity_timeout = *d;
       break;
+    }
     case 'B': {
       auto arg = StringRef{optarg};
       config.base_uri = "";
       config.base_uri_unix = false;
 
-      if (util::istarts_with_l(arg, UNIX_PATH_PREFIX)) {
+      if (util::istarts_with(arg, UNIX_PATH_PREFIX)) {
         // UNIX domain socket path
         sockaddr_un un;
 
-        auto path = StringRef{std::begin(arg) + str_size(UNIX_PATH_PREFIX),
-                              std::end(arg)};
+        auto path =
+            StringRef{std::begin(arg) + UNIX_PATH_PREFIX.size(), std::end(arg)};
 
         if (path.size() == 0 || path.size() + 1 > sizeof(un.sun_path)) {
           std::cerr << "--base-uri: invalid UNIX domain socket path: " << arg
@@ -2555,16 +2562,18 @@ int main(int argc, char **argv) {
         exit(EXIT_FAILURE);
       }
 
-      config.base_uri = arg.str();
+      config.base_uri = arg;
       break;
     }
-    case 'D':
-      config.duration = util::parse_duration_with_unit(optarg);
-      if (!std::isfinite(config.duration)) {
+    case 'D': {
+      auto d = util::parse_duration_with_unit(optarg);
+      if (!d) {
         std::cerr << "-D: value error " << optarg << std::endl;
         exit(EXIT_FAILURE);
       }
+      config.duration = *d;
       break;
+    }
     case 'v':
       config.verbose = true;
       break;
@@ -2589,18 +2598,19 @@ int main(int argc, char **argv) {
         config.ifile = optarg;
         config.timing_script = true;
         break;
-      case 5:
+      case 5: {
         // rate-period
-        config.rate_period = util::parse_duration_with_unit(optarg);
-        if (!std::isfinite(config.rate_period)) {
+        auto d = util::parse_duration_with_unit(optarg);
+        if (!d) {
           std::cerr << "--rate-period: value error " << optarg << std::endl;
           exit(EXIT_FAILURE);
         }
+        config.rate_period = *d;
         break;
+      }
       case 6:
         // --h1
-        config.alpn_list =
-            util::parse_config_str_list(StringRef::from_lit("http/1.1"));
+        config.alpn_list = util::parse_config_str_list("http/1.1"_sr);
         config.no_tls_proto = Config::PROTO_HTTP1_1;
         break;
       case 7:
@@ -2617,14 +2627,16 @@ int main(int argc, char **argv) {
           exit(EXIT_FAILURE);
         }
         break;
-      case 9:
+      case 9: {
         // --warm-up-time
-        config.warm_up_time = util::parse_duration_with_unit(optarg);
-        if (!std::isfinite(config.warm_up_time)) {
+        auto d = util::parse_duration_with_unit(optarg);
+        if (!d) {
           std::cerr << "--warm-up-time: value error " << optarg << std::endl;
           exit(EXIT_FAILURE);
         }
+        config.warm_up_time = *d;
         break;
+      }
       case 10:
         // --log-file
         logfile = optarg;
@@ -2634,11 +2646,12 @@ int main(int argc, char **argv) {
         auto p = util::split_hostport(StringRef{optarg});
         int64_t port = 0;
         if (p.first.empty() ||
-            (!p.second.empty() && (port = util::parse_uint(p.second)) == -1)) {
+            (!p.second.empty() &&
+             (port = util::parse_uint(p.second).value_or(-1)) == -1)) {
           std::cerr << "--connect-to: Invalid value " << optarg << std::endl;
           exit(EXIT_FAILURE);
         }
-        config.connect_to_host = p.first.str();
+        config.connect_to_host = p.first;
         config.connect_to_port = port;
         break;
       }
@@ -2672,17 +2685,17 @@ int main(int argc, char **argv) {
       case 17: {
         // --max-udp-payload-size
         auto n = util::parse_uint_with_unit(optarg);
-        if (n == -1) {
+        if (!n) {
           std::cerr << "--max-udp-payload-size: bad option value: " << optarg
                     << std::endl;
           exit(EXIT_FAILURE);
         }
-        if (static_cast<uint64_t>(n) > 64_k) {
+        if (static_cast<uint64_t>(*n) > 64_k) {
           std::cerr << "--max-udp-payload-size: must not exceed 65536"
                     << std::endl;
           exit(EXIT_FAILURE);
         }
-        config.max_udp_payload_size = n;
+        config.max_udp_payload_size = *n;
         break;
       }
       case 18:
@@ -2723,8 +2736,7 @@ int main(int argc, char **argv) {
   }
 
   if (config.alpn_list.empty()) {
-    config.alpn_list =
-        util::parse_config_str_list(StringRef::from_lit(DEFAULT_ALPN_LIST));
+    config.alpn_list = util::parse_config_str_list(DEFAULT_ALPN_LIST);
   }
 
   // serialize the APLN tokens
@@ -2991,8 +3003,8 @@ int main(int argc, char **argv) {
   shared_nva.emplace_back("user-agent", user_agent);
 
   // list header fields that can be overridden.
-  auto override_hdrs = make_array<std::string>(":authority", "host", ":method",
-                                               ":scheme", "user-agent");
+  auto override_hdrs = std::to_array<std::string_view>(
+      {":authority", "host", ":method", ":scheme", "user-agent"});
 
   for (auto &kv : config.custom_headers) {
     if (std::find(std::begin(override_hdrs), std::end(override_hdrs),
@@ -3059,15 +3071,15 @@ int main(int argc, char **argv) {
     // 2 for :path, and possible content-length
     nva.reserve(2 + shared_nva.size());
 
-    nva.push_back(http2::make_nv_ls(":path", req));
+    nva.push_back(http2::make_field_v(":path"_sr, req));
 
     for (auto &nv : shared_nva) {
-      nva.push_back(http2::make_nv(nv.name, nv.value, false));
+      nva.push_back(http2::make_field_nv(nv.name, nv.value));
     }
 
     if (!content_length_str.empty()) {
-      nva.push_back(http2::make_nv(StringRef::from_lit("content-length"),
-                                   StringRef{content_length_str}));
+      nva.push_back(
+          http2::make_field_nv("content-length"_sr, content_length_str));
     }
 
     config.nva.push_back(std::move(nva));
diff --git a/src/h2load_quic.cc b/src/h2load_quic.cc
index 8b3c552..5187ca0 100644
--- a/src/h2load_quic.cc
+++ b/src/h2load_quic.cc
@@ -646,17 +646,13 @@ int Client::write_quic() {
   }
 
   std::array<nghttp3_vec, 16> vec;
-  size_t pktcnt = 0;
   auto max_udp_payload_size =
       ngtcp2_conn_get_max_tx_udp_payload_size(quic.conn);
-#ifdef UDP_SEGMENT
   auto path_max_udp_payload_size =
       ngtcp2_conn_get_path_max_tx_udp_payload_size(quic.conn);
-#endif // UDP_SEGMENT
-  auto max_pktcnt =
-      std::max(ngtcp2_conn_get_send_quantum(quic.conn) / max_udp_payload_size,
-               static_cast<size_t>(1));
   uint8_t *bufpos = quic.tx.data.get();
+  auto bufleft = std::max(ngtcp2_conn_get_send_quantum(quic.conn),
+                          path_max_udp_payload_size);
   ngtcp2_path_storage ps;
   size_t gso_size = 0;
 
@@ -686,9 +682,11 @@ int Client::write_quic() {
       flags |= NGTCP2_WRITE_STREAM_FLAG_FIN;
     }
 
+    auto buflen = bufleft >= max_udp_payload_size ? max_udp_payload_size
+                                                  : path_max_udp_payload_size;
     auto nwrite = ngtcp2_conn_writev_stream(
-        quic.conn, &ps.path, nullptr, bufpos, max_udp_payload_size, &ndatalen,
-        flags, stream_id, reinterpret_cast<const ngtcp2_vec *>(v), vcnt, ts);
+        quic.conn, &ps.path, nullptr, bufpos, buflen, &ndatalen, flags,
+        stream_id, reinterpret_cast<const ngtcp2_vec *>(v), vcnt, ts);
     if (nwrite < 0) {
       switch (nwrite) {
       case NGTCP2_ERR_STREAM_DATA_BLOCKED:
@@ -730,7 +728,11 @@ int Client::write_quic() {
       return 0;
     }
 
+    auto first_pkt = bufpos == quic.tx.data.get();
+    (void)first_pkt;
+
     bufpos += nwrite;
+    bufleft -= nwrite;
 
 #ifdef UDP_SEGMENT
     if (worker->config->no_udp_gso) {
@@ -745,7 +747,7 @@ int Client::write_quic() {
         return 0;
       }
 
-      if (++pktcnt == max_pktcnt) {
+      if (bufleft < path_max_udp_payload_size) {
         signal_write();
         return 0;
       }
@@ -758,7 +760,7 @@ int Client::write_quic() {
 #endif // UDP_SEGMENT
 
 #ifdef UDP_SEGMENT
-    if (pktcnt == 0) {
+    if (first_pkt) {
       gso_size = nwrite;
     } else if (static_cast<size_t>(nwrite) > gso_size ||
                (gso_size > path_max_udp_payload_size &&
@@ -784,7 +786,8 @@ int Client::write_quic() {
     }
 
     // Assume that the path does not change.
-    if (++pktcnt == max_pktcnt || static_cast<size_t>(nwrite) < gso_size) {
+    if (bufleft < path_max_udp_payload_size ||
+        static_cast<size_t>(nwrite) < gso_size) {
       auto data = quic.tx.data.get();
       auto datalen = bufpos - quic.tx.data.get();
       rv = write_udp(ps.path.remote.addr, ps.path.remote.addrlen, data, datalen,
diff --git a/src/http2.cc b/src/http2.cc
index 661c4c9..2815229 100644
--- a/src/http2.cc
+++ b/src/http2.cc
@@ -35,107 +35,107 @@ namespace http2 {
 StringRef get_reason_phrase(unsigned int status_code) {
   switch (status_code) {
   case 100:
-    return StringRef::from_lit("Continue");
+    return "Continue"_sr;
   case 101:
-    return StringRef::from_lit("Switching Protocols");
+    return "Switching Protocols"_sr;
   case 103:
-    return StringRef::from_lit("Early Hints");
+    return "Early Hints"_sr;
   case 200:
-    return StringRef::from_lit("OK");
+    return "OK"_sr;
   case 201:
-    return StringRef::from_lit("Created");
+    return "Created"_sr;
   case 202:
-    return StringRef::from_lit("Accepted");
+    return "Accepted"_sr;
   case 203:
-    return StringRef::from_lit("Non-Authoritative Information");
+    return "Non-Authoritative Information"_sr;
   case 204:
-    return StringRef::from_lit("No Content");
+    return "No Content"_sr;
   case 205:
-    return StringRef::from_lit("Reset Content");
+    return "Reset Content"_sr;
   case 206:
-    return StringRef::from_lit("Partial Content");
+    return "Partial Content"_sr;
   case 300:
-    return StringRef::from_lit("Multiple Choices");
+    return "Multiple Choices"_sr;
   case 301:
-    return StringRef::from_lit("Moved Permanently");
+    return "Moved Permanently"_sr;
   case 302:
-    return StringRef::from_lit("Found");
+    return "Found"_sr;
   case 303:
-    return StringRef::from_lit("See Other");
+    return "See Other"_sr;
   case 304:
-    return StringRef::from_lit("Not Modified");
+    return "Not Modified"_sr;
   case 305:
-    return StringRef::from_lit("Use Proxy");
-  // case 306: return StringRef::from_lit("(Unused)");
+    return "Use Proxy"_sr;
+  // case 306: return "(Unused)"_sr;
   case 307:
-    return StringRef::from_lit("Temporary Redirect");
+    return "Temporary Redirect"_sr;
   case 308:
-    return StringRef::from_lit("Permanent Redirect");
+    return "Permanent Redirect"_sr;
   case 400:
-    return StringRef::from_lit("Bad Request");
+    return "Bad Request"_sr;
   case 401:
-    return StringRef::from_lit("Unauthorized");
+    return "Unauthorized"_sr;
   case 402:
-    return StringRef::from_lit("Payment Required");
+    return "Payment Required"_sr;
   case 403:
-    return StringRef::from_lit("Forbidden");
+    return "Forbidden"_sr;
   case 404:
-    return StringRef::from_lit("Not Found");
+    return "Not Found"_sr;
   case 405:
-    return StringRef::from_lit("Method Not Allowed");
+    return "Method Not Allowed"_sr;
   case 406:
-    return StringRef::from_lit("Not Acceptable");
+    return "Not Acceptable"_sr;
   case 407:
-    return StringRef::from_lit("Proxy Authentication Required");
+    return "Proxy Authentication Required"_sr;
   case 408:
-    return StringRef::from_lit("Request Timeout");
+    return "Request Timeout"_sr;
   case 409:
-    return StringRef::from_lit("Conflict");
+    return "Conflict"_sr;
   case 410:
-    return StringRef::from_lit("Gone");
+    return "Gone"_sr;
   case 411:
-    return StringRef::from_lit("Length Required");
+    return "Length Required"_sr;
   case 412:
-    return StringRef::from_lit("Precondition Failed");
+    return "Precondition Failed"_sr;
   case 413:
-    return StringRef::from_lit("Payload Too Large");
+    return "Payload Too Large"_sr;
   case 414:
-    return StringRef::from_lit("URI Too Long");
+    return "URI Too Long"_sr;
   case 415:
-    return StringRef::from_lit("Unsupported Media Type");
+    return "Unsupported Media Type"_sr;
   case 416:
-    return StringRef::from_lit("Requested Range Not Satisfiable");
+    return "Requested Range Not Satisfiable"_sr;
   case 417:
-    return StringRef::from_lit("Expectation Failed");
+    return "Expectation Failed"_sr;
   case 421:
-    return StringRef::from_lit("Misdirected Request");
+    return "Misdirected Request"_sr;
   case 425:
     // https://tools.ietf.org/html/rfc8470
-    return StringRef::from_lit("Too Early");
+    return "Too Early"_sr;
   case 426:
-    return StringRef::from_lit("Upgrade Required");
+    return "Upgrade Required"_sr;
   case 428:
-    return StringRef::from_lit("Precondition Required");
+    return "Precondition Required"_sr;
   case 429:
-    return StringRef::from_lit("Too Many Requests");
+    return "Too Many Requests"_sr;
   case 431:
-    return StringRef::from_lit("Request Header Fields Too Large");
+    return "Request Header Fields Too Large"_sr;
   case 451:
-    return StringRef::from_lit("Unavailable For Legal Reasons");
+    return "Unavailable For Legal Reasons"_sr;
   case 500:
-    return StringRef::from_lit("Internal Server Error");
+    return "Internal Server Error"_sr;
   case 501:
-    return StringRef::from_lit("Not Implemented");
+    return "Not Implemented"_sr;
   case 502:
-    return StringRef::from_lit("Bad Gateway");
+    return "Bad Gateway"_sr;
   case 503:
-    return StringRef::from_lit("Service Unavailable");
+    return "Service Unavailable"_sr;
   case 504:
-    return StringRef::from_lit("Gateway Timeout");
+    return "Gateway Timeout"_sr;
   case 505:
-    return StringRef::from_lit("HTTP Version Not Supported");
+    return "HTTP Version Not Supported"_sr;
   case 511:
-    return StringRef::from_lit("Network Authentication Required");
+    return "Network Authentication Required"_sr;
   default:
     return StringRef{};
   }
@@ -144,104 +144,104 @@ StringRef get_reason_phrase(unsigned int status_code) {
 StringRef stringify_status(BlockAllocator &balloc, unsigned int status_code) {
   switch (status_code) {
   case 100:
-    return StringRef::from_lit("100");
+    return "100"_sr;
   case 101:
-    return StringRef::from_lit("101");
+    return "101"_sr;
   case 103:
-    return StringRef::from_lit("103");
+    return "103"_sr;
   case 200:
-    return StringRef::from_lit("200");
+    return "200"_sr;
   case 201:
-    return StringRef::from_lit("201");
+    return "201"_sr;
   case 202:
-    return StringRef::from_lit("202");
+    return "202"_sr;
   case 203:
-    return StringRef::from_lit("203");
+    return "203"_sr;
   case 204:
-    return StringRef::from_lit("204");
+    return "204"_sr;
   case 205:
-    return StringRef::from_lit("205");
+    return "205"_sr;
   case 206:
-    return StringRef::from_lit("206");
+    return "206"_sr;
   case 300:
-    return StringRef::from_lit("300");
+    return "300"_sr;
   case 301:
-    return StringRef::from_lit("301");
+    return "301"_sr;
   case 302:
-    return StringRef::from_lit("302");
+    return "302"_sr;
   case 303:
-    return StringRef::from_lit("303");
+    return "303"_sr;
   case 304:
-    return StringRef::from_lit("304");
+    return "304"_sr;
   case 305:
-    return StringRef::from_lit("305");
-  // case 306: return StringRef::from_lit("306");
+    return "305"_sr;
+  // case 306: return "306"_sr;
   case 307:
-    return StringRef::from_lit("307");
+    return "307"_sr;
   case 308:
-    return StringRef::from_lit("308");
+    return "308"_sr;
   case 400:
-    return StringRef::from_lit("400");
+    return "400"_sr;
   case 401:
-    return StringRef::from_lit("401");
+    return "401"_sr;
   case 402:
-    return StringRef::from_lit("402");
+    return "402"_sr;
   case 403:
-    return StringRef::from_lit("403");
+    return "403"_sr;
   case 404:
-    return StringRef::from_lit("404");
+    return "404"_sr;
   case 405:
-    return StringRef::from_lit("405");
+    return "405"_sr;
   case 406:
-    return StringRef::from_lit("406");
+    return "406"_sr;
   case 407:
-    return StringRef::from_lit("407");
+    return "407"_sr;
   case 408:
-    return StringRef::from_lit("408");
+    return "408"_sr;
   case 409:
-    return StringRef::from_lit("409");
+    return "409"_sr;
   case 410:
-    return StringRef::from_lit("410");
+    return "410"_sr;
   case 411:
-    return StringRef::from_lit("411");
+    return "411"_sr;
   case 412:
-    return StringRef::from_lit("412");
+    return "412"_sr;
   case 413:
-    return StringRef::from_lit("413");
+    return "413"_sr;
   case 414:
-    return StringRef::from_lit("414");
+    return "414"_sr;
   case 415:
-    return StringRef::from_lit("415");
+    return "415"_sr;
   case 416:
-    return StringRef::from_lit("416");
+    return "416"_sr;
   case 417:
-    return StringRef::from_lit("417");
+    return "417"_sr;
   case 421:
-    return StringRef::from_lit("421");
+    return "421"_sr;
   case 426:
-    return StringRef::from_lit("426");
+    return "426"_sr;
   case 428:
-    return StringRef::from_lit("428");
+    return "428"_sr;
   case 429:
-    return StringRef::from_lit("429");
+    return "429"_sr;
   case 431:
-    return StringRef::from_lit("431");
+    return "431"_sr;
   case 451:
-    return StringRef::from_lit("451");
+    return "451"_sr;
   case 500:
-    return StringRef::from_lit("500");
+    return "500"_sr;
   case 501:
-    return StringRef::from_lit("501");
+    return "501"_sr;
   case 502:
-    return StringRef::from_lit("502");
+    return "502"_sr;
   case 503:
-    return StringRef::from_lit("503");
+    return "503"_sr;
   case 504:
-    return StringRef::from_lit("504");
+    return "504"_sr;
   case 505:
-    return StringRef::from_lit("505");
+    return "505"_sr;
   case 511:
-    return StringRef::from_lit("511");
+    return "511"_sr;
   default:
     return util::make_string_ref_uint(balloc, status_code);
   }
@@ -278,27 +278,16 @@ void copy_url_component(std::string &dest, const http_parser_url *u, int field,
   }
 }
 
-Headers::value_type to_header(const uint8_t *name, size_t namelen,
-                              const uint8_t *value, size_t valuelen,
+Headers::value_type to_header(const StringRef &name, const StringRef &value,
                               bool no_index, int32_t token) {
-  return Header(std::string(reinterpret_cast<const char *>(name), namelen),
-                std::string(reinterpret_cast<const char *>(value), valuelen),
-                no_index, token);
+  return Header(std::string{std::begin(name), std::end(name)},
+                std::string{std::begin(value), std::end(value)}, no_index,
+                token);
 }
 
-void add_header(Headers &nva, const uint8_t *name, size_t namelen,
-                const uint8_t *value, size_t valuelen, bool no_index,
-                int32_t token) {
-  if (valuelen > 0) {
-    size_t i, j;
-    for (i = 0; i < valuelen && (value[i] == ' ' || value[i] == '\t'); ++i)
-      ;
-    for (j = valuelen - 1; j > i && (value[j] == ' ' || value[j] == '\t'); --j)
-      ;
-    value += i;
-    valuelen -= i + (valuelen - j - 1);
-  }
-  nva.push_back(to_header(name, namelen, value, valuelen, no_index, token));
+void add_header(Headers &nva, const StringRef &name, const StringRef &value,
+                bool no_index, int32_t token) {
+  nva.push_back(to_header(name, value, no_index, token));
 }
 
 const Headers::value_type *get_header(const Headers &nva, const char *name) {
@@ -316,56 +305,6 @@ bool non_empty_value(const HeaderRefs::value_type *nv) {
 }
 
 namespace {
-nghttp2_nv make_nv_internal(const std::string &name, const std::string &value,
-                            bool no_index, uint8_t nv_flags) {
-  uint8_t flags;
-
-  flags =
-      nv_flags | (no_index ? NGHTTP2_NV_FLAG_NO_INDEX : NGHTTP2_NV_FLAG_NONE);
-
-  return {(uint8_t *)name.c_str(), (uint8_t *)value.c_str(), name.size(),
-          value.size(), flags};
-}
-} // namespace
-
-namespace {
-nghttp2_nv make_nv_internal(const StringRef &name, const StringRef &value,
-                            bool no_index, uint8_t nv_flags) {
-  uint8_t flags;
-
-  flags =
-      nv_flags | (no_index ? NGHTTP2_NV_FLAG_NO_INDEX : NGHTTP2_NV_FLAG_NONE);
-
-  return {(uint8_t *)name.c_str(), (uint8_t *)value.c_str(), name.size(),
-          value.size(), flags};
-}
-} // namespace
-
-nghttp2_nv make_nv(const std::string &name, const std::string &value,
-                   bool no_index) {
-  return make_nv_internal(name, value, no_index, NGHTTP2_NV_FLAG_NONE);
-}
-
-nghttp2_nv make_nv(const StringRef &name, const StringRef &value,
-                   bool no_index) {
-  return make_nv_internal(name, value, no_index, NGHTTP2_NV_FLAG_NONE);
-}
-
-nghttp2_nv make_nv_nocopy(const std::string &name, const std::string &value,
-                          bool no_index) {
-  return make_nv_internal(name, value, no_index,
-                          NGHTTP2_NV_FLAG_NO_COPY_NAME |
-                              NGHTTP2_NV_FLAG_NO_COPY_VALUE);
-}
-
-nghttp2_nv make_nv_nocopy(const StringRef &name, const StringRef &value,
-                          bool no_index) {
-  return make_nv_internal(name, value, no_index,
-                          NGHTTP2_NV_FLAG_NO_COPY_NAME |
-                              NGHTTP2_NV_FLAG_NO_COPY_VALUE);
-}
-
-namespace {
 void copy_headers_to_nva_internal(std::vector<nghttp2_nv> &nva,
                                   const HeaderRefs &headers, uint8_t nv_flags,
                                   uint32_t flags) {
@@ -459,8 +398,8 @@ void copy_headers_to_nva_internal(std::vector<nghttp2_nv> &nva,
       it_via = it;
       break;
     }
-    nva.push_back(
-        make_nv_internal(kv->name, kv->value, kv->no_index, nv_flags));
+    nva.push_back(make_field_flags(kv->name, kv->value,
+                                   nv_flags | no_index(kv->no_index)));
   }
 }
 } // namespace
@@ -617,7 +556,7 @@ void dump_nv(FILE *out, const Headers &nva) {
 
 void dump_nv(FILE *out, const HeaderRefs &nva) {
   for (auto &nv : nva) {
-    fprintf(out, "%s: %s\n", nv.name.c_str(), nv.value.c_str());
+    fprintf(out, "%s: %s\n", nv.name.data(), nv.value.data());
   }
   fputc('\n', out);
   fflush(out);
@@ -665,7 +604,7 @@ StringRef rewrite_location_uri(BlockAllocator &balloc, const StringRef &uri,
   }
 
   auto iov = make_byte_ref(balloc, len + 1);
-  auto p = iov.base;
+  auto p = std::begin(iov);
 
   if (!request_authority.empty()) {
     p = std::copy(std::begin(upstream_scheme), std::end(upstream_scheme), p);
@@ -690,7 +629,7 @@ StringRef rewrite_location_uri(BlockAllocator &balloc, const StringRef &uri,
 
   *p = '\0';
 
-  return StringRef{iov.base, p};
+  return StringRef{std::span{std::begin(iov), p}};
 }
 
 int parse_http_status_code(const StringRef &src) {
@@ -714,18 +653,14 @@ int parse_http_status_code(const StringRef &src) {
   return status;
 }
 
-int lookup_token(const StringRef &name) {
-  return lookup_token(name.byte(), name.size());
-}
-
 // This function was generated by genheaderfunc.py.  Inspired by h2o
 // header lookup.  https://github.com/h2o/h2o
-int lookup_token(const uint8_t *name, size_t namelen) {
-  switch (namelen) {
+int lookup_token(const StringRef &name) {
+  switch (name.size()) {
   case 2:
     switch (name[1]) {
     case 'e':
-      if (util::streq_l("t", name, 1)) {
+      if (util::streq("t"_sr, name, 1)) {
         return HD_TE;
       }
       break;
@@ -734,7 +669,7 @@ int lookup_token(const uint8_t *name, size_t namelen) {
   case 3:
     switch (name[2]) {
     case 'a':
-      if (util::streq_l("vi", name, 2)) {
+      if (util::streq("vi"_sr, name, 2)) {
         return HD_VIA;
       }
       break;
@@ -743,17 +678,17 @@ int lookup_token(const uint8_t *name, size_t namelen) {
   case 4:
     switch (name[3]) {
     case 'e':
-      if (util::streq_l("dat", name, 3)) {
+      if (util::streq("dat"_sr, name, 3)) {
         return HD_DATE;
       }
       break;
     case 'k':
-      if (util::streq_l("lin", name, 3)) {
+      if (util::streq("lin"_sr, name, 3)) {
         return HD_LINK;
       }
       break;
     case 't':
-      if (util::streq_l("hos", name, 3)) {
+      if (util::streq("hos"_sr, name, 3)) {
         return HD_HOST;
       }
       break;
@@ -762,12 +697,12 @@ int lookup_token(const uint8_t *name, size_t namelen) {
   case 5:
     switch (name[4]) {
     case 'h':
-      if (util::streq_l(":pat", name, 4)) {
+      if (util::streq(":pat"_sr, name, 4)) {
         return HD__PATH;
       }
       break;
     case 't':
-      if (util::streq_l(":hos", name, 4)) {
+      if (util::streq(":hos"_sr, name, 4)) {
         return HD__HOST;
       }
       break;
@@ -776,17 +711,17 @@ int lookup_token(const uint8_t *name, size_t namelen) {
   case 6:
     switch (name[5]) {
     case 'e':
-      if (util::streq_l("cooki", name, 5)) {
+      if (util::streq("cooki"_sr, name, 5)) {
         return HD_COOKIE;
       }
       break;
     case 'r':
-      if (util::streq_l("serve", name, 5)) {
+      if (util::streq("serve"_sr, name, 5)) {
         return HD_SERVER;
       }
       break;
     case 't':
-      if (util::streq_l("expec", name, 5)) {
+      if (util::streq("expec"_sr, name, 5)) {
         return HD_EXPECT;
       }
       break;
@@ -795,30 +730,30 @@ int lookup_token(const uint8_t *name, size_t namelen) {
   case 7:
     switch (name[6]) {
     case 'c':
-      if (util::streq_l("alt-sv", name, 6)) {
+      if (util::streq("alt-sv"_sr, name, 6)) {
         return HD_ALT_SVC;
       }
       break;
     case 'd':
-      if (util::streq_l(":metho", name, 6)) {
+      if (util::streq(":metho"_sr, name, 6)) {
         return HD__METHOD;
       }
       break;
     case 'e':
-      if (util::streq_l(":schem", name, 6)) {
+      if (util::streq(":schem"_sr, name, 6)) {
         return HD__SCHEME;
       }
-      if (util::streq_l("upgrad", name, 6)) {
+      if (util::streq("upgrad"_sr, name, 6)) {
         return HD_UPGRADE;
       }
       break;
     case 'r':
-      if (util::streq_l("traile", name, 6)) {
+      if (util::streq("traile"_sr, name, 6)) {
         return HD_TRAILER;
       }
       break;
     case 's':
-      if (util::streq_l(":statu", name, 6)) {
+      if (util::streq(":statu"_sr, name, 6)) {
         return HD__STATUS;
       }
       break;
@@ -827,12 +762,12 @@ int lookup_token(const uint8_t *name, size_t namelen) {
   case 8:
     switch (name[7]) {
     case 'n':
-      if (util::streq_l("locatio", name, 7)) {
+      if (util::streq("locatio"_sr, name, 7)) {
         return HD_LOCATION;
       }
       break;
     case 'y':
-      if (util::streq_l("priorit", name, 7)) {
+      if (util::streq("priorit"_sr, name, 7)) {
         return HD_PRIORITY;
       }
       break;
@@ -841,12 +776,12 @@ int lookup_token(const uint8_t *name, size_t namelen) {
   case 9:
     switch (name[8]) {
     case 'd':
-      if (util::streq_l("forwarde", name, 8)) {
+      if (util::streq("forwarde"_sr, name, 8)) {
         return HD_FORWARDED;
       }
       break;
     case 'l':
-      if (util::streq_l(":protoco", name, 8)) {
+      if (util::streq(":protoco"_sr, name, 8)) {
         return HD__PROTOCOL;
       }
       break;
@@ -855,27 +790,27 @@ int lookup_token(const uint8_t *name, size_t namelen) {
   case 10:
     switch (name[9]) {
     case 'a':
-      if (util::streq_l("early-dat", name, 9)) {
+      if (util::streq("early-dat"_sr, name, 9)) {
         return HD_EARLY_DATA;
       }
       break;
     case 'e':
-      if (util::streq_l("keep-aliv", name, 9)) {
+      if (util::streq("keep-aliv"_sr, name, 9)) {
         return HD_KEEP_ALIVE;
       }
       break;
     case 'n':
-      if (util::streq_l("connectio", name, 9)) {
+      if (util::streq("connectio"_sr, name, 9)) {
         return HD_CONNECTION;
       }
       break;
     case 't':
-      if (util::streq_l("user-agen", name, 9)) {
+      if (util::streq("user-agen"_sr, name, 9)) {
         return HD_USER_AGENT;
       }
       break;
     case 'y':
-      if (util::streq_l(":authorit", name, 9)) {
+      if (util::streq(":authorit"_sr, name, 9)) {
         return HD__AUTHORITY;
       }
       break;
@@ -884,7 +819,7 @@ int lookup_token(const uint8_t *name, size_t namelen) {
   case 12:
     switch (name[11]) {
     case 'e':
-      if (util::streq_l("content-typ", name, 11)) {
+      if (util::streq("content-typ"_sr, name, 11)) {
         return HD_CONTENT_TYPE;
       }
       break;
@@ -893,7 +828,7 @@ int lookup_token(const uint8_t *name, size_t namelen) {
   case 13:
     switch (name[12]) {
     case 'l':
-      if (util::streq_l("cache-contro", name, 12)) {
+      if (util::streq("cache-contro"_sr, name, 12)) {
         return HD_CACHE_CONTROL;
       }
       break;
@@ -902,12 +837,12 @@ int lookup_token(const uint8_t *name, size_t namelen) {
   case 14:
     switch (name[13]) {
     case 'h':
-      if (util::streq_l("content-lengt", name, 13)) {
+      if (util::streq("content-lengt"_sr, name, 13)) {
         return HD_CONTENT_LENGTH;
       }
       break;
     case 's':
-      if (util::streq_l("http2-setting", name, 13)) {
+      if (util::streq("http2-setting"_sr, name, 13)) {
         return HD_HTTP2_SETTINGS;
       }
       break;
@@ -916,17 +851,17 @@ int lookup_token(const uint8_t *name, size_t namelen) {
   case 15:
     switch (name[14]) {
     case 'e':
-      if (util::streq_l("accept-languag", name, 14)) {
+      if (util::streq("accept-languag"_sr, name, 14)) {
         return HD_ACCEPT_LANGUAGE;
       }
       break;
     case 'g':
-      if (util::streq_l("accept-encodin", name, 14)) {
+      if (util::streq("accept-encodin"_sr, name, 14)) {
         return HD_ACCEPT_ENCODING;
       }
       break;
     case 'r':
-      if (util::streq_l("x-forwarded-fo", name, 14)) {
+      if (util::streq("x-forwarded-fo"_sr, name, 14)) {
         return HD_X_FORWARDED_FOR;
       }
       break;
@@ -935,7 +870,7 @@ int lookup_token(const uint8_t *name, size_t namelen) {
   case 16:
     switch (name[15]) {
     case 'n':
-      if (util::streq_l("proxy-connectio", name, 15)) {
+      if (util::streq("proxy-connectio"_sr, name, 15)) {
         return HD_PROXY_CONNECTION;
       }
       break;
@@ -944,22 +879,22 @@ int lookup_token(const uint8_t *name, size_t namelen) {
   case 17:
     switch (name[16]) {
     case 'e':
-      if (util::streq_l("if-modified-sinc", name, 16)) {
+      if (util::streq("if-modified-sinc"_sr, name, 16)) {
         return HD_IF_MODIFIED_SINCE;
       }
       break;
     case 'g':
-      if (util::streq_l("transfer-encodin", name, 16)) {
+      if (util::streq("transfer-encodin"_sr, name, 16)) {
         return HD_TRANSFER_ENCODING;
       }
       break;
     case 'o':
-      if (util::streq_l("x-forwarded-prot", name, 16)) {
+      if (util::streq("x-forwarded-prot"_sr, name, 16)) {
         return HD_X_FORWARDED_PROTO;
       }
       break;
     case 'y':
-      if (util::streq_l("sec-websocket-ke", name, 16)) {
+      if (util::streq("sec-websocket-ke"_sr, name, 16)) {
         return HD_SEC_WEBSOCKET_KEY;
       }
       break;
@@ -968,7 +903,7 @@ int lookup_token(const uint8_t *name, size_t namelen) {
   case 20:
     switch (name[19]) {
     case 't':
-      if (util::streq_l("sec-websocket-accep", name, 19)) {
+      if (util::streq("sec-websocket-accep"_sr, name, 19)) {
         return HD_SEC_WEBSOCKET_ACCEPT;
       }
       break;
@@ -1384,7 +1319,8 @@ std::string path_join(const StringRef &base_path, const StringRef &base_query,
                       const StringRef &rel_path, const StringRef &rel_query) {
   BlockAllocator balloc(1024, 1024);
 
-  return path_join(balloc, base_path, base_query, rel_path, rel_query).str();
+  return std::string{
+      path_join(balloc, base_path, base_query, rel_path, rel_query)};
 }
 
 bool expect_response_body(int status_code) {
@@ -1400,25 +1336,21 @@ bool expect_response_body(int method_token, int status_code) {
   return method_token != HTTP_HEAD && expect_response_body(status_code);
 }
 
-int lookup_method_token(const StringRef &name) {
-  return lookup_method_token(name.byte(), name.size());
-}
-
 // This function was generated by genmethodfunc.py.
-int lookup_method_token(const uint8_t *name, size_t namelen) {
-  switch (namelen) {
+int lookup_method_token(const StringRef &name) {
+  switch (name.size()) {
   case 3:
     switch (name[2]) {
     case 'L':
-      if (util::streq_l("AC", name, 2)) {
+      if (util::streq("AC"_sr, name, 2)) {
         return HTTP_ACL;
       }
       break;
     case 'T':
-      if (util::streq_l("GE", name, 2)) {
+      if (util::streq("GE"_sr, name, 2)) {
         return HTTP_GET;
       }
-      if (util::streq_l("PU", name, 2)) {
+      if (util::streq("PU"_sr, name, 2)) {
         return HTTP_PUT;
       }
       break;
@@ -1427,33 +1359,33 @@ int lookup_method_token(const uint8_t *name, size_t namelen) {
   case 4:
     switch (name[3]) {
     case 'D':
-      if (util::streq_l("BIN", name, 3)) {
+      if (util::streq("BIN"_sr, name, 3)) {
         return HTTP_BIND;
       }
-      if (util::streq_l("HEA", name, 3)) {
+      if (util::streq("HEA"_sr, name, 3)) {
         return HTTP_HEAD;
       }
       break;
     case 'E':
-      if (util::streq_l("MOV", name, 3)) {
+      if (util::streq("MOV"_sr, name, 3)) {
         return HTTP_MOVE;
       }
       break;
     case 'K':
-      if (util::streq_l("LIN", name, 3)) {
+      if (util::streq("LIN"_sr, name, 3)) {
         return HTTP_LINK;
       }
-      if (util::streq_l("LOC", name, 3)) {
+      if (util::streq("LOC"_sr, name, 3)) {
         return HTTP_LOCK;
       }
       break;
     case 'T':
-      if (util::streq_l("POS", name, 3)) {
+      if (util::streq("POS"_sr, name, 3)) {
         return HTTP_POST;
       }
       break;
     case 'Y':
-      if (util::streq_l("COP", name, 3)) {
+      if (util::streq("COP"_sr, name, 3)) {
         return HTTP_COPY;
       }
       break;
@@ -1462,23 +1394,23 @@ int lookup_method_token(const uint8_t *name, size_t namelen) {
   case 5:
     switch (name[4]) {
     case 'E':
-      if (util::streq_l("MERG", name, 4)) {
+      if (util::streq("MERG"_sr, name, 4)) {
         return HTTP_MERGE;
       }
-      if (util::streq_l("PURG", name, 4)) {
+      if (util::streq("PURG"_sr, name, 4)) {
         return HTTP_PURGE;
       }
-      if (util::streq_l("TRAC", name, 4)) {
+      if (util::streq("TRAC"_sr, name, 4)) {
         return HTTP_TRACE;
       }
       break;
     case 'H':
-      if (util::streq_l("PATC", name, 4)) {
+      if (util::streq("PATC"_sr, name, 4)) {
         return HTTP_PATCH;
       }
       break;
     case 'L':
-      if (util::streq_l("MKCO", name, 4)) {
+      if (util::streq("MKCO"_sr, name, 4)) {
         return HTTP_MKCOL;
       }
       break;
@@ -1487,41 +1419,41 @@ int lookup_method_token(const uint8_t *name, size_t namelen) {
   case 6:
     switch (name[5]) {
     case 'D':
-      if (util::streq_l("REBIN", name, 5)) {
+      if (util::streq("REBIN"_sr, name, 5)) {
         return HTTP_REBIND;
       }
-      if (util::streq_l("UNBIN", name, 5)) {
+      if (util::streq("UNBIN"_sr, name, 5)) {
         return HTTP_UNBIND;
       }
       break;
     case 'E':
-      if (util::streq_l("DELET", name, 5)) {
+      if (util::streq("DELET"_sr, name, 5)) {
         return HTTP_DELETE;
       }
-      if (util::streq_l("SOURC", name, 5)) {
+      if (util::streq("SOURC"_sr, name, 5)) {
         return HTTP_SOURCE;
       }
       break;
     case 'H':
-      if (util::streq_l("SEARC", name, 5)) {
+      if (util::streq("SEARC"_sr, name, 5)) {
         return HTTP_SEARCH;
       }
       break;
     case 'K':
-      if (util::streq_l("UNLIN", name, 5)) {
+      if (util::streq("UNLIN"_sr, name, 5)) {
         return HTTP_UNLINK;
       }
-      if (util::streq_l("UNLOC", name, 5)) {
+      if (util::streq("UNLOC"_sr, name, 5)) {
         return HTTP_UNLOCK;
       }
       break;
     case 'T':
-      if (util::streq_l("REPOR", name, 5)) {
+      if (util::streq("REPOR"_sr, name, 5)) {
         return HTTP_REPORT;
       }
       break;
     case 'Y':
-      if (util::streq_l("NOTIF", name, 5)) {
+      if (util::streq("NOTIF"_sr, name, 5)) {
         return HTTP_NOTIFY;
       }
       break;
@@ -1530,17 +1462,17 @@ int lookup_method_token(const uint8_t *name, size_t namelen) {
   case 7:
     switch (name[6]) {
     case 'H':
-      if (util::streq_l("MSEARC", name, 6)) {
+      if (util::streq("MSEARC"_sr, name, 6)) {
         return HTTP_MSEARCH;
       }
       break;
     case 'S':
-      if (util::streq_l("OPTION", name, 6)) {
+      if (util::streq("OPTION"_sr, name, 6)) {
         return HTTP_OPTIONS;
       }
       break;
     case 'T':
-      if (util::streq_l("CONNEC", name, 6)) {
+      if (util::streq("CONNEC"_sr, name, 6)) {
         return HTTP_CONNECT;
       }
       break;
@@ -1549,12 +1481,12 @@ int lookup_method_token(const uint8_t *name, size_t namelen) {
   case 8:
     switch (name[7]) {
     case 'D':
-      if (util::streq_l("PROPFIN", name, 7)) {
+      if (util::streq("PROPFIN"_sr, name, 7)) {
         return HTTP_PROPFIND;
       }
       break;
     case 'T':
-      if (util::streq_l("CHECKOU", name, 7)) {
+      if (util::streq("CHECKOU"_sr, name, 7)) {
         return HTTP_CHECKOUT;
       }
       break;
@@ -1563,12 +1495,12 @@ int lookup_method_token(const uint8_t *name, size_t namelen) {
   case 9:
     switch (name[8]) {
     case 'E':
-      if (util::streq_l("SUBSCRIB", name, 8)) {
+      if (util::streq("SUBSCRIB"_sr, name, 8)) {
         return HTTP_SUBSCRIBE;
       }
       break;
     case 'H':
-      if (util::streq_l("PROPPATC", name, 8)) {
+      if (util::streq("PROPPATC"_sr, name, 8)) {
         return HTTP_PROPPATCH;
       }
       break;
@@ -1577,12 +1509,12 @@ int lookup_method_token(const uint8_t *name, size_t namelen) {
   case 10:
     switch (name[9]) {
     case 'R':
-      if (util::streq_l("MKCALENDA", name, 9)) {
+      if (util::streq("MKCALENDA"_sr, name, 9)) {
         return HTTP_MKCALENDAR;
       }
       break;
     case 'Y':
-      if (util::streq_l("MKACTIVIT", name, 9)) {
+      if (util::streq("MKACTIVIT"_sr, name, 9)) {
         return HTTP_MKACTIVITY;
       }
       break;
@@ -1591,7 +1523,7 @@ int lookup_method_token(const uint8_t *name, size_t namelen) {
   case 11:
     switch (name[10]) {
     case 'E':
-      if (util::streq_l("UNSUBSCRIB", name, 10)) {
+      if (util::streq("UNSUBSCRIB"_sr, name, 10)) {
         return HTTP_UNSUBSCRIBE;
       }
       break;
@@ -1611,17 +1543,17 @@ StringRef get_pure_path_component(const StringRef &uri) {
   int rv;
 
   http_parser_url u{};
-  rv = http_parser_parse_url(uri.c_str(), uri.size(), 0, &u);
+  rv = http_parser_parse_url(uri.data(), uri.size(), 0, &u);
   if (rv != 0) {
     return StringRef{};
   }
 
   if (u.field_set & (1 << UF_PATH)) {
     auto &f = u.field_data[UF_PATH];
-    return StringRef{uri.c_str() + f.off, f.len};
+    return StringRef{uri.data() + f.off, f.len};
   }
 
-  return StringRef::from_lit("/");
+  return "/"_sr;
 }
 
 int construct_push_component(BlockAllocator &balloc, StringRef &scheme,
@@ -1636,7 +1568,7 @@ int construct_push_component(BlockAllocator &balloc, StringRef &scheme,
 
   http_parser_url u{};
 
-  rv = http_parser_parse_url(uri.c_str(), uri.size(), 0, &u);
+  rv = http_parser_parse_url(uri.data(), uri.size(), 0, &u);
 
   if (rv != 0) {
     if (uri[0] == '/') {
@@ -1653,18 +1585,18 @@ int construct_push_component(BlockAllocator &balloc, StringRef &scheme,
     }
   } else {
     if (u.field_set & (1 << UF_SCHEMA)) {
-      scheme = util::get_uri_field(uri.c_str(), u, UF_SCHEMA);
+      scheme = util::get_uri_field(uri.data(), u, UF_SCHEMA);
     }
 
     if (u.field_set & (1 << UF_HOST)) {
-      auto auth = util::get_uri_field(uri.c_str(), u, UF_HOST);
+      auto auth = util::get_uri_field(uri.data(), u, UF_HOST);
       auto len = auth.size();
       auto port_exists = u.field_set & (1 << UF_PORT);
       if (port_exists) {
         len += 1 + str_size("65535");
       }
       auto iov = make_byte_ref(balloc, len + 1);
-      auto p = iov.base;
+      auto p = std::begin(iov);
       p = std::copy(std::begin(auth), std::end(auth), p);
       if (port_exists) {
         *p++ = ':';
@@ -1672,23 +1604,23 @@ int construct_push_component(BlockAllocator &balloc, StringRef &scheme,
       }
       *p = '\0';
 
-      authority = StringRef{iov.base, p};
+      authority = StringRef{std::span{std::begin(iov), p}};
     }
 
     if (u.field_set & (1 << UF_PATH)) {
       auto &f = u.field_data[UF_PATH];
-      rel = StringRef{uri.c_str() + f.off, f.len};
+      rel = StringRef{uri.data() + f.off, f.len};
     } else {
-      rel = StringRef::from_lit("/");
+      rel = "/"_sr;
     }
 
     if (u.field_set & (1 << UF_QUERY)) {
       auto &f = u.field_data[UF_QUERY];
-      relq = StringRef{uri.c_str() + f.off, f.len};
+      relq = StringRef{uri.data() + f.off, f.len};
     }
   }
 
-  path = http2::path_join(balloc, base, StringRef{}, rel, relq);
+  path = path_join(balloc, base, StringRef{}, rel, relq);
 
   return 0;
 }
@@ -1737,7 +1669,7 @@ StringRef path_join(BlockAllocator &balloc, const StringRef &base_path,
       balloc, std::max(static_cast<size_t>(1), base_path.size()) +
                   rel_path.size() + 1 +
                   std::max(base_query.size(), rel_query.size()) + 1);
-  auto p = res.base;
+  auto p = std::begin(res);
 
   if (rel_path.empty()) {
     if (base_path.empty()) {
@@ -1751,12 +1683,12 @@ StringRef path_join(BlockAllocator &balloc, const StringRef &base_path,
         p = std::copy(std::begin(base_query), std::end(base_query), p);
       }
       *p = '\0';
-      return StringRef{res.base, p};
+      return StringRef{std::span{std::begin(res), p}};
     }
     *p++ = '?';
     p = std::copy(std::begin(rel_query), std::end(rel_query), p);
     *p = '\0';
-    return StringRef{res.base, p};
+    return StringRef{std::span{std::begin(res), p}};
   }
 
   auto first = std::begin(rel_path);
@@ -1777,31 +1709,31 @@ StringRef path_join(BlockAllocator &balloc, const StringRef &base_path,
     if (*first == '.') {
       if (first + 1 == last) {
         if (*(p - 1) != '/') {
-          p = eat_file(res.base, p);
+          p = eat_file(std::begin(res), p);
         }
         break;
       }
       if (*(first + 1) == '/') {
         if (*(p - 1) != '/') {
-          p = eat_file(res.base, p);
+          p = eat_file(std::begin(res), p);
         }
         first += 2;
         continue;
       }
       if (*(first + 1) == '.') {
         if (first + 2 == last) {
-          p = eat_dir(res.base, p);
+          p = eat_dir(std::begin(res), p);
           break;
         }
         if (*(first + 2) == '/') {
-          p = eat_dir(res.base, p);
+          p = eat_dir(std::begin(res), p);
           first += 3;
           continue;
         }
       }
     }
     if (*(p - 1) != '/') {
-      p = eat_file(res.base, p);
+      p = eat_file(std::begin(res), p);
     }
     auto slash = std::find(first, last, '/');
     if (slash == last) {
@@ -1818,7 +1750,7 @@ StringRef path_join(BlockAllocator &balloc, const StringRef &base_path,
     p = std::copy(std::begin(rel_query), std::end(rel_query), p);
   }
   *p = '\0';
-  return StringRef{res.base, p};
+  return StringRef{std::span{std::begin(res), p}};
 }
 
 StringRef normalize_path(BlockAllocator &balloc, const StringRef &path,
@@ -1834,7 +1766,7 @@ StringRef normalize_path(BlockAllocator &balloc, const StringRef &path,
 
   // includes last terminal NULL.
   auto result = make_byte_ref(balloc, path.size() + 1);
-  auto p = result.base;
+  auto p = std::begin(result);
 
   auto it = std::begin(path);
   for (; it + 2 < std::end(path);) {
@@ -1864,8 +1796,8 @@ StringRef normalize_path(BlockAllocator &balloc, const StringRef &path,
   p = std::copy(it, std::end(path), p);
   *p = '\0';
 
-  return path_join(balloc, StringRef{}, StringRef{}, StringRef{result.base, p},
-                   query);
+  return path_join(balloc, StringRef{}, StringRef{},
+                   StringRef{std::span{std::begin(result), p}}, query);
 }
 
 StringRef normalize_path_colon(BlockAllocator &balloc, const StringRef &path,
@@ -1881,7 +1813,7 @@ StringRef normalize_path_colon(BlockAllocator &balloc, const StringRef &path,
 
   // includes last terminal NULL.
   auto result = make_byte_ref(balloc, path.size() + 1);
-  auto p = result.base;
+  auto p = std::begin(result);
 
   auto it = std::begin(path);
   for (; it + 2 < std::end(path);) {
@@ -1911,14 +1843,14 @@ StringRef normalize_path_colon(BlockAllocator &balloc, const StringRef &path,
   p = std::copy(it, std::end(path), p);
   *p = '\0';
 
-  return path_join(balloc, StringRef{}, StringRef{}, StringRef{result.base, p},
-                   query);
+  return path_join(balloc, StringRef{}, StringRef{},
+                   StringRef{std::span{std::begin(result), p}}, query);
 }
 
 std::string normalize_path(const StringRef &path, const StringRef &query) {
   BlockAllocator balloc(1024, 1024);
 
-  return normalize_path(balloc, path, query).str();
+  return std::string{normalize_path(balloc, path, query)};
 }
 
 StringRef rewrite_clean_path(BlockAllocator &balloc, const StringRef &src) {
@@ -1938,15 +1870,15 @@ StringRef rewrite_clean_path(BlockAllocator &balloc, const StringRef &src) {
 
 StringRef copy_lower(BlockAllocator &balloc, const StringRef &src) {
   auto iov = make_byte_ref(balloc, src.size() + 1);
-  auto p = iov.base;
+  auto p = std::begin(iov);
   p = std::copy(std::begin(src), std::end(src), p);
   *p = '\0';
-  util::inp_strlower(iov.base, p);
-  return StringRef{iov.base, p};
+  util::inp_strlower(std::begin(iov), p);
+  return StringRef{std::span{std::begin(iov), p}};
 }
 
 bool contains_trailers(const StringRef &s) {
-  constexpr auto trailers = StringRef::from_lit("trailers");
+  constexpr auto trailers = "trailers"_sr;
 
   for (auto p = std::begin(s), end = std::end(s);; ++p) {
     p = std::find_if(p, end, [](char c) { return c != ' ' && c != '\t'; });
@@ -1971,18 +1903,18 @@ bool contains_trailers(const StringRef &s) {
 }
 
 StringRef make_websocket_accept_token(uint8_t *dest, const StringRef &key) {
-  static constexpr uint8_t magic[] = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11";
-  std::array<uint8_t, base64::encode_length(16) + str_size(magic)> s;
+  static constexpr char magic[] = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11";
+  std::array<char, base64::encode_length(16) + str_size(magic)> s;
   auto p = std::copy(std::begin(key), std::end(key), std::begin(s));
   std::copy_n(magic, str_size(magic), p);
 
   std::array<uint8_t, 20> h;
-  if (util::sha1(h.data(), StringRef{std::begin(s), std::end(s)}) != 0) {
+  if (util::sha1(h.data(), StringRef{s}) != 0) {
     return StringRef{};
   }
 
   auto end = base64::encode(std::begin(h), std::end(h), dest);
-  return StringRef{dest, end};
+  return StringRef{std::span{dest, end}};
 }
 
 bool legacy_http1(int major, int minor) {
diff --git a/src/http2.h b/src/http2.h
index 7cfe461..df7f187 100644
--- a/src/http2.h
+++ b/src/http2.h
@@ -113,16 +113,14 @@ bool lws(const char *value);
 void copy_url_component(std::string &dest, const http_parser_url *u, int field,
                         const char *url);
 
-Headers::value_type to_header(const uint8_t *name, size_t namelen,
-                              const uint8_t *value, size_t valuelen,
+Headers::value_type to_header(const StringRef &name, const StringRef &value,
                               bool no_index, int32_t token);
 
 // Add name/value pairs to |nva|.  If |no_index| is true, this
 // name/value pair won't be indexed when it is forwarded to the next
-// hop.  This function strips white spaces around |value|.
-void add_header(Headers &nva, const uint8_t *name, size_t namelen,
-                const uint8_t *value, size_t valuelen, bool no_index,
-                int32_t token);
+// hop.
+void add_header(Headers &nva, const StringRef &name, const StringRef &value,
+                bool no_index, int32_t token);
 
 // Returns pointer to the entry in |nva| which has name |name|.  If
 // more than one entries which have the name |name|, last occurrence
@@ -132,60 +130,48 @@ const Headers::value_type *get_header(const Headers &nva, const char *name);
 // Returns true if the value of |nv| is not empty.
 bool non_empty_value(const HeaderRefs::value_type *nv);
 
-// Creates nghttp2_nv using |name| and |value| and returns it. The
-// returned value only references the data pointer to name.c_str() and
-// value.c_str().  If |no_index| is true, nghttp2_nv flags member has
-// NGHTTP2_NV_FLAG_NO_INDEX flag set.
-nghttp2_nv make_nv(const std::string &name, const std::string &value,
-                   bool no_index = false);
+// Create nghttp2_nv from |name|, |value| and |flags|.
+inline nghttp2_nv make_field_flags(const StringRef &name,
+                                   const StringRef &value,
+                                   uint8_t flags = NGHTTP2_NV_FLAG_NONE) {
+  auto ns = as_uint8_span(std::span{name});
+  auto vs = as_uint8_span(std::span{value});
 
-nghttp2_nv make_nv(const StringRef &name, const StringRef &value,
-                   bool no_index = false);
-
-nghttp2_nv make_nv_nocopy(const std::string &name, const std::string &value,
-                          bool no_index = false);
-
-nghttp2_nv make_nv_nocopy(const StringRef &name, const StringRef &value,
-                          bool no_index = false);
-
-// Create nghttp2_nv from string literal |name| and |value|.
-template <size_t N, size_t M>
-constexpr nghttp2_nv make_nv_ll(const char (&name)[N], const char (&value)[M]) {
-  return {(uint8_t *)name, (uint8_t *)value, N - 1, M - 1,
-          NGHTTP2_NV_FLAG_NO_COPY_NAME | NGHTTP2_NV_FLAG_NO_COPY_VALUE};
-}
-
-// Create nghttp2_nv from string literal |name| and c-string |value|.
-template <size_t N>
-nghttp2_nv make_nv_lc(const char (&name)[N], const char *value) {
-  return {(uint8_t *)name, (uint8_t *)value, N - 1, strlen(value),
-          NGHTTP2_NV_FLAG_NO_COPY_NAME};
+  return {const_cast<uint8_t *>(ns.data()), const_cast<uint8_t *>(vs.data()),
+          ns.size(), vs.size(), flags};
 }
 
-template <size_t N>
-nghttp2_nv make_nv_lc_nocopy(const char (&name)[N], const char *value) {
-  return {(uint8_t *)name, (uint8_t *)value, N - 1, strlen(value),
-          NGHTTP2_NV_FLAG_NO_COPY_NAME | NGHTTP2_NV_FLAG_NO_COPY_VALUE};
+// Creates nghttp2_nv from |name|, |value| and |flags|.  nghttp2
+// library does not copy them.
+inline nghttp2_nv make_field(const StringRef &name, const StringRef &value,
+                             uint8_t flags = NGHTTP2_NV_FLAG_NONE) {
+  return make_field_flags(name, value,
+                          static_cast<uint8_t>(NGHTTP2_NV_FLAG_NO_COPY_NAME |
+                                               NGHTTP2_NV_FLAG_NO_COPY_VALUE |
+                                               flags));
 }
 
-// Create nghttp2_nv from string literal |name| and std::string
-// |value|.
-template <size_t N>
-nghttp2_nv make_nv_ls(const char (&name)[N], const std::string &value) {
-  return {(uint8_t *)name, (uint8_t *)value.c_str(), N - 1, value.size(),
-          NGHTTP2_NV_FLAG_NO_COPY_NAME};
+// Creates nghttp2_nv from |name|, |value| and |flags|.  nghttp2
+// library copies |value| unless |flags| includes
+// NGHTTP2_NV_FLAG_NO_COPY_VALUE.
+inline nghttp2_nv make_field_v(const StringRef &name, const StringRef &value,
+                               uint8_t flags = NGHTTP2_NV_FLAG_NONE) {
+  return make_field_flags(
+      name, value, static_cast<uint8_t>(NGHTTP2_NV_FLAG_NO_COPY_NAME | flags));
 }
 
-template <size_t N>
-nghttp2_nv make_nv_ls_nocopy(const char (&name)[N], const std::string &value) {
-  return {(uint8_t *)name, (uint8_t *)value.c_str(), N - 1, value.size(),
-          NGHTTP2_NV_FLAG_NO_COPY_NAME | NGHTTP2_NV_FLAG_NO_COPY_VALUE};
+// Creates nghttp2_nv from |name|, |value| and |flags|.  nghttp2
+// library copies |name| and |value| unless |flags| includes
+// NGHTTP2_NV_FLAG_NO_COPY_NAME or NGHTTP2_NV_FLAG_NO_COPY_VALUE.
+inline nghttp2_nv make_field_nv(const StringRef &name, const StringRef &value,
+                                uint8_t flags = NGHTTP2_NV_FLAG_NONE) {
+  return make_field_flags(name, value, flags);
 }
 
-template <size_t N>
-nghttp2_nv make_nv_ls_nocopy(const char (&name)[N], const StringRef &value) {
-  return {(uint8_t *)name, (uint8_t *)value.c_str(), N - 1, value.size(),
-          NGHTTP2_NV_FLAG_NO_COPY_NAME | NGHTTP2_NV_FLAG_NO_COPY_VALUE};
+// Returns NGHTTP2_NV_FLAG_NO_INDEX if |no_index| is true, otherwise
+// NGHTTP2_NV_FLAG_NONE.
+inline uint8_t no_index(bool no_index) {
+  return no_index ? NGHTTP2_NV_FLAG_NO_INDEX : NGHTTP2_NV_FLAG_NONE;
 }
 
 enum HeaderBuildOp {
@@ -340,10 +326,9 @@ enum {
 
 using HeaderIndex = std::array<int16_t, HD_MAXIDX>;
 
-// Looks up header token for header name |name| of length |namelen|.
-// Only headers we are interested in are tokenized.  If header name
-// cannot be tokenized, returns -1.
-int lookup_token(const uint8_t *name, size_t namelen);
+// Looks up header token for header name |name|.  Only headers we are
+// interested in are tokenized.  If header name cannot be tokenized,
+// returns -1.
 int lookup_token(const StringRef &name);
 
 // Initializes |hdidx|, header index.  The |hdidx| must point to the
@@ -390,10 +375,9 @@ bool expect_response_body(int method_token, int status_code);
 // true if response has body, taking into account status code only.
 bool expect_response_body(int status_code);
 
-// Looks up method token for method name |name| of length |namelen|.
-// Only methods defined in llhttp.h (llhttp_method) are tokenized.  If
-// method name cannot be tokenized, returns -1.
-int lookup_method_token(const uint8_t *name, size_t namelen);
+// Looks up method token for method name |name|.  Only methods defined
+// in llhttp.h (llhttp_method) are tokenized.  If method name cannot
+// be tokenized, returns -1.
 int lookup_method_token(const StringRef &name);
 
 // Returns string representation of |method_token|.  This is wrapper
diff --git a/src/http2_test.cc b/src/http2_test.cc
index 3cb0b71..304f350 100644
--- a/src/http2_test.cc
+++ b/src/http2_test.cc
@@ -36,6 +36,7 @@
 #include "util.h"
 
 using namespace nghttp2;
+using namespace std::literals;
 
 #define MAKE_NV(K, V)                                                          \
   {                                                                            \
@@ -76,60 +77,32 @@ namespace {
 void check_nv(const HeaderRef &a, const nghttp2_nv *b) {
   assert_size(a.name.size(), ==, b->namelen);
   assert_size(a.value.size(), ==, b->valuelen);
-  assert_memory_equal(b->namelen, a.name.c_str(), b->name);
-  assert_memory_equal(b->valuelen, a.value.c_str(), b->value);
+  assert_memory_equal(b->namelen, a.name.data(), b->name);
+  assert_memory_equal(b->valuelen, a.value.data(), b->value);
 }
 } // namespace
 
 void test_http2_add_header(void) {
   auto nva = Headers();
 
-  http2::add_header(nva, (const uint8_t *)"alpha", 5, (const uint8_t *)"123", 3,
-                    false, -1);
+  http2::add_header(nva, "alpha"_sr, "123"_sr, false, -1);
   assert_true(Headers::value_type("alpha", "123") == nva[0]);
   assert_false(nva[0].no_index);
 
   nva.clear();
 
-  http2::add_header(nva, (const uint8_t *)"alpha", 5, (const uint8_t *)"", 0,
-                    true, -1);
+  http2::add_header(nva, "alpha"_sr, ""_sr, true, -1);
   assert_true(Headers::value_type("alpha", "") == nva[0]);
   assert_true(nva[0].no_index);
 
   nva.clear();
 
-  http2::add_header(nva, (const uint8_t *)"a", 1, (const uint8_t *)" b", 2,
-                    false, -1);
+  http2::add_header(nva, "a"_sr, "b"_sr, false, -1);
   assert_true(Headers::value_type("a", "b") == nva[0]);
 
   nva.clear();
 
-  http2::add_header(nva, (const uint8_t *)"a", 1, (const uint8_t *)"b ", 2,
-                    false, -1);
-  assert_true(Headers::value_type("a", "b") == nva[0]);
-
-  nva.clear();
-
-  http2::add_header(nva, (const uint8_t *)"a", 1, (const uint8_t *)"  b  ", 5,
-                    false, -1);
-  assert_true(Headers::value_type("a", "b") == nva[0]);
-
-  nva.clear();
-
-  http2::add_header(nva, (const uint8_t *)"a", 1, (const uint8_t *)"  bravo  ",
-                    9, false, -1);
-  assert_true(Headers::value_type("a", "bravo") == nva[0]);
-
-  nva.clear();
-
-  http2::add_header(nva, (const uint8_t *)"a", 1, (const uint8_t *)"    ", 4,
-                    false, -1);
-  assert_true(Headers::value_type("a", "") == nva[0]);
-
-  nva.clear();
-
-  http2::add_header(nva, (const uint8_t *)"te", 2, (const uint8_t *)"trailers",
-                    8, false, http2::HD_TE);
+  http2::add_header(nva, "te"_sr, "trailers"_sr, false, http2::HD_TE);
   assert_int32(http2::HD_TE, ==, nva[0].token);
 }
 
@@ -158,43 +131,31 @@ void test_http2_get_header(void) {
 
 namespace {
 auto headers = HeaderRefs{
-    {StringRef::from_lit("alpha"), StringRef::from_lit("0"), true},
-    {StringRef::from_lit("bravo"), StringRef::from_lit("1")},
-    {StringRef::from_lit("connection"), StringRef::from_lit("2"), false,
-     http2::HD_CONNECTION},
-    {StringRef::from_lit("connection"), StringRef::from_lit("3"), false,
-     http2::HD_CONNECTION},
-    {StringRef::from_lit("delta"), StringRef::from_lit("4")},
-    {StringRef::from_lit("expect"), StringRef::from_lit("5")},
-    {StringRef::from_lit("foxtrot"), StringRef::from_lit("6")},
-    {StringRef::from_lit("tango"), StringRef::from_lit("7")},
-    {StringRef::from_lit("te"), StringRef::from_lit("8"), false, http2::HD_TE},
-    {StringRef::from_lit("te"), StringRef::from_lit("9"), false, http2::HD_TE},
-    {StringRef::from_lit("x-forwarded-proto"), StringRef::from_lit("10"), false,
-     http2::HD_X_FORWARDED_FOR},
-    {StringRef::from_lit("x-forwarded-proto"), StringRef::from_lit("11"), false,
-     http2::HD_X_FORWARDED_FOR},
-    {StringRef::from_lit("zulu"), StringRef::from_lit("12")}};
+    {"alpha"_sr, "0"_sr, true},
+    {"bravo"_sr, "1"_sr},
+    {"connection"_sr, "2"_sr, false, http2::HD_CONNECTION},
+    {"connection"_sr, "3"_sr, false, http2::HD_CONNECTION},
+    {"delta"_sr, "4"_sr},
+    {"expect"_sr, "5"_sr},
+    {"foxtrot"_sr, "6"_sr},
+    {"tango"_sr, "7"_sr},
+    {"te"_sr, "8"_sr, false, http2::HD_TE},
+    {"te"_sr, "9"_sr, false, http2::HD_TE},
+    {"x-forwarded-proto"_sr, "10"_sr, false, http2::HD_X_FORWARDED_FOR},
+    {"x-forwarded-proto"_sr, "11"_sr, false, http2::HD_X_FORWARDED_FOR},
+    {"zulu"_sr, "12"_sr}};
 } // namespace
 
 namespace {
 auto headers2 = HeaderRefs{
-    {StringRef::from_lit("x-forwarded-for"), StringRef::from_lit("xff1"), false,
-     http2::HD_X_FORWARDED_FOR},
-    {StringRef::from_lit("x-forwarded-for"), StringRef::from_lit("xff2"), false,
-     http2::HD_X_FORWARDED_FOR},
-    {StringRef::from_lit("x-forwarded-proto"), StringRef::from_lit("xfp1"),
-     false, http2::HD_X_FORWARDED_PROTO},
-    {StringRef::from_lit("x-forwarded-proto"), StringRef::from_lit("xfp2"),
-     false, http2::HD_X_FORWARDED_PROTO},
-    {StringRef::from_lit("forwarded"), StringRef::from_lit("fwd1"), false,
-     http2::HD_FORWARDED},
-    {StringRef::from_lit("forwarded"), StringRef::from_lit("fwd2"), false,
-     http2::HD_FORWARDED},
-    {StringRef::from_lit("via"), StringRef::from_lit("via1"), false,
-     http2::HD_VIA},
-    {StringRef::from_lit("via"), StringRef::from_lit("via2"), false,
-     http2::HD_VIA},
+    {"x-forwarded-for"_sr, "xff1"_sr, false, http2::HD_X_FORWARDED_FOR},
+    {"x-forwarded-for"_sr, "xff2"_sr, false, http2::HD_X_FORWARDED_FOR},
+    {"x-forwarded-proto"_sr, "xfp1"_sr, false, http2::HD_X_FORWARDED_PROTO},
+    {"x-forwarded-proto"_sr, "xfp2"_sr, false, http2::HD_X_FORWARDED_PROTO},
+    {"forwarded"_sr, "fwd1"_sr, false, http2::HD_FORWARDED},
+    {"forwarded"_sr, "fwd2"_sr, false, http2::HD_FORWARDED},
+    {"via"_sr, "via1"_sr, false, http2::HD_VIA},
+    {"via"_sr, "via2"_sr, false, http2::HD_VIA},
 };
 } // namespace
 
@@ -298,7 +259,7 @@ void check_rewrite_location_uri(const std::string &want, const std::string &uri,
   auto got = http2::rewrite_location_uri(
       balloc, StringRef{uri}, u, StringRef{match_host},
       StringRef{req_authority}, StringRef{upstream_scheme});
-  assert_stdstring_equal(want, got.str());
+  assert_stdsv_equal(want, got);
 }
 } // namespace
 
@@ -330,14 +291,12 @@ void test_http2_rewrite_location_uri(void) {
 }
 
 void test_http2_parse_http_status_code(void) {
-  assert_int(200, ==,
-             http2::parse_http_status_code(StringRef::from_lit("200")));
-  assert_int(102, ==,
-             http2::parse_http_status_code(StringRef::from_lit("102")));
-  assert_int(-1, ==, http2::parse_http_status_code(StringRef::from_lit("099")));
-  assert_int(-1, ==, http2::parse_http_status_code(StringRef::from_lit("99")));
-  assert_int(-1, ==, http2::parse_http_status_code(StringRef::from_lit("-1")));
-  assert_int(-1, ==, http2::parse_http_status_code(StringRef::from_lit("20a")));
+  assert_int(200, ==, http2::parse_http_status_code("200"_sr));
+  assert_int(102, ==, http2::parse_http_status_code("102"_sr));
+  assert_int(-1, ==, http2::parse_http_status_code("099"_sr));
+  assert_int(-1, ==, http2::parse_http_status_code("99"_sr));
+  assert_int(-1, ==, http2::parse_http_status_code("-1"_sr));
+  assert_int(-1, ==, http2::parse_http_status_code("20a"_sr));
   assert_int(-1, ==, http2::parse_http_status_code(StringRef{}));
 }
 
@@ -352,536 +311,491 @@ void test_http2_index_header(void) {
 }
 
 void test_http2_lookup_token(void) {
-  assert_int(http2::HD__AUTHORITY, ==,
-             http2::lookup_token(StringRef::from_lit(":authority")));
-  assert_int(-1, ==, http2::lookup_token(StringRef::from_lit(":authorit")));
-  assert_int(-1, ==, http2::lookup_token(StringRef::from_lit(":Authority")));
-  assert_int(http2::HD_EXPECT, ==,
-             http2::lookup_token(StringRef::from_lit("expect")));
+  assert_int(http2::HD__AUTHORITY, ==, http2::lookup_token(":authority"_sr));
+  assert_int(-1, ==, http2::lookup_token(":authorit"_sr));
+  assert_int(-1, ==, http2::lookup_token(":Authority"_sr));
+  assert_int(http2::HD_EXPECT, ==, http2::lookup_token("expect"_sr));
 }
 
 void test_http2_parse_link_header(void) {
   {
     // only URI appears; we don't extract URI unless it bears rel=preload
-    auto res = http2::parse_link_header(StringRef::from_lit("<url>"));
+    auto res = http2::parse_link_header("<url>"_sr);
     assert_size(0, ==, res.size());
   }
   {
     // URI url should be extracted
-    auto res =
-        http2::parse_link_header(StringRef::from_lit("<url>; rel=preload"));
+    auto res = http2::parse_link_header("<url>; rel=preload"_sr);
     assert_size(1, ==, res.size());
-    assert_stdstring_equal("url", res[0].uri.str());
+    assert_stdsv_equal("url"sv, res[0].uri);
   }
   {
     // With extra link-param.  URI url should be extracted
-    auto res = http2::parse_link_header(
-        StringRef::from_lit("<url>; rel=preload; as=file"));
+    auto res = http2::parse_link_header("<url>; rel=preload; as=file"_sr);
     assert_size(1, ==, res.size());
-    assert_stdstring_equal("url", res[0].uri.str());
+    assert_stdsv_equal("url"sv, res[0].uri);
   }
   {
     // With extra link-param.  URI url should be extracted
-    auto res = http2::parse_link_header(
-        StringRef::from_lit("<url>; as=file; rel=preload"));
+    auto res = http2::parse_link_header("<url>; as=file; rel=preload"_sr);
     assert_size(1, ==, res.size());
-    assert_stdstring_equal("url", res[0].uri.str());
+    assert_stdsv_equal("url"sv, res[0].uri);
   }
   {
     // With extra link-param and quote-string.  URI url should be
     // extracted
-    auto res = http2::parse_link_header(
-        StringRef::from_lit(R"(<url>; rel=preload; title="foo,bar")"));
+    auto res =
+        http2::parse_link_header(R"(<url>; rel=preload; title="foo,bar")"_sr);
     assert_size(1, ==, res.size());
-    assert_stdstring_equal("url", res[0].uri.str());
+    assert_stdsv_equal("url"sv, res[0].uri);
   }
   {
     // With extra link-param and quote-string.  URI url should be
     // extracted
-    auto res = http2::parse_link_header(
-        StringRef::from_lit(R"(<url>; title="foo,bar"; rel=preload)"));
+    auto res =
+        http2::parse_link_header(R"(<url>; title="foo,bar"; rel=preload)"_sr);
     assert_size(1, ==, res.size());
-    assert_stdstring_equal("url", res[0].uri.str());
+    assert_stdsv_equal("url"sv, res[0].uri);
   }
   {
     // ',' after quote-string
     auto res = http2::parse_link_header(
-        StringRef::from_lit(R"(<url>; title="foo,bar", <url2>; rel=preload)"));
+        R"(<url>; title="foo,bar", <url2>; rel=preload)"_sr);
     assert_size(1, ==, res.size());
-    assert_stdstring_equal("url2", res[0].uri.str());
+    assert_stdsv_equal("url2"sv, res[0].uri);
   }
   {
     // Only first URI should be extracted.
-    auto res = http2::parse_link_header(
-        StringRef::from_lit("<url>; rel=preload, <url2>"));
+    auto res = http2::parse_link_header("<url>; rel=preload, <url2>"_sr);
     assert_size(1, ==, res.size());
-    assert_stdstring_equal("url", res[0].uri.str());
+    assert_stdsv_equal("url"sv, res[0].uri);
   }
   {
     // Both have rel=preload, so both urls should be extracted
-    auto res = http2::parse_link_header(
-        StringRef::from_lit("<url>; rel=preload, <url2>; rel=preload"));
+    auto res =
+        http2::parse_link_header("<url>; rel=preload, <url2>; rel=preload"_sr);
     assert_size(2, ==, res.size());
-    assert_stdstring_equal("url", res[0].uri.str());
-    assert_stdstring_equal("url2", res[1].uri.str());
+    assert_stdsv_equal("url"sv, res[0].uri);
+    assert_stdsv_equal("url2"sv, res[1].uri);
   }
   {
     // Second URI uri should be extracted.
-    auto res = http2::parse_link_header(
-        StringRef::from_lit("<url>, <url2>;rel=preload"));
+    auto res = http2::parse_link_header("<url>, <url2>;rel=preload"_sr);
     assert_size(1, ==, res.size());
-    assert_stdstring_equal("url2", res[0].uri.str());
+    assert_stdsv_equal("url2"sv, res[0].uri);
   }
   {
     // Error if input ends with ';'
-    auto res =
-        http2::parse_link_header(StringRef::from_lit("<url>;rel=preload;"));
+    auto res = http2::parse_link_header("<url>;rel=preload;"_sr);
     assert_size(0, ==, res.size());
   }
   {
     // Error if link header ends with ';'
-    auto res = http2::parse_link_header(
-        StringRef::from_lit("<url>;rel=preload;, <url>"));
+    auto res = http2::parse_link_header("<url>;rel=preload;, <url>"_sr);
     assert_size(0, ==, res.size());
   }
   {
     // OK if input ends with ','
-    auto res =
-        http2::parse_link_header(StringRef::from_lit("<url>;rel=preload,"));
+    auto res = http2::parse_link_header("<url>;rel=preload,"_sr);
     assert_size(1, ==, res.size());
-    assert_stdstring_equal("url", res[0].uri.str());
+    assert_stdsv_equal("url"sv, res[0].uri);
   }
   {
     // Multiple repeated ','s between fields is OK
-    auto res = http2::parse_link_header(
-        StringRef::from_lit("<url>,,,<url2>;rel=preload"));
+    auto res = http2::parse_link_header("<url>,,,<url2>;rel=preload"_sr);
     assert_size(1, ==, res.size());
-    assert_stdstring_equal("url2", res[0].uri.str());
+    assert_stdsv_equal("url2"sv, res[0].uri);
   }
   {
     // Error if url is not enclosed by <>
-    auto res =
-        http2::parse_link_header(StringRef::from_lit("url>;rel=preload"));
+    auto res = http2::parse_link_header("url>;rel=preload"_sr);
     assert_size(0, ==, res.size());
   }
   {
     // Error if url is not enclosed by <>
-    auto res =
-        http2::parse_link_header(StringRef::from_lit("<url;rel=preload"));
+    auto res = http2::parse_link_header("<url;rel=preload"_sr);
     assert_size(0, ==, res.size());
   }
   {
     // Empty parameter value is not allowed
-    auto res =
-        http2::parse_link_header(StringRef::from_lit("<url>;rel=preload; as="));
+    auto res = http2::parse_link_header("<url>;rel=preload; as="_sr);
     assert_size(0, ==, res.size());
   }
   {
     // Empty parameter value is not allowed
-    auto res =
-        http2::parse_link_header(StringRef::from_lit("<url>;as=;rel=preload"));
+    auto res = http2::parse_link_header("<url>;as=;rel=preload"_sr);
     assert_size(0, ==, res.size());
   }
   {
     // Empty parameter value is not allowed
-    auto res = http2::parse_link_header(
-        StringRef::from_lit("<url>;as=, <url>;rel=preload"));
+    auto res = http2::parse_link_header("<url>;as=, <url>;rel=preload"_sr);
     assert_size(0, ==, res.size());
   }
   {
     // Empty parameter name is not allowed
-    auto res = http2::parse_link_header(
-        StringRef::from_lit("<url>; =file; rel=preload"));
+    auto res = http2::parse_link_header("<url>; =file; rel=preload"_sr);
     assert_size(0, ==, res.size());
   }
   {
     // Without whitespaces
     auto res = http2::parse_link_header(
-        StringRef::from_lit("<url>;as=file;rel=preload,<url2>;rel=preload"));
+        "<url>;as=file;rel=preload,<url2>;rel=preload"_sr);
     assert_size(2, ==, res.size());
-    assert_stdstring_equal("url", res[0].uri.str());
-    assert_stdstring_equal("url2", res[1].uri.str());
+    assert_stdsv_equal("url"sv, res[0].uri);
+    assert_stdsv_equal("url2"sv, res[1].uri);
   }
   {
     // link-extension may have no value
-    auto res =
-        http2::parse_link_header(StringRef::from_lit("<url>; as; rel=preload"));
+    auto res = http2::parse_link_header("<url>; as; rel=preload"_sr);
     assert_size(1, ==, res.size());
-    assert_stdstring_equal("url", res[0].uri.str());
+    assert_stdsv_equal("url"sv, res[0].uri);
   }
   {
     // ext-name-star
-    auto res = http2::parse_link_header(
-        StringRef::from_lit("<url>; foo*=bar; rel=preload"));
+    auto res = http2::parse_link_header("<url>; foo*=bar; rel=preload"_sr);
     assert_size(1, ==, res.size());
-    assert_stdstring_equal("url", res[0].uri.str());
+    assert_stdsv_equal("url"sv, res[0].uri);
   }
   {
     // '*' is not allowed expect for trailing one
-    auto res = http2::parse_link_header(
-        StringRef::from_lit("<url>; *=bar; rel=preload"));
+    auto res = http2::parse_link_header("<url>; *=bar; rel=preload"_sr);
     assert_size(0, ==, res.size());
   }
   {
     // '*' is not allowed expect for trailing one
-    auto res = http2::parse_link_header(
-        StringRef::from_lit("<url>; foo*bar=buzz; rel=preload"));
+    auto res = http2::parse_link_header("<url>; foo*bar=buzz; rel=preload"_sr);
     assert_size(0, ==, res.size());
   }
   {
     // ext-name-star must be followed by '='
-    auto res = http2::parse_link_header(
-        StringRef::from_lit("<url>; foo*; rel=preload"));
+    auto res = http2::parse_link_header("<url>; foo*; rel=preload"_sr);
     assert_size(0, ==, res.size());
   }
   {
     // '>' is not followed by ';'
-    auto res =
-        http2::parse_link_header(StringRef::from_lit("<url> rel=preload"));
+    auto res = http2::parse_link_header("<url> rel=preload"_sr);
     assert_size(0, ==, res.size());
   }
   {
     // Starting with whitespace is no problem.
-    auto res =
-        http2::parse_link_header(StringRef::from_lit("  <url>; rel=preload"));
+    auto res = http2::parse_link_header("  <url>; rel=preload"_sr);
     assert_size(1, ==, res.size());
-    assert_stdstring_equal("url", res[0].uri.str());
+    assert_stdsv_equal("url"sv, res[0].uri);
   }
   {
     // preload is a prefix of bogus rel parameter value
-    auto res =
-        http2::parse_link_header(StringRef::from_lit("<url>; rel=preloadx"));
+    auto res = http2::parse_link_header("<url>; rel=preloadx"_sr);
     assert_size(0, ==, res.size());
   }
   {
     // preload in relation-types list
-    auto res = http2::parse_link_header(
-        StringRef::from_lit(R"(<url>; rel="preload")"));
+    auto res = http2::parse_link_header(R"(<url>; rel="preload")"_sr);
     assert_size(1, ==, res.size());
-    assert_stdstring_equal("url", res[0].uri.str());
+    assert_stdsv_equal("url"sv, res[0].uri);
   }
   {
     // preload in relation-types list followed by another parameter
-    auto res = http2::parse_link_header(
-        StringRef::from_lit(R"(<url>; rel="preload foo")"));
+    auto res = http2::parse_link_header(R"(<url>; rel="preload foo")"_sr);
     assert_size(1, ==, res.size());
-    assert_stdstring_equal("url", res[0].uri.str());
+    assert_stdsv_equal("url"sv, res[0].uri);
   }
   {
     // preload in relation-types list following another parameter
-    auto res = http2::parse_link_header(
-        StringRef::from_lit(R"(<url>; rel="foo preload")"));
+    auto res = http2::parse_link_header(R"(<url>; rel="foo preload")"_sr);
     assert_size(1, ==, res.size());
-    assert_stdstring_equal("url", res[0].uri.str());
+    assert_stdsv_equal("url"sv, res[0].uri);
   }
   {
     // preload in relation-types list between other parameters
-    auto res = http2::parse_link_header(
-        StringRef::from_lit(R"(<url>; rel="foo preload bar")"));
+    auto res = http2::parse_link_header(R"(<url>; rel="foo preload bar")"_sr);
     assert_size(1, ==, res.size());
-    assert_stdstring_equal("url", res[0].uri.str());
+    assert_stdsv_equal("url"sv, res[0].uri);
   }
   {
     // preload in relation-types list between other parameters
-    auto res = http2::parse_link_header(
-        StringRef::from_lit(R"(<url>; rel="foo   preload   bar")"));
+    auto res =
+        http2::parse_link_header(R"(<url>; rel="foo   preload   bar")"_sr);
     assert_size(1, ==, res.size());
-    assert_stdstring_equal("url", res[0].uri.str());
+    assert_stdsv_equal("url"sv, res[0].uri);
   }
   {
     // no preload in relation-types list
-    auto res =
-        http2::parse_link_header(StringRef::from_lit(R"(<url>; rel="foo")"));
+    auto res = http2::parse_link_header(R"(<url>; rel="foo")"_sr);
     assert_size(0, ==, res.size());
   }
   {
     // no preload in relation-types list, multiple unrelated elements.
-    auto res = http2::parse_link_header(
-        StringRef::from_lit(R"(<url>; rel="foo bar")"));
+    auto res = http2::parse_link_header(R"(<url>; rel="foo bar")"_sr);
     assert_size(0, ==, res.size());
   }
   {
     // preload in relation-types list, followed by another link-value.
-    auto res = http2::parse_link_header(
-        StringRef::from_lit(R"(<url>; rel="preload", <url2>)"));
+    auto res = http2::parse_link_header(R"(<url>; rel="preload", <url2>)"_sr);
     assert_size(1, ==, res.size());
-    assert_stdstring_equal("url", res[0].uri.str());
+    assert_stdsv_equal("url"sv, res[0].uri);
   }
   {
     // preload in relation-types list, following another link-value.
-    auto res = http2::parse_link_header(
-        StringRef::from_lit(R"(<url>, <url2>; rel="preload")"));
+    auto res = http2::parse_link_header(R"(<url>, <url2>; rel="preload")"_sr);
     assert_size(1, ==, res.size());
-    assert_stdstring_equal("url2", res[0].uri.str());
+    assert_stdsv_equal("url2"sv, res[0].uri);
   }
   {
     // preload in relation-types list, followed by another link-param.
-    auto res = http2::parse_link_header(
-        StringRef::from_lit(R"(<url>; rel="preload"; as="font")"));
+    auto res =
+        http2::parse_link_header(R"(<url>; rel="preload"; as="font")"_sr);
     assert_size(1, ==, res.size());
-    assert_stdstring_equal("url", res[0].uri.str());
+    assert_stdsv_equal("url"sv, res[0].uri);
   }
   {
     // preload in relation-types list, followed by character other
     // than ';' or ','
-    auto res = http2::parse_link_header(
-        StringRef::from_lit(R"(<url>; rel="preload".)"));
+    auto res = http2::parse_link_header(R"(<url>; rel="preload".)"_sr);
     assert_size(0, ==, res.size());
   }
   {
     // preload in relation-types list, followed by ';' but it
     // terminates input
-    auto res = http2::parse_link_header(
-        StringRef::from_lit(R"(<url>; rel="preload";)"));
+    auto res = http2::parse_link_header(R"(<url>; rel="preload";)"_sr);
     assert_size(0, ==, res.size());
   }
   {
     // preload in relation-types list, followed by ',' but it
     // terminates input
-    auto res = http2::parse_link_header(
-        StringRef::from_lit(R"(<url>; rel="preload",)"));
+    auto res = http2::parse_link_header(R"(<url>; rel="preload",)"_sr);
     assert_size(1, ==, res.size());
-    assert_stdstring_equal("url", res[0].uri.str());
+    assert_stdsv_equal("url"sv, res[0].uri);
   }
   {
     // preload in relation-types list but there is preceding white
     // space.
-    auto res = http2::parse_link_header(
-        StringRef::from_lit(R"(<url>; rel=" preload")"));
+    auto res = http2::parse_link_header(R"(<url>; rel=" preload")"_sr);
     assert_size(0, ==, res.size());
   }
   {
     // preload in relation-types list but there is trailing white
     // space.
-    auto res = http2::parse_link_header(
-        StringRef::from_lit(R"(<url>; rel="preload ")"));
+    auto res = http2::parse_link_header(R"(<url>; rel="preload ")"_sr);
     assert_size(0, ==, res.size());
   }
   {
     // backslash escaped characters in quoted-string
     auto res = http2::parse_link_header(
-        StringRef::from_lit(R"(<url>; rel=preload; title="foo\"baz\"bar")"));
+        R"(<url>; rel=preload; title="foo\"baz\"bar")"_sr);
     assert_size(1, ==, res.size());
-    assert_stdstring_equal("url", res[0].uri.str());
+    assert_stdsv_equal("url"sv, res[0].uri);
   }
   {
     // anchor="" is acceptable
-    auto res = http2::parse_link_header(
-        StringRef::from_lit(R"(<url>; rel=preload; anchor="")"));
+    auto res = http2::parse_link_header(R"(<url>; rel=preload; anchor="")"_sr);
     assert_size(1, ==, res.size());
-    assert_stdstring_equal("url", res[0].uri.str());
+    assert_stdsv_equal("url"sv, res[0].uri);
   }
   {
     // With anchor="#foo", url should be ignored
-    auto res = http2::parse_link_header(
-        StringRef::from_lit(R"(<url>; rel=preload; anchor="#foo")"));
+    auto res =
+        http2::parse_link_header(R"(<url>; rel=preload; anchor="#foo")"_sr);
     assert_size(0, ==, res.size());
   }
   {
     // With anchor=f, url should be ignored
-    auto res = http2::parse_link_header(
-        StringRef::from_lit("<url>; rel=preload; anchor=f"));
+    auto res = http2::parse_link_header("<url>; rel=preload; anchor=f"_sr);
     assert_size(0, ==, res.size());
   }
   {
     // First url is ignored With anchor="#foo", but url should be
     // accepted.
-    auto res = http2::parse_link_header(StringRef::from_lit(
-        R"(<url>; rel=preload; anchor="#foo", <url2>; rel=preload)"));
+    auto res = http2::parse_link_header(
+        R"(<url>; rel=preload; anchor="#foo", <url2>; rel=preload)"_sr);
     assert_size(1, ==, res.size());
-    assert_stdstring_equal("url2", res[0].uri.str());
+    assert_stdsv_equal("url2"sv, res[0].uri);
   }
   {
     // With loadpolicy="next", url should be ignored
-    auto res = http2::parse_link_header(
-        StringRef::from_lit(R"(<url>; rel=preload; loadpolicy="next")"));
+    auto res =
+        http2::parse_link_header(R"(<url>; rel=preload; loadpolicy="next")"_sr);
     assert_size(0, ==, res.size());
   }
   {
     // url should be picked up if empty loadpolicy is specified
-    auto res = http2::parse_link_header(
-        StringRef::from_lit(R"(<url>; rel=preload; loadpolicy="")"));
+    auto res =
+        http2::parse_link_header(R"(<url>; rel=preload; loadpolicy="")"_sr);
     assert_size(1, ==, res.size());
-    assert_stdstring_equal("url", res[0].uri.str());
+    assert_stdsv_equal("url"sv, res[0].uri);
   }
   {
     // case-insensitive match
     auto res = http2::parse_link_header(
-        StringRef::from_lit(R"(<url>; rel=preload; ANCHOR="#foo", <url2>; )"
-                            R"(REL=PRELOAD, <url3>; REL="foo PRELOAD bar")"));
+        R"(<url>; rel=preload; ANCHOR="#foo", <url2>; )"
+        R"(REL=PRELOAD, <url3>; REL="foo PRELOAD bar")"_sr);
     assert_size(2, ==, res.size());
-    assert_stdstring_equal("url2", res[0].uri.str());
-    assert_stdstring_equal("url3", res[1].uri.str());
+    assert_stdsv_equal("url2"sv, res[0].uri);
+    assert_stdsv_equal("url3"sv, res[1].uri);
   }
   {
     // nopush at the end of input
-    auto res = http2::parse_link_header(
-        StringRef::from_lit("<url>; rel=preload; nopush"));
+    auto res = http2::parse_link_header("<url>; rel=preload; nopush"_sr);
     assert_size(0, ==, res.size());
   }
   {
     // nopush followed by ';'
-    auto res = http2::parse_link_header(
-        StringRef::from_lit("<url>; rel=preload; nopush; foo"));
+    auto res = http2::parse_link_header("<url>; rel=preload; nopush; foo"_sr);
     assert_size(0, ==, res.size());
   }
   {
     // nopush followed by ','
-    auto res = http2::parse_link_header(
-        StringRef::from_lit("<url>; nopush; rel=preload"));
+    auto res = http2::parse_link_header("<url>; nopush; rel=preload"_sr);
     assert_size(0, ==, res.size());
   }
   {
     // string whose prefix is nopush
-    auto res = http2::parse_link_header(
-        StringRef::from_lit("<url>; nopushyes; rel=preload"));
+    auto res = http2::parse_link_header("<url>; nopushyes; rel=preload"_sr);
     assert_size(1, ==, res.size());
-    assert_stdstring_equal("url", res[0].uri.str());
+    assert_stdsv_equal("url"sv, res[0].uri);
   }
   {
     // rel=preload twice
-    auto res = http2::parse_link_header(
-        StringRef::from_lit("<url>; rel=preload; rel=preload"));
+    auto res = http2::parse_link_header("<url>; rel=preload; rel=preload"_sr);
     assert_size(1, ==, res.size());
-    assert_stdstring_equal("url", res[0].uri.str());
+    assert_stdsv_equal("url"sv, res[0].uri);
   }
 }
 
 void test_http2_path_join(void) {
   {
-    auto base = StringRef::from_lit("/");
-    auto rel = StringRef::from_lit("/");
+    auto base = "/"_sr;
+    auto rel = "/"_sr;
     assert_stdstring_equal(
         "/", http2::path_join(base, StringRef{}, rel, StringRef{}));
   }
   {
-    auto base = StringRef::from_lit("/");
-    auto rel = StringRef::from_lit("/alpha");
+    auto base = "/"_sr;
+    auto rel = "/alpha"_sr;
     assert_stdstring_equal(
         "/alpha", http2::path_join(base, StringRef{}, rel, StringRef{}));
   }
   {
     // rel ends with trailing '/'
-    auto base = StringRef::from_lit("/");
-    auto rel = StringRef::from_lit("/alpha/");
+    auto base = "/"_sr;
+    auto rel = "/alpha/"_sr;
     assert_stdstring_equal(
         "/alpha/", http2::path_join(base, StringRef{}, rel, StringRef{}));
   }
   {
     // rel contains multiple components
-    auto base = StringRef::from_lit("/");
-    auto rel = StringRef::from_lit("/alpha/bravo");
+    auto base = "/"_sr;
+    auto rel = "/alpha/bravo"_sr;
     assert_stdstring_equal(
         "/alpha/bravo", http2::path_join(base, StringRef{}, rel, StringRef{}));
   }
   {
     // rel is relative
-    auto base = StringRef::from_lit("/");
-    auto rel = StringRef::from_lit("alpha/bravo");
+    auto base = "/"_sr;
+    auto rel = "alpha/bravo"_sr;
     assert_stdstring_equal(
         "/alpha/bravo", http2::path_join(base, StringRef{}, rel, StringRef{}));
   }
   {
     // rel is relative and base ends without /, which means it refers
     // to file.
-    auto base = StringRef::from_lit("/alpha");
-    auto rel = StringRef::from_lit("bravo/charlie");
+    auto base = "/alpha"_sr;
+    auto rel = "bravo/charlie"_sr;
     assert_stdstring_equal(
         "/bravo/charlie",
         http2::path_join(base, StringRef{}, rel, StringRef{}));
   }
   {
     // rel contains repeated '/'s
-    auto base = StringRef::from_lit("/");
-    auto rel = StringRef::from_lit("/alpha/////bravo/////");
+    auto base = "/"_sr;
+    auto rel = "/alpha/////bravo/////"_sr;
     assert_stdstring_equal(
         "/alpha/bravo/", http2::path_join(base, StringRef{}, rel, StringRef{}));
   }
   {
     // base ends with '/', so '..' eats 'bravo'
-    auto base = StringRef::from_lit("/alpha/bravo/");
-    auto rel = StringRef::from_lit("../charlie/delta");
+    auto base = "/alpha/bravo/"_sr;
+    auto rel = "../charlie/delta"_sr;
     assert_stdstring_equal(
         "/alpha/charlie/delta",
         http2::path_join(base, StringRef{}, rel, StringRef{}));
   }
   {
     // base does not end with '/', so '..' eats 'alpha/bravo'
-    auto base = StringRef::from_lit("/alpha/bravo");
-    auto rel = StringRef::from_lit("../charlie");
+    auto base = "/alpha/bravo"_sr;
+    auto rel = "../charlie"_sr;
     assert_stdstring_equal(
         "/charlie", http2::path_join(base, StringRef{}, rel, StringRef{}));
   }
   {
     // 'charlie' is eaten by following '..'
-    auto base = StringRef::from_lit("/alpha/bravo/");
-    auto rel = StringRef::from_lit("../charlie/../delta");
+    auto base = "/alpha/bravo/"_sr;
+    auto rel = "../charlie/../delta"_sr;
     assert_stdstring_equal(
         "/alpha/delta", http2::path_join(base, StringRef{}, rel, StringRef{}));
   }
   {
     // excessive '..' results in '/'
-    auto base = StringRef::from_lit("/alpha/bravo/");
-    auto rel = StringRef::from_lit("../../../");
+    auto base = "/alpha/bravo/"_sr;
+    auto rel = "../../../"_sr;
     assert_stdstring_equal(
         "/", http2::path_join(base, StringRef{}, rel, StringRef{}));
   }
   {
     // excessive '..'  and  path component
-    auto base = StringRef::from_lit("/alpha/bravo/");
-    auto rel = StringRef::from_lit("../../../charlie");
+    auto base = "/alpha/bravo/"_sr;
+    auto rel = "../../../charlie"_sr;
     assert_stdstring_equal(
         "/charlie", http2::path_join(base, StringRef{}, rel, StringRef{}));
   }
   {
     // rel ends with '..'
-    auto base = StringRef::from_lit("/alpha/bravo/");
-    auto rel = StringRef::from_lit("charlie/..");
+    auto base = "/alpha/bravo/"_sr;
+    auto rel = "charlie/.."_sr;
     assert_stdstring_equal(
         "/alpha/bravo/", http2::path_join(base, StringRef{}, rel, StringRef{}));
   }
   {
     // base empty and rel contains '..'
     auto base = StringRef{};
-    auto rel = StringRef::from_lit("charlie/..");
+    auto rel = "charlie/.."_sr;
     assert_stdstring_equal(
         "/", http2::path_join(base, StringRef{}, rel, StringRef{}));
   }
   {
     // '.' is ignored
-    auto base = StringRef::from_lit("/");
-    auto rel = StringRef::from_lit("charlie/././././delta");
+    auto base = "/"_sr;
+    auto rel = "charlie/././././delta"_sr;
     assert_stdstring_equal(
         "/charlie/delta",
         http2::path_join(base, StringRef{}, rel, StringRef{}));
   }
   {
     // trailing '.' is ignored
-    auto base = StringRef::from_lit("/");
-    auto rel = StringRef::from_lit("charlie/.");
+    auto base = "/"_sr;
+    auto rel = "charlie/."_sr;
     assert_stdstring_equal(
         "/charlie/", http2::path_join(base, StringRef{}, rel, StringRef{}));
   }
   {
     // query
-    auto base = StringRef::from_lit("/");
-    auto rel = StringRef::from_lit("/");
-    auto relq = StringRef::from_lit("q");
+    auto base = "/"_sr;
+    auto rel = "/"_sr;
+    auto relq = "q"_sr;
     assert_stdstring_equal("/?q",
                            http2::path_join(base, StringRef{}, rel, relq));
   }
   {
     // empty rel and query
-    auto base = StringRef::from_lit("/alpha");
+    auto base = "/alpha"_sr;
     auto rel = StringRef{};
-    auto relq = StringRef::from_lit("q");
+    auto relq = "q"_sr;
     assert_stdstring_equal("/alpha?q",
                            http2::path_join(base, StringRef{}, rel, relq));
   }
   {
     // both rel and query are empty
-    auto base = StringRef::from_lit("/alpha");
-    auto baseq = StringRef::from_lit("r");
+    auto base = "/alpha"_sr;
+    auto baseq = "r"_sr;
     auto rel = StringRef{};
     auto relq = StringRef{};
     assert_stdstring_equal("/alpha?r",
@@ -890,7 +804,7 @@ void test_http2_path_join(void) {
   {
     // empty base
     auto base = StringRef{};
-    auto rel = StringRef::from_lit("/alpha");
+    auto rel = "/alpha"_sr;
     assert_stdstring_equal(
         "/alpha", http2::path_join(base, StringRef{}, rel, StringRef{}));
   }
@@ -902,7 +816,7 @@ void test_http2_path_join(void) {
   {
     // only baseq is not empty
     auto base = StringRef{};
-    auto baseq = StringRef::from_lit("r");
+    auto baseq = "r"_sr;
     auto rel = StringRef{};
     assert_stdstring_equal("/?r",
                            http2::path_join(base, baseq, rel, StringRef{}));
@@ -911,60 +825,60 @@ void test_http2_path_join(void) {
     // path starts with multiple '/'s.
     auto base = StringRef{};
     auto baseq = StringRef{};
-    auto rel = StringRef::from_lit("//alpha//bravo");
-    auto relq = StringRef::from_lit("charlie");
+    auto rel = "//alpha//bravo"_sr;
+    auto relq = "charlie"_sr;
     assert_stdstring_equal("/alpha/bravo?charlie",
                            http2::path_join(base, baseq, rel, relq));
   }
   // Test cases from RFC 3986, section 5.4.
-  constexpr auto base = StringRef::from_lit("/b/c/d;p");
-  constexpr auto baseq = StringRef::from_lit("q");
+  constexpr auto base = "/b/c/d;p"_sr;
+  constexpr auto baseq = "q"_sr;
   {
-    auto rel = StringRef::from_lit("g");
+    auto rel = "g"_sr;
     auto relq = StringRef{};
     assert_stdstring_equal("/b/c/g", http2::path_join(base, baseq, rel, relq));
   }
   {
-    auto rel = StringRef::from_lit("./g");
+    auto rel = "./g"_sr;
     auto relq = StringRef{};
     assert_stdstring_equal("/b/c/g", http2::path_join(base, baseq, rel, relq));
   }
   {
-    auto rel = StringRef::from_lit("g/");
+    auto rel = "g/"_sr;
     auto relq = StringRef{};
     assert_stdstring_equal("/b/c/g/", http2::path_join(base, baseq, rel, relq));
   }
   {
-    auto rel = StringRef::from_lit("/g");
+    auto rel = "/g"_sr;
     auto relq = StringRef{};
     assert_stdstring_equal("/g", http2::path_join(base, baseq, rel, relq));
   }
   {
     auto rel = StringRef{};
-    auto relq = StringRef::from_lit("y");
+    auto relq = "y"_sr;
     assert_stdstring_equal("/b/c/d;p?y",
                            http2::path_join(base, baseq, rel, relq));
   }
   {
-    auto rel = StringRef::from_lit("g");
-    auto relq = StringRef::from_lit("y");
+    auto rel = "g"_sr;
+    auto relq = "y"_sr;
     assert_stdstring_equal("/b/c/g?y",
                            http2::path_join(base, baseq, rel, relq));
   }
   {
-    auto rel = StringRef::from_lit(";x");
+    auto rel = ";x"_sr;
     auto relq = StringRef{};
     assert_stdstring_equal("/b/c/;x", http2::path_join(base, baseq, rel, relq));
   }
   {
-    auto rel = StringRef::from_lit("g;x");
+    auto rel = "g;x"_sr;
     auto relq = StringRef{};
     assert_stdstring_equal("/b/c/g;x",
                            http2::path_join(base, baseq, rel, relq));
   }
   {
-    auto rel = StringRef::from_lit("g;x");
-    auto relq = StringRef::from_lit("y");
+    auto rel = "g;x"_sr;
+    auto relq = "y"_sr;
     assert_stdstring_equal("/b/c/g;x?y",
                            http2::path_join(base, baseq, rel, relq));
   }
@@ -975,116 +889,116 @@ void test_http2_path_join(void) {
                            http2::path_join(base, baseq, rel, relq));
   }
   {
-    auto rel = StringRef::from_lit(".");
+    auto rel = "."_sr;
     auto relq = StringRef{};
     assert_stdstring_equal("/b/c/", http2::path_join(base, baseq, rel, relq));
   }
   {
-    auto rel = StringRef::from_lit("./");
+    auto rel = "./"_sr;
     auto relq = StringRef{};
     assert_stdstring_equal("/b/c/", http2::path_join(base, baseq, rel, relq));
   }
   {
-    auto rel = StringRef::from_lit("..");
+    auto rel = ".."_sr;
     auto relq = StringRef{};
     assert_stdstring_equal("/b/", http2::path_join(base, baseq, rel, relq));
   }
   {
-    auto rel = StringRef::from_lit("../");
+    auto rel = "../"_sr;
     auto relq = StringRef{};
     assert_stdstring_equal("/b/", http2::path_join(base, baseq, rel, relq));
   }
   {
-    auto rel = StringRef::from_lit("../g");
+    auto rel = "../g"_sr;
     auto relq = StringRef{};
     assert_stdstring_equal("/b/g", http2::path_join(base, baseq, rel, relq));
   }
   {
-    auto rel = StringRef::from_lit("../..");
+    auto rel = "../.."_sr;
     auto relq = StringRef{};
     assert_stdstring_equal("/", http2::path_join(base, baseq, rel, relq));
   }
   {
-    auto rel = StringRef::from_lit("../../");
+    auto rel = "../../"_sr;
     auto relq = StringRef{};
     assert_stdstring_equal("/", http2::path_join(base, baseq, rel, relq));
   }
   {
-    auto rel = StringRef::from_lit("../../g");
+    auto rel = "../../g"_sr;
     auto relq = StringRef{};
     assert_stdstring_equal("/g", http2::path_join(base, baseq, rel, relq));
   }
   {
-    auto rel = StringRef::from_lit("../../../g");
+    auto rel = "../../../g"_sr;
     auto relq = StringRef{};
     assert_stdstring_equal("/g", http2::path_join(base, baseq, rel, relq));
   }
   {
-    auto rel = StringRef::from_lit("../../../../g");
+    auto rel = "../../../../g"_sr;
     auto relq = StringRef{};
     assert_stdstring_equal("/g", http2::path_join(base, baseq, rel, relq));
   }
   {
-    auto rel = StringRef::from_lit("/./g");
+    auto rel = "/./g"_sr;
     auto relq = StringRef{};
     assert_stdstring_equal("/g", http2::path_join(base, baseq, rel, relq));
   }
   {
-    auto rel = StringRef::from_lit("/../g");
+    auto rel = "/../g"_sr;
     auto relq = StringRef{};
     assert_stdstring_equal("/g", http2::path_join(base, baseq, rel, relq));
   }
   {
-    auto rel = StringRef::from_lit("g.");
+    auto rel = "g."_sr;
     auto relq = StringRef{};
     assert_stdstring_equal("/b/c/g.", http2::path_join(base, baseq, rel, relq));
   }
   {
-    auto rel = StringRef::from_lit(".g");
+    auto rel = ".g"_sr;
     auto relq = StringRef{};
     assert_stdstring_equal("/b/c/.g", http2::path_join(base, baseq, rel, relq));
   }
   {
-    auto rel = StringRef::from_lit("g..");
+    auto rel = "g.."_sr;
     auto relq = StringRef{};
     assert_stdstring_equal("/b/c/g..",
                            http2::path_join(base, baseq, rel, relq));
   }
   {
-    auto rel = StringRef::from_lit("..g");
+    auto rel = "..g"_sr;
     auto relq = StringRef{};
     assert_stdstring_equal("/b/c/..g",
                            http2::path_join(base, baseq, rel, relq));
   }
   {
-    auto rel = StringRef::from_lit("./../g");
+    auto rel = "./../g"_sr;
     auto relq = StringRef{};
     assert_stdstring_equal("/b/g", http2::path_join(base, baseq, rel, relq));
   }
   {
-    auto rel = StringRef::from_lit("./g/.");
+    auto rel = "./g/."_sr;
     auto relq = StringRef{};
     assert_stdstring_equal("/b/c/g/", http2::path_join(base, baseq, rel, relq));
   }
   {
-    auto rel = StringRef::from_lit("g/./h");
+    auto rel = "g/./h"_sr;
     auto relq = StringRef{};
     assert_stdstring_equal("/b/c/g/h",
                            http2::path_join(base, baseq, rel, relq));
   }
   {
-    auto rel = StringRef::from_lit("g/../h");
+    auto rel = "g/../h"_sr;
     auto relq = StringRef{};
     assert_stdstring_equal("/b/c/h", http2::path_join(base, baseq, rel, relq));
   }
   {
-    auto rel = StringRef::from_lit("g;x=1/./y");
+    auto rel = "g;x=1/./y"_sr;
     auto relq = StringRef{};
     assert_stdstring_equal("/b/c/g;x=1/y",
                            http2::path_join(base, baseq, rel, relq));
   }
   {
-    auto rel = StringRef::from_lit("g;x=1/../y");
+    auto rel = "g;x=1/../y"_sr;
     auto relq = StringRef{};
     assert_stdstring_equal("/b/c/y", http2::path_join(base, baseq, rel, relq));
   }
@@ -1093,95 +1007,67 @@ void test_http2_path_join(void) {
 void test_http2_normalize_path(void) {
   assert_stdstring_equal(
       "/alpha/charlie",
-      http2::normalize_path(StringRef::from_lit("/alpha/bravo/../charlie"),
-                            StringRef{}));
+      http2::normalize_path("/alpha/bravo/../charlie"_sr, StringRef{}));
 
   assert_stdstring_equal(
-      "/alpha", http2::normalize_path(StringRef::from_lit("/a%6c%70%68%61"),
-                                      StringRef{}));
+      "/alpha", http2::normalize_path("/a%6c%70%68%61"_sr, StringRef{}));
 
-  assert_stdstring_equal(
-      "/alpha%2F%3A",
-      http2::normalize_path(StringRef::from_lit("/alpha%2f%3a"), StringRef{}));
+  assert_stdstring_equal("/alpha%2F%3A",
+                         http2::normalize_path("/alpha%2f%3a"_sr, StringRef{}));
 
-  assert_stdstring_equal(
-      "/%2F", http2::normalize_path(StringRef::from_lit("%2f"), StringRef{}));
+  assert_stdstring_equal("/%2F", http2::normalize_path("%2f"_sr, StringRef{}));
 
-  assert_stdstring_equal(
-      "/%f", http2::normalize_path(StringRef::from_lit("%f"), StringRef{}));
+  assert_stdstring_equal("/%f", http2::normalize_path("%f"_sr, StringRef{}));
 
-  assert_stdstring_equal(
-      "/%", http2::normalize_path(StringRef::from_lit("%"), StringRef{}));
+  assert_stdstring_equal("/%", http2::normalize_path("%"_sr, StringRef{}));
 
   assert_stdstring_equal("/", http2::normalize_path(StringRef{}, StringRef{}));
 
   assert_stdstring_equal("/alpha?bravo",
-                         http2::normalize_path(StringRef::from_lit("/alpha"),
-                                               StringRef::from_lit("bravo")));
+                         http2::normalize_path("/alpha"_sr, "bravo"_sr));
 }
 
 void test_http2_rewrite_clean_path(void) {
   BlockAllocator balloc(4096, 4096);
 
   // unreserved characters
-  assert_stdstring_equal(
-      "/alpha/bravo/",
-      http2::rewrite_clean_path(balloc, StringRef::from_lit("/alpha/%62ravo/"))
-          .str());
+  assert_stdsv_equal("/alpha/bravo/"sv,
+                     http2::rewrite_clean_path(balloc, "/alpha/%62ravo/"_sr));
 
   // percent-encoding is converted to upper case.
-  assert_stdstring_equal(
-      "/delta%3A",
-      http2::rewrite_clean_path(balloc, StringRef::from_lit("/delta%3a"))
-          .str());
+  assert_stdsv_equal("/delta%3A"sv,
+                     http2::rewrite_clean_path(balloc, "/delta%3a"_sr));
 
   // path component is normalized before matching
-  assert_stdstring_equal(
-      "/alpha/bravo/",
-      http2::rewrite_clean_path(
-          balloc, StringRef::from_lit("/alpha/charlie/%2e././bravo/delta/.."))
-          .str());
+  assert_stdsv_equal("/alpha/bravo/"sv,
+                     http2::rewrite_clean_path(
+                         balloc, "/alpha/charlie/%2e././bravo/delta/.."_sr));
 
-  assert_stdstring_equal(
-      "alpha%3a",
-      http2::rewrite_clean_path(balloc, StringRef::from_lit("alpha%3a")).str());
+  assert_stdsv_equal("alpha%3a"sv,
+                     http2::rewrite_clean_path(balloc, "alpha%3a"_sr));
 
-  assert_stdstring_equal("",
-                         http2::rewrite_clean_path(balloc, StringRef{}).str());
+  assert_stdsv_equal(""sv, http2::rewrite_clean_path(balloc, StringRef{}));
 
-  assert_stdstring_equal(
-      "/alpha?bravo",
-      http2::rewrite_clean_path(balloc, StringRef::from_lit("//alpha?bravo"))
-          .str());
+  assert_stdsv_equal("/alpha?bravo"sv,
+                     http2::rewrite_clean_path(balloc, "//alpha?bravo"_sr));
 }
 
 void test_http2_get_pure_path_component(void) {
-  assert_stdstring_equal(
-      "/", http2::get_pure_path_component(StringRef::from_lit("/")).str());
+  assert_stdsv_equal("/"sv, http2::get_pure_path_component("/"_sr));
 
-  assert_stdstring_equal(
-      "/foo",
-      http2::get_pure_path_component(StringRef::from_lit("/foo")).str());
+  assert_stdsv_equal("/foo"sv, http2::get_pure_path_component("/foo"_sr));
 
-  assert_stdstring_equal("/bar",
-                         http2::get_pure_path_component(
-                             StringRef::from_lit("https://example.org/bar"))
-                             .str());
+  assert_stdsv_equal(
+      "/bar"sv, http2::get_pure_path_component("https://example.org/bar"_sr));
 
-  assert_stdstring_equal(
-      "/alpha", http2::get_pure_path_component(
-                    StringRef::from_lit("https://example.org/alpha?q=a"))
-                    .str());
+  assert_stdsv_equal("/alpha"sv, http2::get_pure_path_component(
+                                     "https://example.org/alpha?q=a"_sr));
 
-  assert_stdstring_equal(
-      "/bravo",
-      http2::get_pure_path_component(
-          StringRef::from_lit("https://example.org/bravo?q=a#fragment"))
-          .str());
+  assert_stdsv_equal("/bravo"sv,
+                     http2::get_pure_path_component(
+                         "https://example.org/bravo?q=a#fragment"_sr));
 
-  assert_stdstring_equal(
-      "",
-      http2::get_pure_path_component(StringRef::from_lit("\x01\x02")).str());
+  assert_stdsv_equal(""sv, http2::get_pure_path_component("\x01\x02"_sr));
 }
 
 void test_http2_construct_push_component(void) {
@@ -1189,41 +1075,41 @@ void test_http2_construct_push_component(void) {
   StringRef base, uri;
   StringRef scheme, authority, path;
 
-  base = StringRef::from_lit("/b/");
-  uri = StringRef::from_lit("https://example.org/foo");
+  base = "/b/"_sr;
+  uri = "https://example.org/foo"_sr;
 
   assert_int(0, ==,
              http2::construct_push_component(balloc, scheme, authority, path,
                                              base, uri));
-  assert_stdstring_equal("https", scheme.str());
-  assert_stdstring_equal("example.org", authority.str());
-  assert_stdstring_equal("/foo", path.str());
+  assert_stdsv_equal("https"sv, scheme);
+  assert_stdsv_equal("example.org"sv, authority);
+  assert_stdsv_equal("/foo"sv, path);
 
   scheme = StringRef{};
   authority = StringRef{};
   path = StringRef{};
 
-  uri = StringRef::from_lit("/foo/bar?q=a");
+  uri = "/foo/bar?q=a"_sr;
 
   assert_int(0, ==,
              http2::construct_push_component(balloc, scheme, authority, path,
                                              base, uri));
-  assert_stdstring_equal("", scheme.str());
-  assert_stdstring_equal("", authority.str());
-  assert_stdstring_equal("/foo/bar?q=a", path.str());
+  assert_stdsv_equal(""sv, scheme);
+  assert_stdsv_equal(""sv, authority);
+  assert_stdsv_equal("/foo/bar?q=a"sv, path);
 
   scheme = StringRef{};
   authority = StringRef{};
   path = StringRef{};
 
-  uri = StringRef::from_lit("foo/../bar?q=a");
+  uri = "foo/../bar?q=a"_sr;
 
   assert_int(0, ==,
              http2::construct_push_component(balloc, scheme, authority, path,
                                              base, uri));
-  assert_stdstring_equal("", scheme.str());
-  assert_stdstring_equal("", authority.str());
-  assert_stdstring_equal("/b/bar?q=a", path.str());
+  assert_stdsv_equal(""sv, scheme);
+  assert_stdsv_equal(""sv, authority);
+  assert_stdsv_equal("/b/bar?q=a"sv, path);
 
   scheme = StringRef{};
   authority = StringRef{};
@@ -1238,91 +1124,69 @@ void test_http2_construct_push_component(void) {
   authority = StringRef{};
   path = StringRef{};
 
-  uri = StringRef::from_lit("?q=a");
+  uri = "?q=a"_sr;
 
   assert_int(0, ==,
              http2::construct_push_component(balloc, scheme, authority, path,
                                              base, uri));
-  assert_stdstring_equal("", scheme.str());
-  assert_stdstring_equal("", authority.str());
-  assert_stdstring_equal("/b/?q=a", path.str());
+  assert_stdsv_equal(""sv, scheme);
+  assert_stdsv_equal(""sv, authority);
+  assert_stdsv_equal("/b/?q=a"sv, path);
 }
 
 void test_http2_contains_trailers(void) {
-  assert_false(http2::contains_trailers(StringRef::from_lit("")));
-  assert_true(http2::contains_trailers(StringRef::from_lit("trailers")));
+  assert_false(http2::contains_trailers(""_sr));
+  assert_true(http2::contains_trailers("trailers"_sr));
   // Match must be case-insensitive.
-  assert_true(http2::contains_trailers(StringRef::from_lit("TRAILERS")));
-  assert_false(http2::contains_trailers(StringRef::from_lit("trailer")));
-  assert_false(http2::contains_trailers(StringRef::from_lit("trailers  3")));
-  assert_true(http2::contains_trailers(StringRef::from_lit("trailers,")));
-  assert_true(http2::contains_trailers(StringRef::from_lit("trailers,foo")));
-  assert_true(http2::contains_trailers(StringRef::from_lit("foo,trailers")));
-  assert_true(
-      http2::contains_trailers(StringRef::from_lit("foo,trailers,bar")));
-  assert_true(
-      http2::contains_trailers(StringRef::from_lit("foo, trailers ,bar")));
-  assert_true(http2::contains_trailers(StringRef::from_lit(",trailers")));
+  assert_true(http2::contains_trailers("TRAILERS"_sr));
+  assert_false(http2::contains_trailers("trailer"_sr));
+  assert_false(http2::contains_trailers("trailers  3"_sr));
+  assert_true(http2::contains_trailers("trailers,"_sr));
+  assert_true(http2::contains_trailers("trailers,foo"_sr));
+  assert_true(http2::contains_trailers("foo,trailers"_sr));
+  assert_true(http2::contains_trailers("foo,trailers,bar"_sr));
+  assert_true(http2::contains_trailers("foo, trailers ,bar"_sr));
+  assert_true(http2::contains_trailers(",trailers"_sr));
 }
 
 void test_http2_check_transfer_encoding(void) {
-  assert_true(http2::check_transfer_encoding(StringRef::from_lit("chunked")));
-  assert_true(
-      http2::check_transfer_encoding(StringRef::from_lit("foo,chunked")));
-  assert_true(
-      http2::check_transfer_encoding(StringRef::from_lit("foo,  chunked")));
-  assert_true(
-      http2::check_transfer_encoding(StringRef::from_lit("foo   ,  chunked")));
-  assert_true(
-      http2::check_transfer_encoding(StringRef::from_lit("chunked;foo=bar")));
-  assert_true(
-      http2::check_transfer_encoding(StringRef::from_lit("chunked ; foo=bar")));
-  assert_true(http2::check_transfer_encoding(
-      StringRef::from_lit(R"(chunked;foo="bar")")));
-  assert_true(http2::check_transfer_encoding(
-      StringRef::from_lit(R"(chunked;foo="\bar\"";FOO=BAR)")));
+  assert_true(http2::check_transfer_encoding("chunked"_sr));
+  assert_true(http2::check_transfer_encoding("foo,chunked"_sr));
+  assert_true(http2::check_transfer_encoding("foo,  chunked"_sr));
+  assert_true(http2::check_transfer_encoding("foo   ,  chunked"_sr));
+  assert_true(http2::check_transfer_encoding("chunked;foo=bar"_sr));
+  assert_true(http2::check_transfer_encoding("chunked ; foo=bar"_sr));
+  assert_true(http2::check_transfer_encoding(R"(chunked;foo="bar")"_sr));
   assert_true(
-      http2::check_transfer_encoding(StringRef::from_lit(R"(chunked;foo="")")));
-  assert_true(http2::check_transfer_encoding(
-      StringRef::from_lit(R"(chunked;foo="bar" , gzip)")));
+      http2::check_transfer_encoding(R"(chunked;foo="\bar\"";FOO=BAR)"_sr));
+  assert_true(http2::check_transfer_encoding(R"(chunked;foo="")"_sr));
+  assert_true(http2::check_transfer_encoding(R"(chunked;foo="bar" , gzip)"_sr));
 
   assert_false(http2::check_transfer_encoding(StringRef{}));
-  assert_false(http2::check_transfer_encoding(StringRef::from_lit(",chunked")));
-  assert_false(http2::check_transfer_encoding(StringRef::from_lit("chunked,")));
-  assert_false(
-      http2::check_transfer_encoding(StringRef::from_lit("chunked, ")));
-  assert_false(
-      http2::check_transfer_encoding(StringRef::from_lit("foo,,chunked")));
-  assert_false(
-      http2::check_transfer_encoding(StringRef::from_lit("chunked;foo")));
-  assert_false(http2::check_transfer_encoding(StringRef::from_lit("chunked;")));
-  assert_false(
-      http2::check_transfer_encoding(StringRef::from_lit("chunked;foo=bar;")));
-  assert_false(
-      http2::check_transfer_encoding(StringRef::from_lit("chunked;?=bar")));
-  assert_false(
-      http2::check_transfer_encoding(StringRef::from_lit("chunked;=bar")));
-  assert_false(
-      http2::check_transfer_encoding(StringRef::from_lit("chunked;;")));
-  assert_false(http2::check_transfer_encoding(StringRef::from_lit("chunked?")));
-  assert_false(http2::check_transfer_encoding(StringRef::from_lit(",")));
-  assert_false(http2::check_transfer_encoding(StringRef::from_lit(" ")));
-  assert_false(http2::check_transfer_encoding(StringRef::from_lit(";")));
-  assert_false(http2::check_transfer_encoding(StringRef::from_lit("\"")));
-  assert_false(http2::check_transfer_encoding(
-      StringRef::from_lit(R"(chunked;foo="bar)")));
-  assert_false(http2::check_transfer_encoding(
-      StringRef::from_lit(R"(chunked;foo="bar\)")));
-  assert_false(
-      http2::check_transfer_encoding(StringRef::from_lit(R"(chunked;foo="bar\)"
-                                                         "\x0a"
-                                                         R"(")")));
-  assert_false(
-      http2::check_transfer_encoding(StringRef::from_lit(R"(chunked;foo=")"
-                                                         "\x0a"
-                                                         R"(")")));
-  assert_false(http2::check_transfer_encoding(
-      StringRef::from_lit(R"(chunked;foo="bar",,gzip)")));
+  assert_false(http2::check_transfer_encoding(",chunked"_sr));
+  assert_false(http2::check_transfer_encoding("chunked,"_sr));
+  assert_false(http2::check_transfer_encoding("chunked, "_sr));
+  assert_false(http2::check_transfer_encoding("foo,,chunked"_sr));
+  assert_false(http2::check_transfer_encoding("chunked;foo"_sr));
+  assert_false(http2::check_transfer_encoding("chunked;"_sr));
+  assert_false(http2::check_transfer_encoding("chunked;foo=bar;"_sr));
+  assert_false(http2::check_transfer_encoding("chunked;?=bar"_sr));
+  assert_false(http2::check_transfer_encoding("chunked;=bar"_sr));
+  assert_false(http2::check_transfer_encoding("chunked;;"_sr));
+  assert_false(http2::check_transfer_encoding("chunked?"_sr));
+  assert_false(http2::check_transfer_encoding(","_sr));
+  assert_false(http2::check_transfer_encoding(" "_sr));
+  assert_false(http2::check_transfer_encoding(";"_sr));
+  assert_false(http2::check_transfer_encoding("\""_sr));
+  assert_false(http2::check_transfer_encoding(R"(chunked;foo="bar)"_sr));
+  assert_false(http2::check_transfer_encoding(R"(chunked;foo="bar\)"_sr));
+  assert_false(http2::check_transfer_encoding(R"(chunked;foo="bar\)"
+                                              "\x0a"
+                                              R"(")"_sr));
+  assert_false(http2::check_transfer_encoding(R"(chunked;foo=")"
+                                              "\x0a"
+                                              R"(")"_sr));
+  assert_false(http2::check_transfer_encoding(R"(chunked;foo="bar",,gzip)"_sr));
 }
 
 } // namespace shrpx
diff --git a/src/http3.cc b/src/http3.cc
index 61134ad..9bf33de 100644
--- a/src/http3.cc
+++ b/src/http3.cc
@@ -29,56 +29,6 @@ namespace nghttp2 {
 namespace http3 {
 
 namespace {
-nghttp3_nv make_nv_internal(const std::string &name, const std::string &value,
-                            bool never_index, uint8_t nv_flags) {
-  uint8_t flags;
-
-  flags = nv_flags |
-          (never_index ? NGHTTP3_NV_FLAG_NEVER_INDEX : NGHTTP3_NV_FLAG_NONE);
-
-  return {(uint8_t *)name.c_str(), (uint8_t *)value.c_str(), name.size(),
-          value.size(), flags};
-}
-} // namespace
-
-namespace {
-nghttp3_nv make_nv_internal(const StringRef &name, const StringRef &value,
-                            bool never_index, uint8_t nv_flags) {
-  uint8_t flags;
-
-  flags = nv_flags |
-          (never_index ? NGHTTP3_NV_FLAG_NEVER_INDEX : NGHTTP3_NV_FLAG_NONE);
-
-  return {(uint8_t *)name.c_str(), (uint8_t *)value.c_str(), name.size(),
-          value.size(), flags};
-}
-} // namespace
-
-nghttp3_nv make_nv(const std::string &name, const std::string &value,
-                   bool never_index) {
-  return make_nv_internal(name, value, never_index, NGHTTP3_NV_FLAG_NONE);
-}
-
-nghttp3_nv make_nv(const StringRef &name, const StringRef &value,
-                   bool never_index) {
-  return make_nv_internal(name, value, never_index, NGHTTP3_NV_FLAG_NONE);
-}
-
-nghttp3_nv make_nv_nocopy(const std::string &name, const std::string &value,
-                          bool never_index) {
-  return make_nv_internal(name, value, never_index,
-                          NGHTTP3_NV_FLAG_NO_COPY_NAME |
-                              NGHTTP3_NV_FLAG_NO_COPY_VALUE);
-}
-
-nghttp3_nv make_nv_nocopy(const StringRef &name, const StringRef &value,
-                          bool never_index) {
-  return make_nv_internal(name, value, never_index,
-                          NGHTTP3_NV_FLAG_NO_COPY_NAME |
-                              NGHTTP3_NV_FLAG_NO_COPY_VALUE);
-}
-
-namespace {
 void copy_headers_to_nva_internal(std::vector<nghttp3_nv> &nva,
                                   const HeaderRefs &headers, uint8_t nv_flags,
                                   uint32_t flags) {
@@ -172,17 +122,12 @@ void copy_headers_to_nva_internal(std::vector<nghttp3_nv> &nva,
       it_via = it;
       break;
     }
-    nva.push_back(
-        make_nv_internal(kv->name, kv->value, kv->no_index, nv_flags));
+    nva.push_back(make_field_flags(kv->name, kv->value,
+                                   nv_flags | never_index(kv->no_index)));
   }
 }
 } // namespace
 
-void copy_headers_to_nva(std::vector<nghttp3_nv> &nva,
-                         const HeaderRefs &headers, uint32_t flags) {
-  copy_headers_to_nva_internal(nva, headers, NGHTTP3_NV_FLAG_NONE, flags);
-}
-
 void copy_headers_to_nva_nocopy(std::vector<nghttp3_nv> &nva,
                                 const HeaderRefs &headers, uint32_t flags) {
   copy_headers_to_nva_internal(
@@ -190,17 +135,6 @@ void copy_headers_to_nva_nocopy(std::vector<nghttp3_nv> &nva,
       NGHTTP3_NV_FLAG_NO_COPY_NAME | NGHTTP3_NV_FLAG_NO_COPY_VALUE, flags);
 }
 
-int check_nv(const uint8_t *name, size_t namelen, const uint8_t *value,
-             size_t valuelen) {
-  if (!nghttp3_check_header_name(name, namelen)) {
-    return 0;
-  }
-  if (!nghttp3_check_header_value(value, valuelen)) {
-    return 0;
-  }
-  return 1;
-}
-
 } // namespace http3
 
 } // namespace nghttp2
diff --git a/src/http3.h b/src/http3.h
index 81ee0d7..cd68922 100644
--- a/src/http3.h
+++ b/src/http3.h
@@ -40,82 +40,38 @@ namespace nghttp2 {
 
 namespace http3 {
 
-// Creates nghttp3_nv using |name| and |value| and returns it. The
-// returned value only references the data pointer to name.c_str() and
-// value.c_str().  If |no_index| is true, nghttp3_nv flags member has
-// NGHTTP3_NV_FLAG_NEVER_INDEX flag set.
-nghttp3_nv make_nv(const std::string &name, const std::string &value,
-                   bool never_index = false);
-
-nghttp3_nv make_nv(const StringRef &name, const StringRef &value,
-                   bool never_index = false);
-
-nghttp3_nv make_nv_nocopy(const std::string &name, const std::string &value,
-                          bool never_index = false);
-
-nghttp3_nv make_nv_nocopy(const StringRef &name, const StringRef &value,
-                          bool never_index = false);
-
-// Create nghttp3_nv from string literal |name| and |value|.
-template <size_t N, size_t M>
-constexpr nghttp3_nv make_nv_ll(const char (&name)[N], const char (&value)[M]) {
-  return {(uint8_t *)name, (uint8_t *)value, N - 1, M - 1,
-          NGHTTP3_NV_FLAG_NO_COPY_NAME | NGHTTP3_NV_FLAG_NO_COPY_VALUE};
-}
-
-// Create nghttp3_nv from string literal |name| and c-string |value|.
-template <size_t N>
-nghttp3_nv make_nv_lc(const char (&name)[N], const char *value) {
-  return {(uint8_t *)name, (uint8_t *)value, N - 1, strlen(value),
-          NGHTTP3_NV_FLAG_NO_COPY_NAME};
+// Create nghttp3_nv from |name|, |value| and |flags|.
+inline nghttp3_nv make_field_flags(const StringRef &name,
+                                   const StringRef &value,
+                                   uint8_t flags = NGHTTP3_NV_FLAG_NONE) {
+  auto ns = as_uint8_span(std::span{name});
+  auto vs = as_uint8_span(std::span{value});
+
+  return {const_cast<uint8_t *>(ns.data()), const_cast<uint8_t *>(vs.data()),
+          ns.size(), vs.size(), flags};
 }
 
-template <size_t N>
-nghttp3_nv make_nv_lc_nocopy(const char (&name)[N], const char *value) {
-  return {(uint8_t *)name, (uint8_t *)value, N - 1, strlen(value),
-          NGHTTP3_NV_FLAG_NO_COPY_NAME | NGHTTP3_NV_FLAG_NO_COPY_VALUE};
+// Creates nghttp3_nv from |name|, |value| and |flags|.  nghttp3
+// library does not copy them.
+inline nghttp3_nv make_field(const StringRef &name, const StringRef &value,
+                             uint8_t flags = NGHTTP3_NV_FLAG_NONE) {
+  return make_field_flags(name, value,
+                          static_cast<uint8_t>(NGHTTP3_NV_FLAG_NO_COPY_NAME |
+                                               NGHTTP3_NV_FLAG_NO_COPY_VALUE |
+                                               flags));
 }
 
-// Create nghttp3_nv from string literal |name| and std::string
-// |value|.
-template <size_t N>
-nghttp3_nv make_nv_ls(const char (&name)[N], const std::string &value) {
-  return {(uint8_t *)name, (uint8_t *)value.c_str(), N - 1, value.size(),
-          NGHTTP3_NV_FLAG_NO_COPY_NAME};
+// Returns NGHTTP3_NV_FLAG_NEVER_INDEX if |never_index| is true,
+// otherwise NGHTTP3_NV_FLAG_NONE.
+inline uint8_t never_index(bool never_index) {
+  return never_index ? NGHTTP3_NV_FLAG_NEVER_INDEX : NGHTTP3_NV_FLAG_NONE;
 }
 
-template <size_t N>
-nghttp3_nv make_nv_ls_nocopy(const char (&name)[N], const std::string &value) {
-  return {(uint8_t *)name, (uint8_t *)value.c_str(), N - 1, value.size(),
-          NGHTTP3_NV_FLAG_NO_COPY_NAME | NGHTTP3_NV_FLAG_NO_COPY_VALUE};
-}
-
-template <size_t N>
-nghttp3_nv make_nv_ls_nocopy(const char (&name)[N], const StringRef &value) {
-  return {(uint8_t *)name, (uint8_t *)value.c_str(), N - 1, value.size(),
-          NGHTTP3_NV_FLAG_NO_COPY_NAME | NGHTTP3_NV_FLAG_NO_COPY_VALUE};
-}
-
-// Appends headers in |headers| to |nv|.  |headers| must be indexed
-// before this call (its element's token field is assigned).  Certain
-// headers, including disallowed headers in HTTP/3 spec and headers
-// which require special handling (i.e. via), are not copied.  |flags|
-// is one or more of HeaderBuildOp flags.  They tell function that
-// certain header fields should not be added.
-void copy_headers_to_nva(std::vector<nghttp3_nv> &nva,
-                         const HeaderRefs &headers, uint32_t flags);
-
 // Just like copy_headers_to_nva(), but this adds
 // NGHTTP3_NV_FLAG_NO_COPY_NAME and NGHTTP3_NV_FLAG_NO_COPY_VALUE.
 void copy_headers_to_nva_nocopy(std::vector<nghttp3_nv> &nva,
                                 const HeaderRefs &headers, uint32_t flags);
 
-// Checks the header name/value pair using nghttp3_check_header_name()
-// and nghttp3_check_header_value(). If both function returns nonzero,
-// this function returns nonzero.
-int check_nv(const uint8_t *name, size_t namelen, const uint8_t *value,
-             size_t valuelen);
-
 } // namespace http3
 
 } // namespace nghttp2
diff --git a/src/memchunk.h b/src/memchunk.h
index 7a7f2e9..7026184 100644
--- a/src/memchunk.h
+++ b/src/memchunk.h
@@ -199,7 +199,7 @@ template <typename Memchunk> struct Memchunks {
     return append(s, N - 1);
   }
   size_t append(const std::string &s) { return append(s.c_str(), s.size()); }
-  size_t append(const StringRef &s) { return append(s.c_str(), s.size()); }
+  size_t append(const StringRef &s) { return append(s.data(), s.size()); }
   size_t append(const ImmutableString &s) {
     return append(s.c_str(), s.size());
   }
diff --git a/src/nghttp.cc b/src/nghttp.cc
index 6684374..8ca37bb 100644
--- a/src/nghttp.cc
+++ b/src/nghttp.cc
@@ -89,13 +89,13 @@ enum {
 };
 
 namespace {
-constexpr auto anchors = std::array<Anchor, 5>{{
+constexpr auto anchors = std::to_array<Anchor>({
     {3, 0, 201},
     {5, 0, 101},
     {7, 0, 1},
     {9, 7, 1},
     {11, 3, 1},
-}};
+});
 } // namespace
 
 Config::Config()
@@ -201,9 +201,9 @@ StringRef Request::get_real_host() const {
 uint16_t Request::get_real_port() const {
   auto scheme = get_real_scheme();
   return config.host_override.empty() ? util::has_uri_field(u, UF_PORT) ? u.port
-                                        : scheme == "https"             ? 443
+                                        : scheme == "https"_sr          ? 443
                                                                         : 80
-         : config.port_override == 0  ? scheme == "https" ? 443 : 80
+         : config.port_override == 0  ? scheme == "https"_sr ? 443 : 80
                                       : config.port_override;
 }
 
@@ -215,7 +215,7 @@ void Request::init_html_parser() {
   auto ipv6_lit =
       std::find(std::begin(host), std::end(host), ':') != std::end(host);
 
-  auto base_uri = scheme.str();
+  auto base_uri = std::string{scheme};
   base_uri += "://";
   if (ipv6_lit) {
     base_uri += '[';
@@ -224,8 +224,8 @@ void Request::init_html_parser() {
   if (ipv6_lit) {
     base_uri += ']';
   }
-  if (!((scheme == "https" && port == 443) ||
-        (scheme == "http" && port == 80))) {
+  if (!((scheme == "https"_sr && port == 443) ||
+        (scheme == "http"_sr && port == 80))) {
     base_uri += ':';
     base_uri += util::utos(port);
   }
@@ -247,9 +247,9 @@ int Request::update_html_parser(const uint8_t *data, size_t len, int fin) {
 }
 
 std::string Request::make_reqpath() const {
-  std::string path = util::has_uri_field(u, UF_PATH)
-                         ? util::get_uri_field(uri.c_str(), u, UF_PATH).str()
-                         : "/";
+  auto path = util::has_uri_field(u, UF_PATH)
+                  ? std::string{util::get_uri_field(uri.c_str(), u, UF_PATH)}
+                  : "/"s;
   if (util::has_uri_field(u, UF_QUERY)) {
     path += '?';
     path.append(uri.c_str() + u.field_data[UF_QUERY].off,
@@ -266,15 +266,15 @@ std::string decode_host(const StringRef &host) {
   if (zone_start == std::end(host) ||
       !util::ipv6_numeric_addr(
           std::string(std::begin(host), zone_start).c_str())) {
-    return host.str();
+    return std::string{host};
   }
   // case: ::1%
   if (zone_start + 1 == std::end(host)) {
-    return StringRef{host.c_str(), host.size() - 1}.str();
+    return {host.data(), host.size() - 1};
   }
   // case: ::1%12 or ::1%1
   if (zone_start + 3 >= std::end(host)) {
-    return host.str();
+    return std::string{host};
   }
   // If we see "%25", followed by more characters, then decode %25 as
   // '%'.
@@ -454,7 +454,7 @@ int submit_request(HttpClient *client, const Headers &headers, Request *req) {
   auto scheme = util::get_uri_field(req->uri.c_str(), req->u, UF_SCHEMA);
   auto build_headers = Headers{{":method", req->data_prd ? "POST" : "GET"},
                                {":path", req->make_reqpath()},
-                               {":scheme", scheme.str()},
+                               {":scheme", std::string{scheme}},
                                {":authority", client->hostport},
                                {"accept", "*/*"},
                                {"accept-encoding", "gzip, deflate"},
@@ -500,7 +500,8 @@ int submit_request(HttpClient *client, const Headers &headers, Request *req) {
   nva.reserve(build_headers.size());
 
   for (auto &kv : build_headers) {
-    nva.push_back(http2::make_nv(kv.name, kv.value, kv.no_index));
+    nva.push_back(
+        http2::make_field_nv(kv.name, kv.value, http2::no_index(kv.no_index)));
   }
 
   auto method = http2::get_header(build_headers, ":method");
@@ -515,7 +516,7 @@ int submit_request(HttpClient *client, const Headers &headers, Request *req) {
       trailer_names += ", ";
       trailer_names += config.trailer[i].name;
     }
-    nva.push_back(http2::make_nv_ls("trailer", trailer_names));
+    nva.push_back(http2::make_field_v("trailer"_sr, trailer_names));
   }
 
   int32_t stream_id;
@@ -975,9 +976,9 @@ int HttpClient::on_upgrade_connect() {
     // If the request contains upload data, use OPTIONS * to upgrade
     req = "OPTIONS *";
   } else {
-    auto meth = std::find_if(
-        std::begin(config.headers), std::end(config.headers),
-        [](const Header &kv) { return util::streq_l(":method", kv.name); });
+    auto meth =
+        std::find_if(std::begin(config.headers), std::end(config.headers),
+                     [](const auto &kv) { return ":method"_sr == kv.name; });
 
     if (meth == std::end(config.headers)) {
       req = "GET ";
@@ -1424,8 +1425,7 @@ void HttpClient::update_hostport() {
   if (reqvec.empty()) {
     return;
   }
-  scheme = util::get_uri_field(reqvec[0]->uri.c_str(), reqvec[0]->u, UF_SCHEMA)
-               .str();
+  scheme = util::get_uri_field(reqvec[0]->uri.c_str(), reqvec[0]->u, UF_SCHEMA);
   std::stringstream ss;
   if (reqvec[0]->is_ipv6_literal_addr()) {
     // we may have zone ID, which must start with "%25", or "%".  RFC
@@ -1435,7 +1435,7 @@ void HttpClient::update_hostport() {
         util::get_uri_field(reqvec[0]->uri.c_str(), reqvec[0]->u, UF_HOST);
     auto end = std::find(std::begin(host), std::end(host), '%');
     ss << "[";
-    ss.write(host.c_str(), end - std::begin(host));
+    ss.write(host.data(), end - std::begin(host));
     ss << "]";
   } else {
     util::write_uri_field(ss, reqvec[0]->uri.c_str(), reqvec[0]->u, UF_HOST);
@@ -1688,7 +1688,7 @@ void update_html_parser(HttpClient *client, Request *req, const uint8_t *data,
     }
 
     auto link_port = util::has_uri_field(u, UF_PORT) ? u.port
-                     : scheme == "https"             ? 443
+                     : scheme == "https"_sr          ? 443
                                                      : 80;
 
     if (port != link_port) {
@@ -1800,8 +1800,8 @@ void check_response_header(nghttp2_session *session, Request *req) {
 
   for (auto &nv : req->res_nva) {
     if ("content-encoding" == nv.name) {
-      gzip = util::strieq_l("gzip", nv.value) ||
-             util::strieq_l("deflate", nv.value);
+      gzip = util::strieq("gzip"_sr, nv.value) ||
+             util::strieq("deflate"_sr, nv.value);
       continue;
     }
   }
@@ -1915,10 +1915,12 @@ int on_header_callback(nghttp2_session *session, const nghttp2_frame *frame,
 
     req->header_buffer_size += namelen + valuelen;
 
-    auto token = http2::lookup_token(name, namelen);
+    auto nameref = StringRef{name, namelen};
+    auto valueref = StringRef{value, valuelen};
+    auto token = http2::lookup_token(nameref);
 
     http2::index_header(req->res_hdidx, token, req->res_nva.size());
-    http2::add_header(req->res_nva, name, namelen, value, valuelen,
+    http2::add_header(req->res_nva, nameref, valueref,
                       flags & NGHTTP2_NV_FLAG_NO_INDEX, token);
     break;
   }
@@ -1939,10 +1941,12 @@ int on_header_callback(nghttp2_session *session, const nghttp2_frame *frame,
 
     req->header_buffer_size += namelen + valuelen;
 
-    auto token = http2::lookup_token(name, namelen);
+    auto nameref = StringRef{name, namelen};
+    auto valueref = StringRef{value, valuelen};
+    auto token = http2::lookup_token(nameref);
 
     http2::index_header(req->req_hdidx, token, req->req_nva.size());
-    http2::add_header(req->req_nva, name, namelen, value, valuelen,
+    http2::add_header(req->req_nva, nameref, valueref,
                       flags & NGHTTP2_NV_FLAG_NO_INDEX, token);
     break;
   }
@@ -2283,7 +2287,8 @@ int communicate(
       goto fin;
     }
 
-    if (SSL_CTX_set_cipher_list(ssl_ctx, tls::DEFAULT_CIPHER_LIST) == 0) {
+    if (SSL_CTX_set_cipher_list(ssl_ctx, tls::DEFAULT_CIPHER_LIST.data()) ==
+        0) {
       std::cerr << "[ERROR] " << ERR_error_string(ERR_get_error(), nullptr)
                 << std::endl;
       result = -1;
@@ -2437,7 +2442,8 @@ nghttp2_ssize file_read_callback(nghttp2_session *session, int32_t stream_id,
       std::vector<nghttp2_nv> nva;
       nva.reserve(config.trailer.size());
       for (auto &kv : config.trailer) {
-        nva.push_back(http2::make_nv(kv.name, kv.value, kv.no_index));
+        nva.push_back(http2::make_field_nv(kv.name, kv.value,
+                                           http2::no_index(kv.no_index)));
       }
       rv = nghttp2_submit_trailer(session, stream_id, nva.data(), nva.size());
       if (rv != 0) {
@@ -2609,7 +2615,7 @@ int run(char **uris, int n) {
         }
         requests.clear();
       }
-      prev_scheme = util::get_uri_field(uri.c_str(), u, UF_SCHEMA).str();
+      prev_scheme = util::get_uri_field(uri.c_str(), u, UF_SCHEMA);
       prev_host = std::move(host);
       prev_port = port;
     }
@@ -2818,11 +2824,11 @@ int main(int argc, char **argv) {
     case 'M': {
       // peer-max-concurrent-streams option
       auto n = util::parse_uint(optarg);
-      if (n == -1) {
+      if (!n) {
         std::cerr << "-M: Bad option value: " << optarg << std::endl;
         exit(EXIT_FAILURE);
       }
-      config.peer_max_concurrent_streams = n;
+      config.peer_max_concurrent_streams = *n;
       break;
     }
     case 'O':
@@ -2833,11 +2839,11 @@ int main(int argc, char **argv) {
       exit(EXIT_SUCCESS);
     case 'b': {
       auto n = util::parse_uint(optarg);
-      if (n == -1) {
+      if (!n) {
         std::cerr << "-b: Bad option value: " << optarg << std::endl;
         exit(EXIT_FAILURE);
       }
-      config.padding = n;
+      config.padding = *n;
       break;
     }
     case 'n':
@@ -2845,13 +2851,13 @@ int main(int argc, char **argv) {
       break;
     case 'p': {
       auto n = util::parse_uint(optarg);
-      if (n == -1 || NGHTTP2_MIN_WEIGHT > n || n > NGHTTP2_MAX_WEIGHT) {
+      if (!n || NGHTTP2_MIN_WEIGHT > n || n > NGHTTP2_MAX_WEIGHT) {
         std::cerr << "-p: specify the integer in the range ["
                   << NGHTTP2_MIN_WEIGHT << ", " << NGHTTP2_MAX_WEIGHT
                   << "], inclusive" << std::endl;
         exit(EXIT_FAILURE);
       }
-      config.weight.push_back(n);
+      config.weight.push_back(*n);
       break;
     }
     case 'r':
@@ -2865,29 +2871,31 @@ int main(int argc, char **argv) {
     case 'v':
       ++config.verbose;
       break;
-    case 't':
-      config.timeout = util::parse_duration_with_unit(optarg);
-      if (config.timeout == std::numeric_limits<double>::infinity()) {
+    case 't': {
+      auto d = util::parse_duration_with_unit(optarg);
+      if (!d) {
         std::cerr << "-t: bad timeout value: " << optarg << std::endl;
         exit(EXIT_FAILURE);
       }
+      config.timeout = *d;
       break;
+    }
     case 'u':
       config.upgrade = true;
       break;
     case 'w':
     case 'W': {
       auto n = util::parse_uint(optarg);
-      if (n == -1 || n > 30) {
+      if (!n || n > 30) {
         std::cerr << "-" << static_cast<char>(c)
                   << ": specify the integer in the range [0, 30], inclusive"
                   << std::endl;
         exit(EXIT_FAILURE);
       }
       if (c == 'w') {
-        config.window_bits = n;
+        config.window_bits = *n;
       } else {
-        config.connection_window_bits = n;
+        config.connection_window_bits = *n;
       }
       break;
     }
@@ -2931,16 +2939,16 @@ int main(int argc, char **argv) {
       break;
     case 'm': {
       auto n = util::parse_uint(optarg);
-      if (n == -1) {
+      if (!n) {
         std::cerr << "-m: Bad option value: " << optarg << std::endl;
         exit(EXIT_FAILURE);
       }
-      config.multiply = n;
+      config.multiply = *n;
       break;
     }
     case 'c': {
       auto n = util::parse_uint_with_unit(optarg);
-      if (n == -1) {
+      if (!n) {
         std::cerr << "-c: Bad option value: " << optarg << std::endl;
         exit(EXIT_FAILURE);
       }
@@ -2949,8 +2957,8 @@ int main(int argc, char **argv) {
                   << std::numeric_limits<uint32_t>::max() << std::endl;
         exit(EXIT_FAILURE);
       }
-      config.header_table_size = n;
-      config.min_header_table_size = std::min(config.min_header_table_size, n);
+      config.header_table_size = *n;
+      config.min_header_table_size = std::min(config.min_header_table_size, *n);
       break;
     }
     case 'y':
@@ -3024,12 +3032,12 @@ int main(int argc, char **argv) {
       case 12: {
         // max-concurrent-streams option
         auto n = util::parse_uint(optarg);
-        if (n == -1) {
+        if (!n) {
           std::cerr << "--max-concurrent-streams: Bad option value: " << optarg
                     << std::endl;
           exit(EXIT_FAILURE);
         }
-        config.max_concurrent_streams = n;
+        config.max_concurrent_streams = *n;
         break;
       }
       case 13:
@@ -3039,7 +3047,7 @@ int main(int argc, char **argv) {
       case 14: {
         // encoder-header-table-size option
         auto n = util::parse_uint_with_unit(optarg);
-        if (n == -1) {
+        if (!n) {
           std::cerr << "--encoder-header-table-size: Bad option value: "
                     << optarg << std::endl;
           exit(EXIT_FAILURE);
@@ -3050,7 +3058,7 @@ int main(int argc, char **argv) {
                     << std::numeric_limits<uint32_t>::max() << std::endl;
           exit(EXIT_FAILURE);
         }
-        config.encoder_header_table_size = n;
+        config.encoder_header_table_size = *n;
         break;
       }
       case 15:
@@ -3105,7 +3113,7 @@ int main(int argc, char **argv) {
       exit(EXIT_FAILURE);
     }
 
-    config.host_override = util::get_uri_field(uri.c_str(), u, UF_HOST).str();
+    config.host_override = util::get_uri_field(uri.c_str(), u, UF_HOST);
     if (util::has_uri_field(u, UF_PORT)) {
       config.port_override = u.port;
     }
diff --git a/src/nghttpd.cc b/src/nghttpd.cc
index 9cad874..de62953 100644
--- a/src/nghttpd.cc
+++ b/src/nghttpd.cc
@@ -246,11 +246,11 @@ int main(int argc, char **argv) {
       break;
     case 'b': {
       auto n = util::parse_uint(optarg);
-      if (n == -1) {
+      if (!n) {
         std::cerr << "-b: Bad option value: " << optarg << std::endl;
         exit(EXIT_FAILURE);
       }
-      config.padding = n;
+      config.padding = *n;
       break;
     }
     case 'd':
@@ -262,11 +262,11 @@ int main(int argc, char **argv) {
     case 'm': {
       // max-concurrent-streams option
       auto n = util::parse_uint(optarg);
-      if (n == -1) {
+      if (!n) {
         std::cerr << "-m: invalid argument: " << optarg << std::endl;
         exit(EXIT_FAILURE);
       }
-      config.max_concurrent_streams = n;
+      config.max_concurrent_streams = *n;
       break;
     }
     case 'n': {
@@ -275,11 +275,11 @@ int main(int argc, char **argv) {
                 << "no threads created." << std::endl;
 #else
       auto n = util::parse_uint(optarg);
-      if (n == -1) {
+      if (!n) {
         std::cerr << "-n: Bad option value: " << optarg << std::endl;
         exit(EXIT_FAILURE);
       }
-      config.num_worker = n;
+      config.num_worker = *n;
 #endif // NOTHREADS
       break;
     }
@@ -291,7 +291,7 @@ int main(int argc, char **argv) {
       break;
     case 'c': {
       auto n = util::parse_uint_with_unit(optarg);
-      if (n == -1) {
+      if (!n) {
         std::cerr << "-c: Bad option value: " << optarg << std::endl;
         exit(EXIT_FAILURE);
       }
@@ -300,7 +300,7 @@ int main(int argc, char **argv) {
                   << std::numeric_limits<uint32_t>::max() << std::endl;
         exit(EXIT_FAILURE);
       }
-      config.header_table_size = n;
+      config.header_table_size = *n;
       break;
     }
     case 'p':
@@ -311,7 +311,7 @@ int main(int argc, char **argv) {
     case 'w':
     case 'W': {
       auto n = util::parse_uint(optarg);
-      if (n == -1 || n > 30) {
+      if (!n || n > 30) {
         std::cerr << "-" << static_cast<char>(c)
                   << ": specify the integer in the range [0, 30], inclusive"
                   << std::endl;
@@ -319,9 +319,9 @@ int main(int argc, char **argv) {
       }
 
       if (c == 'w') {
-        config.window_bits = n;
+        config.window_bits = *n;
       } else {
-        config.connection_window_bits = n;
+        config.connection_window_bits = *n;
       }
 
       break;
@@ -395,7 +395,7 @@ int main(int argc, char **argv) {
       case 11: {
         // encoder-header-table-size option
         auto n = util::parse_uint_with_unit(optarg);
-        if (n == -1) {
+        if (!n) {
           std::cerr << "--encoder-header-table-size: Bad option value: "
                     << optarg << std::endl;
           exit(EXIT_FAILURE);
@@ -406,7 +406,7 @@ int main(int argc, char **argv) {
                     << std::numeric_limits<uint32_t>::max() << std::endl;
           exit(EXIT_FAILURE);
         }
-        config.encoder_header_table_size = n;
+        config.encoder_header_table_size = *n;
         break;
       }
       case 12:
@@ -432,11 +432,11 @@ int main(int argc, char **argv) {
   {
     auto portStr = argv[optind++];
     auto n = util::parse_uint(portStr);
-    if (n == -1 || n > std::numeric_limits<uint16_t>::max()) {
+    if (!n || n > std::numeric_limits<uint16_t>::max()) {
       std::cerr << "<PORT>: Bad value: " << portStr << std::endl;
       exit(EXIT_FAILURE);
     }
-    config.port = n;
+    config.port = *n;
   }
 
   if (!config.no_tls) {
diff --git a/src/shrpx.cc b/src/shrpx.cc
index 89a7787..86d00dc 100644
--- a/src/shrpx.cc
+++ b/src/shrpx.cc
@@ -71,6 +71,7 @@
 #include <vector>
 #include <initializer_list>
 #include <random>
+#include <span>
 
 #include <openssl/ssl.h>
 #include <openssl/err.h>
@@ -112,19 +113,19 @@ namespace shrpx {
 
 // Deprecated: Environment variables to tell new binary the listening
 // socket's file descriptors.  They are not close-on-exec.
-constexpr auto ENV_LISTENER4_FD = StringRef::from_lit("NGHTTPX_LISTENER4_FD");
-constexpr auto ENV_LISTENER6_FD = StringRef::from_lit("NGHTTPX_LISTENER6_FD");
+constexpr auto ENV_LISTENER4_FD = "NGHTTPX_LISTENER4_FD"_sr;
+constexpr auto ENV_LISTENER6_FD = "NGHTTPX_LISTENER6_FD"_sr;
 
 // Deprecated: Environment variable to tell new binary the port number
 // the current binary is listening to.
-constexpr auto ENV_PORT = StringRef::from_lit("NGHTTPX_PORT");
+constexpr auto ENV_PORT = "NGHTTPX_PORT"_sr;
 
 // Deprecated: Environment variable to tell new binary the listening
 // socket's file descriptor if frontend listens UNIX domain socket.
-constexpr auto ENV_UNIX_FD = StringRef::from_lit("NGHTTP2_UNIX_FD");
+constexpr auto ENV_UNIX_FD = "NGHTTP2_UNIX_FD"_sr;
 // Deprecated: Environment variable to tell new binary the UNIX domain
 // socket path.
-constexpr auto ENV_UNIX_PATH = StringRef::from_lit("NGHTTP2_UNIX_PATH");
+constexpr auto ENV_UNIX_PATH = "NGHTTP2_UNIX_PATH"_sr;
 
 // Prefix of environment variables to tell new binary the listening
 // socket's file descriptor.  They are not close-on-exec.  For TCP
@@ -132,13 +133,13 @@ constexpr auto ENV_UNIX_PATH = StringRef::from_lit("NGHTTP2_UNIX_PATH");
 // <FD> is file descriptor.  For UNIX domain socket, the value must be
 // comma separated 3 parameters: unix,<FD>,<PATH>.  <FD> is file
 // descriptor.  <PATH> is a path to UNIX domain socket.
-constexpr auto ENV_ACCEPT_PREFIX = StringRef::from_lit("NGHTTPX_ACCEPT_");
+constexpr auto ENV_ACCEPT_PREFIX = "NGHTTPX_ACCEPT_"_sr;
 
 // This environment variable contains PID of the original main
 // process, assuming that it created this main process as a result of
 // SIGUSR2.  The new main process is expected to send QUIT signal to
 // the original main process to shut it down gracefully.
-constexpr auto ENV_ORIG_PID = StringRef::from_lit("NGHTTPX_ORIG_PID");
+constexpr auto ENV_ORIG_PID = "NGHTTPX_ORIG_PID"_sr;
 
 // Prefix of environment variables to tell new binary the QUIC IPC
 // file descriptor and Worker ID of the lingering worker process.  The
@@ -149,7 +150,7 @@ constexpr auto ENV_ORIG_PID = StringRef::from_lit("NGHTTPX_ORIG_PID");
 // <FD> is the file descriptor.  <WORKER_ID_I> is the I-th Worker ID
 // in hex encoded string.
 constexpr auto ENV_QUIC_WORKER_PROCESS_PREFIX =
-    StringRef::from_lit("NGHTTPX_QUIC_WORKER_PROCESS_");
+    "NGHTTPX_QUIC_WORKER_PROCESS_"_sr;
 
 #ifndef _KERNEL_FASTOPEN
 #  define _KERNEL_FASTOPEN
@@ -398,7 +399,7 @@ int save_pid() {
   std::array<char, STRERROR_BUFSIZE> errbuf;
   auto config = get_config();
 
-  constexpr auto SUFFIX = StringRef::from_lit(".XXXXXX");
+  constexpr auto SUFFIX = ".XXXXXX"_sr;
   auto &pid_file = config->pid_file;
 
   auto len = config->pid_file.size() + SUFFIX.size();
@@ -437,7 +438,7 @@ int save_pid() {
 
   close(fd);
 
-  if (rename(temp_path, pid_file.c_str()) == -1) {
+  if (rename(temp_path, pid_file.data()) == -1) {
     auto error = errno;
     LOG(ERROR) << "Could not save PID to file " << pid_file << ": "
                << xsi_strerror(error, errbuf.data(), errbuf.size());
@@ -448,7 +449,7 @@ int save_pid() {
   }
 
   if (config->uid != 0) {
-    if (chown(pid_file.c_str(), config->uid, config->gid) == -1) {
+    if (chown(pid_file.data(), config->uid, config->gid) == -1) {
       auto error = errno;
       LOG(WARN) << "Changing owner of pid file " << pid_file << " failed: "
                 << xsi_strerror(error, errbuf.data(), errbuf.size());
@@ -558,7 +559,7 @@ void exec_binary() {
   std::vector<ImmutableString> fd_envs;
   for (size_t i = 0; i < listenerconf.addrs.size(); ++i) {
     auto &addr = listenerconf.addrs[i];
-    auto s = ENV_ACCEPT_PREFIX.str();
+    auto s = std::string{ENV_ACCEPT_PREFIX};
     s += util::utos(i + 1);
     s += '=';
     if (addr.host_unix) {
@@ -575,7 +576,7 @@ void exec_binary() {
     envp[envidx++] = const_cast<char *>(fd_envs.back().c_str());
   }
 
-  auto ipc_fd_str = ENV_ORIG_PID.str();
+  auto ipc_fd_str = std::string{ENV_ORIG_PID};
   ipc_fd_str += '=';
   ipc_fd_str += util::utos(config->pid);
   envp[envidx++] = const_cast<char *>(ipc_fd_str.c_str());
@@ -584,14 +585,13 @@ void exec_binary() {
   std::vector<ImmutableString> quic_lwps;
   for (size_t i = 0; i < worker_processes.size(); ++i) {
     auto &wp = worker_processes[i];
-    auto s = ENV_QUIC_WORKER_PROCESS_PREFIX.str();
+    auto s = std::string{ENV_QUIC_WORKER_PROCESS_PREFIX};
     s += util::utos(i + 1);
     s += '=';
     s += util::utos(wp->quic_ipc_fd);
     for (auto &wid : wp->worker_ids) {
       s += ',';
-      s += util::format_hex(reinterpret_cast<const unsigned char *>(&wid),
-                            sizeof(wid));
+      s += util::format_hex(std::span{&wid, 1});
     }
 
     quic_lwps.emplace_back(s);
@@ -741,7 +741,7 @@ int create_unix_domain_server_socket(UpstreamAddr &faddr,
                 << (faddr.tls ? ", tls" : "");
     (*found).used = true;
     faddr.fd = (*found).fd;
-    faddr.hostport = StringRef::from_lit("localhost");
+    faddr.hostport = "localhost"_sr;
 
     return 0;
   }
@@ -783,10 +783,10 @@ int create_unix_domain_server_socket(UpstreamAddr &faddr,
     return -1;
   }
   // copy path including terminal NULL
-  std::copy_n(faddr.host.c_str(), faddr.host.size() + 1, addr.un.sun_path);
+  std::copy_n(faddr.host.data(), faddr.host.size() + 1, addr.un.sun_path);
 
   // unlink (remove) already existing UNIX domain socket path
-  unlink(faddr.host.c_str());
+  unlink(faddr.host.data());
 
   if (bind(fd, &addr.sa, sizeof(addr.un)) != 0) {
     auto error = errno;
@@ -810,7 +810,7 @@ int create_unix_domain_server_socket(UpstreamAddr &faddr,
               << (faddr.tls ? ", tls" : "");
 
   faddr.fd = fd;
-  faddr.hostport = StringRef::from_lit("localhost");
+  faddr.hostport = "localhost"_sr;
 
   return 0;
 }
@@ -834,8 +834,7 @@ int create_tcp_server_socket(UpstreamAddr &faddr,
   hints.ai_flags |= AI_ADDRCONFIG;
 #endif // AI_ADDRCONFIG
 
-  auto node =
-      faddr.host == StringRef::from_lit("*") ? nullptr : faddr.host.c_str();
+  auto node = faddr.host == "*"_sr ? nullptr : faddr.host.data();
 
   addrinfo *res, *rp;
   rv = getaddrinfo(node, service.c_str(), &hints, &res);
@@ -867,10 +866,12 @@ int create_tcp_server_socket(UpstreamAddr &faddr,
       continue;
     }
 
+    auto host_sr = StringRef{host.data()};
+
     auto found = std::find_if(std::begin(iaddrs), std::end(iaddrs),
-                              [&host, &faddr](const InheritedAddr &ia) {
+                              [&host_sr, &faddr](const InheritedAddr &ia) {
                                 return !ia.used && !ia.host_unix &&
-                                       ia.host == host.data() &&
+                                       ia.host == host_sr &&
                                        ia.port == faddr.port;
                               });
 
@@ -1056,13 +1057,13 @@ std::vector<InheritedAddr> get_inherited_addr_from_env(Config *config) {
 
   {
     // Upgrade from 1.7.0 or earlier
-    auto portenv = getenv(ENV_PORT.c_str());
+    auto portenv = getenv(ENV_PORT.data());
     if (portenv) {
       size_t i = 1;
       for (const auto &env_name : {ENV_LISTENER4_FD, ENV_LISTENER6_FD}) {
-        auto fdenv = getenv(env_name.c_str());
+        auto fdenv = getenv(env_name.data());
         if (fdenv) {
-          auto name = ENV_ACCEPT_PREFIX.str();
+          auto name = std::string{ENV_ACCEPT_PREFIX};
           name += util::utos(i);
           std::string value = "tcp,";
           value += fdenv;
@@ -1072,20 +1073,20 @@ std::vector<InheritedAddr> get_inherited_addr_from_env(Config *config) {
       }
     } else {
       // The return value of getenv may be allocated statically.
-      if (getenv(ENV_UNIX_PATH.c_str()) && getenv(ENV_UNIX_FD.c_str())) {
-        auto name = ENV_ACCEPT_PREFIX.str();
+      if (getenv(ENV_UNIX_PATH.data()) && getenv(ENV_UNIX_FD.data())) {
+        auto name = std::string{ENV_ACCEPT_PREFIX};
         name += '1';
         std::string value = "unix,";
-        value += getenv(ENV_UNIX_FD.c_str());
+        value += getenv(ENV_UNIX_FD.data());
         value += ',';
-        value += getenv(ENV_UNIX_PATH.c_str());
+        value += getenv(ENV_UNIX_PATH.data());
         setenv(name.c_str(), value.c_str(), 0);
       }
     }
   }
 
   for (size_t i = 1;; ++i) {
-    auto name = ENV_ACCEPT_PREFIX.str();
+    auto name = std::string{ENV_ACCEPT_PREFIX};
     name += util::utos(i);
     auto env = getenv(name.c_str());
     if (!env) {
@@ -1104,14 +1105,13 @@ std::vector<InheritedAddr> get_inherited_addr_from_env(Config *config) {
     auto type = StringRef(env, end_type);
     auto value = end_type + 1;
 
-    if (type == StringRef::from_lit("unix")) {
+    if (type == "unix"_sr) {
       auto endfd = strchr(value, ',');
       if (!endfd) {
         continue;
       }
-      auto fd = util::parse_uint(reinterpret_cast<const uint8_t *>(value),
-                                 endfd - value);
-      if (fd == -1) {
+      auto fd = util::parse_uint(StringRef{value, endfd});
+      if (!fd) {
         LOG(WARN) << "Could not parse file descriptor from "
                   << std::string(value, endfd - value);
         continue;
@@ -1119,26 +1119,26 @@ std::vector<InheritedAddr> get_inherited_addr_from_env(Config *config) {
 
       auto path = endfd + 1;
       if (strlen(path) == 0) {
-        LOG(WARN) << "Empty UNIX domain socket path (fd=" << fd << ")";
-        close(fd);
+        LOG(WARN) << "Empty UNIX domain socket path (fd=" << *fd << ")";
+        close(*fd);
         continue;
       }
 
       if (LOG_ENABLED(INFO)) {
-        LOG(INFO) << "Inherit UNIX domain socket fd=" << fd
+        LOG(INFO) << "Inherit UNIX domain socket fd=" << *fd
                   << ", path=" << path;
       }
 
       InheritedAddr addr{};
       addr.host = make_string_ref(config->balloc, StringRef{path});
       addr.host_unix = true;
-      addr.fd = static_cast<int>(fd);
+      addr.fd = static_cast<int>(*fd);
       iaddrs.push_back(std::move(addr));
     }
 
-    if (type == StringRef::from_lit("tcp")) {
+    if (type == "tcp"_sr) {
       auto fd = util::parse_uint(value);
-      if (fd == -1) {
+      if (!fd) {
         LOG(WARN) << "Could not parse file descriptor from " << value;
         continue;
       }
@@ -1146,11 +1146,11 @@ std::vector<InheritedAddr> get_inherited_addr_from_env(Config *config) {
       sockaddr_union su;
       socklen_t salen = sizeof(su);
 
-      if (getsockname(fd, &su.sa, &salen) != 0) {
+      if (getsockname(*fd, &su.sa, &salen) != 0) {
         auto error = errno;
-        LOG(WARN) << "getsockname() syscall failed (fd=" << fd
+        LOG(WARN) << "getsockname() syscall failed (fd=" << *fd
                   << "): " << xsi_strerror(error, errbuf.data(), errbuf.size());
-        close(fd);
+        close(*fd);
         continue;
       }
 
@@ -1164,7 +1164,7 @@ std::vector<InheritedAddr> get_inherited_addr_from_env(Config *config) {
         port = ntohs(su.in6.sin6_port);
         break;
       default:
-        close(fd);
+        close(*fd);
         continue;
       }
 
@@ -1172,21 +1172,21 @@ std::vector<InheritedAddr> get_inherited_addr_from_env(Config *config) {
       rv = getnameinfo(&su.sa, salen, host.data(), host.size(), nullptr, 0,
                        NI_NUMERICHOST);
       if (rv != 0) {
-        LOG(WARN) << "getnameinfo() failed (fd=" << fd
+        LOG(WARN) << "getnameinfo() failed (fd=" << *fd
                   << "): " << gai_strerror(rv);
-        close(fd);
+        close(*fd);
         continue;
       }
 
       if (LOG_ENABLED(INFO)) {
-        LOG(INFO) << "Inherit TCP socket fd=" << fd
+        LOG(INFO) << "Inherit TCP socket fd=" << *fd
                   << ", address=" << host.data() << ", port=" << port;
       }
 
       InheritedAddr addr{};
       addr.host = make_string_ref(config->balloc, StringRef{host.data()});
       addr.port = static_cast<uint16_t>(port);
-      addr.fd = static_cast<int>(fd);
+      addr.fd = static_cast<int>(*fd);
       iaddrs.push_back(std::move(addr));
       continue;
     }
@@ -1213,11 +1213,11 @@ namespace {
 // Returns the PID of the original main process from environment
 // variable ENV_ORIG_PID.
 pid_t get_orig_pid_from_env() {
-  auto s = getenv(ENV_ORIG_PID.c_str());
+  auto s = getenv(ENV_ORIG_PID.data());
   if (s == nullptr) {
     return -1;
   }
-  return util::parse_uint(s);
+  return util::parse_uint(s).value_or(-1);
 }
 } // namespace
 
@@ -1233,7 +1233,7 @@ get_inherited_quic_lingering_worker_process_from_env() {
   std::vector<QUICLingeringWorkerProcess> lwps;
 
   for (size_t i = 1;; ++i) {
-    auto name = ENV_QUIC_WORKER_PROCESS_PREFIX.str();
+    auto name = std::string{ENV_QUIC_WORKER_PROCESS_PREFIX};
     name += util::utos(i);
     auto env = getenv(name.c_str());
     if (!env) {
@@ -1251,19 +1251,18 @@ get_inherited_quic_lingering_worker_process_from_env() {
       continue;
     }
 
-    auto fd =
-        util::parse_uint(reinterpret_cast<const uint8_t *>(env), end_fd - env);
-    if (fd == -1) {
+    auto fd = util::parse_uint(StringRef{env, end_fd});
+    if (!fd) {
       LOG(WARN) << "Could not parse file descriptor from "
                 << StringRef{env, static_cast<size_t>(end_fd - env)};
       continue;
     }
 
     if (LOG_ENABLED(INFO)) {
-      LOG(INFO) << "Inherit worker process QUIC IPC socket fd=" << fd;
+      LOG(INFO) << "Inherit worker process QUIC IPC socket fd=" << *fd;
     }
 
-    util::make_socket_closeonexec(fd);
+    util::make_socket_closeonexec(*fd);
 
     std::vector<WorkerID> worker_ids;
 
@@ -1294,7 +1293,7 @@ get_inherited_quic_lingering_worker_process_from_env() {
       p = end + 1;
     }
 
-    lwps.emplace_back(std::move(worker_ids), fd);
+    lwps.emplace_back(std::move(worker_ids), *fd);
   }
 
   if (!lwps.empty()) {
@@ -1326,7 +1325,7 @@ int create_acceptor_socket(Config *config, std::vector<InheritedAddr> &iaddrs) {
       if (config->uid != 0) {
         // fd is not associated to inode, so we cannot use fchown(2)
         // here.  https://lkml.org/lkml/2004/11/1/84
-        if (chown(addr.host.c_str(), config->uid, config->gid) == -1) {
+        if (chown(addr.host.data(), config->uid, config->gid) == -1) {
           auto error = errno;
           LOG(WARN) << "Changing owner of UNIX domain socket " << addr.host
                     << " failed: "
@@ -1367,7 +1366,7 @@ namespace {
 // communication is unidirectional; that is main process sends
 // messages to the worker process.  On success, ipc_fd[0] is for
 // reading, and ipc_fd[1] for writing, just like pipe(2).
-int create_ipc_socket(std::array<int, 2> &ipc_fd) {
+int create_ipc_socket(std::span<int, 2> ipc_fd) {
   std::array<char, STRERROR_BUFSIZE> errbuf;
   int rv;
 
@@ -1379,8 +1378,7 @@ int create_ipc_socket(std::array<int, 2> &ipc_fd) {
     return -1;
   }
 
-  for (int i = 0; i < 2; ++i) {
-    auto fd = ipc_fd[i];
+  for (auto fd : ipc_fd) {
     util::make_socket_nonblocking(fd);
     util::make_socket_closeonexec(fd);
   }
@@ -1390,7 +1388,7 @@ int create_ipc_socket(std::array<int, 2> &ipc_fd) {
 } // namespace
 
 namespace {
-int create_worker_process_ready_ipc_socket(std::array<int, 2> &ipc_fd) {
+int create_worker_process_ready_ipc_socket(std::span<int, 2> ipc_fd) {
   std::array<char, STRERROR_BUFSIZE> errbuf;
   int rv;
 
@@ -1415,7 +1413,7 @@ int create_worker_process_ready_ipc_socket(std::array<int, 2> &ipc_fd) {
 
 #ifdef ENABLE_HTTP3
 namespace {
-int create_quic_ipc_socket(std::array<int, 2> &quic_ipc_fd) {
+int create_quic_ipc_socket(std::span<int, 2> quic_ipc_fd) {
   std::array<char, STRERROR_BUFSIZE> errbuf;
   int rv;
 
@@ -1929,30 +1927,29 @@ bool conf_exists(const char *path) {
 } // namespace
 
 namespace {
-constexpr auto DEFAULT_ALPN_LIST =
-    StringRef::from_lit("h2,h2-16,h2-14,http/1.1");
+constexpr auto DEFAULT_ALPN_LIST = "h2,h2-16,h2-14,http/1.1"_sr;
 } // namespace
 
 namespace {
-constexpr auto DEFAULT_TLS_MIN_PROTO_VERSION = StringRef::from_lit("TLSv1.2");
+constexpr auto DEFAULT_TLS_MIN_PROTO_VERSION = "TLSv1.2"_sr;
 #ifdef TLS1_3_VERSION
-constexpr auto DEFAULT_TLS_MAX_PROTO_VERSION = StringRef::from_lit("TLSv1.3");
+constexpr auto DEFAULT_TLS_MAX_PROTO_VERSION = "TLSv1.3"_sr;
 #else  // !TLS1_3_VERSION
-constexpr auto DEFAULT_TLS_MAX_PROTO_VERSION = StringRef::from_lit("TLSv1.2");
+constexpr auto DEFAULT_TLS_MAX_PROTO_VERSION = "TLSv1.2"_sr;
 #endif // !TLS1_3_VERSION
 } // namespace
 
 namespace {
 constexpr auto DEFAULT_ACCESSLOG_FORMAT =
-    StringRef::from_lit(R"($remote_addr - - [$time_local] )"
-                        R"("$request" $status $body_bytes_sent )"
-                        R"("$http_referer" "$http_user_agent")");
+    R"($remote_addr - - [$time_local] )"
+    R"("$request" $status $body_bytes_sent )"
+    R"("$http_referer" "$http_user_agent")"_sr;
 } // namespace
 
 namespace {
 void fill_default_config(Config *config) {
   config->num_worker = 1;
-  config->conf_path = StringRef::from_lit("/etc/nghttpx/nghttpx.conf");
+  config->conf_path = "/etc/nghttpx/nghttpx.conf"_sr;
   config->pid = getpid();
 
 #ifdef NOTHREADS
@@ -1987,8 +1984,7 @@ void fill_default_config(Config *config) {
     auto &ocspconf = tlsconf.ocsp;
     // ocsp update interval = 14400 secs = 4 hours, borrowed from h2o
     ocspconf.update_interval = 4_h;
-    ocspconf.fetch_ocsp_response_file =
-        StringRef::from_lit(PKGDATADIR "/fetch-ocsp-response");
+    ocspconf.fetch_ocsp_response_file = PKGDATADIR "/fetch-ocsp-response"_sr;
   }
 
   {
@@ -1998,28 +1994,26 @@ void fill_default_config(Config *config) {
   }
 
   tlsconf.session_timeout = std::chrono::hours(12);
-  tlsconf.ciphers = StringRef::from_lit(nghttp2::tls::DEFAULT_CIPHER_LIST);
-  tlsconf.tls13_ciphers =
-      StringRef::from_lit(nghttp2::tls::DEFAULT_TLS13_CIPHER_LIST);
-  tlsconf.client.ciphers =
-      StringRef::from_lit(nghttp2::tls::DEFAULT_CIPHER_LIST);
+  tlsconf.ciphers = StringRef{nghttp2::tls::DEFAULT_CIPHER_LIST};
+  tlsconf.tls13_ciphers = StringRef{nghttp2::tls::DEFAULT_TLS13_CIPHER_LIST};
+  tlsconf.client.ciphers = StringRef{nghttp2::tls::DEFAULT_CIPHER_LIST};
   tlsconf.client.tls13_ciphers =
-      StringRef::from_lit(nghttp2::tls::DEFAULT_TLS13_CIPHER_LIST);
+      StringRef{nghttp2::tls::DEFAULT_TLS13_CIPHER_LIST};
   tlsconf.min_proto_version =
       tls::proto_version_from_string(DEFAULT_TLS_MIN_PROTO_VERSION);
   tlsconf.max_proto_version =
       tls::proto_version_from_string(DEFAULT_TLS_MAX_PROTO_VERSION);
   tlsconf.max_early_data = 16_k;
-  tlsconf.ecdh_curves = StringRef::from_lit("X25519:P-256:P-384:P-521");
+  tlsconf.ecdh_curves = "X25519:P-256:P-384:P-521"_sr;
 
   auto &httpconf = config->http;
-  httpconf.server_name = StringRef::from_lit("nghttpx");
+  httpconf.server_name = "nghttpx"_sr;
   httpconf.no_host_rewrite = true;
   httpconf.request_header_field_buffer = 64_k;
   httpconf.max_request_header_fields = 100;
   httpconf.response_header_field_buffer = 64_k;
   httpconf.max_response_header_fields = 500;
-  httpconf.redirect_https_port = StringRef::from_lit("443");
+  httpconf.redirect_https_port = "443"_sr;
   httpconf.max_requests = std::numeric_limits<size_t>::max();
   httpconf.xfp.add = true;
   httpconf.xfp.strip_incoming = true;
@@ -2099,7 +2093,7 @@ void fill_default_config(Config *config) {
     }
 
     auto &bpfconf = quicconf.bpf;
-    bpfconf.prog_file = StringRef::from_lit(PKGLIBDIR "/reuseport_kern.o");
+    bpfconf.prog_file = PKGLIBDIR "/reuseport_kern.o"_sr;
 
     upstreamconf.congestion_controller = NGTCP2_CC_ALGO_CUBIC;
 
@@ -2132,7 +2126,7 @@ void fill_default_config(Config *config) {
         parse_log_format(config->balloc, DEFAULT_ACCESSLOG_FORMAT);
 
     auto &errorconf = loggingconf.error;
-    errorconf.file = StringRef::from_lit("/dev/stderr");
+    errorconf.file = "/dev/stderr"_sr;
   }
 
   loggingconf.syslog_facility = LOG_DAEMON;
@@ -3659,10 +3653,10 @@ int process_options(Config *config,
                     std::vector<std::pair<StringRef, StringRef>> &cmdcfgs) {
   std::array<char, STRERROR_BUFSIZE> errbuf;
   std::map<StringRef, size_t> pattern_addr_indexer;
-  if (conf_exists(config->conf_path.c_str())) {
+  if (conf_exists(config->conf_path.data())) {
     LOG(NOTICE) << "Loading configuration from " << config->conf_path;
     std::set<StringRef> include_set;
-    if (load_config(config, config->conf_path.c_str(), include_set,
+    if (load_config(config, config->conf_path.data(), include_set,
                     pattern_addr_indexer) == -1) {
       LOG(FATAL) << "Failed to load configuration from " << config->conf_path;
       return -1;
@@ -3728,7 +3722,7 @@ int process_options(Config *config,
     auto &dumpconf = http2conf.upstream.debug.dump;
 
     if (!dumpconf.request_header_file.empty()) {
-      auto path = dumpconf.request_header_file.c_str();
+      auto path = dumpconf.request_header_file.data();
       auto f = open_file_for_write(path);
 
       if (f == nullptr) {
@@ -3750,7 +3744,7 @@ int process_options(Config *config,
     }
 
     if (!dumpconf.response_header_file.empty()) {
-      auto path = dumpconf.response_header_file.c_str();
+      auto path = dumpconf.response_header_file.data();
       auto f = open_file_for_write(path);
 
       if (f == nullptr) {
@@ -3801,7 +3795,7 @@ int process_options(Config *config,
 
   if (listenerconf.addrs.empty()) {
     UpstreamAddr addr{};
-    addr.host = StringRef::from_lit("*");
+    addr.host = "*"_sr;
     addr.port = 3000;
     addr.tls = true;
     addr.family = AF_INET;
@@ -3826,7 +3820,7 @@ int process_options(Config *config,
 
   if (tls::upstream_tls_enabled(config->conn) && !tlsconf.ocsp.disabled) {
     struct stat buf;
-    if (stat(tlsconf.ocsp.fetch_ocsp_response_file.c_str(), &buf) != 0) {
+    if (stat(tlsconf.ocsp.fetch_ocsp_response_file.data(), &buf) != 0) {
       tlsconf.ocsp.disabled = true;
       LOG(WARN) << "--fetch-ocsp-response-file: "
                 << tlsconf.ocsp.fetch_ocsp_response_file
@@ -3845,7 +3839,7 @@ int process_options(Config *config,
   if (!proxy.host.empty()) {
     auto hostport = util::make_hostport(std::begin(hostport_buf),
                                         StringRef{proxy.host}, proxy.port);
-    if (resolve_hostname(&proxy.addr, proxy.host.c_str(), proxy.port,
+    if (resolve_hostname(&proxy.addr, proxy.host.data(), proxy.port,
                          AF_UNSPEC) == -1) {
       LOG(FATAL) << "Resolving backend HTTP proxy address failed: " << hostport;
       return -1;
@@ -3860,7 +3854,7 @@ int process_options(Config *config,
       auto hostport = util::make_hostport(std::begin(hostport_buf),
                                           StringRef{memcachedconf.host},
                                           memcachedconf.port);
-      if (resolve_hostname(&memcachedconf.addr, memcachedconf.host.c_str(),
+      if (resolve_hostname(&memcachedconf.addr, memcachedconf.host.data(),
                            memcachedconf.port, memcachedconf.family) == -1) {
         LOG(FATAL)
             << "Resolving memcached address for TLS session cache failed: "
@@ -3882,7 +3876,7 @@ int process_options(Config *config,
       auto hostport = util::make_hostport(std::begin(hostport_buf),
                                           StringRef{memcachedconf.host},
                                           memcachedconf.port);
-      if (resolve_hostname(&memcachedconf.addr, memcachedconf.host.c_str(),
+      if (resolve_hostname(&memcachedconf.addr, memcachedconf.host.data(),
                            memcachedconf.port, memcachedconf.family) == -1) {
         LOG(FATAL) << "Resolving memcached address for TLS ticket key failed: "
                    << hostport;
@@ -3925,12 +3919,12 @@ int process_options(Config *config,
       fwdconf.by_obfuscated.empty()) {
     // 2 for '_' and terminal NULL
     auto iov = make_byte_ref(config->balloc, SHRPX_OBFUSCATED_NODE_LENGTH + 2);
-    auto p = iov.base;
+    auto p = std::begin(iov);
     *p++ = '_';
     auto gen = util::make_mt19937();
     p = util::random_alpha_digit(p, p + SHRPX_OBFUSCATED_NODE_LENGTH, gen);
     *p = '\0';
-    fwdconf.by_obfuscated = StringRef{iov.base, p};
+    fwdconf.by_obfuscated = StringRef{std::span{std::begin(iov), p}};
   }
 
   if (config->http2.upstream.debug.frame_debug) {
@@ -4124,292 +4118,285 @@ int main(int argc, char **argv) {
   while (1) {
     static int flag = 0;
     static constexpr option long_options[] = {
-        {SHRPX_OPT_DAEMON.c_str(), no_argument, nullptr, 'D'},
-        {SHRPX_OPT_LOG_LEVEL.c_str(), required_argument, nullptr, 'L'},
-        {SHRPX_OPT_BACKEND.c_str(), required_argument, nullptr, 'b'},
-        {SHRPX_OPT_HTTP2_MAX_CONCURRENT_STREAMS.c_str(), required_argument,
+        {SHRPX_OPT_DAEMON.data(), no_argument, nullptr, 'D'},
+        {SHRPX_OPT_LOG_LEVEL.data(), required_argument, nullptr, 'L'},
+        {SHRPX_OPT_BACKEND.data(), required_argument, nullptr, 'b'},
+        {SHRPX_OPT_HTTP2_MAX_CONCURRENT_STREAMS.data(), required_argument,
          nullptr, 'c'},
-        {SHRPX_OPT_FRONTEND.c_str(), required_argument, nullptr, 'f'},
+        {SHRPX_OPT_FRONTEND.data(), required_argument, nullptr, 'f'},
         {"help", no_argument, nullptr, 'h'},
-        {SHRPX_OPT_INSECURE.c_str(), no_argument, nullptr, 'k'},
-        {SHRPX_OPT_WORKERS.c_str(), required_argument, nullptr, 'n'},
-        {SHRPX_OPT_CLIENT_PROXY.c_str(), no_argument, nullptr, 'p'},
-        {SHRPX_OPT_HTTP2_PROXY.c_str(), no_argument, nullptr, 's'},
+        {SHRPX_OPT_INSECURE.data(), no_argument, nullptr, 'k'},
+        {SHRPX_OPT_WORKERS.data(), required_argument, nullptr, 'n'},
+        {SHRPX_OPT_CLIENT_PROXY.data(), no_argument, nullptr, 'p'},
+        {SHRPX_OPT_HTTP2_PROXY.data(), no_argument, nullptr, 's'},
         {"version", no_argument, nullptr, 'v'},
-        {SHRPX_OPT_FRONTEND_FRAME_DEBUG.c_str(), no_argument, nullptr, 'o'},
-        {SHRPX_OPT_ADD_X_FORWARDED_FOR.c_str(), no_argument, &flag, 1},
-        {SHRPX_OPT_FRONTEND_HTTP2_READ_TIMEOUT.c_str(), required_argument,
-         &flag, 2},
-        {SHRPX_OPT_FRONTEND_READ_TIMEOUT.c_str(), required_argument, &flag, 3},
-        {SHRPX_OPT_FRONTEND_WRITE_TIMEOUT.c_str(), required_argument, &flag, 4},
-        {SHRPX_OPT_BACKEND_READ_TIMEOUT.c_str(), required_argument, &flag, 5},
-        {SHRPX_OPT_BACKEND_WRITE_TIMEOUT.c_str(), required_argument, &flag, 6},
-        {SHRPX_OPT_ACCESSLOG_FILE.c_str(), required_argument, &flag, 7},
-        {SHRPX_OPT_BACKEND_KEEP_ALIVE_TIMEOUT.c_str(), required_argument, &flag,
+        {SHRPX_OPT_FRONTEND_FRAME_DEBUG.data(), no_argument, nullptr, 'o'},
+        {SHRPX_OPT_ADD_X_FORWARDED_FOR.data(), no_argument, &flag, 1},
+        {SHRPX_OPT_FRONTEND_HTTP2_READ_TIMEOUT.data(), required_argument, &flag,
+         2},
+        {SHRPX_OPT_FRONTEND_READ_TIMEOUT.data(), required_argument, &flag, 3},
+        {SHRPX_OPT_FRONTEND_WRITE_TIMEOUT.data(), required_argument, &flag, 4},
+        {SHRPX_OPT_BACKEND_READ_TIMEOUT.data(), required_argument, &flag, 5},
+        {SHRPX_OPT_BACKEND_WRITE_TIMEOUT.data(), required_argument, &flag, 6},
+        {SHRPX_OPT_ACCESSLOG_FILE.data(), required_argument, &flag, 7},
+        {SHRPX_OPT_BACKEND_KEEP_ALIVE_TIMEOUT.data(), required_argument, &flag,
          8},
-        {SHRPX_OPT_FRONTEND_HTTP2_WINDOW_BITS.c_str(), required_argument, &flag,
+        {SHRPX_OPT_FRONTEND_HTTP2_WINDOW_BITS.data(), required_argument, &flag,
          9},
-        {SHRPX_OPT_PID_FILE.c_str(), required_argument, &flag, 10},
-        {SHRPX_OPT_USER.c_str(), required_argument, &flag, 11},
+        {SHRPX_OPT_PID_FILE.data(), required_argument, &flag, 10},
+        {SHRPX_OPT_USER.data(), required_argument, &flag, 11},
         {"conf", required_argument, &flag, 12},
-        {SHRPX_OPT_SYSLOG_FACILITY.c_str(), required_argument, &flag, 14},
-        {SHRPX_OPT_BACKLOG.c_str(), required_argument, &flag, 15},
-        {SHRPX_OPT_CIPHERS.c_str(), required_argument, &flag, 16},
-        {SHRPX_OPT_CLIENT.c_str(), no_argument, &flag, 17},
-        {SHRPX_OPT_BACKEND_HTTP2_WINDOW_BITS.c_str(), required_argument, &flag,
+        {SHRPX_OPT_SYSLOG_FACILITY.data(), required_argument, &flag, 14},
+        {SHRPX_OPT_BACKLOG.data(), required_argument, &flag, 15},
+        {SHRPX_OPT_CIPHERS.data(), required_argument, &flag, 16},
+        {SHRPX_OPT_CLIENT.data(), no_argument, &flag, 17},
+        {SHRPX_OPT_BACKEND_HTTP2_WINDOW_BITS.data(), required_argument, &flag,
          18},
-        {SHRPX_OPT_CACERT.c_str(), required_argument, &flag, 19},
-        {SHRPX_OPT_BACKEND_IPV4.c_str(), no_argument, &flag, 20},
-        {SHRPX_OPT_BACKEND_IPV6.c_str(), no_argument, &flag, 21},
-        {SHRPX_OPT_PRIVATE_KEY_PASSWD_FILE.c_str(), required_argument, &flag,
+        {SHRPX_OPT_CACERT.data(), required_argument, &flag, 19},
+        {SHRPX_OPT_BACKEND_IPV4.data(), no_argument, &flag, 20},
+        {SHRPX_OPT_BACKEND_IPV6.data(), no_argument, &flag, 21},
+        {SHRPX_OPT_PRIVATE_KEY_PASSWD_FILE.data(), required_argument, &flag,
          22},
-        {SHRPX_OPT_NO_VIA.c_str(), no_argument, &flag, 23},
-        {SHRPX_OPT_SUBCERT.c_str(), required_argument, &flag, 24},
-        {SHRPX_OPT_HTTP2_BRIDGE.c_str(), no_argument, &flag, 25},
-        {SHRPX_OPT_BACKEND_HTTP_PROXY_URI.c_str(), required_argument, &flag,
-         26},
-        {SHRPX_OPT_BACKEND_NO_TLS.c_str(), no_argument, &flag, 27},
-        {SHRPX_OPT_OCSP_STARTUP.c_str(), no_argument, &flag, 28},
-        {SHRPX_OPT_FRONTEND_NO_TLS.c_str(), no_argument, &flag, 29},
-        {SHRPX_OPT_NO_VERIFY_OCSP.c_str(), no_argument, &flag, 30},
-        {SHRPX_OPT_BACKEND_TLS_SNI_FIELD.c_str(), required_argument, &flag, 31},
-        {SHRPX_OPT_DH_PARAM_FILE.c_str(), required_argument, &flag, 33},
-        {SHRPX_OPT_READ_RATE.c_str(), required_argument, &flag, 34},
-        {SHRPX_OPT_READ_BURST.c_str(), required_argument, &flag, 35},
-        {SHRPX_OPT_WRITE_RATE.c_str(), required_argument, &flag, 36},
-        {SHRPX_OPT_WRITE_BURST.c_str(), required_argument, &flag, 37},
-        {SHRPX_OPT_NPN_LIST.c_str(), required_argument, &flag, 38},
-        {SHRPX_OPT_VERIFY_CLIENT.c_str(), no_argument, &flag, 39},
-        {SHRPX_OPT_VERIFY_CLIENT_CACERT.c_str(), required_argument, &flag, 40},
-        {SHRPX_OPT_CLIENT_PRIVATE_KEY_FILE.c_str(), required_argument, &flag,
+        {SHRPX_OPT_NO_VIA.data(), no_argument, &flag, 23},
+        {SHRPX_OPT_SUBCERT.data(), required_argument, &flag, 24},
+        {SHRPX_OPT_HTTP2_BRIDGE.data(), no_argument, &flag, 25},
+        {SHRPX_OPT_BACKEND_HTTP_PROXY_URI.data(), required_argument, &flag, 26},
+        {SHRPX_OPT_BACKEND_NO_TLS.data(), no_argument, &flag, 27},
+        {SHRPX_OPT_OCSP_STARTUP.data(), no_argument, &flag, 28},
+        {SHRPX_OPT_FRONTEND_NO_TLS.data(), no_argument, &flag, 29},
+        {SHRPX_OPT_NO_VERIFY_OCSP.data(), no_argument, &flag, 30},
+        {SHRPX_OPT_BACKEND_TLS_SNI_FIELD.data(), required_argument, &flag, 31},
+        {SHRPX_OPT_DH_PARAM_FILE.data(), required_argument, &flag, 33},
+        {SHRPX_OPT_READ_RATE.data(), required_argument, &flag, 34},
+        {SHRPX_OPT_READ_BURST.data(), required_argument, &flag, 35},
+        {SHRPX_OPT_WRITE_RATE.data(), required_argument, &flag, 36},
+        {SHRPX_OPT_WRITE_BURST.data(), required_argument, &flag, 37},
+        {SHRPX_OPT_NPN_LIST.data(), required_argument, &flag, 38},
+        {SHRPX_OPT_VERIFY_CLIENT.data(), no_argument, &flag, 39},
+        {SHRPX_OPT_VERIFY_CLIENT_CACERT.data(), required_argument, &flag, 40},
+        {SHRPX_OPT_CLIENT_PRIVATE_KEY_FILE.data(), required_argument, &flag,
          41},
-        {SHRPX_OPT_CLIENT_CERT_FILE.c_str(), required_argument, &flag, 42},
-        {SHRPX_OPT_FRONTEND_HTTP2_DUMP_REQUEST_HEADER.c_str(),
-         required_argument, &flag, 43},
-        {SHRPX_OPT_FRONTEND_HTTP2_DUMP_RESPONSE_HEADER.c_str(),
+        {SHRPX_OPT_CLIENT_CERT_FILE.data(), required_argument, &flag, 42},
+        {SHRPX_OPT_FRONTEND_HTTP2_DUMP_REQUEST_HEADER.data(), required_argument,
+         &flag, 43},
+        {SHRPX_OPT_FRONTEND_HTTP2_DUMP_RESPONSE_HEADER.data(),
          required_argument, &flag, 44},
-        {SHRPX_OPT_HTTP2_NO_COOKIE_CRUMBLING.c_str(), no_argument, &flag, 45},
-        {SHRPX_OPT_FRONTEND_HTTP2_CONNECTION_WINDOW_BITS.c_str(),
+        {SHRPX_OPT_HTTP2_NO_COOKIE_CRUMBLING.data(), no_argument, &flag, 45},
+        {SHRPX_OPT_FRONTEND_HTTP2_CONNECTION_WINDOW_BITS.data(),
          required_argument, &flag, 46},
-        {SHRPX_OPT_BACKEND_HTTP2_CONNECTION_WINDOW_BITS.c_str(),
+        {SHRPX_OPT_BACKEND_HTTP2_CONNECTION_WINDOW_BITS.data(),
          required_argument, &flag, 47},
-        {SHRPX_OPT_TLS_PROTO_LIST.c_str(), required_argument, &flag, 48},
-        {SHRPX_OPT_PADDING.c_str(), required_argument, &flag, 49},
-        {SHRPX_OPT_WORKER_READ_RATE.c_str(), required_argument, &flag, 50},
-        {SHRPX_OPT_WORKER_READ_BURST.c_str(), required_argument, &flag, 51},
-        {SHRPX_OPT_WORKER_WRITE_RATE.c_str(), required_argument, &flag, 52},
-        {SHRPX_OPT_WORKER_WRITE_BURST.c_str(), required_argument, &flag, 53},
-        {SHRPX_OPT_ALTSVC.c_str(), required_argument, &flag, 54},
-        {SHRPX_OPT_ADD_RESPONSE_HEADER.c_str(), required_argument, &flag, 55},
-        {SHRPX_OPT_WORKER_FRONTEND_CONNECTIONS.c_str(), required_argument,
-         &flag, 56},
-        {SHRPX_OPT_ACCESSLOG_SYSLOG.c_str(), no_argument, &flag, 57},
-        {SHRPX_OPT_ERRORLOG_FILE.c_str(), required_argument, &flag, 58},
-        {SHRPX_OPT_ERRORLOG_SYSLOG.c_str(), no_argument, &flag, 59},
-        {SHRPX_OPT_STREAM_READ_TIMEOUT.c_str(), required_argument, &flag, 60},
-        {SHRPX_OPT_STREAM_WRITE_TIMEOUT.c_str(), required_argument, &flag, 61},
-        {SHRPX_OPT_NO_LOCATION_REWRITE.c_str(), no_argument, &flag, 62},
-        {SHRPX_OPT_BACKEND_HTTP1_CONNECTIONS_PER_HOST.c_str(),
-         required_argument, &flag, 63},
-        {SHRPX_OPT_LISTENER_DISABLE_TIMEOUT.c_str(), required_argument, &flag,
+        {SHRPX_OPT_TLS_PROTO_LIST.data(), required_argument, &flag, 48},
+        {SHRPX_OPT_PADDING.data(), required_argument, &flag, 49},
+        {SHRPX_OPT_WORKER_READ_RATE.data(), required_argument, &flag, 50},
+        {SHRPX_OPT_WORKER_READ_BURST.data(), required_argument, &flag, 51},
+        {SHRPX_OPT_WORKER_WRITE_RATE.data(), required_argument, &flag, 52},
+        {SHRPX_OPT_WORKER_WRITE_BURST.data(), required_argument, &flag, 53},
+        {SHRPX_OPT_ALTSVC.data(), required_argument, &flag, 54},
+        {SHRPX_OPT_ADD_RESPONSE_HEADER.data(), required_argument, &flag, 55},
+        {SHRPX_OPT_WORKER_FRONTEND_CONNECTIONS.data(), required_argument, &flag,
+         56},
+        {SHRPX_OPT_ACCESSLOG_SYSLOG.data(), no_argument, &flag, 57},
+        {SHRPX_OPT_ERRORLOG_FILE.data(), required_argument, &flag, 58},
+        {SHRPX_OPT_ERRORLOG_SYSLOG.data(), no_argument, &flag, 59},
+        {SHRPX_OPT_STREAM_READ_TIMEOUT.data(), required_argument, &flag, 60},
+        {SHRPX_OPT_STREAM_WRITE_TIMEOUT.data(), required_argument, &flag, 61},
+        {SHRPX_OPT_NO_LOCATION_REWRITE.data(), no_argument, &flag, 62},
+        {SHRPX_OPT_BACKEND_HTTP1_CONNECTIONS_PER_HOST.data(), required_argument,
+         &flag, 63},
+        {SHRPX_OPT_LISTENER_DISABLE_TIMEOUT.data(), required_argument, &flag,
          64},
-        {SHRPX_OPT_STRIP_INCOMING_X_FORWARDED_FOR.c_str(), no_argument, &flag,
+        {SHRPX_OPT_STRIP_INCOMING_X_FORWARDED_FOR.data(), no_argument, &flag,
          65},
-        {SHRPX_OPT_ACCESSLOG_FORMAT.c_str(), required_argument, &flag, 66},
-        {SHRPX_OPT_BACKEND_HTTP1_CONNECTIONS_PER_FRONTEND.c_str(),
+        {SHRPX_OPT_ACCESSLOG_FORMAT.data(), required_argument, &flag, 66},
+        {SHRPX_OPT_BACKEND_HTTP1_CONNECTIONS_PER_FRONTEND.data(),
          required_argument, &flag, 67},
-        {SHRPX_OPT_TLS_TICKET_KEY_FILE.c_str(), required_argument, &flag, 68},
-        {SHRPX_OPT_RLIMIT_NOFILE.c_str(), required_argument, &flag, 69},
-        {SHRPX_OPT_BACKEND_RESPONSE_BUFFER.c_str(), required_argument, &flag,
+        {SHRPX_OPT_TLS_TICKET_KEY_FILE.data(), required_argument, &flag, 68},
+        {SHRPX_OPT_RLIMIT_NOFILE.data(), required_argument, &flag, 69},
+        {SHRPX_OPT_BACKEND_RESPONSE_BUFFER.data(), required_argument, &flag,
          71},
-        {SHRPX_OPT_BACKEND_REQUEST_BUFFER.c_str(), required_argument, &flag,
-         72},
-        {SHRPX_OPT_NO_HOST_REWRITE.c_str(), no_argument, &flag, 73},
-        {SHRPX_OPT_NO_SERVER_PUSH.c_str(), no_argument, &flag, 74},
-        {SHRPX_OPT_BACKEND_HTTP2_CONNECTIONS_PER_WORKER.c_str(),
+        {SHRPX_OPT_BACKEND_REQUEST_BUFFER.data(), required_argument, &flag, 72},
+        {SHRPX_OPT_NO_HOST_REWRITE.data(), no_argument, &flag, 73},
+        {SHRPX_OPT_NO_SERVER_PUSH.data(), no_argument, &flag, 74},
+        {SHRPX_OPT_BACKEND_HTTP2_CONNECTIONS_PER_WORKER.data(),
          required_argument, &flag, 76},
-        {SHRPX_OPT_FETCH_OCSP_RESPONSE_FILE.c_str(), required_argument, &flag,
+        {SHRPX_OPT_FETCH_OCSP_RESPONSE_FILE.data(), required_argument, &flag,
          77},
-        {SHRPX_OPT_OCSP_UPDATE_INTERVAL.c_str(), required_argument, &flag, 78},
-        {SHRPX_OPT_NO_OCSP.c_str(), no_argument, &flag, 79},
-        {SHRPX_OPT_HEADER_FIELD_BUFFER.c_str(), required_argument, &flag, 80},
-        {SHRPX_OPT_MAX_HEADER_FIELDS.c_str(), required_argument, &flag, 81},
-        {SHRPX_OPT_ADD_REQUEST_HEADER.c_str(), required_argument, &flag, 82},
-        {SHRPX_OPT_INCLUDE.c_str(), required_argument, &flag, 83},
-        {SHRPX_OPT_TLS_TICKET_KEY_CIPHER.c_str(), required_argument, &flag, 84},
-        {SHRPX_OPT_HOST_REWRITE.c_str(), no_argument, &flag, 85},
-        {SHRPX_OPT_TLS_SESSION_CACHE_MEMCACHED.c_str(), required_argument,
-         &flag, 86},
-        {SHRPX_OPT_TLS_TICKET_KEY_MEMCACHED.c_str(), required_argument, &flag,
+        {SHRPX_OPT_OCSP_UPDATE_INTERVAL.data(), required_argument, &flag, 78},
+        {SHRPX_OPT_NO_OCSP.data(), no_argument, &flag, 79},
+        {SHRPX_OPT_HEADER_FIELD_BUFFER.data(), required_argument, &flag, 80},
+        {SHRPX_OPT_MAX_HEADER_FIELDS.data(), required_argument, &flag, 81},
+        {SHRPX_OPT_ADD_REQUEST_HEADER.data(), required_argument, &flag, 82},
+        {SHRPX_OPT_INCLUDE.data(), required_argument, &flag, 83},
+        {SHRPX_OPT_TLS_TICKET_KEY_CIPHER.data(), required_argument, &flag, 84},
+        {SHRPX_OPT_HOST_REWRITE.data(), no_argument, &flag, 85},
+        {SHRPX_OPT_TLS_SESSION_CACHE_MEMCACHED.data(), required_argument, &flag,
+         86},
+        {SHRPX_OPT_TLS_TICKET_KEY_MEMCACHED.data(), required_argument, &flag,
          87},
-        {SHRPX_OPT_TLS_TICKET_KEY_MEMCACHED_INTERVAL.c_str(), required_argument,
+        {SHRPX_OPT_TLS_TICKET_KEY_MEMCACHED_INTERVAL.data(), required_argument,
          &flag, 88},
-        {SHRPX_OPT_TLS_TICKET_KEY_MEMCACHED_MAX_RETRY.c_str(),
-         required_argument, &flag, 89},
-        {SHRPX_OPT_TLS_TICKET_KEY_MEMCACHED_MAX_FAIL.c_str(), required_argument,
+        {SHRPX_OPT_TLS_TICKET_KEY_MEMCACHED_MAX_RETRY.data(), required_argument,
+         &flag, 89},
+        {SHRPX_OPT_TLS_TICKET_KEY_MEMCACHED_MAX_FAIL.data(), required_argument,
          &flag, 90},
-        {SHRPX_OPT_MRUBY_FILE.c_str(), required_argument, &flag, 91},
-        {SHRPX_OPT_ACCEPT_PROXY_PROTOCOL.c_str(), no_argument, &flag, 93},
-        {SHRPX_OPT_FASTOPEN.c_str(), required_argument, &flag, 94},
-        {SHRPX_OPT_TLS_DYN_REC_WARMUP_THRESHOLD.c_str(), required_argument,
+        {SHRPX_OPT_MRUBY_FILE.data(), required_argument, &flag, 91},
+        {SHRPX_OPT_ACCEPT_PROXY_PROTOCOL.data(), no_argument, &flag, 93},
+        {SHRPX_OPT_FASTOPEN.data(), required_argument, &flag, 94},
+        {SHRPX_OPT_TLS_DYN_REC_WARMUP_THRESHOLD.data(), required_argument,
          &flag, 95},
-        {SHRPX_OPT_TLS_DYN_REC_IDLE_TIMEOUT.c_str(), required_argument, &flag,
+        {SHRPX_OPT_TLS_DYN_REC_IDLE_TIMEOUT.data(), required_argument, &flag,
          96},
-        {SHRPX_OPT_ADD_FORWARDED.c_str(), required_argument, &flag, 97},
-        {SHRPX_OPT_STRIP_INCOMING_FORWARDED.c_str(), no_argument, &flag, 98},
-        {SHRPX_OPT_FORWARDED_BY.c_str(), required_argument, &flag, 99},
-        {SHRPX_OPT_FORWARDED_FOR.c_str(), required_argument, &flag, 100},
-        {SHRPX_OPT_RESPONSE_HEADER_FIELD_BUFFER.c_str(), required_argument,
+        {SHRPX_OPT_ADD_FORWARDED.data(), required_argument, &flag, 97},
+        {SHRPX_OPT_STRIP_INCOMING_FORWARDED.data(), no_argument, &flag, 98},
+        {SHRPX_OPT_FORWARDED_BY.data(), required_argument, &flag, 99},
+        {SHRPX_OPT_FORWARDED_FOR.data(), required_argument, &flag, 100},
+        {SHRPX_OPT_RESPONSE_HEADER_FIELD_BUFFER.data(), required_argument,
          &flag, 101},
-        {SHRPX_OPT_MAX_RESPONSE_HEADER_FIELDS.c_str(), required_argument, &flag,
+        {SHRPX_OPT_MAX_RESPONSE_HEADER_FIELDS.data(), required_argument, &flag,
          102},
-        {SHRPX_OPT_NO_HTTP2_CIPHER_BLACK_LIST.c_str(), no_argument, &flag, 103},
-        {SHRPX_OPT_REQUEST_HEADER_FIELD_BUFFER.c_str(), required_argument,
-         &flag, 104},
-        {SHRPX_OPT_MAX_REQUEST_HEADER_FIELDS.c_str(), required_argument, &flag,
+        {SHRPX_OPT_NO_HTTP2_CIPHER_BLACK_LIST.data(), no_argument, &flag, 103},
+        {SHRPX_OPT_REQUEST_HEADER_FIELD_BUFFER.data(), required_argument, &flag,
+         104},
+        {SHRPX_OPT_MAX_REQUEST_HEADER_FIELDS.data(), required_argument, &flag,
          105},
-        {SHRPX_OPT_BACKEND_HTTP1_TLS.c_str(), no_argument, &flag, 106},
-        {SHRPX_OPT_TLS_SESSION_CACHE_MEMCACHED_TLS.c_str(), no_argument, &flag,
+        {SHRPX_OPT_BACKEND_HTTP1_TLS.data(), no_argument, &flag, 106},
+        {SHRPX_OPT_TLS_SESSION_CACHE_MEMCACHED_TLS.data(), no_argument, &flag,
          108},
-        {SHRPX_OPT_TLS_SESSION_CACHE_MEMCACHED_CERT_FILE.c_str(),
+        {SHRPX_OPT_TLS_SESSION_CACHE_MEMCACHED_CERT_FILE.data(),
          required_argument, &flag, 109},
-        {SHRPX_OPT_TLS_SESSION_CACHE_MEMCACHED_PRIVATE_KEY_FILE.c_str(),
+        {SHRPX_OPT_TLS_SESSION_CACHE_MEMCACHED_PRIVATE_KEY_FILE.data(),
          required_argument, &flag, 110},
-        {SHRPX_OPT_TLS_TICKET_KEY_MEMCACHED_TLS.c_str(), no_argument, &flag,
+        {SHRPX_OPT_TLS_TICKET_KEY_MEMCACHED_TLS.data(), no_argument, &flag,
          111},
-        {SHRPX_OPT_TLS_TICKET_KEY_MEMCACHED_CERT_FILE.c_str(),
-         required_argument, &flag, 112},
-        {SHRPX_OPT_TLS_TICKET_KEY_MEMCACHED_PRIVATE_KEY_FILE.c_str(),
+        {SHRPX_OPT_TLS_TICKET_KEY_MEMCACHED_CERT_FILE.data(), required_argument,
+         &flag, 112},
+        {SHRPX_OPT_TLS_TICKET_KEY_MEMCACHED_PRIVATE_KEY_FILE.data(),
          required_argument, &flag, 113},
-        {SHRPX_OPT_TLS_TICKET_KEY_MEMCACHED_ADDRESS_FAMILY.c_str(),
+        {SHRPX_OPT_TLS_TICKET_KEY_MEMCACHED_ADDRESS_FAMILY.data(),
          required_argument, &flag, 114},
-        {SHRPX_OPT_TLS_SESSION_CACHE_MEMCACHED_ADDRESS_FAMILY.c_str(),
+        {SHRPX_OPT_TLS_SESSION_CACHE_MEMCACHED_ADDRESS_FAMILY.data(),
          required_argument, &flag, 115},
-        {SHRPX_OPT_BACKEND_ADDRESS_FAMILY.c_str(), required_argument, &flag,
+        {SHRPX_OPT_BACKEND_ADDRESS_FAMILY.data(), required_argument, &flag,
          116},
-        {SHRPX_OPT_FRONTEND_HTTP2_MAX_CONCURRENT_STREAMS.c_str(),
+        {SHRPX_OPT_FRONTEND_HTTP2_MAX_CONCURRENT_STREAMS.data(),
          required_argument, &flag, 117},
-        {SHRPX_OPT_BACKEND_HTTP2_MAX_CONCURRENT_STREAMS.c_str(),
+        {SHRPX_OPT_BACKEND_HTTP2_MAX_CONCURRENT_STREAMS.data(),
          required_argument, &flag, 118},
-        {SHRPX_OPT_BACKEND_CONNECTIONS_PER_FRONTEND.c_str(), required_argument,
+        {SHRPX_OPT_BACKEND_CONNECTIONS_PER_FRONTEND.data(), required_argument,
          &flag, 119},
-        {SHRPX_OPT_BACKEND_TLS.c_str(), no_argument, &flag, 120},
-        {SHRPX_OPT_BACKEND_CONNECTIONS_PER_HOST.c_str(), required_argument,
+        {SHRPX_OPT_BACKEND_TLS.data(), no_argument, &flag, 120},
+        {SHRPX_OPT_BACKEND_CONNECTIONS_PER_HOST.data(), required_argument,
          &flag, 121},
-        {SHRPX_OPT_ERROR_PAGE.c_str(), required_argument, &flag, 122},
-        {SHRPX_OPT_NO_KQUEUE.c_str(), no_argument, &flag, 123},
-        {SHRPX_OPT_FRONTEND_HTTP2_SETTINGS_TIMEOUT.c_str(), required_argument,
+        {SHRPX_OPT_ERROR_PAGE.data(), required_argument, &flag, 122},
+        {SHRPX_OPT_NO_KQUEUE.data(), no_argument, &flag, 123},
+        {SHRPX_OPT_FRONTEND_HTTP2_SETTINGS_TIMEOUT.data(), required_argument,
          &flag, 124},
-        {SHRPX_OPT_BACKEND_HTTP2_SETTINGS_TIMEOUT.c_str(), required_argument,
+        {SHRPX_OPT_BACKEND_HTTP2_SETTINGS_TIMEOUT.data(), required_argument,
          &flag, 125},
-        {SHRPX_OPT_API_MAX_REQUEST_BODY.c_str(), required_argument, &flag, 126},
-        {SHRPX_OPT_BACKEND_MAX_BACKOFF.c_str(), required_argument, &flag, 127},
-        {SHRPX_OPT_SERVER_NAME.c_str(), required_argument, &flag, 128},
-        {SHRPX_OPT_NO_SERVER_REWRITE.c_str(), no_argument, &flag, 129},
-        {SHRPX_OPT_FRONTEND_HTTP2_OPTIMIZE_WRITE_BUFFER_SIZE.c_str(),
+        {SHRPX_OPT_API_MAX_REQUEST_BODY.data(), required_argument, &flag, 126},
+        {SHRPX_OPT_BACKEND_MAX_BACKOFF.data(), required_argument, &flag, 127},
+        {SHRPX_OPT_SERVER_NAME.data(), required_argument, &flag, 128},
+        {SHRPX_OPT_NO_SERVER_REWRITE.data(), no_argument, &flag, 129},
+        {SHRPX_OPT_FRONTEND_HTTP2_OPTIMIZE_WRITE_BUFFER_SIZE.data(),
          no_argument, &flag, 130},
-        {SHRPX_OPT_FRONTEND_HTTP2_OPTIMIZE_WINDOW_SIZE.c_str(), no_argument,
+        {SHRPX_OPT_FRONTEND_HTTP2_OPTIMIZE_WINDOW_SIZE.data(), no_argument,
          &flag, 131},
-        {SHRPX_OPT_FRONTEND_HTTP2_WINDOW_SIZE.c_str(), required_argument, &flag,
+        {SHRPX_OPT_FRONTEND_HTTP2_WINDOW_SIZE.data(), required_argument, &flag,
          132},
-        {SHRPX_OPT_FRONTEND_HTTP2_CONNECTION_WINDOW_SIZE.c_str(),
+        {SHRPX_OPT_FRONTEND_HTTP2_CONNECTION_WINDOW_SIZE.data(),
          required_argument, &flag, 133},
-        {SHRPX_OPT_BACKEND_HTTP2_WINDOW_SIZE.c_str(), required_argument, &flag,
+        {SHRPX_OPT_BACKEND_HTTP2_WINDOW_SIZE.data(), required_argument, &flag,
          134},
-        {SHRPX_OPT_BACKEND_HTTP2_CONNECTION_WINDOW_SIZE.c_str(),
+        {SHRPX_OPT_BACKEND_HTTP2_CONNECTION_WINDOW_SIZE.data(),
          required_argument, &flag, 135},
-        {SHRPX_OPT_FRONTEND_HTTP2_ENCODER_DYNAMIC_TABLE_SIZE.c_str(),
+        {SHRPX_OPT_FRONTEND_HTTP2_ENCODER_DYNAMIC_TABLE_SIZE.data(),
          required_argument, &flag, 136},
-        {SHRPX_OPT_FRONTEND_HTTP2_DECODER_DYNAMIC_TABLE_SIZE.c_str(),
+        {SHRPX_OPT_FRONTEND_HTTP2_DECODER_DYNAMIC_TABLE_SIZE.data(),
          required_argument, &flag, 137},
-        {SHRPX_OPT_BACKEND_HTTP2_ENCODER_DYNAMIC_TABLE_SIZE.c_str(),
+        {SHRPX_OPT_BACKEND_HTTP2_ENCODER_DYNAMIC_TABLE_SIZE.data(),
          required_argument, &flag, 138},
-        {SHRPX_OPT_BACKEND_HTTP2_DECODER_DYNAMIC_TABLE_SIZE.c_str(),
+        {SHRPX_OPT_BACKEND_HTTP2_DECODER_DYNAMIC_TABLE_SIZE.data(),
          required_argument, &flag, 139},
-        {SHRPX_OPT_ECDH_CURVES.c_str(), required_argument, &flag, 140},
-        {SHRPX_OPT_TLS_SCT_DIR.c_str(), required_argument, &flag, 141},
-        {SHRPX_OPT_BACKEND_CONNECT_TIMEOUT.c_str(), required_argument, &flag,
+        {SHRPX_OPT_ECDH_CURVES.data(), required_argument, &flag, 140},
+        {SHRPX_OPT_TLS_SCT_DIR.data(), required_argument, &flag, 141},
+        {SHRPX_OPT_BACKEND_CONNECT_TIMEOUT.data(), required_argument, &flag,
          142},
-        {SHRPX_OPT_DNS_CACHE_TIMEOUT.c_str(), required_argument, &flag, 143},
-        {SHRPX_OPT_DNS_LOOKUP_TIMEOUT.c_str(), required_argument, &flag, 144},
-        {SHRPX_OPT_DNS_MAX_TRY.c_str(), required_argument, &flag, 145},
-        {SHRPX_OPT_FRONTEND_KEEP_ALIVE_TIMEOUT.c_str(), required_argument,
-         &flag, 146},
-        {SHRPX_OPT_PSK_SECRETS.c_str(), required_argument, &flag, 147},
-        {SHRPX_OPT_CLIENT_PSK_SECRETS.c_str(), required_argument, &flag, 148},
-        {SHRPX_OPT_CLIENT_NO_HTTP2_CIPHER_BLACK_LIST.c_str(), no_argument,
-         &flag, 149},
-        {SHRPX_OPT_CLIENT_CIPHERS.c_str(), required_argument, &flag, 150},
-        {SHRPX_OPT_ACCESSLOG_WRITE_EARLY.c_str(), no_argument, &flag, 151},
-        {SHRPX_OPT_TLS_MIN_PROTO_VERSION.c_str(), required_argument, &flag,
-         152},
-        {SHRPX_OPT_TLS_MAX_PROTO_VERSION.c_str(), required_argument, &flag,
-         153},
-        {SHRPX_OPT_REDIRECT_HTTPS_PORT.c_str(), required_argument, &flag, 154},
-        {SHRPX_OPT_FRONTEND_MAX_REQUESTS.c_str(), required_argument, &flag,
-         155},
-        {SHRPX_OPT_SINGLE_THREAD.c_str(), no_argument, &flag, 156},
-        {SHRPX_OPT_NO_ADD_X_FORWARDED_PROTO.c_str(), no_argument, &flag, 157},
-        {SHRPX_OPT_NO_STRIP_INCOMING_X_FORWARDED_PROTO.c_str(), no_argument,
+        {SHRPX_OPT_DNS_CACHE_TIMEOUT.data(), required_argument, &flag, 143},
+        {SHRPX_OPT_DNS_LOOKUP_TIMEOUT.data(), required_argument, &flag, 144},
+        {SHRPX_OPT_DNS_MAX_TRY.data(), required_argument, &flag, 145},
+        {SHRPX_OPT_FRONTEND_KEEP_ALIVE_TIMEOUT.data(), required_argument, &flag,
+         146},
+        {SHRPX_OPT_PSK_SECRETS.data(), required_argument, &flag, 147},
+        {SHRPX_OPT_CLIENT_PSK_SECRETS.data(), required_argument, &flag, 148},
+        {SHRPX_OPT_CLIENT_NO_HTTP2_CIPHER_BLACK_LIST.data(), no_argument, &flag,
+         149},
+        {SHRPX_OPT_CLIENT_CIPHERS.data(), required_argument, &flag, 150},
+        {SHRPX_OPT_ACCESSLOG_WRITE_EARLY.data(), no_argument, &flag, 151},
+        {SHRPX_OPT_TLS_MIN_PROTO_VERSION.data(), required_argument, &flag, 152},
+        {SHRPX_OPT_TLS_MAX_PROTO_VERSION.data(), required_argument, &flag, 153},
+        {SHRPX_OPT_REDIRECT_HTTPS_PORT.data(), required_argument, &flag, 154},
+        {SHRPX_OPT_FRONTEND_MAX_REQUESTS.data(), required_argument, &flag, 155},
+        {SHRPX_OPT_SINGLE_THREAD.data(), no_argument, &flag, 156},
+        {SHRPX_OPT_NO_ADD_X_FORWARDED_PROTO.data(), no_argument, &flag, 157},
+        {SHRPX_OPT_NO_STRIP_INCOMING_X_FORWARDED_PROTO.data(), no_argument,
          &flag, 158},
-        {SHRPX_OPT_SINGLE_PROCESS.c_str(), no_argument, &flag, 159},
-        {SHRPX_OPT_VERIFY_CLIENT_TOLERATE_EXPIRED.c_str(), no_argument, &flag,
+        {SHRPX_OPT_SINGLE_PROCESS.data(), no_argument, &flag, 159},
+        {SHRPX_OPT_VERIFY_CLIENT_TOLERATE_EXPIRED.data(), no_argument, &flag,
          160},
-        {SHRPX_OPT_IGNORE_PER_PATTERN_MRUBY_ERROR.c_str(), no_argument, &flag,
+        {SHRPX_OPT_IGNORE_PER_PATTERN_MRUBY_ERROR.data(), no_argument, &flag,
          161},
-        {SHRPX_OPT_TLS_NO_POSTPONE_EARLY_DATA.c_str(), no_argument, &flag, 162},
-        {SHRPX_OPT_TLS_MAX_EARLY_DATA.c_str(), required_argument, &flag, 163},
-        {SHRPX_OPT_TLS13_CIPHERS.c_str(), required_argument, &flag, 164},
-        {SHRPX_OPT_TLS13_CLIENT_CIPHERS.c_str(), required_argument, &flag, 165},
-        {SHRPX_OPT_NO_STRIP_INCOMING_EARLY_DATA.c_str(), no_argument, &flag,
+        {SHRPX_OPT_TLS_NO_POSTPONE_EARLY_DATA.data(), no_argument, &flag, 162},
+        {SHRPX_OPT_TLS_MAX_EARLY_DATA.data(), required_argument, &flag, 163},
+        {SHRPX_OPT_TLS13_CIPHERS.data(), required_argument, &flag, 164},
+        {SHRPX_OPT_TLS13_CLIENT_CIPHERS.data(), required_argument, &flag, 165},
+        {SHRPX_OPT_NO_STRIP_INCOMING_EARLY_DATA.data(), no_argument, &flag,
          166},
-        {SHRPX_OPT_NO_HTTP2_CIPHER_BLOCK_LIST.c_str(), no_argument, &flag, 167},
-        {SHRPX_OPT_CLIENT_NO_HTTP2_CIPHER_BLOCK_LIST.c_str(), no_argument,
-         &flag, 168},
-        {SHRPX_OPT_QUIC_BPF_PROGRAM_FILE.c_str(), required_argument, &flag,
-         169},
-        {SHRPX_OPT_NO_QUIC_BPF.c_str(), no_argument, &flag, 170},
-        {SHRPX_OPT_HTTP2_ALTSVC.c_str(), required_argument, &flag, 171},
-        {SHRPX_OPT_FRONTEND_HTTP3_READ_TIMEOUT.c_str(), required_argument,
-         &flag, 172},
-        {SHRPX_OPT_FRONTEND_QUIC_IDLE_TIMEOUT.c_str(), required_argument, &flag,
+        {SHRPX_OPT_NO_HTTP2_CIPHER_BLOCK_LIST.data(), no_argument, &flag, 167},
+        {SHRPX_OPT_CLIENT_NO_HTTP2_CIPHER_BLOCK_LIST.data(), no_argument, &flag,
+         168},
+        {SHRPX_OPT_QUIC_BPF_PROGRAM_FILE.data(), required_argument, &flag, 169},
+        {SHRPX_OPT_NO_QUIC_BPF.data(), no_argument, &flag, 170},
+        {SHRPX_OPT_HTTP2_ALTSVC.data(), required_argument, &flag, 171},
+        {SHRPX_OPT_FRONTEND_HTTP3_READ_TIMEOUT.data(), required_argument, &flag,
+         172},
+        {SHRPX_OPT_FRONTEND_QUIC_IDLE_TIMEOUT.data(), required_argument, &flag,
          173},
-        {SHRPX_OPT_FRONTEND_QUIC_DEBUG_LOG.c_str(), no_argument, &flag, 174},
-        {SHRPX_OPT_FRONTEND_HTTP3_WINDOW_SIZE.c_str(), required_argument, &flag,
+        {SHRPX_OPT_FRONTEND_QUIC_DEBUG_LOG.data(), no_argument, &flag, 174},
+        {SHRPX_OPT_FRONTEND_HTTP3_WINDOW_SIZE.data(), required_argument, &flag,
          175},
-        {SHRPX_OPT_FRONTEND_HTTP3_CONNECTION_WINDOW_SIZE.c_str(),
+        {SHRPX_OPT_FRONTEND_HTTP3_CONNECTION_WINDOW_SIZE.data(),
          required_argument, &flag, 176},
-        {SHRPX_OPT_FRONTEND_HTTP3_MAX_WINDOW_SIZE.c_str(), required_argument,
+        {SHRPX_OPT_FRONTEND_HTTP3_MAX_WINDOW_SIZE.data(), required_argument,
          &flag, 177},
-        {SHRPX_OPT_FRONTEND_HTTP3_MAX_CONNECTION_WINDOW_SIZE.c_str(),
+        {SHRPX_OPT_FRONTEND_HTTP3_MAX_CONNECTION_WINDOW_SIZE.data(),
          required_argument, &flag, 178},
-        {SHRPX_OPT_FRONTEND_HTTP3_MAX_CONCURRENT_STREAMS.c_str(),
+        {SHRPX_OPT_FRONTEND_HTTP3_MAX_CONCURRENT_STREAMS.data(),
          required_argument, &flag, 179},
-        {SHRPX_OPT_FRONTEND_QUIC_EARLY_DATA.c_str(), no_argument, &flag, 180},
-        {SHRPX_OPT_FRONTEND_QUIC_QLOG_DIR.c_str(), required_argument, &flag,
+        {SHRPX_OPT_FRONTEND_QUIC_EARLY_DATA.data(), no_argument, &flag, 180},
+        {SHRPX_OPT_FRONTEND_QUIC_QLOG_DIR.data(), required_argument, &flag,
          181},
-        {SHRPX_OPT_FRONTEND_QUIC_REQUIRE_TOKEN.c_str(), no_argument, &flag,
-         182},
-        {SHRPX_OPT_FRONTEND_QUIC_CONGESTION_CONTROLLER.c_str(),
+        {SHRPX_OPT_FRONTEND_QUIC_REQUIRE_TOKEN.data(), no_argument, &flag, 182},
+        {SHRPX_OPT_FRONTEND_QUIC_CONGESTION_CONTROLLER.data(),
          required_argument, &flag, 183},
-        {SHRPX_OPT_QUIC_SERVER_ID.c_str(), required_argument, &flag, 185},
-        {SHRPX_OPT_FRONTEND_QUIC_SECRET_FILE.c_str(), required_argument, &flag,
+        {SHRPX_OPT_QUIC_SERVER_ID.data(), required_argument, &flag, 185},
+        {SHRPX_OPT_FRONTEND_QUIC_SECRET_FILE.data(), required_argument, &flag,
          186},
-        {SHRPX_OPT_RLIMIT_MEMLOCK.c_str(), required_argument, &flag, 187},
-        {SHRPX_OPT_MAX_WORKER_PROCESSES.c_str(), required_argument, &flag, 188},
-        {SHRPX_OPT_WORKER_PROCESS_GRACE_SHUTDOWN_PERIOD.c_str(),
+        {SHRPX_OPT_RLIMIT_MEMLOCK.data(), required_argument, &flag, 187},
+        {SHRPX_OPT_MAX_WORKER_PROCESSES.data(), required_argument, &flag, 188},
+        {SHRPX_OPT_WORKER_PROCESS_GRACE_SHUTDOWN_PERIOD.data(),
          required_argument, &flag, 189},
-        {SHRPX_OPT_FRONTEND_QUIC_INITIAL_RTT.c_str(), required_argument, &flag,
+        {SHRPX_OPT_FRONTEND_QUIC_INITIAL_RTT.data(), required_argument, &flag,
          190},
-        {SHRPX_OPT_REQUIRE_HTTP_SCHEME.c_str(), no_argument, &flag, 191},
-        {SHRPX_OPT_TLS_KTLS.c_str(), no_argument, &flag, 192},
-        {SHRPX_OPT_ALPN_LIST.c_str(), required_argument, &flag, 193},
-        {SHRPX_OPT_FRONTEND_HEADER_TIMEOUT.c_str(), required_argument, &flag,
+        {SHRPX_OPT_REQUIRE_HTTP_SCHEME.data(), no_argument, &flag, 191},
+        {SHRPX_OPT_TLS_KTLS.data(), no_argument, &flag, 192},
+        {SHRPX_OPT_ALPN_LIST.data(), required_argument, &flag, 193},
+        {SHRPX_OPT_FRONTEND_HEADER_TIMEOUT.data(), required_argument, &flag,
          194},
-        {SHRPX_OPT_FRONTEND_HTTP2_IDLE_TIMEOUT.c_str(), required_argument,
-         &flag, 195},
-        {SHRPX_OPT_FRONTEND_HTTP3_IDLE_TIMEOUT.c_str(), required_argument,
-         &flag, 196},
+        {SHRPX_OPT_FRONTEND_HTTP2_IDLE_TIMEOUT.data(), required_argument, &flag,
+         195},
+        {SHRPX_OPT_FRONTEND_HTTP3_IDLE_TIMEOUT.data(), required_argument, &flag,
+         196},
         {nullptr, 0, nullptr, 0}};
 
     int option_index = 0;
@@ -4420,7 +4407,7 @@ int main(int argc, char **argv) {
     }
     switch (c) {
     case 'D':
-      cmdcfgs.emplace_back(SHRPX_OPT_DAEMON, StringRef::from_lit("yes"));
+      cmdcfgs.emplace_back(SHRPX_OPT_DAEMON, "yes"_sr);
       break;
     case 'L':
       cmdcfgs.emplace_back(SHRPX_OPT_LOG_LEVEL, StringRef{optarg});
@@ -4439,20 +4426,19 @@ int main(int argc, char **argv) {
       print_help(std::cout);
       exit(EXIT_SUCCESS);
     case 'k':
-      cmdcfgs.emplace_back(SHRPX_OPT_INSECURE, StringRef::from_lit("yes"));
+      cmdcfgs.emplace_back(SHRPX_OPT_INSECURE, "yes"_sr);
       break;
     case 'n':
       cmdcfgs.emplace_back(SHRPX_OPT_WORKERS, StringRef{optarg});
       break;
     case 'o':
-      cmdcfgs.emplace_back(SHRPX_OPT_FRONTEND_FRAME_DEBUG,
-                           StringRef::from_lit("yes"));
+      cmdcfgs.emplace_back(SHRPX_OPT_FRONTEND_FRAME_DEBUG, "yes"_sr);
       break;
     case 'p':
-      cmdcfgs.emplace_back(SHRPX_OPT_CLIENT_PROXY, StringRef::from_lit("yes"));
+      cmdcfgs.emplace_back(SHRPX_OPT_CLIENT_PROXY, "yes"_sr);
       break;
     case 's':
-      cmdcfgs.emplace_back(SHRPX_OPT_HTTP2_PROXY, StringRef::from_lit("yes"));
+      cmdcfgs.emplace_back(SHRPX_OPT_HTTP2_PROXY, "yes"_sr);
       break;
     case 'v':
       print_version(std::cout);
@@ -4464,8 +4450,7 @@ int main(int argc, char **argv) {
       switch (flag) {
       case 1:
         // --add-x-forwarded-for
-        cmdcfgs.emplace_back(SHRPX_OPT_ADD_X_FORWARDED_FOR,
-                             StringRef::from_lit("yes"));
+        cmdcfgs.emplace_back(SHRPX_OPT_ADD_X_FORWARDED_FOR, "yes"_sr);
         break;
       case 2:
         // --frontend-http2-read-timeout
@@ -4529,7 +4514,7 @@ int main(int argc, char **argv) {
         break;
       case 17:
         // --client
-        cmdcfgs.emplace_back(SHRPX_OPT_CLIENT, StringRef::from_lit("yes"));
+        cmdcfgs.emplace_back(SHRPX_OPT_CLIENT, "yes"_sr);
         break;
       case 18:
         // --backend-http2-window-bits
@@ -4542,13 +4527,11 @@ int main(int argc, char **argv) {
         break;
       case 20:
         // --backend-ipv4
-        cmdcfgs.emplace_back(SHRPX_OPT_BACKEND_IPV4,
-                             StringRef::from_lit("yes"));
+        cmdcfgs.emplace_back(SHRPX_OPT_BACKEND_IPV4, "yes"_sr);
         break;
       case 21:
         // --backend-ipv6
-        cmdcfgs.emplace_back(SHRPX_OPT_BACKEND_IPV6,
-                             StringRef::from_lit("yes"));
+        cmdcfgs.emplace_back(SHRPX_OPT_BACKEND_IPV6, "yes"_sr);
         break;
       case 22:
         // --private-key-passwd-file
@@ -4557,7 +4540,7 @@ int main(int argc, char **argv) {
         break;
       case 23:
         // --no-via
-        cmdcfgs.emplace_back(SHRPX_OPT_NO_VIA, StringRef::from_lit("yes"));
+        cmdcfgs.emplace_back(SHRPX_OPT_NO_VIA, "yes"_sr);
         break;
       case 24:
         // --subcert
@@ -4565,8 +4548,7 @@ int main(int argc, char **argv) {
         break;
       case 25:
         // --http2-bridge
-        cmdcfgs.emplace_back(SHRPX_OPT_HTTP2_BRIDGE,
-                             StringRef::from_lit("yes"));
+        cmdcfgs.emplace_back(SHRPX_OPT_HTTP2_BRIDGE, "yes"_sr);
         break;
       case 26:
         // --backend-http-proxy-uri
@@ -4575,23 +4557,19 @@ int main(int argc, char **argv) {
         break;
       case 27:
         // --backend-no-tls
-        cmdcfgs.emplace_back(SHRPX_OPT_BACKEND_NO_TLS,
-                             StringRef::from_lit("yes"));
+        cmdcfgs.emplace_back(SHRPX_OPT_BACKEND_NO_TLS, "yes"_sr);
         break;
       case 28:
         // --ocsp-startup
-        cmdcfgs.emplace_back(SHRPX_OPT_OCSP_STARTUP,
-                             StringRef::from_lit("yes"));
+        cmdcfgs.emplace_back(SHRPX_OPT_OCSP_STARTUP, "yes"_sr);
         break;
       case 29:
         // --frontend-no-tls
-        cmdcfgs.emplace_back(SHRPX_OPT_FRONTEND_NO_TLS,
-                             StringRef::from_lit("yes"));
+        cmdcfgs.emplace_back(SHRPX_OPT_FRONTEND_NO_TLS, "yes"_sr);
         break;
       case 30:
         // --no-verify-ocsp
-        cmdcfgs.emplace_back(SHRPX_OPT_NO_VERIFY_OCSP,
-                             StringRef::from_lit("yes"));
+        cmdcfgs.emplace_back(SHRPX_OPT_NO_VERIFY_OCSP, "yes"_sr);
         break;
       case 31:
         // --backend-tls-sni-field
@@ -4624,8 +4602,7 @@ int main(int argc, char **argv) {
         break;
       case 39:
         // --verify-client
-        cmdcfgs.emplace_back(SHRPX_OPT_VERIFY_CLIENT,
-                             StringRef::from_lit("yes"));
+        cmdcfgs.emplace_back(SHRPX_OPT_VERIFY_CLIENT, "yes"_sr);
         break;
       case 40:
         // --verify-client-cacert
@@ -4652,8 +4629,7 @@ int main(int argc, char **argv) {
         break;
       case 45:
         // --http2-no-cookie-crumbling
-        cmdcfgs.emplace_back(SHRPX_OPT_HTTP2_NO_COOKIE_CRUMBLING,
-                             StringRef::from_lit("yes"));
+        cmdcfgs.emplace_back(SHRPX_OPT_HTTP2_NO_COOKIE_CRUMBLING, "yes"_sr);
         break;
       case 46:
         // --frontend-http2-connection-window-bits
@@ -4704,8 +4680,7 @@ int main(int argc, char **argv) {
         break;
       case 57:
         // --accesslog-syslog
-        cmdcfgs.emplace_back(SHRPX_OPT_ACCESSLOG_SYSLOG,
-                             StringRef::from_lit("yes"));
+        cmdcfgs.emplace_back(SHRPX_OPT_ACCESSLOG_SYSLOG, "yes"_sr);
         break;
       case 58:
         // --errorlog-file
@@ -4713,8 +4688,7 @@ int main(int argc, char **argv) {
         break;
       case 59:
         // --errorlog-syslog
-        cmdcfgs.emplace_back(SHRPX_OPT_ERRORLOG_SYSLOG,
-                             StringRef::from_lit("yes"));
+        cmdcfgs.emplace_back(SHRPX_OPT_ERRORLOG_SYSLOG, "yes"_sr);
         break;
       case 60:
         // --stream-read-timeout
@@ -4726,8 +4700,7 @@ int main(int argc, char **argv) {
         break;
       case 62:
         // --no-location-rewrite
-        cmdcfgs.emplace_back(SHRPX_OPT_NO_LOCATION_REWRITE,
-                             StringRef::from_lit("yes"));
+        cmdcfgs.emplace_back(SHRPX_OPT_NO_LOCATION_REWRITE, "yes"_sr);
         break;
       case 63:
         // --backend-http1-connections-per-host
@@ -4742,7 +4715,7 @@ int main(int argc, char **argv) {
       case 65:
         // --strip-incoming-x-forwarded-for
         cmdcfgs.emplace_back(SHRPX_OPT_STRIP_INCOMING_X_FORWARDED_FOR,
-                             StringRef::from_lit("yes"));
+                             "yes"_sr);
         break;
       case 66:
         // --accesslog-format
@@ -4773,13 +4746,11 @@ int main(int argc, char **argv) {
         break;
       case 73:
         // --no-host-rewrite
-        cmdcfgs.emplace_back(SHRPX_OPT_NO_HOST_REWRITE,
-                             StringRef::from_lit("yes"));
+        cmdcfgs.emplace_back(SHRPX_OPT_NO_HOST_REWRITE, "yes"_sr);
         break;
       case 74:
         // --no-server-push
-        cmdcfgs.emplace_back(SHRPX_OPT_NO_SERVER_PUSH,
-                             StringRef::from_lit("yes"));
+        cmdcfgs.emplace_back(SHRPX_OPT_NO_SERVER_PUSH, "yes"_sr);
         break;
       case 76:
         // --backend-http2-connections-per-worker
@@ -4797,7 +4768,7 @@ int main(int argc, char **argv) {
         break;
       case 79:
         // --no-ocsp
-        cmdcfgs.emplace_back(SHRPX_OPT_NO_OCSP, StringRef::from_lit("yes"));
+        cmdcfgs.emplace_back(SHRPX_OPT_NO_OCSP, "yes"_sr);
         break;
       case 80:
         // --header-field-buffer
@@ -4822,8 +4793,7 @@ int main(int argc, char **argv) {
         break;
       case 85:
         // --host-rewrite
-        cmdcfgs.emplace_back(SHRPX_OPT_HOST_REWRITE,
-                             StringRef::from_lit("yes"));
+        cmdcfgs.emplace_back(SHRPX_OPT_HOST_REWRITE, "yes"_sr);
         break;
       case 86:
         // --tls-session-cache-memcached
@@ -4856,8 +4826,7 @@ int main(int argc, char **argv) {
         break;
       case 93:
         // --accept-proxy-protocol
-        cmdcfgs.emplace_back(SHRPX_OPT_ACCEPT_PROXY_PROTOCOL,
-                             StringRef::from_lit("yes"));
+        cmdcfgs.emplace_back(SHRPX_OPT_ACCEPT_PROXY_PROTOCOL, "yes"_sr);
         break;
       case 94:
         // --fastopen
@@ -4879,8 +4848,7 @@ int main(int argc, char **argv) {
         break;
       case 98:
         // --strip-incoming-forwarded
-        cmdcfgs.emplace_back(SHRPX_OPT_STRIP_INCOMING_FORWARDED,
-                             StringRef::from_lit("yes"));
+        cmdcfgs.emplace_back(SHRPX_OPT_STRIP_INCOMING_FORWARDED, "yes"_sr);
         break;
       case 99:
         // --forwarded-by
@@ -4902,8 +4870,7 @@ int main(int argc, char **argv) {
         break;
       case 103:
         // --no-http2-cipher-black-list
-        cmdcfgs.emplace_back(SHRPX_OPT_NO_HTTP2_CIPHER_BLACK_LIST,
-                             StringRef::from_lit("yes"));
+        cmdcfgs.emplace_back(SHRPX_OPT_NO_HTTP2_CIPHER_BLACK_LIST, "yes"_sr);
         break;
       case 104:
         // --request-header-field-buffer
@@ -4917,13 +4884,12 @@ int main(int argc, char **argv) {
         break;
       case 106:
         // --backend-http1-tls
-        cmdcfgs.emplace_back(SHRPX_OPT_BACKEND_HTTP1_TLS,
-                             StringRef::from_lit("yes"));
+        cmdcfgs.emplace_back(SHRPX_OPT_BACKEND_HTTP1_TLS, "yes"_sr);
         break;
       case 108:
         // --tls-session-cache-memcached-tls
         cmdcfgs.emplace_back(SHRPX_OPT_TLS_SESSION_CACHE_MEMCACHED_TLS,
-                             StringRef::from_lit("yes"));
+                             "yes"_sr);
         break;
       case 109:
         // --tls-session-cache-memcached-cert-file
@@ -4938,8 +4904,7 @@ int main(int argc, char **argv) {
         break;
       case 111:
         // --tls-ticket-key-memcached-tls
-        cmdcfgs.emplace_back(SHRPX_OPT_TLS_TICKET_KEY_MEMCACHED_TLS,
-                             StringRef::from_lit("yes"));
+        cmdcfgs.emplace_back(SHRPX_OPT_TLS_TICKET_KEY_MEMCACHED_TLS, "yes"_sr);
         break;
       case 112:
         // --tls-ticket-key-memcached-cert-file
@@ -4985,7 +4950,7 @@ int main(int argc, char **argv) {
         break;
       case 120:
         // --backend-tls
-        cmdcfgs.emplace_back(SHRPX_OPT_BACKEND_TLS, StringRef::from_lit("yes"));
+        cmdcfgs.emplace_back(SHRPX_OPT_BACKEND_TLS, "yes"_sr);
         break;
       case 121:
         // --backend-connections-per-host
@@ -4998,7 +4963,7 @@ int main(int argc, char **argv) {
         break;
       case 123:
         // --no-kqueue
-        cmdcfgs.emplace_back(SHRPX_OPT_NO_KQUEUE, StringRef::from_lit("yes"));
+        cmdcfgs.emplace_back(SHRPX_OPT_NO_KQUEUE, "yes"_sr);
         break;
       case 124:
         // --frontend-http2-settings-timeout
@@ -5024,19 +4989,17 @@ int main(int argc, char **argv) {
         break;
       case 129:
         // --no-server-rewrite
-        cmdcfgs.emplace_back(SHRPX_OPT_NO_SERVER_REWRITE,
-                             StringRef::from_lit("yes"));
+        cmdcfgs.emplace_back(SHRPX_OPT_NO_SERVER_REWRITE, "yes"_sr);
         break;
       case 130:
         // --frontend-http2-optimize-write-buffer-size
         cmdcfgs.emplace_back(
-            SHRPX_OPT_FRONTEND_HTTP2_OPTIMIZE_WRITE_BUFFER_SIZE,
-            StringRef::from_lit("yes"));
+            SHRPX_OPT_FRONTEND_HTTP2_OPTIMIZE_WRITE_BUFFER_SIZE, "yes"_sr);
         break;
       case 131:
         // --frontend-http2-optimize-window-size
         cmdcfgs.emplace_back(SHRPX_OPT_FRONTEND_HTTP2_OPTIMIZE_WINDOW_SIZE,
-                             StringRef::from_lit("yes"));
+                             "yes"_sr);
         break;
       case 132:
         // --frontend-http2-window-size
@@ -5121,7 +5084,7 @@ int main(int argc, char **argv) {
       case 149:
         // --client-no-http2-cipher-black-list
         cmdcfgs.emplace_back(SHRPX_OPT_CLIENT_NO_HTTP2_CIPHER_BLACK_LIST,
-                             StringRef::from_lit("yes"));
+                             "yes"_sr);
         break;
       case 150:
         // --client-ciphers
@@ -5129,8 +5092,7 @@ int main(int argc, char **argv) {
         break;
       case 151:
         // --accesslog-write-early
-        cmdcfgs.emplace_back(SHRPX_OPT_ACCESSLOG_WRITE_EARLY,
-                             StringRef::from_lit("yes"));
+        cmdcfgs.emplace_back(SHRPX_OPT_ACCESSLOG_WRITE_EARLY, "yes"_sr);
         break;
       case 152:
         // --tls-min-proto-version
@@ -5153,38 +5115,34 @@ int main(int argc, char **argv) {
         break;
       case 156:
         // --single-thread
-        cmdcfgs.emplace_back(SHRPX_OPT_SINGLE_THREAD,
-                             StringRef::from_lit("yes"));
+        cmdcfgs.emplace_back(SHRPX_OPT_SINGLE_THREAD, "yes"_sr);
         break;
       case 157:
         // --no-add-x-forwarded-proto
-        cmdcfgs.emplace_back(SHRPX_OPT_NO_ADD_X_FORWARDED_PROTO,
-                             StringRef::from_lit("yes"));
+        cmdcfgs.emplace_back(SHRPX_OPT_NO_ADD_X_FORWARDED_PROTO, "yes"_sr);
         break;
       case 158:
         // --no-strip-incoming-x-forwarded-proto
         cmdcfgs.emplace_back(SHRPX_OPT_NO_STRIP_INCOMING_X_FORWARDED_PROTO,
-                             StringRef::from_lit("yes"));
+                             "yes"_sr);
         break;
       case 159:
         // --single-process
-        cmdcfgs.emplace_back(SHRPX_OPT_SINGLE_PROCESS,
-                             StringRef::from_lit("yes"));
+        cmdcfgs.emplace_back(SHRPX_OPT_SINGLE_PROCESS, "yes"_sr);
         break;
       case 160:
         // --verify-client-tolerate-expired
         cmdcfgs.emplace_back(SHRPX_OPT_VERIFY_CLIENT_TOLERATE_EXPIRED,
-                             StringRef::from_lit("yes"));
+                             "yes"_sr);
         break;
       case 161:
         // --ignore-per-pattern-mruby-error
         cmdcfgs.emplace_back(SHRPX_OPT_IGNORE_PER_PATTERN_MRUBY_ERROR,
-                             StringRef::from_lit("yes"));
+                             "yes"_sr);
         break;
       case 162:
         // --tls-no-postpone-early-data
-        cmdcfgs.emplace_back(SHRPX_OPT_TLS_NO_POSTPONE_EARLY_DATA,
-                             StringRef::from_lit("yes"));
+        cmdcfgs.emplace_back(SHRPX_OPT_TLS_NO_POSTPONE_EARLY_DATA, "yes"_sr);
         break;
       case 163:
         // --tls-max-early-data
@@ -5200,18 +5158,16 @@ int main(int argc, char **argv) {
         break;
       case 166:
         // --no-strip-incoming-early-data
-        cmdcfgs.emplace_back(SHRPX_OPT_NO_STRIP_INCOMING_EARLY_DATA,
-                             StringRef::from_lit("yes"));
+        cmdcfgs.emplace_back(SHRPX_OPT_NO_STRIP_INCOMING_EARLY_DATA, "yes"_sr);
         break;
       case 167:
         // --no-http2-cipher-block-list
-        cmdcfgs.emplace_back(SHRPX_OPT_NO_HTTP2_CIPHER_BLOCK_LIST,
-                             StringRef::from_lit("yes"));
+        cmdcfgs.emplace_back(SHRPX_OPT_NO_HTTP2_CIPHER_BLOCK_LIST, "yes"_sr);
         break;
       case 168:
         // --client-no-http2-cipher-block-list
         cmdcfgs.emplace_back(SHRPX_OPT_CLIENT_NO_HTTP2_CIPHER_BLOCK_LIST,
-                             StringRef::from_lit("yes"));
+                             "yes"_sr);
         break;
       case 169:
         // --quic-bpf-program-file
@@ -5220,7 +5176,7 @@ int main(int argc, char **argv) {
         break;
       case 170:
         // --no-quic-bpf
-        cmdcfgs.emplace_back(SHRPX_OPT_NO_QUIC_BPF, StringRef::from_lit("yes"));
+        cmdcfgs.emplace_back(SHRPX_OPT_NO_QUIC_BPF, "yes"_sr);
         break;
       case 171:
         // --http2-altsvc
@@ -5238,8 +5194,7 @@ int main(int argc, char **argv) {
         break;
       case 174:
         // --frontend-quic-debug-log
-        cmdcfgs.emplace_back(SHRPX_OPT_FRONTEND_QUIC_DEBUG_LOG,
-                             StringRef::from_lit("yes"));
+        cmdcfgs.emplace_back(SHRPX_OPT_FRONTEND_QUIC_DEBUG_LOG, "yes"_sr);
         break;
       case 175:
         // --frontend-http3-window-size
@@ -5269,8 +5224,7 @@ int main(int argc, char **argv) {
         break;
       case 180:
         // --frontend-quic-early-data
-        cmdcfgs.emplace_back(SHRPX_OPT_FRONTEND_QUIC_EARLY_DATA,
-                             StringRef::from_lit("yes"));
+        cmdcfgs.emplace_back(SHRPX_OPT_FRONTEND_QUIC_EARLY_DATA, "yes"_sr);
         break;
       case 181:
         // --frontend-quic-qlog-dir
@@ -5279,8 +5233,7 @@ int main(int argc, char **argv) {
         break;
       case 182:
         // --frontend-quic-require-token
-        cmdcfgs.emplace_back(SHRPX_OPT_FRONTEND_QUIC_REQUIRE_TOKEN,
-                             StringRef::from_lit("yes"));
+        cmdcfgs.emplace_back(SHRPX_OPT_FRONTEND_QUIC_REQUIRE_TOKEN, "yes"_sr);
         break;
       case 183:
         // --frontend-quic-congestion-controller
@@ -5316,12 +5269,11 @@ int main(int argc, char **argv) {
         break;
       case 191:
         // --require-http-scheme
-        cmdcfgs.emplace_back(SHRPX_OPT_REQUIRE_HTTP_SCHEME,
-                             StringRef::from_lit("yes"));
+        cmdcfgs.emplace_back(SHRPX_OPT_REQUIRE_HTTP_SCHEME, "yes"_sr);
         break;
       case 192:
         // --tls-ktls
-        cmdcfgs.emplace_back(SHRPX_OPT_TLS_KTLS, StringRef::from_lit("yes"));
+        cmdcfgs.emplace_back(SHRPX_OPT_TLS_KTLS, "yes"_sr);
         break;
       case 193:
         // --alpn-list
diff --git a/src/shrpx_api_downstream_connection.cc b/src/shrpx_api_downstream_connection.cc
index 254ab59..13ebac6 100644
--- a/src/shrpx_api_downstream_connection.cc
+++ b/src/shrpx_api_downstream_connection.cc
@@ -39,33 +39,27 @@
 namespace shrpx {
 
 namespace {
-// List of API endpoints
-const std::array<APIEndpoint, 2> &apis() {
-  static const auto apis = new std::array<APIEndpoint, 2>{
-      APIEndpoint{
-          StringRef::from_lit("/api/v1beta1/backendconfig"),
-          true,
-          (1 << API_METHOD_POST) | (1 << API_METHOD_PUT),
-          &APIDownstreamConnection::handle_backendconfig,
-      },
-      APIEndpoint{
-          StringRef::from_lit("/api/v1beta1/configrevision"),
-          true,
-          (1 << API_METHOD_GET),
-          &APIDownstreamConnection::handle_configrevision,
-      },
-  };
-
-  return *apis;
-}
+const auto backendconfig_endpoint = APIEndpoint{
+    "/api/v1beta1/backendconfig"_sr,
+    true,
+    (1 << API_METHOD_POST) | (1 << API_METHOD_PUT),
+    &APIDownstreamConnection::handle_backendconfig,
+};
+
+const auto configrevision_endpoint = APIEndpoint{
+    "/api/v1beta1/configrevision"_sr,
+    true,
+    (1 << API_METHOD_GET),
+    &APIDownstreamConnection::handle_configrevision,
+};
 } // namespace
 
 namespace {
 // The method string.  This must be same order of APIMethod.
 constexpr StringRef API_METHOD_STRING[] = {
-    StringRef::from_lit("GET"),
-    StringRef::from_lit("POST"),
-    StringRef::from_lit("PUT"),
+    "GET"_sr,
+    "POST"_sr,
+    "PUT"_sr,
 };
 } // namespace
 
@@ -112,18 +106,18 @@ int APIDownstreamConnection::send_reply(unsigned int http_status,
 
   switch (api_status) {
   case APIStatusCode::SUCCESS:
-    api_status_str = StringRef::from_lit("Success");
+    api_status_str = "Success"_sr;
     break;
   case APIStatusCode::FAILURE:
-    api_status_str = StringRef::from_lit("Failure");
+    api_status_str = "Failure"_sr;
     break;
   default:
     assert(0);
   }
 
-  constexpr auto M1 = StringRef::from_lit("{\"status\":\"");
-  constexpr auto M2 = StringRef::from_lit("\",\"code\":");
-  constexpr auto M3 = StringRef::from_lit("}");
+  constexpr auto M1 = "{\"status\":\""_sr;
+  constexpr auto M2 = "\",\"code\":"_sr;
+  constexpr auto M3 = "}"_sr;
 
   // 3 is the number of digits in http_status, assuming it is 3 digits
   // number.
@@ -131,7 +125,7 @@ int APIDownstreamConnection::send_reply(unsigned int http_status,
                 api_status_str.size() + 3;
 
   auto buf = make_byte_ref(balloc, buflen);
-  auto p = buf.base;
+  auto p = std::begin(buf);
 
   p = std::copy(std::begin(M1), std::end(M1), p);
   p = std::copy(std::begin(api_status_str), std::end(api_status_str), p);
@@ -140,24 +134,23 @@ int APIDownstreamConnection::send_reply(unsigned int http_status,
   p = std::copy(std::begin(data), std::end(data), p);
   p = std::copy(std::begin(M3), std::end(M3), p);
 
-  buf.len = p - buf.base;
+  buf = buf.subspan(0, p - std::begin(buf));
 
-  auto content_length = util::make_string_ref_uint(balloc, buf.len);
+  auto content_length = util::make_string_ref_uint(balloc, buf.size());
 
-  resp.fs.add_header_token(StringRef::from_lit("content-length"),
-                           content_length, false, http2::HD_CONTENT_LENGTH);
+  resp.fs.add_header_token("content-length"_sr, content_length, false,
+                           http2::HD_CONTENT_LENGTH);
 
   switch (http_status) {
   case 400:
   case 405:
   case 413:
-    resp.fs.add_header_token(StringRef::from_lit("connection"),
-                             StringRef::from_lit("close"), false,
+    resp.fs.add_header_token("connection"_sr, "close"_sr, false,
                              http2::HD_CONNECTION);
     break;
   }
 
-  if (upstream->send_reply(downstream_, buf.base, buf.len) != 0) {
+  if (upstream->send_reply(downstream_, buf.data(), buf.size()) != 0) {
     return -1;
   }
 
@@ -170,8 +163,8 @@ const APIEndpoint *lookup_api(const StringRef &path) {
   case 26:
     switch (path[25]) {
     case 'g':
-      if (util::streq_l("/api/v1beta1/backendconfi", std::begin(path), 25)) {
-        return &apis()[0];
+      if (util::streq("/api/v1beta1/backendconfi"_sr, path, 25)) {
+        return &backendconfig_endpoint;
       }
       break;
     }
@@ -179,8 +172,8 @@ const APIEndpoint *lookup_api(const StringRef &path) {
   case 27:
     switch (path[26]) {
     case 'n':
-      if (util::streq_l("/api/v1beta1/configrevisio", std::begin(path), 26)) {
-        return &apis()[1];
+      if (util::streq("/api/v1beta1/configrevisio"_sr, path, 26)) {
+        return &configrevision_endpoint;
       }
       break;
     }
@@ -283,7 +276,7 @@ int APIDownstreamConnection::error_method_not_allowed() {
   auto &balloc = downstream_->get_block_allocator();
 
   auto iov = make_byte_ref(balloc, len + 1);
-  auto p = iov.base;
+  auto p = std::begin(iov);
   for (uint8_t i = 0; i < API_METHOD_MAX; ++i) {
     if (api_->allowed_methods & (1 << i)) {
       auto &s = API_METHOD_STRING[i];
@@ -295,7 +288,7 @@ int APIDownstreamConnection::error_method_not_allowed() {
   p -= 2;
   *p = '\0';
 
-  resp.fs.add_header_token(StringRef::from_lit("allow"), StringRef{iov.base, p},
+  resp.fs.add_header_token("allow"_sr, StringRef{std::span{std::begin(iov), p}},
                            false, -1);
   return send_reply(405, APIStatusCode::FAILURE);
 }
@@ -394,10 +387,10 @@ int APIDownstreamConnection::handle_backendconfig() {
       return 0;
     }
 
-    auto opt = StringRef{first, eq};
-    auto optval = StringRef{eq + 1, eol};
+    auto opt = StringRef{std::span{first, eq}};
+    auto optval = StringRef{std::span{eq + 1, eol}};
 
-    auto optid = option_lookup_token(opt.c_str(), opt.size());
+    auto optid = option_lookup_token(opt);
 
     switch (optid) {
     case SHRPX_OPTID_BACKEND:
@@ -442,9 +435,8 @@ int APIDownstreamConnection::handle_configrevision() {
   //     "configRevision": N
   //   }
   auto data = concat_string_ref(
-      balloc, StringRef::from_lit(R"(,"data":{"configRevision":)"),
-      util::make_string_ref_uint(balloc, config->config_revision),
-      StringRef::from_lit("}"));
+      balloc, R"(,"data":{"configRevision":)"_sr,
+      util::make_string_ref_uint(balloc, config->config_revision), "}"_sr);
 
   send_reply(200, APIStatusCode::SUCCESS, data);
 
diff --git a/src/shrpx_client_handler.cc b/src/shrpx_client_handler.cc
index a78b00a..70f0d95 100644
--- a/src/shrpx_client_handler.cc
+++ b/src/shrpx_client_handler.cc
@@ -322,11 +322,11 @@ int ClientHandler::write_tls() {
 int ClientHandler::read_quic(const UpstreamAddr *faddr,
                              const Address &remote_addr,
                              const Address &local_addr,
-                             const ngtcp2_pkt_info &pi, const uint8_t *data,
-                             size_t datalen) {
+                             const ngtcp2_pkt_info &pi,
+                             std::span<const uint8_t> data) {
   auto upstream = static_cast<Http3Upstream *>(upstream_.get());
 
-  return upstream->on_read(faddr, remote_addr, local_addr, pi, data, datalen);
+  return upstream->on_read(faddr, remote_addr, local_addr, pi, data);
 }
 
 int ClientHandler::write_quic() { return upstream_->on_write(); }
@@ -492,13 +492,13 @@ ClientHandler::ClientHandler(Worker *worker, int fd, SSL *ssl,
       auto len = SHRPX_OBFUSCATED_NODE_LENGTH + 1;
       // 1 for terminating NUL.
       auto buf = make_byte_ref(balloc_, len + 1);
-      auto p = buf.base;
+      auto p = std::begin(buf);
       *p++ = '_';
       p = util::random_alpha_digit(p, p + SHRPX_OBFUSCATED_NODE_LENGTH,
                                    worker_->get_randgen());
       *p = '\0';
 
-      forwarded_for_ = StringRef{buf.base, p};
+      forwarded_for_ = StringRef{std::span{std::begin(buf), p}};
     } else {
       init_forwarded_for(family, ipaddr_);
     }
@@ -511,13 +511,13 @@ void ClientHandler::init_forwarded_for(int family, const StringRef &ipaddr) {
     auto len = 2 + ipaddr.size();
     // 1 for terminating NUL.
     auto buf = make_byte_ref(balloc_, len + 1);
-    auto p = buf.base;
+    auto p = std::begin(buf);
     *p++ = '[';
     p = std::copy(std::begin(ipaddr), std::end(ipaddr), p);
     *p++ = ']';
     *p = '\0';
 
-    forwarded_for_ = StringRef{buf.base, p};
+    forwarded_for_ = StringRef{std::span{std::begin(buf), p}};
   } else {
     // family == AF_INET or family == AF_UNIX
     forwarded_for_ = ipaddr;
@@ -535,7 +535,7 @@ void ClientHandler::setup_upstream_io_callback() {
     // upgraded to HTTP/2 through HTTP Upgrade or direct HTTP/2
     // connection.
     upstream_ = std::make_unique<HttpsUpstream>(this);
-    alpn_ = StringRef::from_lit("http/1.1");
+    alpn_ = "http/1.1"_sr;
     read_ = &ClientHandler::read_clear;
     write_ = &ClientHandler::write_clear;
     on_read_ = &ClientHandler::upstream_http1_connhd_read;
@@ -629,7 +629,7 @@ int ClientHandler::validate_next_proto() {
       CLOG(INFO, this) << "No protocol negotiated. Fallback to HTTP/1.1";
     }
 
-    proto = StringRef::from_lit("http/1.1");
+    proto = "http/1.1"_sr;
   }
 
   if (!tls::in_proto_list(get_config()->tls.alpn_list, proto)) {
@@ -657,9 +657,9 @@ int ClientHandler::validate_next_proto() {
     return 0;
   }
 
-  if (proto == StringRef::from_lit("http/1.1")) {
+  if (proto == "http/1.1"_sr) {
     upstream_ = std::make_unique<HttpsUpstream>(this);
-    alpn_ = StringRef::from_lit("http/1.1");
+    alpn_ = "http/1.1"_sr;
 
     // At this point, input buffer is already filled with some bytes.
     // The read callback is not called until new data come. So consume
@@ -802,8 +802,7 @@ uint32_t ClientHandler::get_affinity_cookie(Downstream *downstream,
 
   auto d = std::uniform_int_distribution<uint32_t>(1);
   auto rh = d(worker_->get_randgen());
-  h = util::hash32(StringRef{reinterpret_cast<uint8_t *>(&rh),
-                             reinterpret_cast<uint8_t *>(&rh) + sizeof(rh)});
+  h = util::hash32(StringRef{reinterpret_cast<char *>(&rh), sizeof(rh)});
 
   downstream->renew_affinity_cookie(h);
 
@@ -963,8 +962,7 @@ DownstreamAddr *ClientHandler::get_downstream_addr_strict_affinity(
   } else {
     auto d = std::uniform_int_distribution<uint32_t>(1);
     auto rh = d(worker_->get_randgen());
-    h = util::hash32(StringRef{reinterpret_cast<uint8_t *>(&rh),
-                               reinterpret_cast<uint8_t *>(&rh) + sizeof(rh)});
+    h = util::hash32(StringRef{reinterpret_cast<char *>(&rh), sizeof(rh)});
   }
 
   // Client is not bound to a particular backend, or the bound backend
@@ -1148,7 +1146,7 @@ SSL *ClientHandler::get_ssl() const { return conn_.tls.ssl; }
 
 void ClientHandler::direct_http2_upgrade() {
   upstream_ = std::make_unique<Http2Upstream>(this);
-  alpn_ = StringRef::from_lit(NGHTTP2_CLEARTEXT_PROTO_VERSION_ID);
+  alpn_ = NGHTTP2_CLEARTEXT_PROTO_VERSION_ID ""_sr;
   on_read_ = &ClientHandler::upstream_read;
   write_ = &ClientHandler::write_clear;
 }
@@ -1173,17 +1171,16 @@ int ClientHandler::perform_http2_upgrade(HttpsUpstream *http) {
   upstream_.release();
   // TODO We might get other version id in HTTP2-settings, if we
   // support aliasing for h2, but we just use library default for now.
-  alpn_ = StringRef::from_lit(NGHTTP2_CLEARTEXT_PROTO_VERSION_ID);
+  alpn_ = NGHTTP2_CLEARTEXT_PROTO_VERSION_ID ""_sr;
   on_read_ = &ClientHandler::upstream_http2_connhd_read;
   write_ = &ClientHandler::write_clear;
 
   input->remove(*output, input->rleft());
 
-  constexpr auto res =
-      StringRef::from_lit("HTTP/1.1 101 Switching Protocols\r\n"
-                          "Connection: Upgrade\r\n"
-                          "Upgrade: " NGHTTP2_CLEARTEXT_PROTO_VERSION_ID "\r\n"
-                          "\r\n");
+  constexpr auto res = "HTTP/1.1 101 Switching Protocols\r\n"
+                       "Connection: Upgrade\r\n"
+                       "Upgrade: " NGHTTP2_CLEARTEXT_PROTO_VERSION_ID "\r\n"
+                       "\r\n"_sr;
 
   output->append(res);
   upstream_ = std::move(upstream);
@@ -1196,9 +1193,9 @@ bool ClientHandler::get_http2_upgrade_allowed() const { return !conn_.tls.ssl; }
 
 StringRef ClientHandler::get_upstream_scheme() const {
   if (conn_.tls.ssl) {
-    return StringRef::from_lit("https");
+    return "https"_sr;
   } else {
-    return StringRef::from_lit("http");
+    return "http"_sr;
   }
 }
 
@@ -1324,7 +1321,7 @@ int ClientHandler::proxy_protocol_read() {
   // NULL character really destroys functions which expects NULL
   // terminated string.  We won't expect it in PROXY protocol line, so
   // find it here.
-  auto chrs = std::array<char, 2>{'\n', '\0'};
+  auto chrs = std::to_array({'\n', '\0'});
 
   constexpr size_t MAX_PROXY_LINELEN = 107;
 
@@ -1342,7 +1339,7 @@ int ClientHandler::proxy_protocol_read() {
 
   --end;
 
-  constexpr auto HEADER = StringRef::from_lit("PROXY ");
+  constexpr auto HEADER = "PROXY "_sr;
 
   if (static_cast<size_t>(end - rb_.pos()) < HEADER.size()) {
     if (LOG_ENABLED(INFO)) {
@@ -1351,7 +1348,7 @@ int ClientHandler::proxy_protocol_read() {
     return -1;
   }
 
-  if (!util::streq(HEADER, StringRef{rb_.pos(), HEADER.size()})) {
+  if (HEADER != StringRef{rb_.pos(), HEADER.size()}) {
     if (LOG_ENABLED(INFO)) {
       CLOG(INFO, this) << "PROXY-protocol-v1: Bad PROXY protocol version 1 ID";
     }
@@ -1399,7 +1396,7 @@ int ClientHandler::proxy_protocol_read() {
       }
       return -1;
     }
-    if (!util::streq_l("UNKNOWN", rb_.pos(), 7)) {
+    if ("UNKNOWN"_sr != StringRef{rb_.pos(), 7}) {
       if (LOG_ENABLED(INFO)) {
         CLOG(INFO, this) << "PROXY-protocol-v1: Unknown INET protocol family";
       }
@@ -1482,9 +1479,10 @@ int ClientHandler::proxy_protocol_read() {
 
   rb_.drain(end + 2 - rb_.pos());
 
-  ipaddr_ =
-      make_string_ref(balloc_, StringRef{src_addr, src_addr + src_addrlen});
-  port_ = make_string_ref(balloc_, StringRef{src_port, src_port + src_portlen});
+  ipaddr_ = make_string_ref(
+      balloc_, StringRef{src_addr, static_cast<size_t>(src_addrlen)});
+  port_ = make_string_ref(
+      balloc_, StringRef{src_port, static_cast<size_t>(src_portlen)});
 
   if (LOG_ENABLED(INFO)) {
     CLOG(INFO, this) << "PROXY-protocol-v1: Finished, " << (rb_.pos() - first)
diff --git a/src/shrpx_client_handler.h b/src/shrpx_client_handler.h
index 511dd91..1bb3552 100644
--- a/src/shrpx_client_handler.h
+++ b/src/shrpx_client_handler.h
@@ -153,7 +153,7 @@ public:
   void setup_http3_upstream(std::unique_ptr<Http3Upstream> &&upstream);
   int read_quic(const UpstreamAddr *faddr, const Address &remote_addr,
                 const Address &local_addr, const ngtcp2_pkt_info &pi,
-                const uint8_t *data, size_t datalen);
+                std::span<const uint8_t> data);
   int write_quic();
 #endif // ENABLE_HTTP3
 
diff --git a/src/shrpx_config.cc b/src/shrpx_config.cc
index d856c95..a74b79e 100644
--- a/src/shrpx_config.cc
+++ b/src/shrpx_config.cc
@@ -76,7 +76,7 @@ namespace {
 Config *config;
 } // namespace
 
-constexpr auto SHRPX_UNIX_PATH_PREFIX = StringRef::from_lit("unix:");
+constexpr auto SHRPX_UNIX_PATH_PREFIX = "unix:"_sr;
 
 const Config *get_config() { return config; }
 
@@ -139,8 +139,8 @@ int split_host_port(char *host, size_t hostlen, uint16_t *port_ptr,
 
   auto portstr = StringRef{sep + 1, std::end(hostport)};
   auto d = util::parse_uint(portstr);
-  if (1 <= d && d <= std::numeric_limits<uint16_t>::max()) {
-    *port_ptr = d;
+  if (d && 1 <= d && d <= std::numeric_limits<uint16_t>::max()) {
+    *port_ptr = *d;
     return 0;
   }
 
@@ -152,7 +152,7 @@ int split_host_port(char *host, size_t hostlen, uint16_t *port_ptr,
 namespace {
 bool is_secure(const StringRef &filename) {
   struct stat buf;
-  int rv = stat(filename.c_str(), &buf);
+  int rv = stat(filename.data(), &buf);
   if (rv == 0) {
     if ((buf.st_mode & S_IRWXU) && !(buf.st_mode & S_IRWXG) &&
         !(buf.st_mode & S_IRWXO)) {
@@ -185,7 +185,7 @@ read_tls_ticket_key_file(const std::vector<StringRef> &files,
   for (auto &file : files) {
     struct stat fst {};
 
-    if (stat(file.c_str(), &fst) == -1) {
+    if (stat(file.data(), &fst) == -1) {
       auto error = errno;
       LOG(ERROR) << "tls-ticket-key-file: could not stat file " << file
                  << ", errno=" << error;
@@ -198,7 +198,7 @@ read_tls_ticket_key_file(const std::vector<StringRef> &files,
       return nullptr;
     }
 
-    std::ifstream f(file.c_str());
+    std::ifstream f(file.data());
     if (!f) {
       LOG(ERROR) << "tls-ticket-key-file: could not open file " << file;
       return nullptr;
@@ -245,7 +245,7 @@ read_quic_secret_file(const StringRef &path) {
   auto qkms = std::make_shared<QUICKeyingMaterials>();
   auto &kms = qkms->keying_materials;
 
-  std::ifstream f(path.c_str());
+  std::ifstream f(path.data());
   if (!f) {
     LOG(ERROR) << "frontend-quic-secret-file: could not open file " << path;
     return nullptr;
@@ -350,7 +350,7 @@ std::string read_passwd_from_file(const StringRef &opt,
     return line;
   }
 
-  std::ifstream in(filename.c_str(), std::ios::binary);
+  std::ifstream in(filename.data(), std::ios::binary);
   if (!in) {
     LOG(ERROR) << opt << ": Could not open key passwd file " << filename;
     return line;
@@ -375,13 +375,12 @@ HeaderRefs::value_type parse_header(BlockAllocator &balloc,
 
   auto name_iov =
       make_byte_ref(balloc, std::distance(std::begin(optarg), colon) + 1);
-  auto p = name_iov.base;
-  p = std::copy(std::begin(optarg), colon, p);
-  util::inp_strlower(name_iov.base, p);
+  auto p = std::copy(std::begin(optarg), colon, std::begin(name_iov));
+  util::inp_strlower(std::begin(name_iov), p);
   *p = '\0';
 
   auto nv =
-      HeaderRef(StringRef{name_iov.base, p},
+      HeaderRef(StringRef{std::span{std::begin(name_iov), p}},
                 make_string_ref(balloc, StringRef{value, std::end(optarg)}));
 
   if (!nghttp2_check_header_name(nv.name.byte(), nv.name.size()) ||
@@ -395,12 +394,12 @@ HeaderRefs::value_type parse_header(BlockAllocator &balloc,
 template <typename T>
 int parse_uint(T *dest, const StringRef &opt, const StringRef &optarg) {
   auto val = util::parse_uint(optarg);
-  if (val == -1) {
+  if (!val) {
     LOG(ERROR) << opt << ": bad value.  Specify an integer >= 0.";
     return -1;
   }
 
-  *dest = val;
+  *dest = *val;
 
   return 0;
 }
@@ -410,20 +409,20 @@ template <typename T>
 int parse_uint_with_unit(T *dest, const StringRef &opt,
                          const StringRef &optarg) {
   auto n = util::parse_uint_with_unit(optarg);
-  if (n == -1) {
+  if (!n) {
     LOG(ERROR) << opt << ": bad value: '" << optarg << "'";
     return -1;
   }
 
   if (static_cast<uint64_t>(std::numeric_limits<T>::max()) <
-      static_cast<uint64_t>(n)) {
+      static_cast<uint64_t>(*n)) {
     LOG(ERROR) << opt
                << ": too large.  The value should be less than or equal to "
                << std::numeric_limits<T>::max();
     return -1;
   }
 
-  *dest = n;
+  *dest = *n;
 
   return 0;
 }
@@ -482,12 +481,12 @@ int parse_altsvc(AltSvc &altsvc, const StringRef &opt,
 
 namespace {
 // generated by gennghttpxfun.py
-LogFragmentType log_var_lookup_token(const char *name, size_t namelen) {
-  switch (namelen) {
+LogFragmentType log_var_lookup_token(const StringRef &name) {
+  switch (name.size()) {
   case 3:
     switch (name[2]) {
     case 'd':
-      if (util::strieq_l("pi", name, 2)) {
+      if (util::strieq("pi"_sr, name, 2)) {
         return LogFragmentType::PID;
       }
       break;
@@ -496,12 +495,12 @@ LogFragmentType log_var_lookup_token(const char *name, size_t namelen) {
   case 4:
     switch (name[3]) {
     case 'h':
-      if (util::strieq_l("pat", name, 3)) {
+      if (util::strieq("pat"_sr, name, 3)) {
         return LogFragmentType::PATH;
       }
       break;
     case 'n':
-      if (util::strieq_l("alp", name, 3)) {
+      if (util::strieq("alp"_sr, name, 3)) {
         return LogFragmentType::ALPN;
       }
       break;
@@ -510,12 +509,12 @@ LogFragmentType log_var_lookup_token(const char *name, size_t namelen) {
   case 6:
     switch (name[5]) {
     case 'd':
-      if (util::strieq_l("metho", name, 5)) {
+      if (util::strieq("metho"_sr, name, 5)) {
         return LogFragmentType::METHOD;
       }
       break;
     case 's':
-      if (util::strieq_l("statu", name, 5)) {
+      if (util::strieq("statu"_sr, name, 5)) {
         return LogFragmentType::STATUS;
       }
       break;
@@ -524,12 +523,12 @@ LogFragmentType log_var_lookup_token(const char *name, size_t namelen) {
   case 7:
     switch (name[6]) {
     case 'i':
-      if (util::strieq_l("tls_sn", name, 6)) {
+      if (util::strieq("tls_sn"_sr, name, 6)) {
         return LogFragmentType::TLS_SNI;
       }
       break;
     case 't':
-      if (util::strieq_l("reques", name, 6)) {
+      if (util::strieq("reques"_sr, name, 6)) {
         return LogFragmentType::REQUEST;
       }
       break;
@@ -538,15 +537,15 @@ LogFragmentType log_var_lookup_token(const char *name, size_t namelen) {
   case 10:
     switch (name[9]) {
     case 'l':
-      if (util::strieq_l("time_loca", name, 9)) {
+      if (util::strieq("time_loca"_sr, name, 9)) {
         return LogFragmentType::TIME_LOCAL;
       }
       break;
     case 'r':
-      if (util::strieq_l("ssl_ciphe", name, 9)) {
+      if (util::strieq("ssl_ciphe"_sr, name, 9)) {
         return LogFragmentType::SSL_CIPHER;
       }
-      if (util::strieq_l("tls_ciphe", name, 9)) {
+      if (util::strieq("tls_ciphe"_sr, name, 9)) {
         return LogFragmentType::TLS_CIPHER;
       }
       break;
@@ -555,15 +554,15 @@ LogFragmentType log_var_lookup_token(const char *name, size_t namelen) {
   case 11:
     switch (name[10]) {
     case 'r':
-      if (util::strieq_l("remote_add", name, 10)) {
+      if (util::strieq("remote_add"_sr, name, 10)) {
         return LogFragmentType::REMOTE_ADDR;
       }
       break;
     case 't':
-      if (util::strieq_l("remote_por", name, 10)) {
+      if (util::strieq("remote_por"_sr, name, 10)) {
         return LogFragmentType::REMOTE_PORT;
       }
-      if (util::strieq_l("server_por", name, 10)) {
+      if (util::strieq("server_por"_sr, name, 10)) {
         return LogFragmentType::SERVER_PORT;
       }
       break;
@@ -572,28 +571,28 @@ LogFragmentType log_var_lookup_token(const char *name, size_t namelen) {
   case 12:
     switch (name[11]) {
     case '1':
-      if (util::strieq_l("time_iso860", name, 11)) {
+      if (util::strieq("time_iso860"_sr, name, 11)) {
         return LogFragmentType::TIME_ISO8601;
       }
       break;
     case 'e':
-      if (util::strieq_l("request_tim", name, 11)) {
+      if (util::strieq("request_tim"_sr, name, 11)) {
         return LogFragmentType::REQUEST_TIME;
       }
       break;
     case 'l':
-      if (util::strieq_l("ssl_protoco", name, 11)) {
+      if (util::strieq("ssl_protoco"_sr, name, 11)) {
         return LogFragmentType::SSL_PROTOCOL;
       }
-      if (util::strieq_l("tls_protoco", name, 11)) {
+      if (util::strieq("tls_protoco"_sr, name, 11)) {
         return LogFragmentType::TLS_PROTOCOL;
       }
       break;
     case 't':
-      if (util::strieq_l("backend_hos", name, 11)) {
+      if (util::strieq("backend_hos"_sr, name, 11)) {
         return LogFragmentType::BACKEND_HOST;
       }
-      if (util::strieq_l("backend_por", name, 11)) {
+      if (util::strieq("backend_por"_sr, name, 11)) {
         return LogFragmentType::BACKEND_PORT;
       }
       break;
@@ -602,10 +601,10 @@ LogFragmentType log_var_lookup_token(const char *name, size_t namelen) {
   case 14:
     switch (name[13]) {
     case 'd':
-      if (util::strieq_l("ssl_session_i", name, 13)) {
+      if (util::strieq("ssl_session_i"_sr, name, 13)) {
         return LogFragmentType::SSL_SESSION_ID;
       }
-      if (util::strieq_l("tls_session_i", name, 13)) {
+      if (util::strieq("tls_session_i"_sr, name, 13)) {
         return LogFragmentType::TLS_SESSION_ID;
       }
       break;
@@ -614,7 +613,7 @@ LogFragmentType log_var_lookup_token(const char *name, size_t namelen) {
   case 15:
     switch (name[14]) {
     case 't':
-      if (util::strieq_l("body_bytes_sen", name, 14)) {
+      if (util::strieq("body_bytes_sen"_sr, name, 14)) {
         return LogFragmentType::BODY_BYTES_SENT;
       }
       break;
@@ -623,7 +622,7 @@ LogFragmentType log_var_lookup_token(const char *name, size_t namelen) {
   case 16:
     switch (name[15]) {
     case 'n':
-      if (util::strieq_l("protocol_versio", name, 15)) {
+      if (util::strieq("protocol_versio"_sr, name, 15)) {
         return LogFragmentType::PROTOCOL_VERSION;
       }
       break;
@@ -632,7 +631,7 @@ LogFragmentType log_var_lookup_token(const char *name, size_t namelen) {
   case 17:
     switch (name[16]) {
     case 'l':
-      if (util::strieq_l("tls_client_seria", name, 16)) {
+      if (util::strieq("tls_client_seria"_sr, name, 16)) {
         return LogFragmentType::TLS_CLIENT_SERIAL;
       }
       break;
@@ -641,15 +640,15 @@ LogFragmentType log_var_lookup_token(const char *name, size_t namelen) {
   case 18:
     switch (name[17]) {
     case 'd':
-      if (util::strieq_l("ssl_session_reuse", name, 17)) {
+      if (util::strieq("ssl_session_reuse"_sr, name, 17)) {
         return LogFragmentType::SSL_SESSION_REUSED;
       }
-      if (util::strieq_l("tls_session_reuse", name, 17)) {
+      if (util::strieq("tls_session_reuse"_sr, name, 17)) {
         return LogFragmentType::TLS_SESSION_REUSED;
       }
       break;
     case 'y':
-      if (util::strieq_l("path_without_quer", name, 17)) {
+      if (util::strieq("path_without_quer"_sr, name, 17)) {
         return LogFragmentType::PATH_WITHOUT_QUERY;
       }
       break;
@@ -658,7 +657,7 @@ LogFragmentType log_var_lookup_token(const char *name, size_t namelen) {
   case 22:
     switch (name[21]) {
     case 'e':
-      if (util::strieq_l("tls_client_issuer_nam", name, 21)) {
+      if (util::strieq("tls_client_issuer_nam"_sr, name, 21)) {
         return LogFragmentType::TLS_CLIENT_ISSUER_NAME;
       }
       break;
@@ -667,7 +666,7 @@ LogFragmentType log_var_lookup_token(const char *name, size_t namelen) {
   case 23:
     switch (name[22]) {
     case 'e':
-      if (util::strieq_l("tls_client_subject_nam", name, 22)) {
+      if (util::strieq("tls_client_subject_nam"_sr, name, 22)) {
         return LogFragmentType::TLS_CLIENT_SUBJECT_NAME;
       }
       break;
@@ -676,7 +675,7 @@ LogFragmentType log_var_lookup_token(const char *name, size_t namelen) {
   case 27:
     switch (name[26]) {
     case '1':
-      if (util::strieq_l("tls_client_fingerprint_sha", name, 26)) {
+      if (util::strieq("tls_client_fingerprint_sha"_sr, name, 26)) {
         return LogFragmentType::TLS_CLIENT_FINGERPRINT_SHA1;
       }
       break;
@@ -685,7 +684,7 @@ LogFragmentType log_var_lookup_token(const char *name, size_t namelen) {
   case 29:
     switch (name[28]) {
     case '6':
-      if (util::strieq_l("tls_client_fingerprint_sha25", name, 28)) {
+      if (util::strieq("tls_client_fingerprint_sha25"_sr, name, 28)) {
         return LogFragmentType::TLS_CLIENT_FINGERPRINT_SHA256;
       }
       break;
@@ -720,10 +719,9 @@ std::vector<LogFragment> parse_log_format(BlockAllocator &balloc,
 
     ++p;
 
-    const char *var_name;
-    size_t var_namelen;
+    StringRef var_name;
     if (p != eop && *p == '{') {
-      var_name = ++p;
+      auto var_name_start = ++p;
       for (; p != eop && var_token(*p); ++p)
         ;
 
@@ -732,35 +730,33 @@ std::vector<LogFragment> parse_log_format(BlockAllocator &balloc,
         continue;
       }
 
-      var_namelen = p - var_name;
+      var_name = StringRef{var_name_start, p};
       ++p;
     } else {
-      var_name = p;
+      auto var_name_start = p;
       for (; p != eop && var_token(*p); ++p)
         ;
 
-      var_namelen = p - var_name;
+      var_name = StringRef{var_name_start, p};
     }
 
-    const char *value = nullptr;
+    auto value = std::begin(var_name);
 
-    auto type = log_var_lookup_token(var_name, var_namelen);
+    auto type = log_var_lookup_token(var_name);
 
     if (type == LogFragmentType::NONE) {
-      if (util::istarts_with_l(StringRef{var_name, var_namelen}, "http_")) {
-        if (util::streq_l("host", StringRef{var_name + str_size("http_"),
-                                            var_namelen - str_size("http_")})) {
+      if (util::istarts_with(var_name, "http_"_sr)) {
+        if ("host"_sr == var_name.substr(str_size("http_"))) {
           // Special handling of host header field.  We will use
           // :authority header field if host header is missing.  This
           // is a typical case in HTTP/2.
           type = LogFragmentType::AUTHORITY;
         } else {
           type = LogFragmentType::HTTP;
-          value = var_name + str_size("http_");
+          value += str_size("http_");
         }
       } else {
-        LOG(WARN) << "Unrecognized log format variable: "
-                  << StringRef{var_name, var_namelen};
+        LOG(WARN) << "Unrecognized log format variable: " << var_name;
         continue;
       }
     }
@@ -773,23 +769,19 @@ std::vector<LogFragment> parse_log_format(BlockAllocator &balloc,
 
     literal_start = p;
 
-    if (value == nullptr) {
+    if (value == std::begin(var_name)) {
       res.emplace_back(type);
       continue;
     }
 
     {
-      auto iov = make_byte_ref(
-          balloc, std::distance(value, var_name + var_namelen) + 1);
-      auto p = iov.base;
-      p = std::copy(value, var_name + var_namelen, p);
-      for (auto cp = iov.base; cp != p; ++cp) {
-        if (*cp == '_') {
-          *cp = '-';
-        }
-      }
+      auto iov =
+          make_byte_ref(balloc, std::distance(value, std::end(var_name)) + 1);
+      auto p = std::copy(value, std::end(var_name), std::begin(iov));
+      std::transform(std::begin(iov), p, std::begin(iov),
+                     [](auto c) { return c == '_' ? '-' : c; });
       *p = '\0';
-      res.emplace_back(type, StringRef{iov.base, p});
+      res.emplace_back(type, StringRef{std::span{std::begin(iov), p}});
     }
   }
 
@@ -804,15 +796,15 @@ std::vector<LogFragment> parse_log_format(BlockAllocator &balloc,
 namespace {
 int parse_address_family(int *dest, const StringRef &opt,
                          const StringRef &optarg) {
-  if (util::strieq_l("auto", optarg)) {
+  if (util::strieq("auto"_sr, optarg)) {
     *dest = AF_UNSPEC;
     return 0;
   }
-  if (util::strieq_l("IPv4", optarg)) {
+  if (util::strieq("IPv4"_sr, optarg)) {
     *dest = AF_INET;
     return 0;
   }
-  if (util::strieq_l("IPv6", optarg)) {
+  if (util::strieq("IPv6"_sr, optarg)) {
     *dest = AF_INET6;
     return 0;
   }
@@ -826,12 +818,12 @@ namespace {
 int parse_duration(ev_tstamp *dest, const StringRef &opt,
                    const StringRef &optarg) {
   auto t = util::parse_duration_with_unit(optarg);
-  if (t == std::numeric_limits<double>::infinity()) {
+  if (!t) {
     LOG(ERROR) << opt << ": bad value: '" << optarg << "'";
     return -1;
   }
 
-  *dest = t;
+  *dest = *t;
 
   return 0;
 }
@@ -868,9 +860,9 @@ int parse_memcached_connection_params(MemcachedConnectionParams &out,
     auto end = std::find(first, last, ';');
     auto param = StringRef{first, end};
 
-    if (util::strieq_l("tls", param)) {
+    if (util::strieq("tls"_sr, param)) {
       out.tls = true;
-    } else if (util::strieq_l("no-tls", param)) {
+    } else if (util::strieq("no-tls"_sr, param)) {
       out.tls = false;
     } else if (!param.empty()) {
       LOG(ERROR) << opt << ": " << param << ": unknown keyword";
@@ -906,29 +898,29 @@ int parse_upstream_params(UpstreamParams &out, const StringRef &src_params) {
     auto end = std::find(first, last, ';');
     auto param = StringRef{first, end};
 
-    if (util::strieq_l("tls", param)) {
+    if (util::strieq("tls"_sr, param)) {
       out.tls = true;
-    } else if (util::strieq_l("sni-fwd", param)) {
+    } else if (util::strieq("sni-fwd"_sr, param)) {
       out.sni_fwd = true;
-    } else if (util::strieq_l("no-tls", param)) {
+    } else if (util::strieq("no-tls"_sr, param)) {
       out.tls = false;
-    } else if (util::strieq_l("api", param)) {
+    } else if (util::strieq("api"_sr, param)) {
       if (out.alt_mode != UpstreamAltMode::NONE &&
           out.alt_mode != UpstreamAltMode::API) {
         LOG(ERROR) << "frontend: api and healthmon are mutually exclusive";
         return -1;
       }
       out.alt_mode = UpstreamAltMode::API;
-    } else if (util::strieq_l("healthmon", param)) {
+    } else if (util::strieq("healthmon"_sr, param)) {
       if (out.alt_mode != UpstreamAltMode::NONE &&
           out.alt_mode != UpstreamAltMode::HEALTHMON) {
         LOG(ERROR) << "frontend: api and healthmon are mutually exclusive";
         return -1;
       }
       out.alt_mode = UpstreamAltMode::HEALTHMON;
-    } else if (util::strieq_l("proxyproto", param)) {
+    } else if (util::strieq("proxyproto"_sr, param)) {
       out.proxyproto = true;
-    } else if (util::strieq_l("quic", param)) {
+    } else if (util::strieq("quic"_sr, param)) {
 #ifdef ENABLE_HTTP3
       out.quic = true;
 #else  // !ENABLE_HTTP3
@@ -977,11 +969,11 @@ namespace {
 int parse_downstream_param_duration(ev_tstamp &dest, const StringRef &name,
                                     const StringRef &value) {
   auto t = util::parse_duration_with_unit(value);
-  if (t == std::numeric_limits<double>::infinity()) {
+  if (!t) {
     LOG(ERROR) << "backend: " << name << ": bad value: '" << value << "'";
     return -1;
   }
-  dest = t;
+  dest = *t;
   return 0;
 }
 } // namespace
@@ -997,23 +989,22 @@ int parse_downstream_params(DownstreamParams &out,
     auto end = std::find(first, last, ';');
     auto param = StringRef{first, end};
 
-    if (util::istarts_with_l(param, "proto=")) {
+    if (util::istarts_with(param, "proto="_sr)) {
       auto protostr = StringRef{first + str_size("proto="), end};
       if (protostr.empty()) {
         LOG(ERROR) << "backend: proto: protocol is empty";
         return -1;
       }
 
-      if (util::streq_l("h2", std::begin(protostr), protostr.size())) {
+      if ("h2"_sr == protostr) {
         out.proto = Proto::HTTP2;
-      } else if (util::streq_l("http/1.1", std::begin(protostr),
-                               protostr.size())) {
+      } else if ("http/1.1"_sr == protostr) {
         out.proto = Proto::HTTP1;
       } else {
         LOG(ERROR) << "backend: proto: unknown protocol " << protostr;
         return -1;
       }
-    } else if (util::istarts_with_l(param, "fall=")) {
+    } else if (util::istarts_with(param, "fall="_sr)) {
       auto valstr = StringRef{first + str_size("fall="), end};
       if (valstr.empty()) {
         LOG(ERROR) << "backend: fall: non-negative integer is expected";
@@ -1021,13 +1012,13 @@ int parse_downstream_params(DownstreamParams &out,
       }
 
       auto n = util::parse_uint(valstr);
-      if (n == -1) {
+      if (!n) {
         LOG(ERROR) << "backend: fall: non-negative integer is expected";
         return -1;
       }
 
-      out.fall = n;
-    } else if (util::istarts_with_l(param, "rise=")) {
+      out.fall = *n;
+    } else if (util::istarts_with(param, "rise="_sr)) {
       auto valstr = StringRef{first + str_size("rise="), end};
       if (valstr.empty()) {
         LOG(ERROR) << "backend: rise: non-negative integer is expected";
@@ -1035,32 +1026,32 @@ int parse_downstream_params(DownstreamParams &out,
       }
 
       auto n = util::parse_uint(valstr);
-      if (n == -1) {
+      if (!n) {
         LOG(ERROR) << "backend: rise: non-negative integer is expected";
         return -1;
       }
 
-      out.rise = n;
-    } else if (util::strieq_l("tls", param)) {
+      out.rise = *n;
+    } else if (util::strieq("tls"_sr, param)) {
       out.tls = true;
-    } else if (util::strieq_l("no-tls", param)) {
+    } else if (util::strieq("no-tls"_sr, param)) {
       out.tls = false;
-    } else if (util::istarts_with_l(param, "sni=")) {
+    } else if (util::istarts_with(param, "sni="_sr)) {
       out.sni = StringRef{first + str_size("sni="), end};
-    } else if (util::istarts_with_l(param, "affinity=")) {
+    } else if (util::istarts_with(param, "affinity="_sr)) {
       auto valstr = StringRef{first + str_size("affinity="), end};
-      if (util::strieq_l("none", valstr)) {
+      if (util::strieq("none"_sr, valstr)) {
         out.affinity.type = SessionAffinity::NONE;
-      } else if (util::strieq_l("ip", valstr)) {
+      } else if (util::strieq("ip"_sr, valstr)) {
         out.affinity.type = SessionAffinity::IP;
-      } else if (util::strieq_l("cookie", valstr)) {
+      } else if (util::strieq("cookie"_sr, valstr)) {
         out.affinity.type = SessionAffinity::COOKIE;
       } else {
         LOG(ERROR)
             << "backend: affinity: value must be one of none, ip, and cookie";
         return -1;
       }
-    } else if (util::istarts_with_l(param, "affinity-cookie-name=")) {
+    } else if (util::istarts_with(param, "affinity-cookie-name="_sr)) {
       auto val = StringRef{first + str_size("affinity-cookie-name="), end};
       if (val.empty()) {
         LOG(ERROR)
@@ -1068,28 +1059,28 @@ int parse_downstream_params(DownstreamParams &out,
         return -1;
       }
       out.affinity.cookie.name = val;
-    } else if (util::istarts_with_l(param, "affinity-cookie-path=")) {
+    } else if (util::istarts_with(param, "affinity-cookie-path="_sr)) {
       out.affinity.cookie.path =
           StringRef{first + str_size("affinity-cookie-path="), end};
-    } else if (util::istarts_with_l(param, "affinity-cookie-secure=")) {
+    } else if (util::istarts_with(param, "affinity-cookie-secure="_sr)) {
       auto valstr = StringRef{first + str_size("affinity-cookie-secure="), end};
-      if (util::strieq_l("auto", valstr)) {
+      if (util::strieq("auto"_sr, valstr)) {
         out.affinity.cookie.secure = SessionAffinityCookieSecure::AUTO;
-      } else if (util::strieq_l("yes", valstr)) {
+      } else if (util::strieq("yes"_sr, valstr)) {
         out.affinity.cookie.secure = SessionAffinityCookieSecure::YES;
-      } else if (util::strieq_l("no", valstr)) {
+      } else if (util::strieq("no"_sr, valstr)) {
         out.affinity.cookie.secure = SessionAffinityCookieSecure::NO;
       } else {
         LOG(ERROR) << "backend: affinity-cookie-secure: value must be one of "
                       "auto, yes, and no";
         return -1;
       }
-    } else if (util::istarts_with_l(param, "affinity-cookie-stickiness=")) {
+    } else if (util::istarts_with(param, "affinity-cookie-stickiness="_sr)) {
       auto valstr =
           StringRef{first + str_size("affinity-cookie-stickiness="), end};
-      if (util::strieq_l("loose", valstr)) {
+      if (util::strieq("loose"_sr, valstr)) {
         out.affinity.cookie.stickiness = SessionAffinityCookieStickiness::LOOSE;
-      } else if (util::strieq_l("strict", valstr)) {
+      } else if (util::strieq("strict"_sr, valstr)) {
         out.affinity.cookie.stickiness =
             SessionAffinityCookieStickiness::STRICT;
       } else {
@@ -1097,28 +1088,28 @@ int parse_downstream_params(DownstreamParams &out,
                       "either loose or strict";
         return -1;
       }
-    } else if (util::strieq_l("dns", param)) {
+    } else if (util::strieq("dns"_sr, param)) {
       out.dns = true;
-    } else if (util::strieq_l("redirect-if-not-tls", param)) {
+    } else if (util::strieq("redirect-if-not-tls"_sr, param)) {
       out.redirect_if_not_tls = true;
-    } else if (util::strieq_l("upgrade-scheme", param)) {
+    } else if (util::strieq("upgrade-scheme"_sr, param)) {
       out.upgrade_scheme = true;
-    } else if (util::istarts_with_l(param, "mruby=")) {
+    } else if (util::istarts_with(param, "mruby="_sr)) {
       auto valstr = StringRef{first + str_size("mruby="), end};
       out.mruby = valstr;
-    } else if (util::istarts_with_l(param, "read-timeout=")) {
+    } else if (util::istarts_with(param, "read-timeout="_sr)) {
       if (parse_downstream_param_duration(
-              out.read_timeout, StringRef::from_lit("read-timeout"),
+              out.read_timeout, "read-timeout"_sr,
               StringRef{first + str_size("read-timeout="), end}) == -1) {
         return -1;
       }
-    } else if (util::istarts_with_l(param, "write-timeout=")) {
+    } else if (util::istarts_with(param, "write-timeout="_sr)) {
       if (parse_downstream_param_duration(
-              out.write_timeout, StringRef::from_lit("write-timeout"),
+              out.write_timeout, "write-timeout"_sr,
               StringRef{first + str_size("write-timeout="), end}) == -1) {
         return -1;
       }
-    } else if (util::istarts_with_l(param, "weight=")) {
+    } else if (util::istarts_with(param, "weight="_sr)) {
       auto valstr = StringRef{first + str_size("weight="), end};
       if (valstr.empty()) {
         LOG(ERROR)
@@ -1127,20 +1118,20 @@ int parse_downstream_params(DownstreamParams &out,
       }
 
       auto n = util::parse_uint(valstr);
-      if (n < 1 || n > 256) {
+      if (!n || (n < 1 || n > 256)) {
         LOG(ERROR)
             << "backend: weight: non-negative integer [1, 256] is expected";
         return -1;
       }
-      out.weight = n;
-    } else if (util::istarts_with_l(param, "group=")) {
+      out.weight = *n;
+    } else if (util::istarts_with(param, "group="_sr)) {
       auto valstr = StringRef{first + str_size("group="), end};
       if (valstr.empty()) {
         LOG(ERROR) << "backend: group: empty string is not allowed";
         return -1;
       }
       out.group = valstr;
-    } else if (util::istarts_with_l(param, "group-weight=")) {
+    } else if (util::istarts_with(param, "group-weight="_sr)) {
       auto valstr = StringRef{first + str_size("group-weight="), end};
       if (valstr.empty()) {
         LOG(ERROR) << "backend: group-weight: non-negative integer [1, 256] is "
@@ -1149,13 +1140,13 @@ int parse_downstream_params(DownstreamParams &out,
       }
 
       auto n = util::parse_uint(valstr);
-      if (n < 1 || n > 256) {
+      if (!n || (n < 1 || n > 256)) {
         LOG(ERROR) << "backend: group-weight: non-negative integer [1, 256] is "
                       "expected";
         return -1;
       }
-      out.group_weight = n;
-    } else if (util::strieq_l("dnf", param)) {
+      out.group_weight = *n;
+    } else if (util::strieq("dnf"_sr, param)) {
       out.dnf = true;
     } else if (!param.empty()) {
       LOG(ERROR) << "backend: " << param << ": unknown keyword";
@@ -1235,12 +1226,12 @@ int parse_mapping(Config *config, DownstreamAddrConfig &addr,
       // This effectively makes empty pattern to "/".  2 for '/' and
       // terminal NULL character.
       auto iov = make_byte_ref(downstreamconf.balloc, raw_pattern.size() + 2);
-      auto p = iov.base;
-      p = std::copy(std::begin(raw_pattern), std::end(raw_pattern), p);
-      util::inp_strlower(iov.base, p);
+      auto p = std::copy(std::begin(raw_pattern), std::end(raw_pattern),
+                         std::begin(iov));
+      util::inp_strlower(std::begin(iov), p);
       *p++ = '/';
       *p = '\0';
-      pattern = StringRef{iov.base, p};
+      pattern = StringRef{std::span{std::begin(iov), p}};
     } else {
       auto path = http2::normalize_path_colon(
           downstreamconf.balloc, StringRef{slash, std::end(raw_pattern)},
@@ -1248,12 +1239,11 @@ int parse_mapping(Config *config, DownstreamAddrConfig &addr,
       auto iov = make_byte_ref(downstreamconf.balloc,
                                std::distance(std::begin(raw_pattern), slash) +
                                    path.size() + 1);
-      auto p = iov.base;
-      p = std::copy(std::begin(raw_pattern), slash, p);
-      util::inp_strlower(iov.base, p);
+      auto p = std::copy(std::begin(raw_pattern), slash, std::begin(iov));
+      util::inp_strlower(std::begin(iov), p);
       p = std::copy(std::begin(path), std::end(path), p);
       *p = '\0';
-      pattern = StringRef{iov.base, p};
+      pattern = StringRef{std::span{std::begin(iov), p}};
     }
     auto it = pattern_addr_indexer.find(pattern);
     if (it != std::end(pattern_addr_indexer)) {
@@ -1385,10 +1375,10 @@ int parse_mapping(Config *config, DownstreamAddrConfig &addr,
         router.add_route(path, idx, path_is_wildcard);
 
         auto iov = make_byte_ref(downstreamconf.balloc, host.size() + 1);
-        auto p = iov.base;
-        p = std::reverse_copy(std::begin(host), std::end(host), p);
+        auto p = std::reverse_copy(std::begin(host), std::end(host),
+                                   std::begin(iov));
         *p = '\0';
-        auto rev_host = StringRef{iov.base, p};
+        auto rev_host = StringRef{std::span{std::begin(iov), p}};
 
         rw_router.add_route(rev_host, wildcard_patterns.size() - 1);
       } else {
@@ -1413,11 +1403,11 @@ int parse_mapping(Config *config, DownstreamAddrConfig &addr,
 
 namespace {
 ForwardedNode parse_forwarded_node_type(const StringRef &optarg) {
-  if (util::strieq_l("obfuscated", optarg)) {
+  if (util::strieq("obfuscated"_sr, optarg)) {
     return ForwardedNode::OBFUSCATED;
   }
 
-  if (util::strieq_l("ip", optarg)) {
+  if (util::strieq("ip"_sr, optarg)) {
     return ForwardedNode::IP;
   }
 
@@ -1450,23 +1440,23 @@ int parse_error_page(std::vector<ErrorPage> &error_pages, const StringRef &opt,
   auto codestr = StringRef{std::begin(optarg), eq};
   unsigned int code;
 
-  if (codestr == StringRef::from_lit("*")) {
+  if (codestr == "*"_sr) {
     code = 0;
   } else {
     auto n = util::parse_uint(codestr);
 
-    if (n == -1 || n < 400 || n > 599) {
+    if (!n || n < 400 || n > 599) {
       LOG(ERROR) << opt << ": bad code: '" << codestr << "'";
       return -1;
     }
 
-    code = static_cast<unsigned int>(n);
+    code = static_cast<unsigned int>(*n);
   }
 
   auto path = StringRef{eq + 1, std::end(optarg)};
 
   std::vector<uint8_t> content;
-  auto fd = open(path.c_str(), O_RDONLY);
+  auto fd = open(path.data(), O_RDONLY);
   if (fd == -1) {
     auto error = errno;
     LOG(ERROR) << opt << ": " << optarg << ": "
@@ -1515,7 +1505,7 @@ int parse_subcert_params(SubcertParams &out, const StringRef &src_params) {
     auto end = std::find(first, last, ';');
     auto param = StringRef{first, end};
 
-    if (util::istarts_with_l(param, "sct-dir=")) {
+    if (util::istarts_with(param, "sct-dir="_sr)) {
 #if defined(NGHTTP2_GENUINE_OPENSSL) || defined(NGHTTP2_OPENSSL_IS_BORINGSSL)
       auto sct_dir =
           StringRef{std::begin(param) + str_size("sct-dir="), std::end(param)};
@@ -1551,7 +1541,7 @@ int read_tls_sct_from_dir(std::vector<uint8_t> &dst, const StringRef &opt,
                           const StringRef &dir_path) {
   std::array<char, STRERROR_BUFSIZE> errbuf;
 
-  auto dir = opendir(dir_path.c_str());
+  auto dir = opendir(dir_path.data());
   if (dir == nullptr) {
     auto error = errno;
     LOG(ERROR) << opt << ": " << dir_path << ": "
@@ -1580,7 +1570,7 @@ int read_tls_sct_from_dir(std::vector<uint8_t> &dst, const StringRef &opt,
 
     auto name = StringRef{ent->d_name};
 
-    if (name[0] == '.' || !util::iends_with_l(name, ".sct")) {
+    if (name[0] == '.' || !util::iends_with(name, ".sct"_sr)) {
       continue;
     }
 
@@ -1667,7 +1657,7 @@ namespace {
 int parse_psk_secrets(Config *config, const StringRef &path) {
   auto &tlsconf = config->tls;
 
-  std::ifstream f(path.c_str(), std::ios::binary);
+  std::ifstream f(path.data(), std::ios::binary);
   if (!f) {
     LOG(ERROR) << SHRPX_OPT_PSK_SECRETS << ": could not open file " << path;
     return -1;
@@ -1733,7 +1723,7 @@ namespace {
 int parse_client_psk_secrets(Config *config, const StringRef &path) {
   auto &tlsconf = config->tls;
 
-  std::ifstream f(path.c_str(), std::ios::binary);
+  std::ifstream f(path.data(), std::ios::binary);
   if (!f) {
     LOG(ERROR) << SHRPX_OPT_CLIENT_PSK_SECRETS << ": could not open file "
                << path;
@@ -1776,8 +1766,8 @@ int parse_client_psk_secrets(Config *config, const StringRef &path) {
     tlsconf.client.psk.identity =
         make_string_ref(config->balloc, StringRef{std::begin(line), sep_it});
 
-    tlsconf.client.psk.secret =
-        util::decode_hex(config->balloc, StringRef{sep_it + 1, std::end(line)});
+    tlsconf.client.psk.secret = StringRef{util::decode_hex(
+        config->balloc, StringRef{sep_it + 1, std::end(line)})};
 
     return 0;
   }
@@ -1788,17 +1778,17 @@ int parse_client_psk_secrets(Config *config, const StringRef &path) {
 #endif // !OPENSSL_NO_PSK
 
 // generated by gennghttpxfun.py
-int option_lookup_token(const char *name, size_t namelen) {
-  switch (namelen) {
+int option_lookup_token(const StringRef &name) {
+  switch (name.size()) {
   case 4:
     switch (name[3]) {
     case 'f':
-      if (util::strieq_l("con", name, 3)) {
+      if (util::strieq("con"_sr, name, 3)) {
         return SHRPX_OPTID_CONF;
       }
       break;
     case 'r':
-      if (util::strieq_l("use", name, 3)) {
+      if (util::strieq("use"_sr, name, 3)) {
         return SHRPX_OPTID_USER;
       }
       break;
@@ -1807,25 +1797,25 @@ int option_lookup_token(const char *name, size_t namelen) {
   case 6:
     switch (name[5]) {
     case 'a':
-      if (util::strieq_l("no-vi", name, 5)) {
+      if (util::strieq("no-vi"_sr, name, 5)) {
         return SHRPX_OPTID_NO_VIA;
       }
       break;
     case 'c':
-      if (util::strieq_l("altsv", name, 5)) {
+      if (util::strieq("altsv"_sr, name, 5)) {
         return SHRPX_OPTID_ALTSVC;
       }
       break;
     case 'n':
-      if (util::strieq_l("daemo", name, 5)) {
+      if (util::strieq("daemo"_sr, name, 5)) {
         return SHRPX_OPTID_DAEMON;
       }
       break;
     case 't':
-      if (util::strieq_l("cacer", name, 5)) {
+      if (util::strieq("cacer"_sr, name, 5)) {
         return SHRPX_OPTID_CACERT;
       }
-      if (util::strieq_l("clien", name, 5)) {
+      if (util::strieq("clien"_sr, name, 5)) {
         return SHRPX_OPTID_CLIENT;
       }
       break;
@@ -1834,38 +1824,38 @@ int option_lookup_token(const char *name, size_t namelen) {
   case 7:
     switch (name[6]) {
     case 'd':
-      if (util::strieq_l("backen", name, 6)) {
+      if (util::strieq("backen"_sr, name, 6)) {
         return SHRPX_OPTID_BACKEND;
       }
       break;
     case 'e':
-      if (util::strieq_l("includ", name, 6)) {
+      if (util::strieq("includ"_sr, name, 6)) {
         return SHRPX_OPTID_INCLUDE;
       }
       break;
     case 'g':
-      if (util::strieq_l("backlo", name, 6)) {
+      if (util::strieq("backlo"_sr, name, 6)) {
         return SHRPX_OPTID_BACKLOG;
       }
-      if (util::strieq_l("paddin", name, 6)) {
+      if (util::strieq("paddin"_sr, name, 6)) {
         return SHRPX_OPTID_PADDING;
       }
       break;
     case 'p':
-      if (util::strieq_l("no-ocs", name, 6)) {
+      if (util::strieq("no-ocs"_sr, name, 6)) {
         return SHRPX_OPTID_NO_OCSP;
       }
       break;
     case 's':
-      if (util::strieq_l("cipher", name, 6)) {
+      if (util::strieq("cipher"_sr, name, 6)) {
         return SHRPX_OPTID_CIPHERS;
       }
-      if (util::strieq_l("worker", name, 6)) {
+      if (util::strieq("worker"_sr, name, 6)) {
         return SHRPX_OPTID_WORKERS;
       }
       break;
     case 't':
-      if (util::strieq_l("subcer", name, 6)) {
+      if (util::strieq("subcer"_sr, name, 6)) {
         return SHRPX_OPTID_SUBCERT;
       }
       break;
@@ -1874,30 +1864,30 @@ int option_lookup_token(const char *name, size_t namelen) {
   case 8:
     switch (name[7]) {
     case 'd':
-      if (util::strieq_l("fronten", name, 7)) {
+      if (util::strieq("fronten"_sr, name, 7)) {
         return SHRPX_OPTID_FRONTEND;
       }
       break;
     case 'e':
-      if (util::strieq_l("insecur", name, 7)) {
+      if (util::strieq("insecur"_sr, name, 7)) {
         return SHRPX_OPTID_INSECURE;
       }
-      if (util::strieq_l("pid-fil", name, 7)) {
+      if (util::strieq("pid-fil"_sr, name, 7)) {
         return SHRPX_OPTID_PID_FILE;
       }
       break;
     case 'n':
-      if (util::strieq_l("fastope", name, 7)) {
+      if (util::strieq("fastope"_sr, name, 7)) {
         return SHRPX_OPTID_FASTOPEN;
       }
       break;
     case 's':
-      if (util::strieq_l("tls-ktl", name, 7)) {
+      if (util::strieq("tls-ktl"_sr, name, 7)) {
         return SHRPX_OPTID_TLS_KTLS;
       }
       break;
     case 't':
-      if (util::strieq_l("npn-lis", name, 7)) {
+      if (util::strieq("npn-lis"_sr, name, 7)) {
         return SHRPX_OPTID_NPN_LIST;
       }
       break;
@@ -1906,20 +1896,20 @@ int option_lookup_token(const char *name, size_t namelen) {
   case 9:
     switch (name[8]) {
     case 'e':
-      if (util::strieq_l("no-kqueu", name, 8)) {
+      if (util::strieq("no-kqueu"_sr, name, 8)) {
         return SHRPX_OPTID_NO_KQUEUE;
       }
-      if (util::strieq_l("read-rat", name, 8)) {
+      if (util::strieq("read-rat"_sr, name, 8)) {
         return SHRPX_OPTID_READ_RATE;
       }
       break;
     case 'l':
-      if (util::strieq_l("log-leve", name, 8)) {
+      if (util::strieq("log-leve"_sr, name, 8)) {
         return SHRPX_OPTID_LOG_LEVEL;
       }
       break;
     case 't':
-      if (util::strieq_l("alpn-lis", name, 8)) {
+      if (util::strieq("alpn-lis"_sr, name, 8)) {
         return SHRPX_OPTID_ALPN_LIST;
       }
       break;
@@ -1928,18 +1918,18 @@ int option_lookup_token(const char *name, size_t namelen) {
   case 10:
     switch (name[9]) {
     case 'e':
-      if (util::strieq_l("error-pag", name, 9)) {
+      if (util::strieq("error-pag"_sr, name, 9)) {
         return SHRPX_OPTID_ERROR_PAGE;
       }
-      if (util::strieq_l("mruby-fil", name, 9)) {
+      if (util::strieq("mruby-fil"_sr, name, 9)) {
         return SHRPX_OPTID_MRUBY_FILE;
       }
-      if (util::strieq_l("write-rat", name, 9)) {
+      if (util::strieq("write-rat"_sr, name, 9)) {
         return SHRPX_OPTID_WRITE_RATE;
       }
       break;
     case 't':
-      if (util::strieq_l("read-burs", name, 9)) {
+      if (util::strieq("read-burs"_sr, name, 9)) {
         return SHRPX_OPTID_READ_BURST;
       }
       break;
@@ -1948,41 +1938,41 @@ int option_lookup_token(const char *name, size_t namelen) {
   case 11:
     switch (name[10]) {
     case 'e':
-      if (util::strieq_l("server-nam", name, 10)) {
+      if (util::strieq("server-nam"_sr, name, 10)) {
         return SHRPX_OPTID_SERVER_NAME;
       }
       break;
     case 'f':
-      if (util::strieq_l("no-quic-bp", name, 10)) {
+      if (util::strieq("no-quic-bp"_sr, name, 10)) {
         return SHRPX_OPTID_NO_QUIC_BPF;
       }
       break;
     case 'r':
-      if (util::strieq_l("tls-sct-di", name, 10)) {
+      if (util::strieq("tls-sct-di"_sr, name, 10)) {
         return SHRPX_OPTID_TLS_SCT_DIR;
       }
       break;
     case 's':
-      if (util::strieq_l("backend-tl", name, 10)) {
+      if (util::strieq("backend-tl"_sr, name, 10)) {
         return SHRPX_OPTID_BACKEND_TLS;
       }
-      if (util::strieq_l("ecdh-curve", name, 10)) {
+      if (util::strieq("ecdh-curve"_sr, name, 10)) {
         return SHRPX_OPTID_ECDH_CURVES;
       }
-      if (util::strieq_l("psk-secret", name, 10)) {
+      if (util::strieq("psk-secret"_sr, name, 10)) {
         return SHRPX_OPTID_PSK_SECRETS;
       }
       break;
     case 't':
-      if (util::strieq_l("write-burs", name, 10)) {
+      if (util::strieq("write-burs"_sr, name, 10)) {
         return SHRPX_OPTID_WRITE_BURST;
       }
       break;
     case 'y':
-      if (util::strieq_l("dns-max-tr", name, 10)) {
+      if (util::strieq("dns-max-tr"_sr, name, 10)) {
         return SHRPX_OPTID_DNS_MAX_TRY;
       }
-      if (util::strieq_l("http2-prox", name, 10)) {
+      if (util::strieq("http2-prox"_sr, name, 10)) {
         return SHRPX_OPTID_HTTP2_PROXY;
       }
       break;
@@ -1991,38 +1981,38 @@ int option_lookup_token(const char *name, size_t namelen) {
   case 12:
     switch (name[11]) {
     case '4':
-      if (util::strieq_l("backend-ipv", name, 11)) {
+      if (util::strieq("backend-ipv"_sr, name, 11)) {
         return SHRPX_OPTID_BACKEND_IPV4;
       }
       break;
     case '6':
-      if (util::strieq_l("backend-ipv", name, 11)) {
+      if (util::strieq("backend-ipv"_sr, name, 11)) {
         return SHRPX_OPTID_BACKEND_IPV6;
       }
       break;
     case 'c':
-      if (util::strieq_l("http2-altsv", name, 11)) {
+      if (util::strieq("http2-altsv"_sr, name, 11)) {
         return SHRPX_OPTID_HTTP2_ALTSVC;
       }
       break;
     case 'e':
-      if (util::strieq_l("host-rewrit", name, 11)) {
+      if (util::strieq("host-rewrit"_sr, name, 11)) {
         return SHRPX_OPTID_HOST_REWRITE;
       }
-      if (util::strieq_l("http2-bridg", name, 11)) {
+      if (util::strieq("http2-bridg"_sr, name, 11)) {
         return SHRPX_OPTID_HTTP2_BRIDGE;
       }
       break;
     case 'p':
-      if (util::strieq_l("ocsp-startu", name, 11)) {
+      if (util::strieq("ocsp-startu"_sr, name, 11)) {
         return SHRPX_OPTID_OCSP_STARTUP;
       }
       break;
     case 'y':
-      if (util::strieq_l("client-prox", name, 11)) {
+      if (util::strieq("client-prox"_sr, name, 11)) {
         return SHRPX_OPTID_CLIENT_PROXY;
       }
-      if (util::strieq_l("forwarded-b", name, 11)) {
+      if (util::strieq("forwarded-b"_sr, name, 11)) {
         return SHRPX_OPTID_FORWARDED_BY;
       }
       break;
@@ -2031,36 +2021,36 @@ int option_lookup_token(const char *name, size_t namelen) {
   case 13:
     switch (name[12]) {
     case 'd':
-      if (util::strieq_l("add-forwarde", name, 12)) {
+      if (util::strieq("add-forwarde"_sr, name, 12)) {
         return SHRPX_OPTID_ADD_FORWARDED;
       }
-      if (util::strieq_l("single-threa", name, 12)) {
+      if (util::strieq("single-threa"_sr, name, 12)) {
         return SHRPX_OPTID_SINGLE_THREAD;
       }
       break;
     case 'e':
-      if (util::strieq_l("dh-param-fil", name, 12)) {
+      if (util::strieq("dh-param-fil"_sr, name, 12)) {
         return SHRPX_OPTID_DH_PARAM_FILE;
       }
-      if (util::strieq_l("errorlog-fil", name, 12)) {
+      if (util::strieq("errorlog-fil"_sr, name, 12)) {
         return SHRPX_OPTID_ERRORLOG_FILE;
       }
-      if (util::strieq_l("rlimit-nofil", name, 12)) {
+      if (util::strieq("rlimit-nofil"_sr, name, 12)) {
         return SHRPX_OPTID_RLIMIT_NOFILE;
       }
       break;
     case 'r':
-      if (util::strieq_l("forwarded-fo", name, 12)) {
+      if (util::strieq("forwarded-fo"_sr, name, 12)) {
         return SHRPX_OPTID_FORWARDED_FOR;
       }
       break;
     case 's':
-      if (util::strieq_l("tls13-cipher", name, 12)) {
+      if (util::strieq("tls13-cipher"_sr, name, 12)) {
         return SHRPX_OPTID_TLS13_CIPHERS;
       }
       break;
     case 't':
-      if (util::strieq_l("verify-clien", name, 12)) {
+      if (util::strieq("verify-clien"_sr, name, 12)) {
         return SHRPX_OPTID_VERIFY_CLIENT;
       }
       break;
@@ -2069,43 +2059,43 @@ int option_lookup_token(const char *name, size_t namelen) {
   case 14:
     switch (name[13]) {
     case 'd':
-      if (util::strieq_l("quic-server-i", name, 13)) {
+      if (util::strieq("quic-server-i"_sr, name, 13)) {
         return SHRPX_OPTID_QUIC_SERVER_ID;
       }
       break;
     case 'e':
-      if (util::strieq_l("accesslog-fil", name, 13)) {
+      if (util::strieq("accesslog-fil"_sr, name, 13)) {
         return SHRPX_OPTID_ACCESSLOG_FILE;
       }
       break;
     case 'h':
-      if (util::strieq_l("no-server-pus", name, 13)) {
+      if (util::strieq("no-server-pus"_sr, name, 13)) {
         return SHRPX_OPTID_NO_SERVER_PUSH;
       }
       break;
     case 'k':
-      if (util::strieq_l("rlimit-memloc", name, 13)) {
+      if (util::strieq("rlimit-memloc"_sr, name, 13)) {
         return SHRPX_OPTID_RLIMIT_MEMLOCK;
       }
       break;
     case 'p':
-      if (util::strieq_l("no-verify-ocs", name, 13)) {
+      if (util::strieq("no-verify-ocs"_sr, name, 13)) {
         return SHRPX_OPTID_NO_VERIFY_OCSP;
       }
       break;
     case 's':
-      if (util::strieq_l("backend-no-tl", name, 13)) {
+      if (util::strieq("backend-no-tl"_sr, name, 13)) {
         return SHRPX_OPTID_BACKEND_NO_TLS;
       }
-      if (util::strieq_l("client-cipher", name, 13)) {
+      if (util::strieq("client-cipher"_sr, name, 13)) {
         return SHRPX_OPTID_CLIENT_CIPHERS;
       }
-      if (util::strieq_l("single-proces", name, 13)) {
+      if (util::strieq("single-proces"_sr, name, 13)) {
         return SHRPX_OPTID_SINGLE_PROCESS;
       }
       break;
     case 't':
-      if (util::strieq_l("tls-proto-lis", name, 13)) {
+      if (util::strieq("tls-proto-lis"_sr, name, 13)) {
         return SHRPX_OPTID_TLS_PROTO_LIST;
       }
       break;
@@ -2114,22 +2104,22 @@ int option_lookup_token(const char *name, size_t namelen) {
   case 15:
     switch (name[14]) {
     case 'e':
-      if (util::strieq_l("no-host-rewrit", name, 14)) {
+      if (util::strieq("no-host-rewrit"_sr, name, 14)) {
         return SHRPX_OPTID_NO_HOST_REWRITE;
       }
       break;
     case 'g':
-      if (util::strieq_l("errorlog-syslo", name, 14)) {
+      if (util::strieq("errorlog-syslo"_sr, name, 14)) {
         return SHRPX_OPTID_ERRORLOG_SYSLOG;
       }
       break;
     case 's':
-      if (util::strieq_l("frontend-no-tl", name, 14)) {
+      if (util::strieq("frontend-no-tl"_sr, name, 14)) {
         return SHRPX_OPTID_FRONTEND_NO_TLS;
       }
       break;
     case 'y':
-      if (util::strieq_l("syslog-facilit", name, 14)) {
+      if (util::strieq("syslog-facilit"_sr, name, 14)) {
         return SHRPX_OPTID_SYSLOG_FACILITY;
       }
       break;
@@ -2138,26 +2128,26 @@ int option_lookup_token(const char *name, size_t namelen) {
   case 16:
     switch (name[15]) {
     case 'e':
-      if (util::strieq_l("certificate-fil", name, 15)) {
+      if (util::strieq("certificate-fil"_sr, name, 15)) {
         return SHRPX_OPTID_CERTIFICATE_FILE;
       }
-      if (util::strieq_l("client-cert-fil", name, 15)) {
+      if (util::strieq("client-cert-fil"_sr, name, 15)) {
         return SHRPX_OPTID_CLIENT_CERT_FILE;
       }
-      if (util::strieq_l("private-key-fil", name, 15)) {
+      if (util::strieq("private-key-fil"_sr, name, 15)) {
         return SHRPX_OPTID_PRIVATE_KEY_FILE;
       }
-      if (util::strieq_l("worker-read-rat", name, 15)) {
+      if (util::strieq("worker-read-rat"_sr, name, 15)) {
         return SHRPX_OPTID_WORKER_READ_RATE;
       }
       break;
     case 'g':
-      if (util::strieq_l("accesslog-syslo", name, 15)) {
+      if (util::strieq("accesslog-syslo"_sr, name, 15)) {
         return SHRPX_OPTID_ACCESSLOG_SYSLOG;
       }
       break;
     case 't':
-      if (util::strieq_l("accesslog-forma", name, 15)) {
+      if (util::strieq("accesslog-forma"_sr, name, 15)) {
         return SHRPX_OPTID_ACCESSLOG_FORMAT;
       }
       break;
@@ -2166,26 +2156,26 @@ int option_lookup_token(const char *name, size_t namelen) {
   case 17:
     switch (name[16]) {
     case 'e':
-      if (util::strieq_l("no-server-rewrit", name, 16)) {
+      if (util::strieq("no-server-rewrit"_sr, name, 16)) {
         return SHRPX_OPTID_NO_SERVER_REWRITE;
       }
-      if (util::strieq_l("worker-write-rat", name, 16)) {
+      if (util::strieq("worker-write-rat"_sr, name, 16)) {
         return SHRPX_OPTID_WORKER_WRITE_RATE;
       }
       break;
     case 's':
-      if (util::strieq_l("backend-http1-tl", name, 16)) {
+      if (util::strieq("backend-http1-tl"_sr, name, 16)) {
         return SHRPX_OPTID_BACKEND_HTTP1_TLS;
       }
-      if (util::strieq_l("max-header-field", name, 16)) {
+      if (util::strieq("max-header-field"_sr, name, 16)) {
         return SHRPX_OPTID_MAX_HEADER_FIELDS;
       }
       break;
     case 't':
-      if (util::strieq_l("dns-cache-timeou", name, 16)) {
+      if (util::strieq("dns-cache-timeou"_sr, name, 16)) {
         return SHRPX_OPTID_DNS_CACHE_TIMEOUT;
       }
-      if (util::strieq_l("worker-read-burs", name, 16)) {
+      if (util::strieq("worker-read-burs"_sr, name, 16)) {
         return SHRPX_OPTID_WORKER_READ_BURST;
       }
       break;
@@ -2194,25 +2184,25 @@ int option_lookup_token(const char *name, size_t namelen) {
   case 18:
     switch (name[17]) {
     case 'a':
-      if (util::strieq_l("tls-max-early-dat", name, 17)) {
+      if (util::strieq("tls-max-early-dat"_sr, name, 17)) {
         return SHRPX_OPTID_TLS_MAX_EARLY_DATA;
       }
       break;
     case 'r':
-      if (util::strieq_l("add-request-heade", name, 17)) {
+      if (util::strieq("add-request-heade"_sr, name, 17)) {
         return SHRPX_OPTID_ADD_REQUEST_HEADER;
       }
       break;
     case 's':
-      if (util::strieq_l("client-psk-secret", name, 17)) {
+      if (util::strieq("client-psk-secret"_sr, name, 17)) {
         return SHRPX_OPTID_CLIENT_PSK_SECRETS;
       }
       break;
     case 't':
-      if (util::strieq_l("dns-lookup-timeou", name, 17)) {
+      if (util::strieq("dns-lookup-timeou"_sr, name, 17)) {
         return SHRPX_OPTID_DNS_LOOKUP_TIMEOUT;
       }
-      if (util::strieq_l("worker-write-burs", name, 17)) {
+      if (util::strieq("worker-write-burs"_sr, name, 17)) {
         return SHRPX_OPTID_WORKER_WRITE_BURST;
       }
       break;
@@ -2221,37 +2211,37 @@ int option_lookup_token(const char *name, size_t namelen) {
   case 19:
     switch (name[18]) {
     case 'e':
-      if (util::strieq_l("no-location-rewrit", name, 18)) {
+      if (util::strieq("no-location-rewrit"_sr, name, 18)) {
         return SHRPX_OPTID_NO_LOCATION_REWRITE;
       }
-      if (util::strieq_l("require-http-schem", name, 18)) {
+      if (util::strieq("require-http-schem"_sr, name, 18)) {
         return SHRPX_OPTID_REQUIRE_HTTP_SCHEME;
       }
-      if (util::strieq_l("tls-ticket-key-fil", name, 18)) {
+      if (util::strieq("tls-ticket-key-fil"_sr, name, 18)) {
         return SHRPX_OPTID_TLS_TICKET_KEY_FILE;
       }
       break;
     case 'f':
-      if (util::strieq_l("backend-max-backof", name, 18)) {
+      if (util::strieq("backend-max-backof"_sr, name, 18)) {
         return SHRPX_OPTID_BACKEND_MAX_BACKOFF;
       }
       break;
     case 'r':
-      if (util::strieq_l("add-response-heade", name, 18)) {
+      if (util::strieq("add-response-heade"_sr, name, 18)) {
         return SHRPX_OPTID_ADD_RESPONSE_HEADER;
       }
-      if (util::strieq_l("add-x-forwarded-fo", name, 18)) {
+      if (util::strieq("add-x-forwarded-fo"_sr, name, 18)) {
         return SHRPX_OPTID_ADD_X_FORWARDED_FOR;
       }
-      if (util::strieq_l("header-field-buffe", name, 18)) {
+      if (util::strieq("header-field-buffe"_sr, name, 18)) {
         return SHRPX_OPTID_HEADER_FIELD_BUFFER;
       }
       break;
     case 't':
-      if (util::strieq_l("redirect-https-por", name, 18)) {
+      if (util::strieq("redirect-https-por"_sr, name, 18)) {
         return SHRPX_OPTID_REDIRECT_HTTPS_PORT;
       }
-      if (util::strieq_l("stream-read-timeou", name, 18)) {
+      if (util::strieq("stream-read-timeou"_sr, name, 18)) {
         return SHRPX_OPTID_STREAM_READ_TIMEOUT;
       }
       break;
@@ -2260,36 +2250,36 @@ int option_lookup_token(const char *name, size_t namelen) {
   case 20:
     switch (name[19]) {
     case 'g':
-      if (util::strieq_l("frontend-frame-debu", name, 19)) {
+      if (util::strieq("frontend-frame-debu"_sr, name, 19)) {
         return SHRPX_OPTID_FRONTEND_FRAME_DEBUG;
       }
       break;
     case 'l':
-      if (util::strieq_l("ocsp-update-interva", name, 19)) {
+      if (util::strieq("ocsp-update-interva"_sr, name, 19)) {
         return SHRPX_OPTID_OCSP_UPDATE_INTERVAL;
       }
       break;
     case 's':
-      if (util::strieq_l("max-worker-processe", name, 19)) {
+      if (util::strieq("max-worker-processe"_sr, name, 19)) {
         return SHRPX_OPTID_MAX_WORKER_PROCESSES;
       }
-      if (util::strieq_l("tls13-client-cipher", name, 19)) {
+      if (util::strieq("tls13-client-cipher"_sr, name, 19)) {
         return SHRPX_OPTID_TLS13_CLIENT_CIPHERS;
       }
       break;
     case 't':
-      if (util::strieq_l("backend-read-timeou", name, 19)) {
+      if (util::strieq("backend-read-timeou"_sr, name, 19)) {
         return SHRPX_OPTID_BACKEND_READ_TIMEOUT;
       }
-      if (util::strieq_l("stream-write-timeou", name, 19)) {
+      if (util::strieq("stream-write-timeou"_sr, name, 19)) {
         return SHRPX_OPTID_STREAM_WRITE_TIMEOUT;
       }
-      if (util::strieq_l("verify-client-cacer", name, 19)) {
+      if (util::strieq("verify-client-cacer"_sr, name, 19)) {
         return SHRPX_OPTID_VERIFY_CLIENT_CACERT;
       }
       break;
     case 'y':
-      if (util::strieq_l("api-max-request-bod", name, 19)) {
+      if (util::strieq("api-max-request-bod"_sr, name, 19)) {
         return SHRPX_OPTID_API_MAX_REQUEST_BODY;
       }
       break;
@@ -2298,48 +2288,48 @@ int option_lookup_token(const char *name, size_t namelen) {
   case 21:
     switch (name[20]) {
     case 'd':
-      if (util::strieq_l("backend-tls-sni-fiel", name, 20)) {
+      if (util::strieq("backend-tls-sni-fiel"_sr, name, 20)) {
         return SHRPX_OPTID_BACKEND_TLS_SNI_FIELD;
       }
       break;
     case 'e':
-      if (util::strieq_l("quic-bpf-program-fil", name, 20)) {
+      if (util::strieq("quic-bpf-program-fil"_sr, name, 20)) {
         return SHRPX_OPTID_QUIC_BPF_PROGRAM_FILE;
       }
       break;
     case 'l':
-      if (util::strieq_l("accept-proxy-protoco", name, 20)) {
+      if (util::strieq("accept-proxy-protoco"_sr, name, 20)) {
         return SHRPX_OPTID_ACCEPT_PROXY_PROTOCOL;
       }
       break;
     case 'n':
-      if (util::strieq_l("tls-max-proto-versio", name, 20)) {
+      if (util::strieq("tls-max-proto-versio"_sr, name, 20)) {
         return SHRPX_OPTID_TLS_MAX_PROTO_VERSION;
       }
-      if (util::strieq_l("tls-min-proto-versio", name, 20)) {
+      if (util::strieq("tls-min-proto-versio"_sr, name, 20)) {
         return SHRPX_OPTID_TLS_MIN_PROTO_VERSION;
       }
       break;
     case 'r':
-      if (util::strieq_l("tls-ticket-key-ciphe", name, 20)) {
+      if (util::strieq("tls-ticket-key-ciphe"_sr, name, 20)) {
         return SHRPX_OPTID_TLS_TICKET_KEY_CIPHER;
       }
       break;
     case 's':
-      if (util::strieq_l("frontend-max-request", name, 20)) {
+      if (util::strieq("frontend-max-request"_sr, name, 20)) {
         return SHRPX_OPTID_FRONTEND_MAX_REQUESTS;
       }
       break;
     case 't':
-      if (util::strieq_l("backend-write-timeou", name, 20)) {
+      if (util::strieq("backend-write-timeou"_sr, name, 20)) {
         return SHRPX_OPTID_BACKEND_WRITE_TIMEOUT;
       }
-      if (util::strieq_l("frontend-read-timeou", name, 20)) {
+      if (util::strieq("frontend-read-timeou"_sr, name, 20)) {
         return SHRPX_OPTID_FRONTEND_READ_TIMEOUT;
       }
       break;
     case 'y':
-      if (util::strieq_l("accesslog-write-earl", name, 20)) {
+      if (util::strieq("accesslog-write-earl"_sr, name, 20)) {
         return SHRPX_OPTID_ACCESSLOG_WRITE_EARLY;
       }
       break;
@@ -2348,25 +2338,25 @@ int option_lookup_token(const char *name, size_t namelen) {
   case 22:
     switch (name[21]) {
     case 'i':
-      if (util::strieq_l("backend-http-proxy-ur", name, 21)) {
+      if (util::strieq("backend-http-proxy-ur"_sr, name, 21)) {
         return SHRPX_OPTID_BACKEND_HTTP_PROXY_URI;
       }
       break;
     case 'r':
-      if (util::strieq_l("backend-request-buffe", name, 21)) {
+      if (util::strieq("backend-request-buffe"_sr, name, 21)) {
         return SHRPX_OPTID_BACKEND_REQUEST_BUFFER;
       }
-      if (util::strieq_l("frontend-quic-qlog-di", name, 21)) {
+      if (util::strieq("frontend-quic-qlog-di"_sr, name, 21)) {
         return SHRPX_OPTID_FRONTEND_QUIC_QLOG_DIR;
       }
       break;
     case 't':
-      if (util::strieq_l("frontend-write-timeou", name, 21)) {
+      if (util::strieq("frontend-write-timeou"_sr, name, 21)) {
         return SHRPX_OPTID_FRONTEND_WRITE_TIMEOUT;
       }
       break;
     case 'y':
-      if (util::strieq_l("backend-address-famil", name, 21)) {
+      if (util::strieq("backend-address-famil"_sr, name, 21)) {
         return SHRPX_OPTID_BACKEND_ADDRESS_FAMILY;
       }
       break;
@@ -2375,28 +2365,28 @@ int option_lookup_token(const char *name, size_t namelen) {
   case 23:
     switch (name[22]) {
     case 'e':
-      if (util::strieq_l("client-private-key-fil", name, 22)) {
+      if (util::strieq("client-private-key-fil"_sr, name, 22)) {
         return SHRPX_OPTID_CLIENT_PRIVATE_KEY_FILE;
       }
-      if (util::strieq_l("private-key-passwd-fil", name, 22)) {
+      if (util::strieq("private-key-passwd-fil"_sr, name, 22)) {
         return SHRPX_OPTID_PRIVATE_KEY_PASSWD_FILE;
       }
       break;
     case 'g':
-      if (util::strieq_l("frontend-quic-debug-lo", name, 22)) {
+      if (util::strieq("frontend-quic-debug-lo"_sr, name, 22)) {
         return SHRPX_OPTID_FRONTEND_QUIC_DEBUG_LOG;
       }
       break;
     case 'r':
-      if (util::strieq_l("backend-response-buffe", name, 22)) {
+      if (util::strieq("backend-response-buffe"_sr, name, 22)) {
         return SHRPX_OPTID_BACKEND_RESPONSE_BUFFER;
       }
       break;
     case 't':
-      if (util::strieq_l("backend-connect-timeou", name, 22)) {
+      if (util::strieq("backend-connect-timeou"_sr, name, 22)) {
         return SHRPX_OPTID_BACKEND_CONNECT_TIMEOUT;
       }
-      if (util::strieq_l("frontend-header-timeou", name, 22)) {
+      if (util::strieq("frontend-header-timeou"_sr, name, 22)) {
         return SHRPX_OPTID_FRONTEND_HEADER_TIMEOUT;
       }
       break;
@@ -2405,33 +2395,33 @@ int option_lookup_token(const char *name, size_t namelen) {
   case 24:
     switch (name[23]) {
     case 'a':
-      if (util::strieq_l("frontend-quic-early-dat", name, 23)) {
+      if (util::strieq("frontend-quic-early-dat"_sr, name, 23)) {
         return SHRPX_OPTID_FRONTEND_QUIC_EARLY_DATA;
       }
       break;
     case 'd':
-      if (util::strieq_l("strip-incoming-forwarde", name, 23)) {
+      if (util::strieq("strip-incoming-forwarde"_sr, name, 23)) {
         return SHRPX_OPTID_STRIP_INCOMING_FORWARDED;
       }
-      if (util::strieq_l("tls-ticket-key-memcache", name, 23)) {
+      if (util::strieq("tls-ticket-key-memcache"_sr, name, 23)) {
         return SHRPX_OPTID_TLS_TICKET_KEY_MEMCACHED;
       }
       break;
     case 'e':
-      if (util::strieq_l("fetch-ocsp-response-fil", name, 23)) {
+      if (util::strieq("fetch-ocsp-response-fil"_sr, name, 23)) {
         return SHRPX_OPTID_FETCH_OCSP_RESPONSE_FILE;
       }
       break;
     case 'o':
-      if (util::strieq_l("no-add-x-forwarded-prot", name, 23)) {
+      if (util::strieq("no-add-x-forwarded-prot"_sr, name, 23)) {
         return SHRPX_OPTID_NO_ADD_X_FORWARDED_PROTO;
       }
       break;
     case 't':
-      if (util::strieq_l("listener-disable-timeou", name, 23)) {
+      if (util::strieq("listener-disable-timeou"_sr, name, 23)) {
         return SHRPX_OPTID_LISTENER_DISABLE_TIMEOUT;
       }
-      if (util::strieq_l("tls-dyn-rec-idle-timeou", name, 23)) {
+      if (util::strieq("tls-dyn-rec-idle-timeou"_sr, name, 23)) {
         return SHRPX_OPTID_TLS_DYN_REC_IDLE_TIMEOUT;
       }
       break;
@@ -2440,28 +2430,28 @@ int option_lookup_token(const char *name, size_t namelen) {
   case 25:
     switch (name[24]) {
     case 'e':
-      if (util::strieq_l("backend-http2-window-siz", name, 24)) {
+      if (util::strieq("backend-http2-window-siz"_sr, name, 24)) {
         return SHRPX_OPTID_BACKEND_HTTP2_WINDOW_SIZE;
       }
-      if (util::strieq_l("frontend-quic-secret-fil", name, 24)) {
+      if (util::strieq("frontend-quic-secret-fil"_sr, name, 24)) {
         return SHRPX_OPTID_FRONTEND_QUIC_SECRET_FILE;
       }
       break;
     case 'g':
-      if (util::strieq_l("http2-no-cookie-crumblin", name, 24)) {
+      if (util::strieq("http2-no-cookie-crumblin"_sr, name, 24)) {
         return SHRPX_OPTID_HTTP2_NO_COOKIE_CRUMBLING;
       }
       break;
     case 's':
-      if (util::strieq_l("backend-http2-window-bit", name, 24)) {
+      if (util::strieq("backend-http2-window-bit"_sr, name, 24)) {
         return SHRPX_OPTID_BACKEND_HTTP2_WINDOW_BITS;
       }
-      if (util::strieq_l("max-request-header-field", name, 24)) {
+      if (util::strieq("max-request-header-field"_sr, name, 24)) {
         return SHRPX_OPTID_MAX_REQUEST_HEADER_FIELDS;
       }
       break;
     case 't':
-      if (util::strieq_l("frontend-quic-initial-rt", name, 24)) {
+      if (util::strieq("frontend-quic-initial-rt"_sr, name, 24)) {
         return SHRPX_OPTID_FRONTEND_QUIC_INITIAL_RTT;
       }
       break;
@@ -2470,37 +2460,37 @@ int option_lookup_token(const char *name, size_t namelen) {
   case 26:
     switch (name[25]) {
     case 'a':
-      if (util::strieq_l("tls-no-postpone-early-dat", name, 25)) {
+      if (util::strieq("tls-no-postpone-early-dat"_sr, name, 25)) {
         return SHRPX_OPTID_TLS_NO_POSTPONE_EARLY_DATA;
       }
       break;
     case 'e':
-      if (util::strieq_l("frontend-http2-window-siz", name, 25)) {
+      if (util::strieq("frontend-http2-window-siz"_sr, name, 25)) {
         return SHRPX_OPTID_FRONTEND_HTTP2_WINDOW_SIZE;
       }
-      if (util::strieq_l("frontend-http3-window-siz", name, 25)) {
+      if (util::strieq("frontend-http3-window-siz"_sr, name, 25)) {
         return SHRPX_OPTID_FRONTEND_HTTP3_WINDOW_SIZE;
       }
       break;
     case 's':
-      if (util::strieq_l("frontend-http2-window-bit", name, 25)) {
+      if (util::strieq("frontend-http2-window-bit"_sr, name, 25)) {
         return SHRPX_OPTID_FRONTEND_HTTP2_WINDOW_BITS;
       }
-      if (util::strieq_l("max-response-header-field", name, 25)) {
+      if (util::strieq("max-response-header-field"_sr, name, 25)) {
         return SHRPX_OPTID_MAX_RESPONSE_HEADER_FIELDS;
       }
       break;
     case 't':
-      if (util::strieq_l("backend-keep-alive-timeou", name, 25)) {
+      if (util::strieq("backend-keep-alive-timeou"_sr, name, 25)) {
         return SHRPX_OPTID_BACKEND_KEEP_ALIVE_TIMEOUT;
       }
-      if (util::strieq_l("frontend-quic-idle-timeou", name, 25)) {
+      if (util::strieq("frontend-quic-idle-timeou"_sr, name, 25)) {
         return SHRPX_OPTID_FRONTEND_QUIC_IDLE_TIMEOUT;
       }
-      if (util::strieq_l("no-http2-cipher-black-lis", name, 25)) {
+      if (util::strieq("no-http2-cipher-black-lis"_sr, name, 25)) {
         return SHRPX_OPTID_NO_HTTP2_CIPHER_BLACK_LIST;
       }
-      if (util::strieq_l("no-http2-cipher-block-lis", name, 25)) {
+      if (util::strieq("no-http2-cipher-block-lis"_sr, name, 25)) {
         return SHRPX_OPTID_NO_HTTP2_CIPHER_BLOCK_LIST;
       }
       break;
@@ -2509,39 +2499,39 @@ int option_lookup_token(const char *name, size_t namelen) {
   case 27:
     switch (name[26]) {
     case 'd':
-      if (util::strieq_l("tls-session-cache-memcache", name, 26)) {
+      if (util::strieq("tls-session-cache-memcache"_sr, name, 26)) {
         return SHRPX_OPTID_TLS_SESSION_CACHE_MEMCACHED;
       }
       break;
     case 'n':
-      if (util::strieq_l("frontend-quic-require-toke", name, 26)) {
+      if (util::strieq("frontend-quic-require-toke"_sr, name, 26)) {
         return SHRPX_OPTID_FRONTEND_QUIC_REQUIRE_TOKEN;
       }
       break;
     case 'r':
-      if (util::strieq_l("request-header-field-buffe", name, 26)) {
+      if (util::strieq("request-header-field-buffe"_sr, name, 26)) {
         return SHRPX_OPTID_REQUEST_HEADER_FIELD_BUFFER;
       }
       break;
     case 's':
-      if (util::strieq_l("worker-frontend-connection", name, 26)) {
+      if (util::strieq("worker-frontend-connection"_sr, name, 26)) {
         return SHRPX_OPTID_WORKER_FRONTEND_CONNECTIONS;
       }
       break;
     case 't':
-      if (util::strieq_l("frontend-http2-idle-timeou", name, 26)) {
+      if (util::strieq("frontend-http2-idle-timeou"_sr, name, 26)) {
         return SHRPX_OPTID_FRONTEND_HTTP2_IDLE_TIMEOUT;
       }
-      if (util::strieq_l("frontend-http2-read-timeou", name, 26)) {
+      if (util::strieq("frontend-http2-read-timeou"_sr, name, 26)) {
         return SHRPX_OPTID_FRONTEND_HTTP2_READ_TIMEOUT;
       }
-      if (util::strieq_l("frontend-http3-idle-timeou", name, 26)) {
+      if (util::strieq("frontend-http3-idle-timeou"_sr, name, 26)) {
         return SHRPX_OPTID_FRONTEND_HTTP3_IDLE_TIMEOUT;
       }
-      if (util::strieq_l("frontend-http3-read-timeou", name, 26)) {
+      if (util::strieq("frontend-http3-read-timeou"_sr, name, 26)) {
         return SHRPX_OPTID_FRONTEND_HTTP3_READ_TIMEOUT;
       }
-      if (util::strieq_l("frontend-keep-alive-timeou", name, 26)) {
+      if (util::strieq("frontend-keep-alive-timeou"_sr, name, 26)) {
         return SHRPX_OPTID_FRONTEND_KEEP_ALIVE_TIMEOUT;
       }
       break;
@@ -2550,30 +2540,30 @@ int option_lookup_token(const char *name, size_t namelen) {
   case 28:
     switch (name[27]) {
     case 'a':
-      if (util::strieq_l("no-strip-incoming-early-dat", name, 27)) {
+      if (util::strieq("no-strip-incoming-early-dat"_sr, name, 27)) {
         return SHRPX_OPTID_NO_STRIP_INCOMING_EARLY_DATA;
       }
       break;
     case 'd':
-      if (util::strieq_l("tls-dyn-rec-warmup-threshol", name, 27)) {
+      if (util::strieq("tls-dyn-rec-warmup-threshol"_sr, name, 27)) {
         return SHRPX_OPTID_TLS_DYN_REC_WARMUP_THRESHOLD;
       }
       break;
     case 'r':
-      if (util::strieq_l("response-header-field-buffe", name, 27)) {
+      if (util::strieq("response-header-field-buffe"_sr, name, 27)) {
         return SHRPX_OPTID_RESPONSE_HEADER_FIELD_BUFFER;
       }
       break;
     case 's':
-      if (util::strieq_l("http2-max-concurrent-stream", name, 27)) {
+      if (util::strieq("http2-max-concurrent-stream"_sr, name, 27)) {
         return SHRPX_OPTID_HTTP2_MAX_CONCURRENT_STREAMS;
       }
-      if (util::strieq_l("tls-ticket-key-memcached-tl", name, 27)) {
+      if (util::strieq("tls-ticket-key-memcached-tl"_sr, name, 27)) {
         return SHRPX_OPTID_TLS_TICKET_KEY_MEMCACHED_TLS;
       }
       break;
     case 't':
-      if (util::strieq_l("backend-connections-per-hos", name, 27)) {
+      if (util::strieq("backend-connections-per-hos"_sr, name, 27)) {
         return SHRPX_OPTID_BACKEND_CONNECTIONS_PER_HOST;
       }
       break;
@@ -2582,25 +2572,25 @@ int option_lookup_token(const char *name, size_t namelen) {
   case 30:
     switch (name[29]) {
     case 'd':
-      if (util::strieq_l("verify-client-tolerate-expire", name, 29)) {
+      if (util::strieq("verify-client-tolerate-expire"_sr, name, 29)) {
         return SHRPX_OPTID_VERIFY_CLIENT_TOLERATE_EXPIRED;
       }
       break;
     case 'e':
-      if (util::strieq_l("frontend-http3-max-window-siz", name, 29)) {
+      if (util::strieq("frontend-http3-max-window-siz"_sr, name, 29)) {
         return SHRPX_OPTID_FRONTEND_HTTP3_MAX_WINDOW_SIZE;
       }
       break;
     case 'r':
-      if (util::strieq_l("ignore-per-pattern-mruby-erro", name, 29)) {
+      if (util::strieq("ignore-per-pattern-mruby-erro"_sr, name, 29)) {
         return SHRPX_OPTID_IGNORE_PER_PATTERN_MRUBY_ERROR;
       }
-      if (util::strieq_l("strip-incoming-x-forwarded-fo", name, 29)) {
+      if (util::strieq("strip-incoming-x-forwarded-fo"_sr, name, 29)) {
         return SHRPX_OPTID_STRIP_INCOMING_X_FORWARDED_FOR;
       }
       break;
     case 't':
-      if (util::strieq_l("backend-http2-settings-timeou", name, 29)) {
+      if (util::strieq("backend-http2-settings-timeou"_sr, name, 29)) {
         return SHRPX_OPTID_BACKEND_HTTP2_SETTINGS_TIMEOUT;
       }
       break;
@@ -2609,12 +2599,12 @@ int option_lookup_token(const char *name, size_t namelen) {
   case 31:
     switch (name[30]) {
     case 's':
-      if (util::strieq_l("tls-session-cache-memcached-tl", name, 30)) {
+      if (util::strieq("tls-session-cache-memcached-tl"_sr, name, 30)) {
         return SHRPX_OPTID_TLS_SESSION_CACHE_MEMCACHED_TLS;
       }
       break;
     case 't':
-      if (util::strieq_l("frontend-http2-settings-timeou", name, 30)) {
+      if (util::strieq("frontend-http2-settings-timeou"_sr, name, 30)) {
         return SHRPX_OPTID_FRONTEND_HTTP2_SETTINGS_TIMEOUT;
       }
       break;
@@ -2623,7 +2613,7 @@ int option_lookup_token(const char *name, size_t namelen) {
   case 32:
     switch (name[31]) {
     case 'd':
-      if (util::strieq_l("backend-connections-per-fronten", name, 31)) {
+      if (util::strieq("backend-connections-per-fronten"_sr, name, 31)) {
         return SHRPX_OPTID_BACKEND_CONNECTIONS_PER_FRONTEND;
       }
       break;
@@ -2632,18 +2622,18 @@ int option_lookup_token(const char *name, size_t namelen) {
   case 33:
     switch (name[32]) {
     case 'l':
-      if (util::strieq_l("tls-ticket-key-memcached-interva", name, 32)) {
+      if (util::strieq("tls-ticket-key-memcached-interva"_sr, name, 32)) {
         return SHRPX_OPTID_TLS_TICKET_KEY_MEMCACHED_INTERVAL;
       }
-      if (util::strieq_l("tls-ticket-key-memcached-max-fai", name, 32)) {
+      if (util::strieq("tls-ticket-key-memcached-max-fai"_sr, name, 32)) {
         return SHRPX_OPTID_TLS_TICKET_KEY_MEMCACHED_MAX_FAIL;
       }
       break;
     case 't':
-      if (util::strieq_l("client-no-http2-cipher-black-lis", name, 32)) {
+      if (util::strieq("client-no-http2-cipher-black-lis"_sr, name, 32)) {
         return SHRPX_OPTID_CLIENT_NO_HTTP2_CIPHER_BLACK_LIST;
       }
-      if (util::strieq_l("client-no-http2-cipher-block-lis", name, 32)) {
+      if (util::strieq("client-no-http2-cipher-block-lis"_sr, name, 32)) {
         return SHRPX_OPTID_CLIENT_NO_HTTP2_CIPHER_BLOCK_LIST;
       }
       break;
@@ -2652,22 +2642,22 @@ int option_lookup_token(const char *name, size_t namelen) {
   case 34:
     switch (name[33]) {
     case 'e':
-      if (util::strieq_l("tls-ticket-key-memcached-cert-fil", name, 33)) {
+      if (util::strieq("tls-ticket-key-memcached-cert-fil"_sr, name, 33)) {
         return SHRPX_OPTID_TLS_TICKET_KEY_MEMCACHED_CERT_FILE;
       }
       break;
     case 'r':
-      if (util::strieq_l("frontend-http2-dump-request-heade", name, 33)) {
+      if (util::strieq("frontend-http2-dump-request-heade"_sr, name, 33)) {
         return SHRPX_OPTID_FRONTEND_HTTP2_DUMP_REQUEST_HEADER;
       }
       break;
     case 't':
-      if (util::strieq_l("backend-http1-connections-per-hos", name, 33)) {
+      if (util::strieq("backend-http1-connections-per-hos"_sr, name, 33)) {
         return SHRPX_OPTID_BACKEND_HTTP1_CONNECTIONS_PER_HOST;
       }
       break;
     case 'y':
-      if (util::strieq_l("tls-ticket-key-memcached-max-retr", name, 33)) {
+      if (util::strieq("tls-ticket-key-memcached-max-retr"_sr, name, 33)) {
         return SHRPX_OPTID_TLS_TICKET_KEY_MEMCACHED_MAX_RETRY;
       }
       break;
@@ -2676,20 +2666,20 @@ int option_lookup_token(const char *name, size_t namelen) {
   case 35:
     switch (name[34]) {
     case 'e':
-      if (util::strieq_l("frontend-http2-optimize-window-siz", name, 34)) {
+      if (util::strieq("frontend-http2-optimize-window-siz"_sr, name, 34)) {
         return SHRPX_OPTID_FRONTEND_HTTP2_OPTIMIZE_WINDOW_SIZE;
       }
       break;
     case 'o':
-      if (util::strieq_l("no-strip-incoming-x-forwarded-prot", name, 34)) {
+      if (util::strieq("no-strip-incoming-x-forwarded-prot"_sr, name, 34)) {
         return SHRPX_OPTID_NO_STRIP_INCOMING_X_FORWARDED_PROTO;
       }
       break;
     case 'r':
-      if (util::strieq_l("frontend-http2-dump-response-heade", name, 34)) {
+      if (util::strieq("frontend-http2-dump-response-heade"_sr, name, 34)) {
         return SHRPX_OPTID_FRONTEND_HTTP2_DUMP_RESPONSE_HEADER;
       }
-      if (util::strieq_l("frontend-quic-congestion-controlle", name, 34)) {
+      if (util::strieq("frontend-quic-congestion-controlle"_sr, name, 34)) {
         return SHRPX_OPTID_FRONTEND_QUIC_CONGESTION_CONTROLLER;
       }
       break;
@@ -2698,25 +2688,25 @@ int option_lookup_token(const char *name, size_t namelen) {
   case 36:
     switch (name[35]) {
     case 'd':
-      if (util::strieq_l("worker-process-grace-shutdown-perio", name, 35)) {
+      if (util::strieq("worker-process-grace-shutdown-perio"_sr, name, 35)) {
         return SHRPX_OPTID_WORKER_PROCESS_GRACE_SHUTDOWN_PERIOD;
       }
       break;
     case 'e':
-      if (util::strieq_l("backend-http2-connection-window-siz", name, 35)) {
+      if (util::strieq("backend-http2-connection-window-siz"_sr, name, 35)) {
         return SHRPX_OPTID_BACKEND_HTTP2_CONNECTION_WINDOW_SIZE;
       }
       break;
     case 'r':
-      if (util::strieq_l("backend-http2-connections-per-worke", name, 35)) {
+      if (util::strieq("backend-http2-connections-per-worke"_sr, name, 35)) {
         return SHRPX_OPTID_BACKEND_HTTP2_CONNECTIONS_PER_WORKER;
       }
       break;
     case 's':
-      if (util::strieq_l("backend-http2-connection-window-bit", name, 35)) {
+      if (util::strieq("backend-http2-connection-window-bit"_sr, name, 35)) {
         return SHRPX_OPTID_BACKEND_HTTP2_CONNECTION_WINDOW_BITS;
       }
-      if (util::strieq_l("backend-http2-max-concurrent-stream", name, 35)) {
+      if (util::strieq("backend-http2-max-concurrent-stream"_sr, name, 35)) {
         return SHRPX_OPTID_BACKEND_HTTP2_MAX_CONCURRENT_STREAMS;
       }
       break;
@@ -2725,24 +2715,24 @@ int option_lookup_token(const char *name, size_t namelen) {
   case 37:
     switch (name[36]) {
     case 'e':
-      if (util::strieq_l("frontend-http2-connection-window-siz", name, 36)) {
+      if (util::strieq("frontend-http2-connection-window-siz"_sr, name, 36)) {
         return SHRPX_OPTID_FRONTEND_HTTP2_CONNECTION_WINDOW_SIZE;
       }
-      if (util::strieq_l("frontend-http3-connection-window-siz", name, 36)) {
+      if (util::strieq("frontend-http3-connection-window-siz"_sr, name, 36)) {
         return SHRPX_OPTID_FRONTEND_HTTP3_CONNECTION_WINDOW_SIZE;
       }
-      if (util::strieq_l("tls-session-cache-memcached-cert-fil", name, 36)) {
+      if (util::strieq("tls-session-cache-memcached-cert-fil"_sr, name, 36)) {
         return SHRPX_OPTID_TLS_SESSION_CACHE_MEMCACHED_CERT_FILE;
       }
       break;
     case 's':
-      if (util::strieq_l("frontend-http2-connection-window-bit", name, 36)) {
+      if (util::strieq("frontend-http2-connection-window-bit"_sr, name, 36)) {
         return SHRPX_OPTID_FRONTEND_HTTP2_CONNECTION_WINDOW_BITS;
       }
-      if (util::strieq_l("frontend-http2-max-concurrent-stream", name, 36)) {
+      if (util::strieq("frontend-http2-max-concurrent-stream"_sr, name, 36)) {
         return SHRPX_OPTID_FRONTEND_HTTP2_MAX_CONCURRENT_STREAMS;
       }
-      if (util::strieq_l("frontend-http3-max-concurrent-stream", name, 36)) {
+      if (util::strieq("frontend-http3-max-concurrent-stream"_sr, name, 36)) {
         return SHRPX_OPTID_FRONTEND_HTTP3_MAX_CONCURRENT_STREAMS;
       }
       break;
@@ -2751,7 +2741,7 @@ int option_lookup_token(const char *name, size_t namelen) {
   case 38:
     switch (name[37]) {
     case 'd':
-      if (util::strieq_l("backend-http1-connections-per-fronten", name, 37)) {
+      if (util::strieq("backend-http1-connections-per-fronten"_sr, name, 37)) {
         return SHRPX_OPTID_BACKEND_HTTP1_CONNECTIONS_PER_FRONTEND;
       }
       break;
@@ -2760,7 +2750,7 @@ int option_lookup_token(const char *name, size_t namelen) {
   case 39:
     switch (name[38]) {
     case 'y':
-      if (util::strieq_l("tls-ticket-key-memcached-address-famil", name, 38)) {
+      if (util::strieq("tls-ticket-key-memcached-address-famil"_sr, name, 38)) {
         return SHRPX_OPTID_TLS_TICKET_KEY_MEMCACHED_ADDRESS_FAMILY;
       }
       break;
@@ -2769,10 +2759,12 @@ int option_lookup_token(const char *name, size_t namelen) {
   case 40:
     switch (name[39]) {
     case 'e':
-      if (util::strieq_l("backend-http2-decoder-dynamic-table-siz", name, 39)) {
+      if (util::strieq("backend-http2-decoder-dynamic-table-siz"_sr, name,
+                       39)) {
         return SHRPX_OPTID_BACKEND_HTTP2_DECODER_DYNAMIC_TABLE_SIZE;
       }
-      if (util::strieq_l("backend-http2-encoder-dynamic-table-siz", name, 39)) {
+      if (util::strieq("backend-http2-encoder-dynamic-table-siz"_sr, name,
+                       39)) {
         return SHRPX_OPTID_BACKEND_HTTP2_ENCODER_DYNAMIC_TABLE_SIZE;
       }
       break;
@@ -2781,24 +2773,24 @@ int option_lookup_token(const char *name, size_t namelen) {
   case 41:
     switch (name[40]) {
     case 'e':
-      if (util::strieq_l("frontend-http2-decoder-dynamic-table-siz", name,
-                         40)) {
+      if (util::strieq("frontend-http2-decoder-dynamic-table-siz"_sr, name,
+                       40)) {
         return SHRPX_OPTID_FRONTEND_HTTP2_DECODER_DYNAMIC_TABLE_SIZE;
       }
-      if (util::strieq_l("frontend-http2-encoder-dynamic-table-siz", name,
-                         40)) {
+      if (util::strieq("frontend-http2-encoder-dynamic-table-siz"_sr, name,
+                       40)) {
         return SHRPX_OPTID_FRONTEND_HTTP2_ENCODER_DYNAMIC_TABLE_SIZE;
       }
-      if (util::strieq_l("frontend-http2-optimize-write-buffer-siz", name,
-                         40)) {
+      if (util::strieq("frontend-http2-optimize-write-buffer-siz"_sr, name,
+                       40)) {
         return SHRPX_OPTID_FRONTEND_HTTP2_OPTIMIZE_WRITE_BUFFER_SIZE;
       }
-      if (util::strieq_l("frontend-http3-max-connection-window-siz", name,
-                         40)) {
+      if (util::strieq("frontend-http3-max-connection-window-siz"_sr, name,
+                       40)) {
         return SHRPX_OPTID_FRONTEND_HTTP3_MAX_CONNECTION_WINDOW_SIZE;
       }
-      if (util::strieq_l("tls-ticket-key-memcached-private-key-fil", name,
-                         40)) {
+      if (util::strieq("tls-ticket-key-memcached-private-key-fil"_sr, name,
+                       40)) {
         return SHRPX_OPTID_TLS_TICKET_KEY_MEMCACHED_PRIVATE_KEY_FILE;
       }
       break;
@@ -2807,8 +2799,8 @@ int option_lookup_token(const char *name, size_t namelen) {
   case 42:
     switch (name[41]) {
     case 'y':
-      if (util::strieq_l("tls-session-cache-memcached-address-famil", name,
-                         41)) {
+      if (util::strieq("tls-session-cache-memcached-address-famil"_sr, name,
+                       41)) {
         return SHRPX_OPTID_TLS_SESSION_CACHE_MEMCACHED_ADDRESS_FAMILY;
       }
       break;
@@ -2817,8 +2809,8 @@ int option_lookup_token(const char *name, size_t namelen) {
   case 44:
     switch (name[43]) {
     case 'e':
-      if (util::strieq_l("tls-session-cache-memcached-private-key-fil", name,
-                         43)) {
+      if (util::strieq("tls-session-cache-memcached-private-key-fil"_sr, name,
+                       43)) {
         return SHRPX_OPTID_TLS_SESSION_CACHE_MEMCACHED_PRIVATE_KEY_FILE;
       }
       break;
@@ -2831,7 +2823,7 @@ int option_lookup_token(const char *name, size_t namelen) {
 int parse_config(Config *config, const StringRef &opt, const StringRef &optarg,
                  std::set<StringRef> &included_set,
                  std::map<StringRef, size_t> &pattern_addr_indexer) {
-  auto optid = option_lookup_token(opt.c_str(), opt.size());
+  auto optid = option_lookup_token(opt);
   return parse_config(config, optid, opt, optarg, included_set,
                       pattern_addr_indexer);
 }
@@ -3022,11 +3014,11 @@ int parse_config(Config *config, int optid, const StringRef &opt,
     return 0;
   }
   case SHRPX_OPTID_DAEMON:
-    config->daemon = util::strieq_l("yes", optarg);
+    config->daemon = util::strieq("yes"_sr, optarg);
 
     return 0;
   case SHRPX_OPTID_HTTP2_PROXY:
-    config->http2_proxy = util::strieq_l("yes", optarg);
+    config->http2_proxy = util::strieq("yes"_sr, optarg);
 
     return 0;
   case SHRPX_OPTID_HTTP2_BRIDGE:
@@ -3040,15 +3032,15 @@ int parse_config(Config *config, int optid, const StringRef &opt,
            "and backend=<addr>,<port>;;proto=h2;tls";
     return -1;
   case SHRPX_OPTID_ADD_X_FORWARDED_FOR:
-    config->http.xff.add = util::strieq_l("yes", optarg);
+    config->http.xff.add = util::strieq("yes"_sr, optarg);
 
     return 0;
   case SHRPX_OPTID_STRIP_INCOMING_X_FORWARDED_FOR:
-    config->http.xff.strip_incoming = util::strieq_l("yes", optarg);
+    config->http.xff.strip_incoming = util::strieq("yes"_sr, optarg);
 
     return 0;
   case SHRPX_OPTID_NO_VIA:
-    config->http.no_via = util::strieq_l("yes", optarg);
+    config->http.no_via = util::strieq("yes"_sr, optarg);
 
     return 0;
   case SHRPX_OPTID_FRONTEND_HTTP2_READ_TIMEOUT:
@@ -3081,7 +3073,7 @@ int parse_config(Config *config, int optid, const StringRef &opt,
 
     return 0;
   case SHRPX_OPTID_ACCESSLOG_SYSLOG:
-    config->logging.access.syslog = util::strieq_l("yes", optarg);
+    config->logging.access.syslog = util::strieq("yes"_sr, optarg);
 
     return 0;
   case SHRPX_OPTID_ACCESSLOG_FORMAT:
@@ -3093,7 +3085,7 @@ int parse_config(Config *config, int optid, const StringRef &opt,
 
     return 0;
   case SHRPX_OPTID_ERRORLOG_SYSLOG:
-    config->logging.error.syslog = util::strieq_l("yes", optarg);
+    config->logging.error.syslog = util::strieq("yes"_sr, optarg);
 
     return 0;
   case SHRPX_OPTID_FASTOPEN:
@@ -3191,7 +3183,7 @@ int parse_config(Config *config, int optid, const StringRef &opt,
 
     return 0;
   case SHRPX_OPTID_USER: {
-    auto pwd = getpwnam(optarg.c_str());
+    auto pwd = getpwnam(optarg.data());
     if (!pwd) {
       LOG(ERROR) << opt << ": failed to get uid from " << optarg << ": "
                  << xsi_strerror(errno, errbuf.data(), errbuf.size());
@@ -3240,7 +3232,7 @@ int parse_config(Config *config, int optid, const StringRef &opt,
     if (!params.sct_dir.empty()) {
       // Make sure that dir_path is NULL terminated string.
       if (read_tls_sct_from_dir(sct_data, opt,
-                                StringRef{params.sct_dir.str()}) != 0) {
+                                StringRef{std::string{params.sct_dir}}) != 0) {
         return -1;
       }
     }
@@ -3301,7 +3293,7 @@ int parse_config(Config *config, int optid, const StringRef &opt,
                   "backend=<addr>,<port>;;proto=h2;tls";
     return -1;
   case SHRPX_OPTID_INSECURE:
-    config->tls.insecure = util::strieq_l("yes", optarg);
+    config->tls.insecure = util::strieq("yes"_sr, optarg);
 
     return 0;
   case SHRPX_OPTID_CACERT:
@@ -3329,10 +3321,10 @@ int parse_config(Config *config, int optid, const StringRef &opt,
     proxy = {};
     // parse URI and get hostname, port and optionally userinfo.
     http_parser_url u{};
-    int rv = http_parser_parse_url(optarg.c_str(), optarg.size(), 0, &u);
+    int rv = http_parser_parse_url(optarg.data(), optarg.size(), 0, &u);
     if (rv == 0) {
       if (u.field_set & UF_USERINFO) {
-        auto uf = util::get_uri_field(optarg.c_str(), u, UF_USERINFO);
+        auto uf = util::get_uri_field(optarg.data(), u, UF_USERINFO);
         // Surprisingly, u.field_set & UF_USERINFO is nonzero even if
         // userinfo component is empty string.
         if (!uf.empty()) {
@@ -3341,7 +3333,7 @@ int parse_config(Config *config, int optid, const StringRef &opt,
       }
       if (u.field_set & UF_HOST) {
         proxy.host = make_string_ref(
-            config->balloc, util::get_uri_field(optarg.c_str(), u, UF_HOST));
+            config->balloc, util::get_uri_field(optarg.data(), u, UF_HOST));
       } else {
         LOG(ERROR) << opt << ": no hostname specified";
         return -1;
@@ -3396,7 +3388,7 @@ int parse_config(Config *config, int optid, const StringRef &opt,
     return 0;
   }
   case SHRPX_OPTID_VERIFY_CLIENT:
-    config->tls.client_verify.enabled = util::strieq_l("yes", optarg);
+    config->tls.client_verify.enabled = util::strieq("yes"_sr, optarg);
 
     return 0;
   case SHRPX_OPTID_VERIFY_CLIENT_CACERT:
@@ -3423,11 +3415,11 @@ int parse_config(Config *config, int optid, const StringRef &opt,
 
     return 0;
   case SHRPX_OPTID_HTTP2_NO_COOKIE_CRUMBLING:
-    config->http2.no_cookie_crumbling = util::strieq_l("yes", optarg);
+    config->http2.no_cookie_crumbling = util::strieq("yes"_sr, optarg);
 
     return 0;
   case SHRPX_OPTID_FRONTEND_FRAME_DEBUG:
-    config->http2.upstream.debug.frame_debug = util::strieq_l("yes", optarg);
+    config->http2.upstream.debug.frame_debug = util::strieq("yes"_sr, optarg);
 
     return 0;
   case SHRPX_OPTID_PADDING:
@@ -3460,7 +3452,7 @@ int parse_config(Config *config, int optid, const StringRef &opt,
   case SHRPX_OPTID_WORKER_FRONTEND_CONNECTIONS:
     return parse_uint(&config->conn.upstream.worker_connections, opt, optarg);
   case SHRPX_OPTID_NO_LOCATION_REWRITE:
-    config->http.no_location_rewrite = util::strieq_l("yes", optarg);
+    config->http.no_location_rewrite = util::strieq("yes"_sr, optarg);
 
     return 0;
   case SHRPX_OPTID_NO_HOST_REWRITE:
@@ -3544,7 +3536,7 @@ int parse_config(Config *config, int optid, const StringRef &opt,
   }
 
   case SHRPX_OPTID_NO_SERVER_PUSH:
-    config->http2.no_server_push = util::strieq_l("yes", optarg);
+    config->http2.no_server_push = util::strieq("yes"_sr, optarg);
 
     return 0;
   case SHRPX_OPTID_BACKEND_HTTP2_CONNECTIONS_PER_WORKER:
@@ -3558,7 +3550,7 @@ int parse_config(Config *config, int optid, const StringRef &opt,
   case SHRPX_OPTID_OCSP_UPDATE_INTERVAL:
     return parse_duration(&config->tls.ocsp.update_interval, opt, optarg);
   case SHRPX_OPTID_NO_OCSP:
-    config->tls.ocsp.disabled = util::strieq_l("yes", optarg);
+    config->tls.ocsp.disabled = util::strieq("yes"_sr, optarg);
 
     return 0;
   case SHRPX_OPTID_HEADER_FIELD_BUFFER:
@@ -3586,7 +3578,7 @@ int parse_config(Config *config, int optid, const StringRef &opt,
 
     included_set.insert(optarg);
     auto rv =
-        load_config(config, optarg.c_str(), included_set, pattern_addr_indexer);
+        load_config(config, optarg.data(), included_set, pattern_addr_indexer);
     included_set.erase(optarg);
 
     if (rv != 0) {
@@ -3596,9 +3588,9 @@ int parse_config(Config *config, int optid, const StringRef &opt,
     return 0;
   }
   case SHRPX_OPTID_TLS_TICKET_KEY_CIPHER:
-    if (util::strieq_l("aes-128-cbc", optarg)) {
+    if (util::strieq("aes-128-cbc"_sr, optarg)) {
       config->tls.ticket.cipher = EVP_aes_128_cbc();
-    } else if (util::strieq_l("aes-256-cbc", optarg)) {
+    } else if (util::strieq("aes-256-cbc"_sr, optarg)) {
       config->tls.ticket.cipher = EVP_aes_256_cbc();
     } else {
       LOG(ERROR) << opt
@@ -3609,7 +3601,7 @@ int parse_config(Config *config, int optid, const StringRef &opt,
 
     return 0;
   case SHRPX_OPTID_HOST_REWRITE:
-    config->http.no_host_rewrite = !util::strieq_l("yes", optarg);
+    config->http.no_host_rewrite = !util::strieq("yes"_sr, optarg);
 
     return 0;
   case SHRPX_OPTID_TLS_SESSION_CACHE_MEMCACHED:
@@ -3690,26 +3682,27 @@ int parse_config(Config *config, int optid, const StringRef &opt,
   case SHRPX_OPTID_ACCEPT_PROXY_PROTOCOL:
     LOG(WARN) << opt << ": deprecated.  Use proxyproto keyword in "
               << SHRPX_OPT_FRONTEND << " instead.";
-    config->conn.upstream.accept_proxy_protocol = util::strieq_l("yes", optarg);
+    config->conn.upstream.accept_proxy_protocol =
+        util::strieq("yes"_sr, optarg);
 
     return 0;
   case SHRPX_OPTID_ADD_FORWARDED: {
     auto &fwdconf = config->http.forwarded;
     fwdconf.params = FORWARDED_NONE;
     for (const auto &param : util::split_str(optarg, ',')) {
-      if (util::strieq_l("by", param)) {
+      if (util::strieq("by"_sr, param)) {
         fwdconf.params |= FORWARDED_BY;
         continue;
       }
-      if (util::strieq_l("for", param)) {
+      if (util::strieq("for"_sr, param)) {
         fwdconf.params |= FORWARDED_FOR;
         continue;
       }
-      if (util::strieq_l("host", param)) {
+      if (util::strieq("host"_sr, param)) {
         fwdconf.params |= FORWARDED_HOST;
         continue;
       }
-      if (util::strieq_l("proto", param)) {
+      if (util::strieq("proto"_sr, param)) {
         fwdconf.params |= FORWARDED_PROTO;
         continue;
       }
@@ -3722,7 +3715,7 @@ int parse_config(Config *config, int optid, const StringRef &opt,
     return 0;
   }
   case SHRPX_OPTID_STRIP_INCOMING_FORWARDED:
-    config->http.forwarded.strip_incoming = util::strieq_l("yes", optarg);
+    config->http.forwarded.strip_incoming = util::strieq("yes"_sr, optarg);
 
     return 0;
   case SHRPX_OPTID_FORWARDED_BY:
@@ -3744,7 +3737,7 @@ int parse_config(Config *config, int optid, const StringRef &opt,
       if (optarg[0] == '_') {
         fwdconf.by_obfuscated = make_string_ref(config->balloc, optarg);
       } else {
-        fwdconf.by_obfuscated = StringRef::from_lit("");
+        fwdconf.by_obfuscated = ""_sr;
       }
       break;
     case SHRPX_OPTID_FORWARDED_FOR:
@@ -3759,7 +3752,7 @@ int parse_config(Config *config, int optid, const StringRef &opt,
               << SHRPX_OPT_NO_HTTP2_CIPHER_BLOCK_LIST << " instead.";
     // fall through
   case SHRPX_OPTID_NO_HTTP2_CIPHER_BLOCK_LIST:
-    config->tls.no_http2_cipher_block_list = util::strieq_l("yes", optarg);
+    config->tls.no_http2_cipher_block_list = util::strieq("yes"_sr, optarg);
     return 0;
   case SHRPX_OPTID_BACKEND_HTTP1_TLS:
   case SHRPX_OPTID_BACKEND_TLS:
@@ -3835,16 +3828,17 @@ int parse_config(Config *config, int optid, const StringRef &opt,
 
     return 0;
   case SHRPX_OPTID_NO_SERVER_REWRITE:
-    config->http.no_server_rewrite = util::strieq_l("yes", optarg);
+    config->http.no_server_rewrite = util::strieq("yes"_sr, optarg);
 
     return 0;
   case SHRPX_OPTID_FRONTEND_HTTP2_OPTIMIZE_WRITE_BUFFER_SIZE:
     config->http2.upstream.optimize_write_buffer_size =
-        util::strieq_l("yes", optarg);
+        util::strieq("yes"_sr, optarg);
 
     return 0;
   case SHRPX_OPTID_FRONTEND_HTTP2_OPTIMIZE_WINDOW_SIZE:
-    config->http2.upstream.optimize_window_size = util::strieq_l("yes", optarg);
+    config->http2.upstream.optimize_window_size =
+        util::strieq("yes"_sr, optarg);
 
     return 0;
   case SHRPX_OPTID_FRONTEND_HTTP2_WINDOW_SIZE:
@@ -3963,7 +3957,7 @@ int parse_config(Config *config, int optid, const StringRef &opt,
     // fall through
   case SHRPX_OPTID_CLIENT_NO_HTTP2_CIPHER_BLOCK_LIST:
     config->tls.client.no_http2_cipher_block_list =
-        util::strieq_l("yes", optarg);
+        util::strieq("yes"_sr, optarg);
 
     return 0;
   case SHRPX_OPTID_CLIENT_CIPHERS:
@@ -3975,7 +3969,7 @@ int parse_config(Config *config, int optid, const StringRef &opt,
 
     return 0;
   case SHRPX_OPTID_ACCESSLOG_WRITE_EARLY:
-    config->logging.access.write_early = util::strieq_l("yes", optarg);
+    config->logging.access.write_early = util::strieq("yes"_sr, optarg);
 
     return 0;
   case SHRPX_OPTID_TLS_MIN_PROTO_VERSION:
@@ -3984,7 +3978,7 @@ int parse_config(Config *config, int optid, const StringRef &opt,
     return parse_tls_proto_version(config->tls.max_proto_version, opt, optarg);
   case SHRPX_OPTID_REDIRECT_HTTPS_PORT: {
     auto n = util::parse_uint(optarg);
-    if (n == -1 || n < 0 || n > 65535) {
+    if (!n || n < 0 || n > 65535) {
       LOG(ERROR) << opt
                  << ": bad value.  Specify an integer in the range [0, "
                     "65535], inclusive";
@@ -3996,46 +3990,46 @@ int parse_config(Config *config, int optid, const StringRef &opt,
   case SHRPX_OPTID_FRONTEND_MAX_REQUESTS:
     return parse_uint(&config->http.max_requests, opt, optarg);
   case SHRPX_OPTID_SINGLE_THREAD:
-    config->single_thread = util::strieq_l("yes", optarg);
+    config->single_thread = util::strieq("yes"_sr, optarg);
 
     return 0;
   case SHRPX_OPTID_SINGLE_PROCESS:
-    config->single_process = util::strieq_l("yes", optarg);
+    config->single_process = util::strieq("yes"_sr, optarg);
 
     return 0;
   case SHRPX_OPTID_NO_ADD_X_FORWARDED_PROTO:
-    config->http.xfp.add = !util::strieq_l("yes", optarg);
+    config->http.xfp.add = !util::strieq("yes"_sr, optarg);
 
     return 0;
   case SHRPX_OPTID_NO_STRIP_INCOMING_X_FORWARDED_PROTO:
-    config->http.xfp.strip_incoming = !util::strieq_l("yes", optarg);
+    config->http.xfp.strip_incoming = !util::strieq("yes"_sr, optarg);
 
     return 0;
   case SHRPX_OPTID_OCSP_STARTUP:
-    config->tls.ocsp.startup = util::strieq_l("yes", optarg);
+    config->tls.ocsp.startup = util::strieq("yes"_sr, optarg);
 
     return 0;
   case SHRPX_OPTID_NO_VERIFY_OCSP:
-    config->tls.ocsp.no_verify = util::strieq_l("yes", optarg);
+    config->tls.ocsp.no_verify = util::strieq("yes"_sr, optarg);
 
     return 0;
   case SHRPX_OPTID_VERIFY_CLIENT_TOLERATE_EXPIRED:
-    config->tls.client_verify.tolerate_expired = util::strieq_l("yes", optarg);
+    config->tls.client_verify.tolerate_expired = util::strieq("yes"_sr, optarg);
 
     return 0;
   case SHRPX_OPTID_IGNORE_PER_PATTERN_MRUBY_ERROR:
-    config->ignore_per_pattern_mruby_error = util::strieq_l("yes", optarg);
+    config->ignore_per_pattern_mruby_error = util::strieq("yes"_sr, optarg);
 
     return 0;
   case SHRPX_OPTID_TLS_NO_POSTPONE_EARLY_DATA:
-    config->tls.no_postpone_early_data = util::strieq_l("yes", optarg);
+    config->tls.no_postpone_early_data = util::strieq("yes"_sr, optarg);
 
     return 0;
   case SHRPX_OPTID_TLS_MAX_EARLY_DATA: {
     return parse_uint_with_unit(&config->tls.max_early_data, opt, optarg);
   }
   case SHRPX_OPTID_NO_STRIP_INCOMING_EARLY_DATA:
-    config->http.early_data.strip_incoming = !util::strieq_l("yes", optarg);
+    config->http.early_data.strip_incoming = !util::strieq("yes"_sr, optarg);
 
     return 0;
   case SHRPX_OPTID_QUIC_BPF_PROGRAM_FILE:
@@ -4046,7 +4040,7 @@ int parse_config(Config *config, int optid, const StringRef &opt,
     return 0;
   case SHRPX_OPTID_NO_QUIC_BPF:
 #ifdef ENABLE_HTTP3
-    config->quic.bpf.disabled = util::strieq_l("yes", optarg);
+    config->quic.bpf.disabled = util::strieq("yes"_sr, optarg);
 #endif // ENABLE_HTTP3
 
     return 0;
@@ -4079,7 +4073,7 @@ int parse_config(Config *config, int optid, const StringRef &opt,
 #endif // !ENABLE_HTTP3
   case SHRPX_OPTID_FRONTEND_QUIC_DEBUG_LOG:
 #ifdef ENABLE_HTTP3
-    config->quic.upstream.debug.log = util::strieq_l("yes", optarg);
+    config->quic.upstream.debug.log = util::strieq("yes"_sr, optarg);
 #endif // ENABLE_HTTP3
 
     return 0;
@@ -4128,7 +4122,7 @@ int parse_config(Config *config, int optid, const StringRef &opt,
 #endif // !ENABLE_HTTP3
   case SHRPX_OPTID_FRONTEND_QUIC_EARLY_DATA:
 #ifdef ENABLE_HTTP3
-    config->quic.upstream.early_data = util::strieq_l("yes", optarg);
+    config->quic.upstream.early_data = util::strieq("yes"_sr, optarg);
 #endif // ENABLE_HTTP3
 
     return 0;
@@ -4140,15 +4134,15 @@ int parse_config(Config *config, int optid, const StringRef &opt,
     return 0;
   case SHRPX_OPTID_FRONTEND_QUIC_REQUIRE_TOKEN:
 #ifdef ENABLE_HTTP3
-    config->quic.upstream.require_token = util::strieq_l("yes", optarg);
+    config->quic.upstream.require_token = util::strieq("yes"_sr, optarg);
 #endif // ENABLE_HTTP3
 
     return 0;
   case SHRPX_OPTID_FRONTEND_QUIC_CONGESTION_CONTROLLER:
 #ifdef ENABLE_HTTP3
-    if (util::strieq_l("cubic", optarg)) {
+    if (util::strieq("cubic"_sr, optarg)) {
       config->quic.upstream.congestion_controller = NGTCP2_CC_ALGO_CUBIC;
-    } else if (util::strieq_l("bbr", optarg)) {
+    } else if (util::strieq("bbr"_sr, optarg)) {
       config->quic.upstream.congestion_controller = NGTCP2_CC_ALGO_BBR;
     } else {
       LOG(ERROR) << opt << ": must be either cubic or bbr";
@@ -4205,10 +4199,10 @@ int parse_config(Config *config, int optid, const StringRef &opt,
     return 0;
   }
   case SHRPX_OPTID_REQUIRE_HTTP_SCHEME:
-    config->http.require_http_scheme = util::strieq_l("yes", optarg);
+    config->http.require_http_scheme = util::strieq("yes"_sr, optarg);
     return 0;
   case SHRPX_OPTID_TLS_KTLS:
-    config->tls.ktls = util::strieq_l("yes", optarg);
+    config->tls.ktls = util::strieq("yes"_sr, optarg);
     return 0;
   case SHRPX_OPTID_NPN_LIST:
     LOG(WARN) << opt << ": deprecated.  Use alpn-list instead.";
@@ -4268,134 +4262,134 @@ int load_config(Config *config, const char *filename,
 StringRef str_syslog_facility(int facility) {
   switch (facility) {
   case (LOG_AUTH):
-    return StringRef::from_lit("auth");
+    return "auth"_sr;
 #ifdef LOG_AUTHPRIV
   case (LOG_AUTHPRIV):
-    return StringRef::from_lit("authpriv");
+    return "authpriv"_sr;
 #endif // LOG_AUTHPRIV
   case (LOG_CRON):
-    return StringRef::from_lit("cron");
+    return "cron"_sr;
   case (LOG_DAEMON):
-    return StringRef::from_lit("daemon");
+    return "daemon"_sr;
 #ifdef LOG_FTP
   case (LOG_FTP):
-    return StringRef::from_lit("ftp");
+    return "ftp"_sr;
 #endif // LOG_FTP
   case (LOG_KERN):
-    return StringRef::from_lit("kern");
+    return "kern"_sr;
   case (LOG_LOCAL0):
-    return StringRef::from_lit("local0");
+    return "local0"_sr;
   case (LOG_LOCAL1):
-    return StringRef::from_lit("local1");
+    return "local1"_sr;
   case (LOG_LOCAL2):
-    return StringRef::from_lit("local2");
+    return "local2"_sr;
   case (LOG_LOCAL3):
-    return StringRef::from_lit("local3");
+    return "local3"_sr;
   case (LOG_LOCAL4):
-    return StringRef::from_lit("local4");
+    return "local4"_sr;
   case (LOG_LOCAL5):
-    return StringRef::from_lit("local5");
+    return "local5"_sr;
   case (LOG_LOCAL6):
-    return StringRef::from_lit("local6");
+    return "local6"_sr;
   case (LOG_LOCAL7):
-    return StringRef::from_lit("local7");
+    return "local7"_sr;
   case (LOG_LPR):
-    return StringRef::from_lit("lpr");
+    return "lpr"_sr;
   case (LOG_MAIL):
-    return StringRef::from_lit("mail");
+    return "mail"_sr;
   case (LOG_SYSLOG):
-    return StringRef::from_lit("syslog");
+    return "syslog"_sr;
   case (LOG_USER):
-    return StringRef::from_lit("user");
+    return "user"_sr;
   case (LOG_UUCP):
-    return StringRef::from_lit("uucp");
+    return "uucp"_sr;
   default:
-    return StringRef::from_lit("(unknown)");
+    return "(unknown)"_sr;
   }
 }
 
 int int_syslog_facility(const StringRef &strfacility) {
-  if (util::strieq_l("auth", strfacility)) {
+  if (util::strieq("auth"_sr, strfacility)) {
     return LOG_AUTH;
   }
 
 #ifdef LOG_AUTHPRIV
-  if (util::strieq_l("authpriv", strfacility)) {
+  if (util::strieq("authpriv"_sr, strfacility)) {
     return LOG_AUTHPRIV;
   }
 #endif // LOG_AUTHPRIV
 
-  if (util::strieq_l("cron", strfacility)) {
+  if (util::strieq("cron"_sr, strfacility)) {
     return LOG_CRON;
   }
 
-  if (util::strieq_l("daemon", strfacility)) {
+  if (util::strieq("daemon"_sr, strfacility)) {
     return LOG_DAEMON;
   }
 
 #ifdef LOG_FTP
-  if (util::strieq_l("ftp", strfacility)) {
+  if (util::strieq("ftp"_sr, strfacility)) {
     return LOG_FTP;
   }
 #endif // LOG_FTP
 
-  if (util::strieq_l("kern", strfacility)) {
+  if (util::strieq("kern"_sr, strfacility)) {
     return LOG_KERN;
   }
 
-  if (util::strieq_l("local0", strfacility)) {
+  if (util::strieq("local0"_sr, strfacility)) {
     return LOG_LOCAL0;
   }
 
-  if (util::strieq_l("local1", strfacility)) {
+  if (util::strieq("local1"_sr, strfacility)) {
     return LOG_LOCAL1;
   }
 
-  if (util::strieq_l("local2", strfacility)) {
+  if (util::strieq("local2"_sr, strfacility)) {
     return LOG_LOCAL2;
   }
 
-  if (util::strieq_l("local3", strfacility)) {
+  if (util::strieq("local3"_sr, strfacility)) {
     return LOG_LOCAL3;
   }
 
-  if (util::strieq_l("local4", strfacility)) {
+  if (util::strieq("local4"_sr, strfacility)) {
     return LOG_LOCAL4;
   }
 
-  if (util::strieq_l("local5", strfacility)) {
+  if (util::strieq("local5"_sr, strfacility)) {
     return LOG_LOCAL5;
   }
 
-  if (util::strieq_l("local6", strfacility)) {
+  if (util::strieq("local6"_sr, strfacility)) {
     return LOG_LOCAL6;
   }
 
-  if (util::strieq_l("local7", strfacility)) {
+  if (util::strieq("local7"_sr, strfacility)) {
     return LOG_LOCAL7;
   }
 
-  if (util::strieq_l("lpr", strfacility)) {
+  if (util::strieq("lpr"_sr, strfacility)) {
     return LOG_LPR;
   }
 
-  if (util::strieq_l("mail", strfacility)) {
+  if (util::strieq("mail"_sr, strfacility)) {
     return LOG_MAIL;
   }
 
-  if (util::strieq_l("news", strfacility)) {
+  if (util::strieq("news"_sr, strfacility)) {
     return LOG_NEWS;
   }
 
-  if (util::strieq_l("syslog", strfacility)) {
+  if (util::strieq("syslog"_sr, strfacility)) {
     return LOG_SYSLOG;
   }
 
-  if (util::strieq_l("user", strfacility)) {
+  if (util::strieq("user"_sr, strfacility)) {
     return LOG_USER;
   }
 
-  if (util::strieq_l("uucp", strfacility)) {
+  if (util::strieq("uucp"_sr, strfacility)) {
     return LOG_UUCP;
   }
 
@@ -4405,15 +4399,15 @@ int int_syslog_facility(const StringRef &strfacility) {
 StringRef strproto(Proto proto) {
   switch (proto) {
   case Proto::NONE:
-    return StringRef::from_lit("none");
+    return "none"_sr;
   case Proto::HTTP1:
-    return StringRef::from_lit("http/1.1");
+    return "http/1.1"_sr;
   case Proto::HTTP2:
-    return StringRef::from_lit("h2");
+    return "h2"_sr;
   case Proto::HTTP3:
-    return StringRef::from_lit("h3");
+    return "h3"_sr;
   case Proto::MEMCACHED:
-    return StringRef::from_lit("memcached");
+    return "memcached"_sr;
   }
 
   // gcc needs this.
@@ -4436,7 +4430,7 @@ int compute_affinity_hash(std::vector<AffinityHash> &res, size_t idx,
   std::array<uint8_t, 32> buf;
 
   for (auto i = 0; i < 20; ++i) {
-    auto t = s.str();
+    auto t = std::string{s};
     t += i;
 
     rv = util::sha256(buf.data(), StringRef{t});
@@ -4473,13 +4467,13 @@ int configure_downstream_group(Config *config, bool http2_proxy,
 
   if (addr_groups.empty()) {
     DownstreamAddrConfig addr{};
-    addr.host = StringRef::from_lit(DEFAULT_DOWNSTREAM_HOST);
+    addr.host = DEFAULT_DOWNSTREAM_HOST;
     addr.port = DEFAULT_DOWNSTREAM_PORT;
     addr.proto = Proto::HTTP1;
     addr.weight = 1;
     addr.group_weight = 1;
 
-    DownstreamAddrGroupConfig g(StringRef::from_lit("/"));
+    DownstreamAddrGroupConfig g("/"_sr);
     g.addrs.push_back(std::move(addr));
     router.add_route(g.pattern, addr_groups.size());
     addr_groups.push_back(std::move(g));
@@ -4503,14 +4497,14 @@ int configure_downstream_group(Config *config, bool http2_proxy,
   ssize_t catch_all_group = -1;
   for (size_t i = 0; i < addr_groups.size(); ++i) {
     auto &g = addr_groups[i];
-    if (g.pattern == StringRef::from_lit("/")) {
+    if (g.pattern == "/"_sr) {
       catch_all_group = i;
     }
     if (LOG_ENABLED(INFO)) {
       LOG(INFO) << "Host-path pattern: group " << i << ": '" << g.pattern
                 << "'";
       for (auto &addr : g.addrs) {
-        LOG(INFO) << "group " << i << " -> " << addr.host.c_str()
+        LOG(INFO) << "group " << i << " -> " << addr.host.data()
                   << (addr.host_unix ? "" : ":" + util::utos(addr.port))
                   << ", proto=" << strproto(addr.proto)
                   << (addr.tls ? ", tls" : "");
@@ -4575,9 +4569,9 @@ int configure_downstream_group(Config *config, bool http2_proxy,
         // for AF_UNIX socket, we use "localhost" as host for backend
         // hostport.  This is used as Host header field to backend and
         // not going to be passed to any syscalls.
-        addr.hostport = StringRef::from_lit("localhost");
+        addr.hostport = "localhost"_sr;
 
-        auto path = addr.host.c_str();
+        auto path = addr.host.data();
         auto pathlen = addr.host.size();
 
         if (pathlen + 1 > sizeof(addr.addr.su.un.sun_path)) {
@@ -4606,7 +4600,7 @@ int configure_downstream_group(Config *config, bool http2_proxy,
           util::make_hostport(std::begin(hostport_buf), addr.host, addr.port);
 
       if (!addr.dns) {
-        if (resolve_hostname(&addr.addr, addr.host.c_str(), addr.port,
+        if (resolve_hostname(&addr.addr, addr.host.data(), addr.port,
                              downstreamconf.family, resolve_flags) == -1) {
           LOG(FATAL) << "Resolving backend address failed: " << hostport;
           return -1;
diff --git a/src/shrpx_config.h b/src/shrpx_config.h
index f264b6a..b0225d1 100644
--- a/src/shrpx_config.h
+++ b/src/shrpx_config.h
@@ -51,6 +51,7 @@
 
 #include <nghttp2/nghttp2.h>
 
+#include "shrpx_log.h"
 #include "shrpx_router.h"
 #if ENABLE_HTTP3
 #  include "shrpx_quic.h"
@@ -74,348 +75,289 @@ class CertLookupTree;
 
 } // namespace tls
 
-constexpr auto SHRPX_OPT_PRIVATE_KEY_FILE =
-    StringRef::from_lit("private-key-file");
-constexpr auto SHRPX_OPT_PRIVATE_KEY_PASSWD_FILE =
-    StringRef::from_lit("private-key-passwd-file");
-constexpr auto SHRPX_OPT_CERTIFICATE_FILE =
-    StringRef::from_lit("certificate-file");
-constexpr auto SHRPX_OPT_DH_PARAM_FILE = StringRef::from_lit("dh-param-file");
-constexpr auto SHRPX_OPT_SUBCERT = StringRef::from_lit("subcert");
-constexpr auto SHRPX_OPT_BACKEND = StringRef::from_lit("backend");
-constexpr auto SHRPX_OPT_FRONTEND = StringRef::from_lit("frontend");
-constexpr auto SHRPX_OPT_WORKERS = StringRef::from_lit("workers");
+constexpr auto SHRPX_OPT_PRIVATE_KEY_FILE = "private-key-file"_sr;
+constexpr auto SHRPX_OPT_PRIVATE_KEY_PASSWD_FILE = "private-key-passwd-file"_sr;
+constexpr auto SHRPX_OPT_CERTIFICATE_FILE = "certificate-file"_sr;
+constexpr auto SHRPX_OPT_DH_PARAM_FILE = "dh-param-file"_sr;
+constexpr auto SHRPX_OPT_SUBCERT = "subcert"_sr;
+constexpr auto SHRPX_OPT_BACKEND = "backend"_sr;
+constexpr auto SHRPX_OPT_FRONTEND = "frontend"_sr;
+constexpr auto SHRPX_OPT_WORKERS = "workers"_sr;
 constexpr auto SHRPX_OPT_HTTP2_MAX_CONCURRENT_STREAMS =
-    StringRef::from_lit("http2-max-concurrent-streams");
-constexpr auto SHRPX_OPT_LOG_LEVEL = StringRef::from_lit("log-level");
-constexpr auto SHRPX_OPT_DAEMON = StringRef::from_lit("daemon");
-constexpr auto SHRPX_OPT_HTTP2_PROXY = StringRef::from_lit("http2-proxy");
-constexpr auto SHRPX_OPT_HTTP2_BRIDGE = StringRef::from_lit("http2-bridge");
-constexpr auto SHRPX_OPT_CLIENT_PROXY = StringRef::from_lit("client-proxy");
-constexpr auto SHRPX_OPT_ADD_X_FORWARDED_FOR =
-    StringRef::from_lit("add-x-forwarded-for");
+    "http2-max-concurrent-streams"_sr;
+constexpr auto SHRPX_OPT_LOG_LEVEL = "log-level"_sr;
+constexpr auto SHRPX_OPT_DAEMON = "daemon"_sr;
+constexpr auto SHRPX_OPT_HTTP2_PROXY = "http2-proxy"_sr;
+constexpr auto SHRPX_OPT_HTTP2_BRIDGE = "http2-bridge"_sr;
+constexpr auto SHRPX_OPT_CLIENT_PROXY = "client-proxy"_sr;
+constexpr auto SHRPX_OPT_ADD_X_FORWARDED_FOR = "add-x-forwarded-for"_sr;
 constexpr auto SHRPX_OPT_STRIP_INCOMING_X_FORWARDED_FOR =
-    StringRef::from_lit("strip-incoming-x-forwarded-for");
-constexpr auto SHRPX_OPT_NO_VIA = StringRef::from_lit("no-via");
+    "strip-incoming-x-forwarded-for"_sr;
+constexpr auto SHRPX_OPT_NO_VIA = "no-via"_sr;
 constexpr auto SHRPX_OPT_FRONTEND_HTTP2_READ_TIMEOUT =
-    StringRef::from_lit("frontend-http2-read-timeout");
-constexpr auto SHRPX_OPT_FRONTEND_READ_TIMEOUT =
-    StringRef::from_lit("frontend-read-timeout");
-constexpr auto SHRPX_OPT_FRONTEND_WRITE_TIMEOUT =
-    StringRef::from_lit("frontend-write-timeout");
-constexpr auto SHRPX_OPT_BACKEND_READ_TIMEOUT =
-    StringRef::from_lit("backend-read-timeout");
-constexpr auto SHRPX_OPT_BACKEND_WRITE_TIMEOUT =
-    StringRef::from_lit("backend-write-timeout");
-constexpr auto SHRPX_OPT_STREAM_READ_TIMEOUT =
-    StringRef::from_lit("stream-read-timeout");
-constexpr auto SHRPX_OPT_STREAM_WRITE_TIMEOUT =
-    StringRef::from_lit("stream-write-timeout");
-constexpr auto SHRPX_OPT_ACCESSLOG_FILE = StringRef::from_lit("accesslog-file");
-constexpr auto SHRPX_OPT_ACCESSLOG_SYSLOG =
-    StringRef::from_lit("accesslog-syslog");
-constexpr auto SHRPX_OPT_ACCESSLOG_FORMAT =
-    StringRef::from_lit("accesslog-format");
-constexpr auto SHRPX_OPT_ERRORLOG_FILE = StringRef::from_lit("errorlog-file");
-constexpr auto SHRPX_OPT_ERRORLOG_SYSLOG =
-    StringRef::from_lit("errorlog-syslog");
+    "frontend-http2-read-timeout"_sr;
+constexpr auto SHRPX_OPT_FRONTEND_READ_TIMEOUT = "frontend-read-timeout"_sr;
+constexpr auto SHRPX_OPT_FRONTEND_WRITE_TIMEOUT = "frontend-write-timeout"_sr;
+constexpr auto SHRPX_OPT_BACKEND_READ_TIMEOUT = "backend-read-timeout"_sr;
+constexpr auto SHRPX_OPT_BACKEND_WRITE_TIMEOUT = "backend-write-timeout"_sr;
+constexpr auto SHRPX_OPT_STREAM_READ_TIMEOUT = "stream-read-timeout"_sr;
+constexpr auto SHRPX_OPT_STREAM_WRITE_TIMEOUT = "stream-write-timeout"_sr;
+constexpr auto SHRPX_OPT_ACCESSLOG_FILE = "accesslog-file"_sr;
+constexpr auto SHRPX_OPT_ACCESSLOG_SYSLOG = "accesslog-syslog"_sr;
+constexpr auto SHRPX_OPT_ACCESSLOG_FORMAT = "accesslog-format"_sr;
+constexpr auto SHRPX_OPT_ERRORLOG_FILE = "errorlog-file"_sr;
+constexpr auto SHRPX_OPT_ERRORLOG_SYSLOG = "errorlog-syslog"_sr;
 constexpr auto SHRPX_OPT_BACKEND_KEEP_ALIVE_TIMEOUT =
-    StringRef::from_lit("backend-keep-alive-timeout");
+    "backend-keep-alive-timeout"_sr;
 constexpr auto SHRPX_OPT_FRONTEND_HTTP2_WINDOW_BITS =
-    StringRef::from_lit("frontend-http2-window-bits");
+    "frontend-http2-window-bits"_sr;
 constexpr auto SHRPX_OPT_BACKEND_HTTP2_WINDOW_BITS =
-    StringRef::from_lit("backend-http2-window-bits");
+    "backend-http2-window-bits"_sr;
 constexpr auto SHRPX_OPT_FRONTEND_HTTP2_CONNECTION_WINDOW_BITS =
-    StringRef::from_lit("frontend-http2-connection-window-bits");
+    "frontend-http2-connection-window-bits"_sr;
 constexpr auto SHRPX_OPT_BACKEND_HTTP2_CONNECTION_WINDOW_BITS =
-    StringRef::from_lit("backend-http2-connection-window-bits");
-constexpr auto SHRPX_OPT_FRONTEND_NO_TLS =
-    StringRef::from_lit("frontend-no-tls");
-constexpr auto SHRPX_OPT_BACKEND_NO_TLS = StringRef::from_lit("backend-no-tls");
-constexpr auto SHRPX_OPT_BACKEND_TLS_SNI_FIELD =
-    StringRef::from_lit("backend-tls-sni-field");
-constexpr auto SHRPX_OPT_PID_FILE = StringRef::from_lit("pid-file");
-constexpr auto SHRPX_OPT_USER = StringRef::from_lit("user");
-constexpr auto SHRPX_OPT_SYSLOG_FACILITY =
-    StringRef::from_lit("syslog-facility");
-constexpr auto SHRPX_OPT_BACKLOG = StringRef::from_lit("backlog");
-constexpr auto SHRPX_OPT_CIPHERS = StringRef::from_lit("ciphers");
-constexpr auto SHRPX_OPT_CLIENT = StringRef::from_lit("client");
-constexpr auto SHRPX_OPT_INSECURE = StringRef::from_lit("insecure");
-constexpr auto SHRPX_OPT_CACERT = StringRef::from_lit("cacert");
-constexpr auto SHRPX_OPT_BACKEND_IPV4 = StringRef::from_lit("backend-ipv4");
-constexpr auto SHRPX_OPT_BACKEND_IPV6 = StringRef::from_lit("backend-ipv6");
-constexpr auto SHRPX_OPT_BACKEND_HTTP_PROXY_URI =
-    StringRef::from_lit("backend-http-proxy-uri");
-constexpr auto SHRPX_OPT_READ_RATE = StringRef::from_lit("read-rate");
-constexpr auto SHRPX_OPT_READ_BURST = StringRef::from_lit("read-burst");
-constexpr auto SHRPX_OPT_WRITE_RATE = StringRef::from_lit("write-rate");
-constexpr auto SHRPX_OPT_WRITE_BURST = StringRef::from_lit("write-burst");
-constexpr auto SHRPX_OPT_WORKER_READ_RATE =
-    StringRef::from_lit("worker-read-rate");
-constexpr auto SHRPX_OPT_WORKER_READ_BURST =
-    StringRef::from_lit("worker-read-burst");
-constexpr auto SHRPX_OPT_WORKER_WRITE_RATE =
-    StringRef::from_lit("worker-write-rate");
-constexpr auto SHRPX_OPT_WORKER_WRITE_BURST =
-    StringRef::from_lit("worker-write-burst");
-constexpr auto SHRPX_OPT_NPN_LIST = StringRef::from_lit("npn-list");
-constexpr auto SHRPX_OPT_TLS_PROTO_LIST = StringRef::from_lit("tls-proto-list");
-constexpr auto SHRPX_OPT_VERIFY_CLIENT = StringRef::from_lit("verify-client");
-constexpr auto SHRPX_OPT_VERIFY_CLIENT_CACERT =
-    StringRef::from_lit("verify-client-cacert");
-constexpr auto SHRPX_OPT_CLIENT_PRIVATE_KEY_FILE =
-    StringRef::from_lit("client-private-key-file");
-constexpr auto SHRPX_OPT_CLIENT_CERT_FILE =
-    StringRef::from_lit("client-cert-file");
+    "backend-http2-connection-window-bits"_sr;
+constexpr auto SHRPX_OPT_FRONTEND_NO_TLS = "frontend-no-tls"_sr;
+constexpr auto SHRPX_OPT_BACKEND_NO_TLS = "backend-no-tls"_sr;
+constexpr auto SHRPX_OPT_BACKEND_TLS_SNI_FIELD = "backend-tls-sni-field"_sr;
+constexpr auto SHRPX_OPT_PID_FILE = "pid-file"_sr;
+constexpr auto SHRPX_OPT_USER = "user"_sr;
+constexpr auto SHRPX_OPT_SYSLOG_FACILITY = "syslog-facility"_sr;
+constexpr auto SHRPX_OPT_BACKLOG = "backlog"_sr;
+constexpr auto SHRPX_OPT_CIPHERS = "ciphers"_sr;
+constexpr auto SHRPX_OPT_CLIENT = "client"_sr;
+constexpr auto SHRPX_OPT_INSECURE = "insecure"_sr;
+constexpr auto SHRPX_OPT_CACERT = "cacert"_sr;
+constexpr auto SHRPX_OPT_BACKEND_IPV4 = "backend-ipv4"_sr;
+constexpr auto SHRPX_OPT_BACKEND_IPV6 = "backend-ipv6"_sr;
+constexpr auto SHRPX_OPT_BACKEND_HTTP_PROXY_URI = "backend-http-proxy-uri"_sr;
+constexpr auto SHRPX_OPT_READ_RATE = "read-rate"_sr;
+constexpr auto SHRPX_OPT_READ_BURST = "read-burst"_sr;
+constexpr auto SHRPX_OPT_WRITE_RATE = "write-rate"_sr;
+constexpr auto SHRPX_OPT_WRITE_BURST = "write-burst"_sr;
+constexpr auto SHRPX_OPT_WORKER_READ_RATE = "worker-read-rate"_sr;
+constexpr auto SHRPX_OPT_WORKER_READ_BURST = "worker-read-burst"_sr;
+constexpr auto SHRPX_OPT_WORKER_WRITE_RATE = "worker-write-rate"_sr;
+constexpr auto SHRPX_OPT_WORKER_WRITE_BURST = "worker-write-burst"_sr;
+constexpr auto SHRPX_OPT_NPN_LIST = "npn-list"_sr;
+constexpr auto SHRPX_OPT_TLS_PROTO_LIST = "tls-proto-list"_sr;
+constexpr auto SHRPX_OPT_VERIFY_CLIENT = "verify-client"_sr;
+constexpr auto SHRPX_OPT_VERIFY_CLIENT_CACERT = "verify-client-cacert"_sr;
+constexpr auto SHRPX_OPT_CLIENT_PRIVATE_KEY_FILE = "client-private-key-file"_sr;
+constexpr auto SHRPX_OPT_CLIENT_CERT_FILE = "client-cert-file"_sr;
 constexpr auto SHRPX_OPT_FRONTEND_HTTP2_DUMP_REQUEST_HEADER =
-    StringRef::from_lit("frontend-http2-dump-request-header");
+    "frontend-http2-dump-request-header"_sr;
 constexpr auto SHRPX_OPT_FRONTEND_HTTP2_DUMP_RESPONSE_HEADER =
-    StringRef::from_lit("frontend-http2-dump-response-header");
+    "frontend-http2-dump-response-header"_sr;
 constexpr auto SHRPX_OPT_HTTP2_NO_COOKIE_CRUMBLING =
-    StringRef::from_lit("http2-no-cookie-crumbling");
-constexpr auto SHRPX_OPT_FRONTEND_FRAME_DEBUG =
-    StringRef::from_lit("frontend-frame-debug");
-constexpr auto SHRPX_OPT_PADDING = StringRef::from_lit("padding");
-constexpr auto SHRPX_OPT_ALTSVC = StringRef::from_lit("altsvc");
-constexpr auto SHRPX_OPT_ADD_REQUEST_HEADER =
-    StringRef::from_lit("add-request-header");
-constexpr auto SHRPX_OPT_ADD_RESPONSE_HEADER =
-    StringRef::from_lit("add-response-header");
+    "http2-no-cookie-crumbling"_sr;
+constexpr auto SHRPX_OPT_FRONTEND_FRAME_DEBUG = "frontend-frame-debug"_sr;
+constexpr auto SHRPX_OPT_PADDING = "padding"_sr;
+constexpr auto SHRPX_OPT_ALTSVC = "altsvc"_sr;
+constexpr auto SHRPX_OPT_ADD_REQUEST_HEADER = "add-request-header"_sr;
+constexpr auto SHRPX_OPT_ADD_RESPONSE_HEADER = "add-response-header"_sr;
 constexpr auto SHRPX_OPT_WORKER_FRONTEND_CONNECTIONS =
-    StringRef::from_lit("worker-frontend-connections");
-constexpr auto SHRPX_OPT_NO_LOCATION_REWRITE =
-    StringRef::from_lit("no-location-rewrite");
-constexpr auto SHRPX_OPT_NO_HOST_REWRITE =
-    StringRef::from_lit("no-host-rewrite");
+    "worker-frontend-connections"_sr;
+constexpr auto SHRPX_OPT_NO_LOCATION_REWRITE = "no-location-rewrite"_sr;
+constexpr auto SHRPX_OPT_NO_HOST_REWRITE = "no-host-rewrite"_sr;
 constexpr auto SHRPX_OPT_BACKEND_HTTP1_CONNECTIONS_PER_HOST =
-    StringRef::from_lit("backend-http1-connections-per-host");
+    "backend-http1-connections-per-host"_sr;
 constexpr auto SHRPX_OPT_BACKEND_HTTP1_CONNECTIONS_PER_FRONTEND =
-    StringRef::from_lit("backend-http1-connections-per-frontend");
+    "backend-http1-connections-per-frontend"_sr;
 constexpr auto SHRPX_OPT_LISTENER_DISABLE_TIMEOUT =
-    StringRef::from_lit("listener-disable-timeout");
-constexpr auto SHRPX_OPT_TLS_TICKET_KEY_FILE =
-    StringRef::from_lit("tls-ticket-key-file");
-constexpr auto SHRPX_OPT_RLIMIT_NOFILE = StringRef::from_lit("rlimit-nofile");
-constexpr auto SHRPX_OPT_BACKEND_REQUEST_BUFFER =
-    StringRef::from_lit("backend-request-buffer");
-constexpr auto SHRPX_OPT_BACKEND_RESPONSE_BUFFER =
-    StringRef::from_lit("backend-response-buffer");
-constexpr auto SHRPX_OPT_NO_SERVER_PUSH = StringRef::from_lit("no-server-push");
+    "listener-disable-timeout"_sr;
+constexpr auto SHRPX_OPT_TLS_TICKET_KEY_FILE = "tls-ticket-key-file"_sr;
+constexpr auto SHRPX_OPT_RLIMIT_NOFILE = "rlimit-nofile"_sr;
+constexpr auto SHRPX_OPT_BACKEND_REQUEST_BUFFER = "backend-request-buffer"_sr;
+constexpr auto SHRPX_OPT_BACKEND_RESPONSE_BUFFER = "backend-response-buffer"_sr;
+constexpr auto SHRPX_OPT_NO_SERVER_PUSH = "no-server-push"_sr;
 constexpr auto SHRPX_OPT_BACKEND_HTTP2_CONNECTIONS_PER_WORKER =
-    StringRef::from_lit("backend-http2-connections-per-worker");
+    "backend-http2-connections-per-worker"_sr;
 constexpr auto SHRPX_OPT_FETCH_OCSP_RESPONSE_FILE =
-    StringRef::from_lit("fetch-ocsp-response-file");
-constexpr auto SHRPX_OPT_OCSP_UPDATE_INTERVAL =
-    StringRef::from_lit("ocsp-update-interval");
-constexpr auto SHRPX_OPT_NO_OCSP = StringRef::from_lit("no-ocsp");
-constexpr auto SHRPX_OPT_HEADER_FIELD_BUFFER =
-    StringRef::from_lit("header-field-buffer");
-constexpr auto SHRPX_OPT_MAX_HEADER_FIELDS =
-    StringRef::from_lit("max-header-fields");
-constexpr auto SHRPX_OPT_INCLUDE = StringRef::from_lit("include");
-constexpr auto SHRPX_OPT_TLS_TICKET_KEY_CIPHER =
-    StringRef::from_lit("tls-ticket-key-cipher");
-constexpr auto SHRPX_OPT_HOST_REWRITE = StringRef::from_lit("host-rewrite");
+    "fetch-ocsp-response-file"_sr;
+constexpr auto SHRPX_OPT_OCSP_UPDATE_INTERVAL = "ocsp-update-interval"_sr;
+constexpr auto SHRPX_OPT_NO_OCSP = "no-ocsp"_sr;
+constexpr auto SHRPX_OPT_HEADER_FIELD_BUFFER = "header-field-buffer"_sr;
+constexpr auto SHRPX_OPT_MAX_HEADER_FIELDS = "max-header-fields"_sr;
+constexpr auto SHRPX_OPT_INCLUDE = "include"_sr;
+constexpr auto SHRPX_OPT_TLS_TICKET_KEY_CIPHER = "tls-ticket-key-cipher"_sr;
+constexpr auto SHRPX_OPT_HOST_REWRITE = "host-rewrite"_sr;
 constexpr auto SHRPX_OPT_TLS_SESSION_CACHE_MEMCACHED =
-    StringRef::from_lit("tls-session-cache-memcached");
+    "tls-session-cache-memcached"_sr;
 constexpr auto SHRPX_OPT_TLS_TICKET_KEY_MEMCACHED =
-    StringRef::from_lit("tls-ticket-key-memcached");
+    "tls-ticket-key-memcached"_sr;
 constexpr auto SHRPX_OPT_TLS_TICKET_KEY_MEMCACHED_INTERVAL =
-    StringRef::from_lit("tls-ticket-key-memcached-interval");
+    "tls-ticket-key-memcached-interval"_sr;
 constexpr auto SHRPX_OPT_TLS_TICKET_KEY_MEMCACHED_MAX_RETRY =
-    StringRef::from_lit("tls-ticket-key-memcached-max-retry");
+    "tls-ticket-key-memcached-max-retry"_sr;
 constexpr auto SHRPX_OPT_TLS_TICKET_KEY_MEMCACHED_MAX_FAIL =
-    StringRef::from_lit("tls-ticket-key-memcached-max-fail");
-constexpr auto SHRPX_OPT_MRUBY_FILE = StringRef::from_lit("mruby-file");
-constexpr auto SHRPX_OPT_ACCEPT_PROXY_PROTOCOL =
-    StringRef::from_lit("accept-proxy-protocol");
-constexpr auto SHRPX_OPT_FASTOPEN = StringRef::from_lit("fastopen");
+    "tls-ticket-key-memcached-max-fail"_sr;
+constexpr auto SHRPX_OPT_MRUBY_FILE = "mruby-file"_sr;
+constexpr auto SHRPX_OPT_ACCEPT_PROXY_PROTOCOL = "accept-proxy-protocol"_sr;
+constexpr auto SHRPX_OPT_FASTOPEN = "fastopen"_sr;
 constexpr auto SHRPX_OPT_TLS_DYN_REC_WARMUP_THRESHOLD =
-    StringRef::from_lit("tls-dyn-rec-warmup-threshold");
+    "tls-dyn-rec-warmup-threshold"_sr;
 constexpr auto SHRPX_OPT_TLS_DYN_REC_IDLE_TIMEOUT =
-    StringRef::from_lit("tls-dyn-rec-idle-timeout");
-constexpr auto SHRPX_OPT_ADD_FORWARDED = StringRef::from_lit("add-forwarded");
+    "tls-dyn-rec-idle-timeout"_sr;
+constexpr auto SHRPX_OPT_ADD_FORWARDED = "add-forwarded"_sr;
 constexpr auto SHRPX_OPT_STRIP_INCOMING_FORWARDED =
-    StringRef::from_lit("strip-incoming-forwarded");
-constexpr auto SHRPX_OPT_FORWARDED_BY = StringRef::from_lit("forwarded-by");
-constexpr auto SHRPX_OPT_FORWARDED_FOR = StringRef::from_lit("forwarded-for");
+    "strip-incoming-forwarded"_sr;
+constexpr auto SHRPX_OPT_FORWARDED_BY = "forwarded-by"_sr;
+constexpr auto SHRPX_OPT_FORWARDED_FOR = "forwarded-for"_sr;
 constexpr auto SHRPX_OPT_REQUEST_HEADER_FIELD_BUFFER =
-    StringRef::from_lit("request-header-field-buffer");
+    "request-header-field-buffer"_sr;
 constexpr auto SHRPX_OPT_MAX_REQUEST_HEADER_FIELDS =
-    StringRef::from_lit("max-request-header-fields");
+    "max-request-header-fields"_sr;
 constexpr auto SHRPX_OPT_RESPONSE_HEADER_FIELD_BUFFER =
-    StringRef::from_lit("response-header-field-buffer");
+    "response-header-field-buffer"_sr;
 constexpr auto SHRPX_OPT_MAX_RESPONSE_HEADER_FIELDS =
-    StringRef::from_lit("max-response-header-fields");
+    "max-response-header-fields"_sr;
 constexpr auto SHRPX_OPT_NO_HTTP2_CIPHER_BLOCK_LIST =
-    StringRef::from_lit("no-http2-cipher-block-list");
+    "no-http2-cipher-block-list"_sr;
 constexpr auto SHRPX_OPT_NO_HTTP2_CIPHER_BLACK_LIST =
-    StringRef::from_lit("no-http2-cipher-black-list");
-constexpr auto SHRPX_OPT_BACKEND_HTTP1_TLS =
-    StringRef::from_lit("backend-http1-tls");
+    "no-http2-cipher-black-list"_sr;
+constexpr auto SHRPX_OPT_BACKEND_HTTP1_TLS = "backend-http1-tls"_sr;
 constexpr auto SHRPX_OPT_TLS_SESSION_CACHE_MEMCACHED_TLS =
-    StringRef::from_lit("tls-session-cache-memcached-tls");
+    "tls-session-cache-memcached-tls"_sr;
 constexpr auto SHRPX_OPT_TLS_SESSION_CACHE_MEMCACHED_CERT_FILE =
-    StringRef::from_lit("tls-session-cache-memcached-cert-file");
+    "tls-session-cache-memcached-cert-file"_sr;
 constexpr auto SHRPX_OPT_TLS_SESSION_CACHE_MEMCACHED_PRIVATE_KEY_FILE =
-    StringRef::from_lit("tls-session-cache-memcached-private-key-file");
+    "tls-session-cache-memcached-private-key-file"_sr;
 constexpr auto SHRPX_OPT_TLS_SESSION_CACHE_MEMCACHED_ADDRESS_FAMILY =
-    StringRef::from_lit("tls-session-cache-memcached-address-family");
+    "tls-session-cache-memcached-address-family"_sr;
 constexpr auto SHRPX_OPT_TLS_TICKET_KEY_MEMCACHED_TLS =
-    StringRef::from_lit("tls-ticket-key-memcached-tls");
+    "tls-ticket-key-memcached-tls"_sr;
 constexpr auto SHRPX_OPT_TLS_TICKET_KEY_MEMCACHED_CERT_FILE =
-    StringRef::from_lit("tls-ticket-key-memcached-cert-file");
+    "tls-ticket-key-memcached-cert-file"_sr;
 constexpr auto SHRPX_OPT_TLS_TICKET_KEY_MEMCACHED_PRIVATE_KEY_FILE =
-    StringRef::from_lit("tls-ticket-key-memcached-private-key-file");
+    "tls-ticket-key-memcached-private-key-file"_sr;
 constexpr auto SHRPX_OPT_TLS_TICKET_KEY_MEMCACHED_ADDRESS_FAMILY =
-    StringRef::from_lit("tls-ticket-key-memcached-address-family");
-constexpr auto SHRPX_OPT_BACKEND_ADDRESS_FAMILY =
-    StringRef::from_lit("backend-address-family");
+    "tls-ticket-key-memcached-address-family"_sr;
+constexpr auto SHRPX_OPT_BACKEND_ADDRESS_FAMILY = "backend-address-family"_sr;
 constexpr auto SHRPX_OPT_FRONTEND_HTTP2_MAX_CONCURRENT_STREAMS =
-    StringRef::from_lit("frontend-http2-max-concurrent-streams");
+    "frontend-http2-max-concurrent-streams"_sr;
 constexpr auto SHRPX_OPT_BACKEND_HTTP2_MAX_CONCURRENT_STREAMS =
-    StringRef::from_lit("backend-http2-max-concurrent-streams");
+    "backend-http2-max-concurrent-streams"_sr;
 constexpr auto SHRPX_OPT_BACKEND_CONNECTIONS_PER_FRONTEND =
-    StringRef::from_lit("backend-connections-per-frontend");
-constexpr auto SHRPX_OPT_BACKEND_TLS = StringRef::from_lit("backend-tls");
+    "backend-connections-per-frontend"_sr;
+constexpr auto SHRPX_OPT_BACKEND_TLS = "backend-tls"_sr;
 constexpr auto SHRPX_OPT_BACKEND_CONNECTIONS_PER_HOST =
-    StringRef::from_lit("backend-connections-per-host");
-constexpr auto SHRPX_OPT_ERROR_PAGE = StringRef::from_lit("error-page");
-constexpr auto SHRPX_OPT_NO_KQUEUE = StringRef::from_lit("no-kqueue");
+    "backend-connections-per-host"_sr;
+constexpr auto SHRPX_OPT_ERROR_PAGE = "error-page"_sr;
+constexpr auto SHRPX_OPT_NO_KQUEUE = "no-kqueue"_sr;
 constexpr auto SHRPX_OPT_FRONTEND_HTTP2_SETTINGS_TIMEOUT =
-    StringRef::from_lit("frontend-http2-settings-timeout");
+    "frontend-http2-settings-timeout"_sr;
 constexpr auto SHRPX_OPT_BACKEND_HTTP2_SETTINGS_TIMEOUT =
-    StringRef::from_lit("backend-http2-settings-timeout");
-constexpr auto SHRPX_OPT_API_MAX_REQUEST_BODY =
-    StringRef::from_lit("api-max-request-body");
-constexpr auto SHRPX_OPT_BACKEND_MAX_BACKOFF =
-    StringRef::from_lit("backend-max-backoff");
-constexpr auto SHRPX_OPT_SERVER_NAME = StringRef::from_lit("server-name");
-constexpr auto SHRPX_OPT_NO_SERVER_REWRITE =
-    StringRef::from_lit("no-server-rewrite");
+    "backend-http2-settings-timeout"_sr;
+constexpr auto SHRPX_OPT_API_MAX_REQUEST_BODY = "api-max-request-body"_sr;
+constexpr auto SHRPX_OPT_BACKEND_MAX_BACKOFF = "backend-max-backoff"_sr;
+constexpr auto SHRPX_OPT_SERVER_NAME = "server-name"_sr;
+constexpr auto SHRPX_OPT_NO_SERVER_REWRITE = "no-server-rewrite"_sr;
 constexpr auto SHRPX_OPT_FRONTEND_HTTP2_OPTIMIZE_WRITE_BUFFER_SIZE =
-    StringRef::from_lit("frontend-http2-optimize-write-buffer-size");
+    "frontend-http2-optimize-write-buffer-size"_sr;
 constexpr auto SHRPX_OPT_FRONTEND_HTTP2_OPTIMIZE_WINDOW_SIZE =
-    StringRef::from_lit("frontend-http2-optimize-window-size");
+    "frontend-http2-optimize-window-size"_sr;
 constexpr auto SHRPX_OPT_FRONTEND_HTTP2_WINDOW_SIZE =
-    StringRef::from_lit("frontend-http2-window-size");
+    "frontend-http2-window-size"_sr;
 constexpr auto SHRPX_OPT_FRONTEND_HTTP2_CONNECTION_WINDOW_SIZE =
-    StringRef::from_lit("frontend-http2-connection-window-size");
+    "frontend-http2-connection-window-size"_sr;
 constexpr auto SHRPX_OPT_BACKEND_HTTP2_WINDOW_SIZE =
-    StringRef::from_lit("backend-http2-window-size");
+    "backend-http2-window-size"_sr;
 constexpr auto SHRPX_OPT_BACKEND_HTTP2_CONNECTION_WINDOW_SIZE =
-    StringRef::from_lit("backend-http2-connection-window-size");
+    "backend-http2-connection-window-size"_sr;
 constexpr auto SHRPX_OPT_FRONTEND_HTTP2_ENCODER_DYNAMIC_TABLE_SIZE =
-    StringRef::from_lit("frontend-http2-encoder-dynamic-table-size");
+    "frontend-http2-encoder-dynamic-table-size"_sr;
 constexpr auto SHRPX_OPT_FRONTEND_HTTP2_DECODER_DYNAMIC_TABLE_SIZE =
-    StringRef::from_lit("frontend-http2-decoder-dynamic-table-size");
+    "frontend-http2-decoder-dynamic-table-size"_sr;
 constexpr auto SHRPX_OPT_BACKEND_HTTP2_ENCODER_DYNAMIC_TABLE_SIZE =
-    StringRef::from_lit("backend-http2-encoder-dynamic-table-size");
+    "backend-http2-encoder-dynamic-table-size"_sr;
 constexpr auto SHRPX_OPT_BACKEND_HTTP2_DECODER_DYNAMIC_TABLE_SIZE =
-    StringRef::from_lit("backend-http2-decoder-dynamic-table-size");
-constexpr auto SHRPX_OPT_ECDH_CURVES = StringRef::from_lit("ecdh-curves");
-constexpr auto SHRPX_OPT_TLS_SCT_DIR = StringRef::from_lit("tls-sct-dir");
-constexpr auto SHRPX_OPT_BACKEND_CONNECT_TIMEOUT =
-    StringRef::from_lit("backend-connect-timeout");
-constexpr auto SHRPX_OPT_DNS_CACHE_TIMEOUT =
-    StringRef::from_lit("dns-cache-timeout");
-constexpr auto SHRPX_OPT_DNS_LOOKUP_TIMEOUT =
-    StringRef::from_lit("dns-lookup-timeout");
-constexpr auto SHRPX_OPT_DNS_MAX_TRY = StringRef::from_lit("dns-max-try");
+    "backend-http2-decoder-dynamic-table-size"_sr;
+constexpr auto SHRPX_OPT_ECDH_CURVES = "ecdh-curves"_sr;
+constexpr auto SHRPX_OPT_TLS_SCT_DIR = "tls-sct-dir"_sr;
+constexpr auto SHRPX_OPT_BACKEND_CONNECT_TIMEOUT = "backend-connect-timeout"_sr;
+constexpr auto SHRPX_OPT_DNS_CACHE_TIMEOUT = "dns-cache-timeout"_sr;
+constexpr auto SHRPX_OPT_DNS_LOOKUP_TIMEOUT = "dns-lookup-timeout"_sr;
+constexpr auto SHRPX_OPT_DNS_MAX_TRY = "dns-max-try"_sr;
 constexpr auto SHRPX_OPT_FRONTEND_KEEP_ALIVE_TIMEOUT =
-    StringRef::from_lit("frontend-keep-alive-timeout");
-constexpr auto SHRPX_OPT_PSK_SECRETS = StringRef::from_lit("psk-secrets");
-constexpr auto SHRPX_OPT_CLIENT_PSK_SECRETS =
-    StringRef::from_lit("client-psk-secrets");
+    "frontend-keep-alive-timeout"_sr;
+constexpr auto SHRPX_OPT_PSK_SECRETS = "psk-secrets"_sr;
+constexpr auto SHRPX_OPT_CLIENT_PSK_SECRETS = "client-psk-secrets"_sr;
 constexpr auto SHRPX_OPT_CLIENT_NO_HTTP2_CIPHER_BLOCK_LIST =
-    StringRef::from_lit("client-no-http2-cipher-block-list");
+    "client-no-http2-cipher-block-list"_sr;
 constexpr auto SHRPX_OPT_CLIENT_NO_HTTP2_CIPHER_BLACK_LIST =
-    StringRef::from_lit("client-no-http2-cipher-black-list");
-constexpr auto SHRPX_OPT_CLIENT_CIPHERS = StringRef::from_lit("client-ciphers");
-constexpr auto SHRPX_OPT_ACCESSLOG_WRITE_EARLY =
-    StringRef::from_lit("accesslog-write-early");
-constexpr auto SHRPX_OPT_TLS_MIN_PROTO_VERSION =
-    StringRef::from_lit("tls-min-proto-version");
-constexpr auto SHRPX_OPT_TLS_MAX_PROTO_VERSION =
-    StringRef::from_lit("tls-max-proto-version");
-constexpr auto SHRPX_OPT_REDIRECT_HTTPS_PORT =
-    StringRef::from_lit("redirect-https-port");
-constexpr auto SHRPX_OPT_FRONTEND_MAX_REQUESTS =
-    StringRef::from_lit("frontend-max-requests");
-constexpr auto SHRPX_OPT_SINGLE_THREAD = StringRef::from_lit("single-thread");
-constexpr auto SHRPX_OPT_SINGLE_PROCESS = StringRef::from_lit("single-process");
+    "client-no-http2-cipher-black-list"_sr;
+constexpr auto SHRPX_OPT_CLIENT_CIPHERS = "client-ciphers"_sr;
+constexpr auto SHRPX_OPT_ACCESSLOG_WRITE_EARLY = "accesslog-write-early"_sr;
+constexpr auto SHRPX_OPT_TLS_MIN_PROTO_VERSION = "tls-min-proto-version"_sr;
+constexpr auto SHRPX_OPT_TLS_MAX_PROTO_VERSION = "tls-max-proto-version"_sr;
+constexpr auto SHRPX_OPT_REDIRECT_HTTPS_PORT = "redirect-https-port"_sr;
+constexpr auto SHRPX_OPT_FRONTEND_MAX_REQUESTS = "frontend-max-requests"_sr;
+constexpr auto SHRPX_OPT_SINGLE_THREAD = "single-thread"_sr;
+constexpr auto SHRPX_OPT_SINGLE_PROCESS = "single-process"_sr;
 constexpr auto SHRPX_OPT_NO_ADD_X_FORWARDED_PROTO =
-    StringRef::from_lit("no-add-x-forwarded-proto");
+    "no-add-x-forwarded-proto"_sr;
 constexpr auto SHRPX_OPT_NO_STRIP_INCOMING_X_FORWARDED_PROTO =
-    StringRef::from_lit("no-strip-incoming-x-forwarded-proto");
-constexpr auto SHRPX_OPT_OCSP_STARTUP = StringRef::from_lit("ocsp-startup");
-constexpr auto SHRPX_OPT_NO_VERIFY_OCSP = StringRef::from_lit("no-verify-ocsp");
+    "no-strip-incoming-x-forwarded-proto"_sr;
+constexpr auto SHRPX_OPT_OCSP_STARTUP = "ocsp-startup"_sr;
+constexpr auto SHRPX_OPT_NO_VERIFY_OCSP = "no-verify-ocsp"_sr;
 constexpr auto SHRPX_OPT_VERIFY_CLIENT_TOLERATE_EXPIRED =
-    StringRef::from_lit("verify-client-tolerate-expired");
+    "verify-client-tolerate-expired"_sr;
 constexpr auto SHRPX_OPT_IGNORE_PER_PATTERN_MRUBY_ERROR =
-    StringRef::from_lit("ignore-per-pattern-mruby-error");
+    "ignore-per-pattern-mruby-error"_sr;
 constexpr auto SHRPX_OPT_TLS_NO_POSTPONE_EARLY_DATA =
-    StringRef::from_lit("tls-no-postpone-early-data");
-constexpr auto SHRPX_OPT_TLS_MAX_EARLY_DATA =
-    StringRef::from_lit("tls-max-early-data");
-constexpr auto SHRPX_OPT_TLS13_CIPHERS = StringRef::from_lit("tls13-ciphers");
-constexpr auto SHRPX_OPT_TLS13_CLIENT_CIPHERS =
-    StringRef::from_lit("tls13-client-ciphers");
+    "tls-no-postpone-early-data"_sr;
+constexpr auto SHRPX_OPT_TLS_MAX_EARLY_DATA = "tls-max-early-data"_sr;
+constexpr auto SHRPX_OPT_TLS13_CIPHERS = "tls13-ciphers"_sr;
+constexpr auto SHRPX_OPT_TLS13_CLIENT_CIPHERS = "tls13-client-ciphers"_sr;
 constexpr auto SHRPX_OPT_NO_STRIP_INCOMING_EARLY_DATA =
-    StringRef::from_lit("no-strip-incoming-early-data");
-constexpr auto SHRPX_OPT_QUIC_BPF_PROGRAM_FILE =
-    StringRef::from_lit("quic-bpf-program-file");
-constexpr auto SHRPX_OPT_NO_QUIC_BPF = StringRef::from_lit("no-quic-bpf");
-constexpr auto SHRPX_OPT_HTTP2_ALTSVC = StringRef::from_lit("http2-altsvc");
+    "no-strip-incoming-early-data"_sr;
+constexpr auto SHRPX_OPT_QUIC_BPF_PROGRAM_FILE = "quic-bpf-program-file"_sr;
+constexpr auto SHRPX_OPT_NO_QUIC_BPF = "no-quic-bpf"_sr;
+constexpr auto SHRPX_OPT_HTTP2_ALTSVC = "http2-altsvc"_sr;
 constexpr auto SHRPX_OPT_FRONTEND_HTTP3_READ_TIMEOUT =
-    StringRef::from_lit("frontend-http3-read-timeout");
+    "frontend-http3-read-timeout"_sr;
 constexpr auto SHRPX_OPT_FRONTEND_QUIC_IDLE_TIMEOUT =
-    StringRef::from_lit("frontend-quic-idle-timeout");
-constexpr auto SHRPX_OPT_FRONTEND_QUIC_DEBUG_LOG =
-    StringRef::from_lit("frontend-quic-debug-log");
+    "frontend-quic-idle-timeout"_sr;
+constexpr auto SHRPX_OPT_FRONTEND_QUIC_DEBUG_LOG = "frontend-quic-debug-log"_sr;
 constexpr auto SHRPX_OPT_FRONTEND_HTTP3_WINDOW_SIZE =
-    StringRef::from_lit("frontend-http3-window-size");
+    "frontend-http3-window-size"_sr;
 constexpr auto SHRPX_OPT_FRONTEND_HTTP3_CONNECTION_WINDOW_SIZE =
-    StringRef::from_lit("frontend-http3-connection-window-size");
+    "frontend-http3-connection-window-size"_sr;
 constexpr auto SHRPX_OPT_FRONTEND_HTTP3_MAX_WINDOW_SIZE =
-    StringRef::from_lit("frontend-http3-max-window-size");
+    "frontend-http3-max-window-size"_sr;
 constexpr auto SHRPX_OPT_FRONTEND_HTTP3_MAX_CONNECTION_WINDOW_SIZE =
-    StringRef::from_lit("frontend-http3-max-connection-window-size");
+    "frontend-http3-max-connection-window-size"_sr;
 constexpr auto SHRPX_OPT_FRONTEND_HTTP3_MAX_CONCURRENT_STREAMS =
-    StringRef::from_lit("frontend-http3-max-concurrent-streams");
+    "frontend-http3-max-concurrent-streams"_sr;
 constexpr auto SHRPX_OPT_FRONTEND_QUIC_EARLY_DATA =
-    StringRef::from_lit("frontend-quic-early-data");
-constexpr auto SHRPX_OPT_FRONTEND_QUIC_QLOG_DIR =
-    StringRef::from_lit("frontend-quic-qlog-dir");
+    "frontend-quic-early-data"_sr;
+constexpr auto SHRPX_OPT_FRONTEND_QUIC_QLOG_DIR = "frontend-quic-qlog-dir"_sr;
 constexpr auto SHRPX_OPT_FRONTEND_QUIC_REQUIRE_TOKEN =
-    StringRef::from_lit("frontend-quic-require-token");
+    "frontend-quic-require-token"_sr;
 constexpr auto SHRPX_OPT_FRONTEND_QUIC_CONGESTION_CONTROLLER =
-    StringRef::from_lit("frontend-quic-congestion-controller");
-constexpr auto SHRPX_OPT_QUIC_SERVER_ID = StringRef::from_lit("quic-server-id");
+    "frontend-quic-congestion-controller"_sr;
+constexpr auto SHRPX_OPT_QUIC_SERVER_ID = "quic-server-id"_sr;
 constexpr auto SHRPX_OPT_FRONTEND_QUIC_SECRET_FILE =
-    StringRef::from_lit("frontend-quic-secret-file");
-constexpr auto SHRPX_OPT_RLIMIT_MEMLOCK = StringRef::from_lit("rlimit-memlock");
-constexpr auto SHRPX_OPT_MAX_WORKER_PROCESSES =
-    StringRef::from_lit("max-worker-processes");
+    "frontend-quic-secret-file"_sr;
+constexpr auto SHRPX_OPT_RLIMIT_MEMLOCK = "rlimit-memlock"_sr;
+constexpr auto SHRPX_OPT_MAX_WORKER_PROCESSES = "max-worker-processes"_sr;
 constexpr auto SHRPX_OPT_WORKER_PROCESS_GRACE_SHUTDOWN_PERIOD =
-    StringRef::from_lit("worker-process-grace-shutdown-period");
+    "worker-process-grace-shutdown-period"_sr;
 constexpr auto SHRPX_OPT_FRONTEND_QUIC_INITIAL_RTT =
-    StringRef::from_lit("frontend-quic-initial-rtt");
-constexpr auto SHRPX_OPT_REQUIRE_HTTP_SCHEME =
-    StringRef::from_lit("require-http-scheme");
-constexpr auto SHRPX_OPT_TLS_KTLS = StringRef::from_lit("tls-ktls");
-constexpr auto SHRPX_OPT_ALPN_LIST = StringRef::from_lit("alpn-list");
-constexpr auto SHRPX_OPT_FRONTEND_HEADER_TIMEOUT =
-    StringRef::from_lit("frontend-header-timeout");
+    "frontend-quic-initial-rtt"_sr;
+constexpr auto SHRPX_OPT_REQUIRE_HTTP_SCHEME = "require-http-scheme"_sr;
+constexpr auto SHRPX_OPT_TLS_KTLS = "tls-ktls"_sr;
+constexpr auto SHRPX_OPT_ALPN_LIST = "alpn-list"_sr;
+constexpr auto SHRPX_OPT_FRONTEND_HEADER_TIMEOUT = "frontend-header-timeout"_sr;
 constexpr auto SHRPX_OPT_FRONTEND_HTTP2_IDLE_TIMEOUT =
-    StringRef::from_lit("frontend-http2-idle-timeout");
+    "frontend-http2-idle-timeout"_sr;
 constexpr auto SHRPX_OPT_FRONTEND_HTTP3_IDLE_TIMEOUT =
-    StringRef::from_lit("frontend-http3-idle-timeout");
+    "frontend-http3-idle-timeout"_sr;
 
 constexpr size_t SHRPX_OBFUSCATED_NODE_LENGTH = 8;
 
-constexpr char DEFAULT_DOWNSTREAM_HOST[] = "127.0.0.1";
+constexpr auto DEFAULT_DOWNSTREAM_HOST = "127.0.0.1"_sr;
 constexpr int16_t DEFAULT_DOWNSTREAM_PORT = 80;
 
 enum class Proto {
@@ -1393,8 +1335,8 @@ enum {
   SHRPX_OPTID_MAXIDX,
 };
 
-// Looks up token for given option name |name| of length |namelen|.
-int option_lookup_token(const char *name, size_t namelen);
+// Looks up token for given option name |name|.
+int option_lookup_token(const StringRef &name);
 
 // Parses option name |opt| and value |optarg|.  The results are
 // stored into the object pointed by |config|. This function returns 0
diff --git a/src/shrpx_config_test.cc b/src/shrpx_config_test.cc
index 068f185..9e08f81 100644
--- a/src/shrpx_config_test.cc
+++ b/src/shrpx_config_test.cc
@@ -35,6 +35,8 @@
 #include "shrpx_config.h"
 #include "shrpx_log.h"
 
+using namespace std::literals;
+
 namespace shrpx {
 
 namespace {
@@ -54,32 +56,32 @@ const MunitSuite config_suite{
 void test_shrpx_config_parse_header(void) {
   BlockAllocator balloc(4096, 4096);
 
-  auto p = parse_header(balloc, StringRef::from_lit("a: b"));
-  assert_stdstring_equal("a", p.name.str());
-  assert_stdstring_equal("b", p.value.str());
+  auto p = parse_header(balloc, "a: b"_sr);
+  assert_stdsv_equal("a"sv, p.name);
+  assert_stdsv_equal("b"sv, p.value);
 
-  p = parse_header(balloc, StringRef::from_lit("a:  b"));
-  assert_stdstring_equal("a", p.name.str());
-  assert_stdstring_equal("b", p.value.str());
+  p = parse_header(balloc, "a:  b"_sr);
+  assert_stdsv_equal("a"sv, p.name);
+  assert_stdsv_equal("b"sv, p.value);
 
-  p = parse_header(balloc, StringRef::from_lit(":a: b"));
+  p = parse_header(balloc, ":a: b"_sr);
   assert_true(p.name.empty());
 
-  p = parse_header(balloc, StringRef::from_lit("a: :b"));
-  assert_stdstring_equal("a", p.name.str());
-  assert_stdstring_equal(":b", p.value.str());
+  p = parse_header(balloc, "a: :b"_sr);
+  assert_stdsv_equal("a"sv, p.name);
+  assert_stdsv_equal(":b"sv, p.value);
 
-  p = parse_header(balloc, StringRef::from_lit(": b"));
+  p = parse_header(balloc, ": b"_sr);
   assert_true(p.name.empty());
 
-  p = parse_header(balloc, StringRef::from_lit("alpha: bravo charlie"));
-  assert_stdstring_equal("alpha", p.name.str());
-  assert_stdstring_equal("bravo charlie", p.value.str());
+  p = parse_header(balloc, "alpha: bravo charlie"_sr);
+  assert_stdsv_equal("alpha", p.name);
+  assert_stdsv_equal("bravo charlie", p.value);
 
-  p = parse_header(balloc, StringRef::from_lit("a,: b"));
+  p = parse_header(balloc, "a,: b"_sr);
   assert_true(p.name.empty());
 
-  p = parse_header(balloc, StringRef::from_lit("a: b\x0a"));
+  p = parse_header(balloc, "a: b\x0a"_sr);
   assert_true(p.name.empty());
 }
 
@@ -87,91 +89,90 @@ void test_shrpx_config_parse_log_format(void) {
   BlockAllocator balloc(4096, 4096);
 
   auto res = parse_log_format(
-      balloc, StringRef::from_lit(
-                  R"($remote_addr - $remote_user [$time_local] )"
-                  R"("$request" $status $body_bytes_sent )"
-                  R"("${http_referer}" $http_host "$http_user_agent")"));
+      balloc, R"($remote_addr - $remote_user [$time_local] )"
+              R"("$request" $status $body_bytes_sent )"
+              R"("${http_referer}" $http_host "$http_user_agent")"_sr);
   assert_size(16, ==, res.size());
 
   assert_enum_class(LogFragmentType::REMOTE_ADDR, ==, res[0].type);
 
   assert_enum_class(LogFragmentType::LITERAL, ==, res[1].type);
-  assert_stdstring_equal(" - $remote_user [", res[1].value.str());
+  assert_stdsv_equal(" - $remote_user ["sv, res[1].value);
 
   assert_enum_class(LogFragmentType::TIME_LOCAL, ==, res[2].type);
 
   assert_enum_class(LogFragmentType::LITERAL, ==, res[3].type);
-  assert_stdstring_equal("] \"", res[3].value.str());
+  assert_stdsv_equal("] \""sv, res[3].value);
 
   assert_enum_class(LogFragmentType::REQUEST, ==, res[4].type);
 
   assert_enum_class(LogFragmentType::LITERAL, ==, res[5].type);
-  assert_stdstring_equal("\" ", res[5].value.str());
+  assert_stdsv_equal("\" "sv, res[5].value);
 
   assert_enum_class(LogFragmentType::STATUS, ==, res[6].type);
 
   assert_enum_class(LogFragmentType::LITERAL, ==, res[7].type);
-  assert_stdstring_equal(" ", res[7].value.str());
+  assert_stdsv_equal(" "sv, res[7].value);
 
   assert_enum_class(LogFragmentType::BODY_BYTES_SENT, ==, res[8].type);
 
   assert_enum_class(LogFragmentType::LITERAL, ==, res[9].type);
-  assert_stdstring_equal(" \"", res[9].value.str());
+  assert_stdsv_equal(" \""sv, res[9].value);
 
   assert_enum_class(LogFragmentType::HTTP, ==, res[10].type);
-  assert_stdstring_equal("referer", res[10].value.str());
+  assert_stdsv_equal("referer"sv, res[10].value);
 
   assert_enum_class(LogFragmentType::LITERAL, ==, res[11].type);
-  assert_stdstring_equal("\" ", res[11].value.str());
+  assert_stdsv_equal("\" "sv, res[11].value);
 
   assert_enum_class(LogFragmentType::AUTHORITY, ==, res[12].type);
 
   assert_enum_class(LogFragmentType::LITERAL, ==, res[13].type);
-  assert_stdstring_equal(" \"", res[13].value.str());
+  assert_stdsv_equal(" \""sv, res[13].value);
 
   assert_enum_class(LogFragmentType::HTTP, ==, res[14].type);
-  assert_stdstring_equal("user-agent", res[14].value.str());
+  assert_stdsv_equal("user-agent"sv, res[14].value);
 
   assert_enum_class(LogFragmentType::LITERAL, ==, res[15].type);
-  assert_stdstring_equal("\"", res[15].value.str());
+  assert_stdsv_equal("\""sv, res[15].value);
 
-  res = parse_log_format(balloc, StringRef::from_lit("$"));
+  res = parse_log_format(balloc, "$"_sr);
 
   assert_size(1, ==, res.size());
 
   assert_enum_class(LogFragmentType::LITERAL, ==, res[0].type);
-  assert_stdstring_equal("$", res[0].value.str());
+  assert_stdsv_equal("$"sv, res[0].value);
 
-  res = parse_log_format(balloc, StringRef::from_lit("${"));
+  res = parse_log_format(balloc, "${"_sr);
 
   assert_size(1, ==, res.size());
 
   assert_enum_class(LogFragmentType::LITERAL, ==, res[0].type);
-  assert_stdstring_equal("${", res[0].value.str());
+  assert_stdsv_equal("${"sv, res[0].value);
 
-  res = parse_log_format(balloc, StringRef::from_lit("${a"));
+  res = parse_log_format(balloc, "${a"_sr);
 
   assert_size(1, ==, res.size());
 
   assert_enum_class(LogFragmentType::LITERAL, ==, res[0].type);
-  assert_stdstring_equal("${a", res[0].value.str());
+  assert_stdsv_equal("${a"sv, res[0].value);
 
-  res = parse_log_format(balloc, StringRef::from_lit("${a "));
+  res = parse_log_format(balloc, "${a "_sr);
 
   assert_size(1, ==, res.size());
 
   assert_enum_class(LogFragmentType::LITERAL, ==, res[0].type);
-  assert_stdstring_equal("${a ", res[0].value.str());
+  assert_stdsv_equal("${a "sv, res[0].value);
 
-  res = parse_log_format(balloc, StringRef::from_lit("$$remote_addr"));
+  res = parse_log_format(balloc, "$$remote_addr"_sr);
 
   assert_size(2, ==, res.size());
 
   assert_enum_class(LogFragmentType::LITERAL, ==, res[0].type);
-  assert_stdstring_equal("$", res[0].value.str());
+  assert_stdsv_equal("$"sv, res[0].value);
 
   assert_enum_class(LogFragmentType::REMOTE_ADDR, ==, res[1].type);
-  assert_stdstring_equal("", res[1].value.str());
+  assert_stdsv_equal(""sv, res[1].value);
 }
 
 void test_shrpx_config_read_tls_ticket_key_file(void) {
diff --git a/src/shrpx_connection.cc b/src/shrpx_connection.cc
index d863284..972faf4 100644
--- a/src/shrpx_connection.cc
+++ b/src/shrpx_connection.cc
@@ -782,8 +782,8 @@ int Connection::write_tls_pending_handshake() {
                 << " protocol=" << tls_info.protocol
                 << " resumption=" << (tls_info.session_reused ? "yes" : "no")
                 << " session_id="
-                << util::format_hex(tls_info.session_id,
-                                    tls_info.session_id_length);
+                << util::format_hex(std::span{tls_info.session_id,
+                                              tls_info.session_id_length});
     }
   }
 
diff --git a/src/shrpx_connection_handler.cc b/src/shrpx_connection_handler.cc
index b29ce9a..ad88aa6 100644
--- a/src/shrpx_connection_handler.cc
+++ b/src/shrpx_connection_handler.cc
@@ -647,7 +647,7 @@ int ConnectionHandler::start_ocsp_update(const char *cert_file) {
 
   char *const argv[] = {
       const_cast<char *>(
-          get_config()->tls.ocsp.fetch_ocsp_response_file.c_str()),
+          get_config()->tls.ocsp.fetch_ocsp_response_file.data()),
       const_cast<char *>(cert_file), nullptr};
 
   Process proc;
@@ -740,8 +740,7 @@ void ConnectionHandler::handle_ocsp_complete() {
       auto quic_tls_ctx_data = static_cast<tls::TLSContextData *>(
           SSL_CTX_get_app_data(quic_ssl_ctx));
 #  ifdef HAVE_ATOMIC_STD_SHARED_PTR
-      std::atomic_store_explicit(
-          &quic_tls_ctx_data->ocsp_data,
+      quic_tls_ctx_data->ocsp_data.store(
           std::make_shared<std::vector<uint8_t>>(ocsp_.resp),
           std::memory_order_release);
 #  else  // !HAVE_ATOMIC_STD_SHARED_PTR
@@ -753,8 +752,7 @@ void ConnectionHandler::handle_ocsp_complete() {
 #endif // ENABLE_HTTP3
 
 #ifdef HAVE_ATOMIC_STD_SHARED_PTR
-    std::atomic_store_explicit(
-        &tls_ctx_data->ocsp_data,
+    tls_ctx_data->ocsp_data.store(
         std::make_shared<std::vector<uint8_t>>(std::move(ocsp_.resp)),
         std::memory_order_release);
 #else  // !HAVE_ATOMIC_STD_SHARED_PTR
@@ -1004,10 +1002,12 @@ void ConnectionHandler::set_enable_acceptor_on_ocsp_completion(bool f) {
 }
 
 #ifdef ENABLE_HTTP3
-int ConnectionHandler::forward_quic_packet(
-    const UpstreamAddr *faddr, const Address &remote_addr,
-    const Address &local_addr, const ngtcp2_pkt_info &pi, const WorkerID &wid,
-    const uint8_t *data, size_t datalen) {
+int ConnectionHandler::forward_quic_packet(const UpstreamAddr *faddr,
+                                           const Address &remote_addr,
+                                           const Address &local_addr,
+                                           const ngtcp2_pkt_info &pi,
+                                           const WorkerID &wid,
+                                           std::span<const uint8_t> data) {
   assert(!get_config()->single_thread);
 
   auto worker = find_worker(wid);
@@ -1018,7 +1018,7 @@ int ConnectionHandler::forward_quic_packet(
   WorkerEvent wev{};
   wev.type = WorkerEventType::QUIC_PKT_FORWARD;
   wev.quic_pkt = std::make_unique<QUICPacket>(faddr->index, remote_addr,
-                                              local_addr, pi, data, datalen);
+                                              local_addr, pi, data);
 
   worker->send(std::move(wev));
 
@@ -1104,8 +1104,8 @@ void ConnectionHandler::set_quic_lingering_worker_processes(
 
 int ConnectionHandler::forward_quic_packet_to_lingering_worker_process(
     QUICLingeringWorkerProcess *quic_lwp, const Address &remote_addr,
-    const Address &local_addr, const ngtcp2_pkt_info &pi, const uint8_t *data,
-    size_t datalen) {
+    const Address &local_addr, const ngtcp2_pkt_info &pi,
+    std::span<const uint8_t> data) {
   std::array<uint8_t, 512> header;
 
   assert(header.size() >= 1 + 1 + 1 + 1 + sizeof(sockaddr_storage) * 2);
@@ -1129,8 +1129,8 @@ int ConnectionHandler::forward_quic_packet_to_lingering_worker_process(
           .iov_len = static_cast<size_t>(p - header.data()),
       },
       {
-          .iov_base = const_cast<uint8_t *>(data),
-          .iov_len = datalen,
+          .iov_base = const_cast<uint8_t *>(data.data()),
+          .iov_len = data.size(),
       },
   };
 
@@ -1279,8 +1279,7 @@ int ConnectionHandler::quic_ipc_read() {
 
     // Ignore return value
     quic_conn_handler->handle_packet(faddr, pkt->remote_addr, pkt->local_addr,
-                                     pkt->pi, pkt->data.data(),
-                                     pkt->data.size());
+                                     pkt->pi, pkt->data);
 
     return 0;
   }
diff --git a/src/shrpx_connection_handler.h b/src/shrpx_connection_handler.h
index 47ec209..16e56e0 100644
--- a/src/shrpx_connection_handler.h
+++ b/src/shrpx_connection_handler.h
@@ -195,8 +195,7 @@ public:
 
   int forward_quic_packet(const UpstreamAddr *faddr, const Address &remote_addr,
                           const Address &local_addr, const ngtcp2_pkt_info &pi,
-                          const WorkerID &wid, const uint8_t *data,
-                          size_t datalen);
+                          const WorkerID &wid, std::span<const uint8_t> data);
 
   void set_quic_keying_materials(std::shared_ptr<QUICKeyingMaterials> qkms);
   const std::shared_ptr<QUICKeyingMaterials> &get_quic_keying_materials() const;
@@ -215,8 +214,8 @@ public:
 
   int forward_quic_packet_to_lingering_worker_process(
       QUICLingeringWorkerProcess *quic_lwp, const Address &remote_addr,
-      const Address &local_addr, const ngtcp2_pkt_info &pi, const uint8_t *data,
-      size_t datalen);
+      const Address &local_addr, const ngtcp2_pkt_info &pi,
+      std::span<const uint8_t> data);
 
   void set_quic_ipc_fd(int fd);
 
diff --git a/src/shrpx_dns_resolver.cc b/src/shrpx_dns_resolver.cc
index 8253942..ceda612 100644
--- a/src/shrpx_dns_resolver.cc
+++ b/src/shrpx_dns_resolver.cc
@@ -178,7 +178,7 @@ int DNSResolver::resolve(const StringRef &name, int family) {
   ares_addrinfo_hints hints{};
   hints.ai_family = family_;
 
-  ares_getaddrinfo(channel_, name_.c_str(), nullptr, &hints, addrinfo_cb, this);
+  ares_getaddrinfo(channel_, name_.data(), nullptr, &hints, addrinfo_cb, this);
   reset_timeout();
 
   return 0;
diff --git a/src/shrpx_downstream.cc b/src/shrpx_downstream.cc
index 5fd717e..73d7f11 100644
--- a/src/shrpx_downstream.cc
+++ b/src/shrpx_downstream.cc
@@ -344,7 +344,7 @@ StringRef Downstream::assemble_request_cookie() {
   }
 
   auto iov = make_byte_ref(balloc_, len + 1);
-  auto p = iov.base;
+  auto p = std::begin(iov);
 
   for (auto &kv : req_.fs.headers()) {
     if (kv.token != http2::HD_COOKIE || kv.value.empty()) {
@@ -367,11 +367,11 @@ StringRef Downstream::assemble_request_cookie() {
   }
 
   // cut trailing "; "
-  if (p - iov.base >= 2) {
+  if (p - std::begin(iov) >= 2) {
     p -= 2;
   }
 
-  return StringRef{iov.base, p};
+  return StringRef{std::span{std::begin(iov), p}};
 }
 
 uint32_t Downstream::find_affinity_cookie(const StringRef &name) {
@@ -391,7 +391,7 @@ uint32_t Downstream::find_affinity_cookie(const StringRef &name) {
         return 0;
       }
 
-      if (!util::streq(name, StringRef{it, end})) {
+      if (name != StringRef{it, end}) {
         it = std::find(it, std::end(kv.value), ';');
         continue;
       }
@@ -474,12 +474,11 @@ void add_header(size_t &sum, HeaderRefs &headers, const StringRef &name,
 namespace {
 StringRef alloc_header_name(BlockAllocator &balloc, const StringRef &name) {
   auto iov = make_byte_ref(balloc, name.size() + 1);
-  auto p = iov.base;
-  p = std::copy(std::begin(name), std::end(name), p);
-  util::inp_strlower(iov.base, p);
+  auto p = std::copy(std::begin(name), std::end(name), std::begin(iov));
+  util::inp_strlower(std::begin(iov), p);
   *p = '\0';
 
-  return StringRef{iov.base, p};
+  return StringRef{std::span{std::begin(iov), p}};
 }
 } // namespace
 
@@ -521,13 +520,13 @@ int FieldStore::parse_content_length() {
     }
 
     auto len = util::parse_uint(kv.value);
-    if (len == -1) {
+    if (!len) {
       return -1;
     }
     if (content_length != -1) {
       return -1;
     }
-    content_length = len;
+    content_length = *len;
   }
   return 0;
 }
@@ -732,7 +731,7 @@ void Downstream::rewrite_location_response_header(
   }
 
   http_parser_url u{};
-  auto rv = http_parser_parse_url(hd->value.c_str(), hd->value.size(), 0, &u);
+  auto rv = http_parser_parse_url(hd->value.data(), hd->value.size(), 0, &u);
   if (rv != 0) {
     return;
   }
@@ -841,7 +840,7 @@ void Downstream::check_upgrade_fulfilled_http1() {
       auto expected =
           http2::make_websocket_accept_token(accept_buf.data(), ws_key_);
 
-      upgraded_ = expected != "" && expected == accept->value;
+      upgraded_ = !expected.empty() && expected == accept->value;
     } else {
       upgraded_ = resp_.http_status / 100 == 2;
     }
@@ -871,15 +870,14 @@ void Downstream::inspect_http1_request() {
     if (upgrade) {
       const auto &val = upgrade->value;
       // TODO Perform more strict checking for upgrade headers
-      if (util::streq_l(NGHTTP2_CLEARTEXT_PROTO_VERSION_ID, val.c_str(),
-                        val.size())) {
+      if (NGHTTP2_CLEARTEXT_PROTO_VERSION_ID ""_sr == val) {
         req_.http2_upgrade_seen = true;
       } else {
         req_.upgrade_request = true;
 
         // TODO Should we check Sec-WebSocket-Key, and
         // Sec-WebSocket-Version as well?
-        if (util::strieq_l("websocket", val)) {
+        if (util::strieq("websocket"_sr, val)) {
           req_.connect_proto = ConnectProto::WEBSOCKET;
         }
       }
@@ -892,8 +890,7 @@ void Downstream::inspect_http1_request() {
 
   auto expect = req_.fs.header(http2::HD_EXPECT);
   expect_100_continue_ =
-      expect &&
-      util::strieq(expect->value, StringRef::from_lit("100-continue"));
+      expect && util::strieq(expect->value, "100-continue"_sr);
 }
 
 void Downstream::inspect_http1_response() {
diff --git a/src/shrpx_downstream_test.cc b/src/shrpx_downstream_test.cc
index 46db9b7..bbccea8 100644
--- a/src/shrpx_downstream_test.cc
+++ b/src/shrpx_downstream_test.cc
@@ -30,6 +30,8 @@
 
 #include "shrpx_downstream.h"
 
+using namespace std::literals;
+
 namespace shrpx {
 
 namespace {
@@ -52,40 +54,35 @@ const MunitSuite downstream_suite{
 void test_downstream_field_store_append_last_header(void) {
   BlockAllocator balloc(16, 16);
   FieldStore fs(balloc, 0);
-  fs.alloc_add_header_name(StringRef::from_lit("alpha"));
-  auto bravo = StringRef::from_lit("BRAVO");
-  fs.append_last_header_key(bravo.c_str(), bravo.size());
+  fs.alloc_add_header_name("alpha"_sr);
+  auto bravo = "BRAVO"_sr;
+  fs.append_last_header_key(bravo.data(), bravo.size());
   // Add more characters so that relloc occurs
-  auto golf = StringRef::from_lit("golF0123456789");
-  fs.append_last_header_key(golf.c_str(), golf.size());
+  auto golf = "golF0123456789"_sr;
+  fs.append_last_header_key(golf.data(), golf.size());
 
-  auto charlie = StringRef::from_lit("Charlie");
-  fs.append_last_header_value(charlie.c_str(), charlie.size());
-  auto delta = StringRef::from_lit("deltA");
-  fs.append_last_header_value(delta.c_str(), delta.size());
+  auto charlie = "Charlie"_sr;
+  fs.append_last_header_value(charlie.data(), charlie.size());
+  auto delta = "deltA"_sr;
+  fs.append_last_header_value(delta.data(), delta.size());
   // Add more characters so that relloc occurs
-  auto echo = StringRef::from_lit("echo0123456789");
-  fs.append_last_header_value(echo.c_str(), echo.size());
+  auto echo = "echo0123456789"_sr;
+  fs.append_last_header_value(echo.data(), echo.size());
 
-  fs.add_header_token(StringRef::from_lit("echo"),
-                      StringRef::from_lit("foxtrot"), false, -1);
+  fs.add_header_token("echo"_sr, "foxtrot"_sr, false, -1);
 
-  auto ans =
-      HeaderRefs{{StringRef::from_lit("alphabravogolf0123456789"),
-                  StringRef::from_lit("CharliedeltAecho0123456789")},
-                 {StringRef::from_lit("echo"), StringRef::from_lit("foxtrot")}};
+  auto ans = HeaderRefs{
+      {"alphabravogolf0123456789"_sr, "CharliedeltAecho0123456789"_sr},
+      {"echo"_sr, "foxtrot"_sr}};
   assert_true(ans == fs.headers());
 }
 
 void test_downstream_field_store_header(void) {
   BlockAllocator balloc(16, 16);
   FieldStore fs(balloc, 0);
-  fs.add_header_token(StringRef::from_lit("alpha"), StringRef::from_lit("0"),
-                      false, -1);
-  fs.add_header_token(StringRef::from_lit(":authority"),
-                      StringRef::from_lit("1"), false, http2::HD__AUTHORITY);
-  fs.add_header_token(StringRef::from_lit("content-length"),
-                      StringRef::from_lit("2"), false,
+  fs.add_header_token("alpha"_sr, "0"_sr, false, -1);
+  fs.add_header_token(":authority"_sr, "1"_sr, false, http2::HD__AUTHORITY);
+  fs.add_header_token("content-length"_sr, "2"_sr, false,
                       http2::HD_CONTENT_LENGTH);
 
   // By token
@@ -95,25 +92,19 @@ void test_downstream_field_store_header(void) {
 
   // By name
   assert_true(HeaderRef(StringRef{"alpha"}, StringRef{"0"}) ==
-              *fs.header(StringRef::from_lit("alpha")));
-  assert_null(fs.header(StringRef::from_lit("bravo")));
+              *fs.header("alpha"_sr));
+  assert_null(fs.header("bravo"_sr));
 }
 
 void test_downstream_crumble_request_cookie(void) {
   Downstream d(nullptr, nullptr, 0);
   auto &req = d.request();
-  req.fs.add_header_token(StringRef::from_lit(":method"),
-                          StringRef::from_lit("get"), false, -1);
-  req.fs.add_header_token(StringRef::from_lit(":path"),
-                          StringRef::from_lit("/"), false, -1);
-  req.fs.add_header_token(StringRef::from_lit("cookie"),
-                          StringRef::from_lit("alpha; bravo; ; ;; charlie;;"),
-                          true, http2::HD_COOKIE);
-  req.fs.add_header_token(StringRef::from_lit("cookie"),
-                          StringRef::from_lit(";delta"), false,
+  req.fs.add_header_token(":method"_sr, "get"_sr, false, -1);
+  req.fs.add_header_token(":path"_sr, "/"_sr, false, -1);
+  req.fs.add_header_token("cookie"_sr, "alpha; bravo; ; ;; charlie;;"_sr, true,
                           http2::HD_COOKIE);
-  req.fs.add_header_token(StringRef::from_lit("cookie"),
-                          StringRef::from_lit("echo"), false, http2::HD_COOKIE);
+  req.fs.add_header_token("cookie"_sr, ";delta"_sr, false, http2::HD_COOKIE);
+  req.fs.add_header_token("cookie"_sr, "echo"_sr, false, http2::HD_COOKIE);
 
   std::vector<nghttp2_nv> nva;
   d.crumble_request_cookie(nva);
@@ -131,12 +122,11 @@ void test_downstream_crumble_request_cookie(void) {
                                     nv.flags & NGHTTP2_NV_FLAG_NO_INDEX);
                  });
 
-  HeaderRefs ans = {
-      {StringRef::from_lit("cookie"), StringRef::from_lit("alpha")},
-      {StringRef::from_lit("cookie"), StringRef::from_lit("bravo")},
-      {StringRef::from_lit("cookie"), StringRef::from_lit("charlie")},
-      {StringRef::from_lit("cookie"), StringRef::from_lit("delta")},
-      {StringRef::from_lit("cookie"), StringRef::from_lit("echo")}};
+  HeaderRefs ans = {{"cookie"_sr, "alpha"_sr},
+                    {"cookie"_sr, "bravo"_sr},
+                    {"cookie"_sr, "charlie"_sr},
+                    {"cookie"_sr, "delta"_sr},
+                    {"cookie"_sr, "echo"_sr}};
 
   assert_true(ans == cookies);
   assert_true(cookies[0].no_index);
@@ -148,38 +138,27 @@ void test_downstream_assemble_request_cookie(void) {
   Downstream d(nullptr, nullptr, 0);
   auto &req = d.request();
 
-  req.fs.add_header_token(StringRef::from_lit(":method"),
-                          StringRef::from_lit("get"), false, -1);
-  req.fs.add_header_token(StringRef::from_lit(":path"),
-                          StringRef::from_lit("/"), false, -1);
-  req.fs.add_header_token(StringRef::from_lit("cookie"),
-                          StringRef::from_lit("alpha"), false,
-                          http2::HD_COOKIE);
-  req.fs.add_header_token(StringRef::from_lit("cookie"),
-                          StringRef::from_lit("bravo;"), false,
-                          http2::HD_COOKIE);
-  req.fs.add_header_token(StringRef::from_lit("cookie"),
-                          StringRef::from_lit("charlie; "), false,
-                          http2::HD_COOKIE);
-  req.fs.add_header_token(StringRef::from_lit("cookie"),
-                          StringRef::from_lit("delta;;"), false,
-                          http2::HD_COOKIE);
-  assert_stdstring_equal("alpha; bravo; charlie; delta",
-                         d.assemble_request_cookie().str());
+  req.fs.add_header_token(":method"_sr, "get"_sr, false, -1);
+  req.fs.add_header_token(":path"_sr, "/"_sr, false, -1);
+  req.fs.add_header_token("cookie"_sr, "alpha"_sr, false, http2::HD_COOKIE);
+  req.fs.add_header_token("cookie"_sr, "bravo;"_sr, false, http2::HD_COOKIE);
+  req.fs.add_header_token("cookie"_sr, "charlie; "_sr, false, http2::HD_COOKIE);
+  req.fs.add_header_token("cookie"_sr, "delta;;"_sr, false, http2::HD_COOKIE);
+  assert_stdsv_equal("alpha; bravo; charlie; delta"sv,
+                     d.assemble_request_cookie());
 }
 
 void test_downstream_rewrite_location_response_header(void) {
   Downstream d(nullptr, nullptr, 0);
   auto &req = d.request();
   auto &resp = d.response();
-  d.set_request_downstream_host(StringRef::from_lit("localhost2"));
-  req.authority = StringRef::from_lit("localhost:8443");
-  resp.fs.add_header_token(StringRef::from_lit("location"),
-                           StringRef::from_lit("http://localhost2:3000/"),
-                           false, http2::HD_LOCATION);
-  d.rewrite_location_response_header(StringRef::from_lit("https"));
+  d.set_request_downstream_host("localhost2"_sr);
+  req.authority = "localhost:8443"_sr;
+  resp.fs.add_header_token("location"_sr, "http://localhost2:3000/"_sr, false,
+                           http2::HD_LOCATION);
+  d.rewrite_location_response_header("https"_sr);
   auto location = resp.fs.header(http2::HD_LOCATION);
-  assert_stdstring_equal("https://localhost:8443/", (*location).value.str());
+  assert_stdsv_equal("https://localhost:8443/"sv, (*location).value);
 }
 
 void test_downstream_supports_non_final_response(void) {
@@ -216,32 +195,26 @@ void test_downstream_find_affinity_cookie(void) {
   Downstream d(nullptr, nullptr, 0);
 
   auto &req = d.request();
-  req.fs.add_header_token(StringRef::from_lit("cookie"), StringRef{}, false,
-                          http2::HD_COOKIE);
-  req.fs.add_header_token(StringRef::from_lit("cookie"),
-                          StringRef::from_lit("a=b;;c=d"), false,
-                          http2::HD_COOKIE);
-  req.fs.add_header_token(StringRef::from_lit("content-length"),
-                          StringRef::from_lit("599"), false,
+  req.fs.add_header_token("cookie"_sr, StringRef{}, false, http2::HD_COOKIE);
+  req.fs.add_header_token("cookie"_sr, "a=b;;c=d"_sr, false, http2::HD_COOKIE);
+  req.fs.add_header_token("content-length"_sr, "599"_sr, false,
                           http2::HD_CONTENT_LENGTH);
-  req.fs.add_header_token(StringRef::from_lit("cookie"),
-                          StringRef::from_lit("lb=deadbeef;LB=f1f2f3f4"), false,
+  req.fs.add_header_token("cookie"_sr, "lb=deadbeef;LB=f1f2f3f4"_sr, false,
                           http2::HD_COOKIE);
-  req.fs.add_header_token(StringRef::from_lit("cookie"),
-                          StringRef::from_lit("short=e1e2e3e"), false,
+  req.fs.add_header_token("cookie"_sr, "short=e1e2e3e"_sr, false,
                           http2::HD_COOKIE);
 
   uint32_t aff;
 
-  aff = d.find_affinity_cookie(StringRef::from_lit("lb"));
+  aff = d.find_affinity_cookie("lb"_sr);
 
   assert_uint32(0xdeadbeef, ==, aff);
 
-  aff = d.find_affinity_cookie(StringRef::from_lit("LB"));
+  aff = d.find_affinity_cookie("LB"_sr);
 
   assert_uint32(0xf1f2f3f4, ==, aff);
 
-  aff = d.find_affinity_cookie(StringRef::from_lit("short"));
+  aff = d.find_affinity_cookie("short"_sr);
 
   assert_uint32(0, ==, aff);
 }
diff --git a/src/shrpx_health_monitor_downstream_connection.cc b/src/shrpx_health_monitor_downstream_connection.cc
index 89e5396..710de96 100644
--- a/src/shrpx_health_monitor_downstream_connection.cc
+++ b/src/shrpx_health_monitor_downstream_connection.cc
@@ -74,8 +74,7 @@ int HealthMonitorDownstreamConnection::end_upload_data() {
 
   resp.http_status = 200;
 
-  resp.fs.add_header_token(StringRef::from_lit("content-length"),
-                           StringRef::from_lit("0"), false,
+  resp.fs.add_header_token("content-length"_sr, "0"_sr, false,
                            http2::HD_CONTENT_LENGTH);
 
   if (upstream->send_reply(downstream_, nullptr, 0) != 0) {
diff --git a/src/shrpx_http.cc b/src/shrpx_http.cc
index 4750500..cd7e14b 100644
--- a/src/shrpx_http.cc
+++ b/src/shrpx_http.cc
@@ -41,7 +41,7 @@ StringRef create_error_html(BlockAllocator &balloc, unsigned int http_status) {
   const auto &error_pages = httpconf.error_pages;
   for (const auto &page : error_pages) {
     if (page.http_status == 0 || page.http_status == http_status) {
-      return StringRef{std::begin(page.content), std::end(page.content)};
+      return StringRef{std::span{page.content}};
     }
   }
 
@@ -49,12 +49,10 @@ StringRef create_error_html(BlockAllocator &balloc, unsigned int http_status) {
   auto reason_phrase = http2::get_reason_phrase(http_status);
 
   return concat_string_ref(
-      balloc, StringRef::from_lit(R"(<!DOCTYPE html><html lang="en"><title>)"),
-      status_string, StringRef::from_lit(" "), reason_phrase,
-      StringRef::from_lit("</title><body><h1>"), status_string,
-      StringRef::from_lit(" "), reason_phrase,
-      StringRef::from_lit("</h1><footer>"), httpconf.server_name,
-      StringRef::from_lit("</footer></body></html>"));
+      balloc, R"(<!DOCTYPE html><html lang="en"><title>)"_sr, status_string,
+      " "_sr, reason_phrase, "</title><body><h1>"_sr, status_string, " "_sr,
+      reason_phrase, "</h1><footer>"_sr, httpconf.server_name,
+      "</footer></body></html>"_sr);
 }
 
 StringRef create_forwarded(BlockAllocator &balloc, int params,
@@ -75,7 +73,7 @@ StringRef create_forwarded(BlockAllocator &balloc, int params,
   }
 
   auto iov = make_byte_ref(balloc, len + 1);
-  auto p = iov.base;
+  auto p = std::begin(iov);
 
   if ((params & FORWARDED_BY) && !node_by.empty()) {
     // This must be quoted-string unless it is obfuscated version
@@ -118,14 +116,14 @@ StringRef create_forwarded(BlockAllocator &balloc, int params,
     *p++ = ';';
   }
 
-  if (iov.base == p) {
+  if (std::begin(iov) == p) {
     return StringRef{};
   }
 
   --p;
   *p = '\0';
 
-  return StringRef{iov.base, p};
+  return StringRef{std::span{std::begin(iov), p}};
 }
 
 std::string colorizeHeaders(const char *hdrs) {
@@ -146,7 +144,7 @@ std::string colorizeHeaders(const char *hdrs) {
     nhdrs += TTY_HTTP_HD;
     nhdrs.append(p, np);
     nhdrs += TTY_RST;
-    auto redact = util::strieq_l("authorization", StringRef{p, np});
+    auto redact = util::strieq("authorization"_sr, StringRef{p, np});
     p = np;
     np = strchr(p, '\n');
     if (!np) {
@@ -176,8 +174,8 @@ nghttp2_ssize select_padding_callback(nghttp2_session *session,
 StringRef create_affinity_cookie(BlockAllocator &balloc, const StringRef &name,
                                  uint32_t affinity_cookie,
                                  const StringRef &path, bool secure) {
-  static constexpr auto PATH_PREFIX = StringRef::from_lit("; Path=");
-  static constexpr auto SECURE = StringRef::from_lit("; Secure");
+  static constexpr auto PATH_PREFIX = "; Path="_sr;
+  static constexpr auto SECURE = "; Secure"_sr;
   // <name>=<value>[; Path=<path>][; Secure]
   size_t len = name.size() + 1 + 8;
 
@@ -189,14 +187,10 @@ StringRef create_affinity_cookie(BlockAllocator &balloc, const StringRef &name,
   }
 
   auto iov = make_byte_ref(balloc, len + 1);
-  auto p = iov.base;
-  p = std::copy(std::begin(name), std::end(name), p);
+  auto p = std::copy(std::begin(name), std::end(name), std::begin(iov));
   *p++ = '=';
   affinity_cookie = htonl(affinity_cookie);
-  p = util::format_hex(p,
-                       StringRef{reinterpret_cast<uint8_t *>(&affinity_cookie),
-                                 reinterpret_cast<uint8_t *>(&affinity_cookie) +
-                                     sizeof(affinity_cookie)});
+  p = util::format_hex(p, std::span{&affinity_cookie, 1});
   if (!path.empty()) {
     p = std::copy(std::begin(PATH_PREFIX), std::end(PATH_PREFIX), p);
     p = std::copy(std::begin(path), std::end(path), p);
@@ -205,14 +199,14 @@ StringRef create_affinity_cookie(BlockAllocator &balloc, const StringRef &name,
     p = std::copy(std::begin(SECURE), std::end(SECURE), p);
   }
   *p = '\0';
-  return StringRef{iov.base, p};
+  return StringRef{std::span{std::begin(iov), p}};
 }
 
 bool require_cookie_secure_attribute(SessionAffinityCookieSecure secure,
                                      const StringRef &scheme) {
   switch (secure) {
   case SessionAffinityCookieSecure::AUTO:
-    return scheme == "https";
+    return scheme == "https"_sr;
   case SessionAffinityCookieSecure::YES:
     return true;
   default:
@@ -247,7 +241,7 @@ StringRef create_altsvc_header_value(BlockAllocator &balloc,
 
   // We will write additional ", " at the end, and cut it later.
   auto iov = make_byte_ref(balloc, len + 2);
-  auto p = iov.base;
+  auto p = std::begin(iov);
 
   for (auto &altsvc : altsvcs) {
     p = util::percent_encode_token(p, altsvc.protocol_id);
@@ -266,13 +260,13 @@ StringRef create_altsvc_header_value(BlockAllocator &balloc,
   p -= 2;
   *p = '\0';
 
-  assert(static_cast<size_t>(p - iov.base) == len);
+  assert(static_cast<size_t>(p - std::begin(iov)) == len);
 
-  return StringRef{iov.base, p};
+  return StringRef{std::span{std::begin(iov), p}};
 }
 
 bool check_http_scheme(const StringRef &scheme, bool encrypted) {
-  return encrypted ? scheme == "https" : scheme == "http";
+  return encrypted ? scheme == "https"_sr : scheme == "http"_sr;
 }
 
 } // namespace http
diff --git a/src/shrpx_http2_downstream_connection.cc b/src/shrpx_http2_downstream_connection.cc
index a6c9d53..dadf10a 100644
--- a/src/shrpx_http2_downstream_connection.cc
+++ b/src/shrpx_http2_downstream_connection.cc
@@ -295,11 +295,11 @@ int Http2DownstreamConnection::push_request_headers() {
               httpconf.add_request_headers.size());
 
   if (req.connect_proto == ConnectProto::WEBSOCKET) {
-    nva.push_back(http2::make_nv_ll(":method", "CONNECT"));
-    nva.push_back(http2::make_nv_ll(":protocol", "websocket"));
+    nva.push_back(http2::make_field(":method"_sr, "CONNECT"_sr));
+    nva.push_back(http2::make_field(":protocol"_sr, "websocket"_sr));
   } else {
-    nva.push_back(http2::make_nv_ls_nocopy(
-        ":method", http2::to_method_string(req.method)));
+    nva.push_back(
+        http2::make_field(":method"_sr, http2::to_method_string(req.method)));
   }
 
   if (!req.regular_connect_method()) {
@@ -308,25 +308,25 @@ int Http2DownstreamConnection::push_request_headers() {
     auto addr = http2session_->get_addr();
     assert(addr);
     // We will handle more protocol scheme upgrade in the future.
-    if (addr->tls && addr->upgrade_scheme && req.scheme == "http") {
-      nva.push_back(http2::make_nv_ll(":scheme", "https"));
+    if (addr->tls && addr->upgrade_scheme && req.scheme == "http"_sr) {
+      nva.push_back(http2::make_field(":scheme"_sr, "https"_sr));
     } else {
-      nva.push_back(http2::make_nv_ls_nocopy(":scheme", req.scheme));
+      nva.push_back(http2::make_field(":scheme"_sr, req.scheme));
     }
 
     if (req.method == HTTP_OPTIONS && req.path.empty()) {
-      nva.push_back(http2::make_nv_ll(":path", "*"));
+      nva.push_back(http2::make_field(":path"_sr, "*"_sr));
     } else {
-      nva.push_back(http2::make_nv_ls_nocopy(":path", req.path));
+      nva.push_back(http2::make_field(":path"_sr, req.path));
     }
 
     if (!req.no_authority || req.connect_proto != ConnectProto::NONE) {
-      nva.push_back(http2::make_nv_ls_nocopy(":authority", authority));
+      nva.push_back(http2::make_field(":authority"_sr, authority));
     } else {
-      nva.push_back(http2::make_nv_ls_nocopy("host", authority));
+      nva.push_back(http2::make_field("host"_sr, authority));
     }
   } else {
-    nva.push_back(http2::make_nv_ls_nocopy(":authority", authority));
+    nva.push_back(http2::make_field(":authority"_sr, authority));
   }
 
   auto &fwdconf = httpconf.forwarded;
@@ -354,7 +354,7 @@ int Http2DownstreamConnection::push_request_headers() {
   auto conn = handler->get_connection();
 
   if (conn->tls.ssl && !SSL_is_init_finished(conn->tls.ssl)) {
-    nva.push_back(http2::make_nv_ll("early-data", "1"));
+    nva.push_back(http2::make_field("early-data"_sr, "1"_sr));
   }
 #endif // NGHTTP2_GENUINE_OPENSSL || NGHTTP2_OPENSSL_IS_BORINGSSL
 
@@ -377,15 +377,14 @@ int Http2DownstreamConnection::push_request_headers() {
         if (value.empty()) {
           value = fwd->value;
         } else {
-          value = concat_string_ref(balloc, fwd->value,
-                                    StringRef::from_lit(", "), value);
+          value = concat_string_ref(balloc, fwd->value, ", "_sr, value);
         }
       }
 
-      nva.push_back(http2::make_nv_ls_nocopy("forwarded", value));
+      nva.push_back(http2::make_field("forwarded"_sr, value));
     }
   } else if (fwd) {
-    nva.push_back(http2::make_nv_ls_nocopy("forwarded", fwd->value));
+    nva.push_back(http2::make_field("forwarded"_sr, fwd->value));
   }
 
   auto xff = xffconf.strip_incoming ? nullptr
@@ -395,14 +394,13 @@ int Http2DownstreamConnection::push_request_headers() {
     StringRef xff_value;
     const auto &addr = upstream->get_client_handler()->get_ipaddr();
     if (xff) {
-      xff_value = concat_string_ref(balloc, xff->value,
-                                    StringRef::from_lit(", "), addr);
+      xff_value = concat_string_ref(balloc, xff->value, ", "_sr, addr);
     } else {
       xff_value = addr;
     }
-    nva.push_back(http2::make_nv_ls_nocopy("x-forwarded-for", xff_value));
+    nva.push_back(http2::make_field("x-forwarded-for"_sr, xff_value));
   } else if (xff) {
-    nva.push_back(http2::make_nv_ls_nocopy("x-forwarded-for", xff->value));
+    nva.push_back(http2::make_field("x-forwarded-for"_sr, xff->value));
   }
 
   if (!config->http2_proxy && !req.regular_connect_method()) {
@@ -414,21 +412,20 @@ int Http2DownstreamConnection::push_request_headers() {
       StringRef xfp_value;
       // We use same protocol with :scheme header field
       if (xfp) {
-        xfp_value = concat_string_ref(balloc, xfp->value,
-                                      StringRef::from_lit(", "), req.scheme);
+        xfp_value = concat_string_ref(balloc, xfp->value, ", "_sr, req.scheme);
       } else {
         xfp_value = req.scheme;
       }
-      nva.push_back(http2::make_nv_ls_nocopy("x-forwarded-proto", xfp_value));
+      nva.push_back(http2::make_field("x-forwarded-proto"_sr, xfp_value));
     } else if (xfp) {
-      nva.push_back(http2::make_nv_ls_nocopy("x-forwarded-proto", xfp->value));
+      nva.push_back(http2::make_field("x-forwarded-proto"_sr, xfp->value));
     }
   }
 
   auto via = req.fs.header(http2::HD_VIA);
   if (httpconf.no_via) {
     if (via) {
-      nva.push_back(http2::make_nv_ls_nocopy("via", (*via).value));
+      nva.push_back(http2::make_field("via"_sr, (*via).value));
     }
   } else {
     size_t vialen = 16;
@@ -437,7 +434,7 @@ int Http2DownstreamConnection::push_request_headers() {
     }
 
     auto iov = make_byte_ref(balloc, vialen + 1);
-    auto p = iov.base;
+    auto p = std::begin(iov);
 
     if (via) {
       p = std::copy(std::begin(via->value), std::end(via->value), p);
@@ -446,7 +443,8 @@ int Http2DownstreamConnection::push_request_headers() {
     p = http::create_via_header_value(p, req.http_major, req.http_minor);
     *p = '\0';
 
-    nva.push_back(http2::make_nv_ls_nocopy("via", StringRef{iov.base, p}));
+    nva.push_back(
+        http2::make_field("via"_sr, StringRef{std::span{std::begin(iov), p}}));
   }
 
   auto te = req.fs.header(http2::HD_TE);
@@ -454,22 +452,23 @@ int Http2DownstreamConnection::push_request_headers() {
   // "trailers".  We just forward "trailers".
   // TODO more strict handling required here.
   if (te && http2::contains_trailers(te->value)) {
-    nva.push_back(http2::make_nv_ll("te", "trailers"));
+    nva.push_back(http2::make_field("te"_sr, "trailers"_sr));
   }
 
   for (auto &p : httpconf.add_request_headers) {
-    nva.push_back(http2::make_nv_nocopy(p.name, p.value));
+    nva.push_back(http2::make_field(p.name, p.value));
   }
 
   if (LOG_ENABLED(INFO)) {
     std::stringstream ss;
     for (auto &nv : nva) {
-      if (util::streq_l("authorization", nv.name, nv.namelen)) {
-        ss << TTY_HTTP_HD << StringRef{nv.name, nv.namelen} << TTY_RST
-           << ": <redacted>\n";
+      auto name = StringRef{nv.name, nv.namelen};
+
+      if ("authorization"_sr == name) {
+        ss << TTY_HTTP_HD << name << TTY_RST << ": <redacted>\n";
         continue;
       }
-      ss << TTY_HTTP_HD << StringRef{nv.name, nv.namelen} << TTY_RST << ": "
+      ss << TTY_HTTP_HD << name << TTY_RST << ": "
          << StringRef{nv.value, nv.valuelen} << "\n";
     }
     DCLOG(INFO, this) << "HTTP request headers\n" << ss.str();
diff --git a/src/shrpx_http2_session.cc b/src/shrpx_http2_session.cc
index dccdae4..4fc73ba 100644
--- a/src/shrpx_http2_session.cc
+++ b/src/shrpx_http2_session.cc
@@ -468,11 +468,11 @@ int Http2Session::initiate_connection() {
         auto sni_name =
             addr_->sni.empty() ? StringRef{addr_->host} : StringRef{addr_->sni};
 
-        if (!util::numeric_host(sni_name.c_str())) {
+        if (!util::numeric_host(sni_name.data())) {
           // TLS extensions: SNI. There is no documentation about the return
           // code for this function (actually this is macro wrapping SSL_ctrl
           // at the time of this writing).
-          SSL_set_tlsext_host_name(conn_.tls.ssl, sni_name.c_str());
+          SSL_set_tlsext_host_name(conn_.tls.ssl, sni_name.data());
         }
 
         auto tls_session = tls::reuse_tls_session(addr_->tls_session_cache);
@@ -693,7 +693,7 @@ int Http2Session::downstream_connect_proxy() {
   }
 
   std::string req = "CONNECT ";
-  req.append(addr_->hostport.c_str(), addr_->hostport.size());
+  req.append(addr_->hostport.data(), addr_->hostport.size());
   if (addr_->port == 80 || addr_->port == 443) {
     req += ':';
     req += util::utos(addr_->port);
@@ -939,7 +939,9 @@ int on_header_callback2(nghttp2_session *session, const nghttp2_frame *frame,
       return NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE;
     }
 
-    auto token = http2::lookup_token(namebuf.base, namebuf.len);
+    auto nameref = StringRef{namebuf.base, namebuf.len};
+    auto valueref = StringRef{valuebuf.base, valuebuf.len};
+    auto token = http2::lookup_token(nameref);
     auto no_index = flags & NGHTTP2_NV_FLAG_NO_INDEX;
 
     downstream->add_rcbuf(name);
@@ -947,15 +949,11 @@ int on_header_callback2(nghttp2_session *session, const nghttp2_frame *frame,
 
     if (trailer) {
       // just store header fields for trailer part
-      resp.fs.add_trailer_token(StringRef{namebuf.base, namebuf.len},
-                                StringRef{valuebuf.base, valuebuf.len},
-                                no_index, token);
+      resp.fs.add_trailer_token(nameref, valueref, no_index, token);
       return 0;
     }
 
-    resp.fs.add_header_token(StringRef{namebuf.base, namebuf.len},
-                             StringRef{valuebuf.base, valuebuf.len}, no_index,
-                             token);
+    resp.fs.add_header_token(nameref, valueref, no_index, token);
     return 0;
   }
   case NGHTTP2_PUSH_PROMISE: {
@@ -993,9 +991,10 @@ int on_header_callback2(nghttp2_session *session, const nghttp2_frame *frame,
     promised_downstream->add_rcbuf(name);
     promised_downstream->add_rcbuf(value);
 
-    auto token = http2::lookup_token(namebuf.base, namebuf.len);
-    promised_req.fs.add_header_token(StringRef{namebuf.base, namebuf.len},
-                                     StringRef{valuebuf.base, valuebuf.len},
+    auto nameref = StringRef{namebuf.base, namebuf.len};
+    auto valueref = StringRef{valuebuf.base, valuebuf.len};
+    auto token = http2::lookup_token(nameref);
+    promised_req.fs.add_header_token(nameref, valueref,
                                      flags & NGHTTP2_NV_FLAG_NO_INDEX, token);
 
     return 0;
@@ -1171,7 +1170,8 @@ int on_response_headers(Http2Session *http2session, Downstream *downstream,
     auto content_length = resp.fs.header(http2::HD_CONTENT_LENGTH);
     if (content_length) {
       // libnghttp2 guarantees this can be parsed
-      resp.fs.content_length = util::parse_uint(content_length->value);
+      resp.fs.content_length =
+          util::parse_uint(content_length->value).value_or(-1);
     }
 
     if (resp.fs.content_length == -1 && downstream->expect_response_body()) {
@@ -1184,8 +1184,7 @@ int on_response_headers(Http2Session *http2session, Downstream *downstream,
         // Otherwise, use chunked encoding to keep upstream connection
         // open.  In HTTP2, we are supposed not to receive
         // transfer-encoding.
-        resp.fs.add_header_token(StringRef::from_lit("transfer-encoding"),
-                                 StringRef::from_lit("chunked"), false,
+        resp.fs.add_header_token("transfer-encoding"_sr, "chunked"_sr, false,
                                  http2::HD_TRANSFER_ENCODING);
         downstream->set_chunked_response(true);
       }
@@ -2279,7 +2278,7 @@ int Http2Session::handle_downstream_push_promise_complete(
   }
 
   // For server-wide OPTIONS request, path is empty.
-  if (method_token != HTTP_OPTIONS || path->value != "*") {
+  if (method_token != HTTP_OPTIONS || path->value != "*"_sr) {
     promised_req.path = http2::rewrite_clean_path(promised_balloc, path->value);
   }
 
diff --git a/src/shrpx_http2_upstream.cc b/src/shrpx_http2_upstream.cc
index 7816f5f..4c59ddc 100644
--- a/src/shrpx_http2_upstream.cc
+++ b/src/shrpx_http2_upstream.cc
@@ -118,7 +118,7 @@ int Http2Upstream::upgrade_upstream(HttpsUpstream *http) {
                                          std::end(http2_settings));
 
   rv = nghttp2_session_upgrade2(
-      session_, settings_payload.byte(), settings_payload.size(),
+      session_, settings_payload.data(), settings_payload.size(),
       http->get_downstream()->request().method == HTTP_HEAD, nullptr);
   if (rv != 0) {
     if (LOG_ENABLED(INFO)) {
@@ -209,7 +209,9 @@ int on_header_callback2(nghttp2_session *session, const nghttp2_frame *frame,
     return 0;
   }
 
-  auto token = http2::lookup_token(namebuf.base, namebuf.len);
+  auto nameref = StringRef{namebuf.base, namebuf.len};
+  auto valueref = StringRef{valuebuf.base, valuebuf.len};
+  auto token = http2::lookup_token(nameref);
   auto no_index = flags & NGHTTP2_NV_FLAG_NO_INDEX;
 
   downstream->add_rcbuf(name);
@@ -217,15 +219,11 @@ int on_header_callback2(nghttp2_session *session, const nghttp2_frame *frame,
 
   if (frame->headers.cat == NGHTTP2_HCAT_HEADERS) {
     // just store header fields for trailer part
-    req.fs.add_trailer_token(StringRef{namebuf.base, namebuf.len},
-                             StringRef{valuebuf.base, valuebuf.len}, no_index,
-                             token);
+    req.fs.add_trailer_token(nameref, valueref, no_index, token);
     return 0;
   }
 
-  req.fs.add_header_token(StringRef{namebuf.base, namebuf.len},
-                          StringRef{valuebuf.base, valuebuf.len}, no_index,
-                          token);
+  req.fs.add_header_token(nameref, valueref, no_index, token);
   return 0;
 }
 } // namespace
@@ -322,7 +320,7 @@ int Http2Upstream::on_request_headers(Downstream *downstream,
   if (LOG_ENABLED(INFO)) {
     std::stringstream ss;
     for (auto &nv : nva) {
-      if (nv.name == "authorization") {
+      if (nv.name == "authorization"_sr) {
         ss << TTY_HTTP_HD << nv.name << TTY_RST << ": <redacted>\n";
         continue;
       }
@@ -343,7 +341,8 @@ int Http2Upstream::on_request_headers(Downstream *downstream,
   auto content_length = req.fs.header(http2::HD_CONTENT_LENGTH);
   if (content_length) {
     // libnghttp2 guarantees this can be parsed
-    req.fs.content_length = util::parse_uint(content_length->value);
+    req.fs.content_length =
+        util::parse_uint(content_length->value).value_or(-1);
   }
 
   // presence of mandatory header fields are guaranteed by libnghttp2.
@@ -385,8 +384,7 @@ int Http2Upstream::on_request_headers(Downstream *downstream,
   }
 
   if (path) {
-    if (method_token == HTTP_OPTIONS &&
-        path->value == StringRef::from_lit("*")) {
+    if (method_token == HTTP_OPTIONS && path->value == "*"_sr) {
       // Server-wide OPTIONS request.  Path is empty.
     } else if (config->http2_proxy &&
                faddr->alt_mode == UpstreamAltMode::NONE) {
@@ -399,7 +397,7 @@ int Http2Upstream::on_request_headers(Downstream *downstream,
 
   auto connect_proto = req.fs.header(http2::HD__PROTOCOL);
   if (connect_proto) {
-    if (connect_proto->value != "websocket") {
+    if (connect_proto->value != "websocket"_sr) {
       if (error_reply(downstream, 400) != 0) {
         return NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE;
       }
@@ -744,7 +742,7 @@ int on_frame_send_callback(nghttp2_session *session, const nghttp2_frame *frame,
       auto value =
           make_string_ref(promised_balloc, StringRef{nv.value, nv.valuelen});
 
-      auto token = http2::lookup_token(nv.name, nv.namelen);
+      auto token = http2::lookup_token(name);
       switch (token) {
       case http2::HD__METHOD:
         req.method = http2::lookup_method_token(value);
@@ -1510,10 +1508,16 @@ int Http2Upstream::send_reply(Downstream *downstream, const uint8_t *body,
 
   nghttp2_data_provider2 data_prd, *data_prd_ptr = nullptr;
 
-  if (bodylen) {
+  const auto &req = downstream->request();
+
+  if (req.method != HTTP_HEAD && bodylen) {
     data_prd.source.ptr = downstream;
     data_prd.read_callback = downstream_data_read_callback;
     data_prd_ptr = &data_prd;
+
+    auto buf = downstream->get_response_buf();
+
+    buf->append(body, bodylen);
   }
 
   const auto &resp = downstream->response();
@@ -1529,7 +1533,7 @@ int Http2Upstream::send_reply(Downstream *downstream, const uint8_t *body,
 
   auto response_status = http2::stringify_status(balloc, resp.http_status);
 
-  nva.push_back(http2::make_nv_ls_nocopy(":status", response_status));
+  nva.push_back(http2::make_field(":status"_sr, response_status));
 
   for (auto &kv : headers) {
     if (kv.name.empty() || kv.name[0] == ':') {
@@ -1544,15 +1548,16 @@ int Http2Upstream::send_reply(Downstream *downstream, const uint8_t *body,
     case http2::HD_UPGRADE:
       continue;
     }
-    nva.push_back(http2::make_nv_nocopy(kv.name, kv.value, kv.no_index));
+    nva.push_back(
+        http2::make_field(kv.name, kv.value, http2::no_index(kv.no_index)));
   }
 
   if (!resp.fs.header(http2::HD_SERVER)) {
-    nva.push_back(http2::make_nv_ls_nocopy("server", config->http.server_name));
+    nva.push_back(http2::make_field("server"_sr, config->http.server_name));
   }
 
   for (auto &p : httpconf.add_response_headers) {
-    nva.push_back(http2::make_nv_nocopy(p.name, p.value));
+    nva.push_back(http2::make_field(p.name, p.value));
   }
 
   rv = nghttp2_submit_response2(session_, downstream->get_stream_id(),
@@ -1563,10 +1568,6 @@ int Http2Upstream::send_reply(Downstream *downstream, const uint8_t *body,
     return -1;
   }
 
-  auto buf = downstream->get_response_buf();
-
-  buf->append(body, bodylen);
-
   downstream->set_response_state(DownstreamState::MSG_COMPLETE);
 
   if (data_prd_ptr) {
@@ -1585,13 +1586,22 @@ int Http2Upstream::error_reply(Downstream *downstream,
 
   auto html = http::create_error_html(balloc, status_code);
   resp.http_status = status_code;
-  auto body = downstream->get_response_buf();
-  body->append(html);
-  downstream->set_response_state(DownstreamState::MSG_COMPLETE);
 
-  nghttp2_data_provider2 data_prd;
-  data_prd.source.ptr = downstream;
-  data_prd.read_callback = downstream_data_read_callback;
+  nghttp2_data_provider2 data_prd, *data_prd_ptr = nullptr;
+
+  const auto &req = downstream->request();
+
+  if (req.method != HTTP_HEAD) {
+    data_prd.source.ptr = downstream;
+    data_prd.read_callback = downstream_data_read_callback;
+    data_prd_ptr = &data_prd;
+
+    auto body = downstream->get_response_buf();
+
+    body->append(html);
+  }
+
+  downstream->set_response_state(DownstreamState::MSG_COMPLETE);
 
   auto lgconf = log_config();
   lgconf->update_tstamp(std::chrono::system_clock::now());
@@ -1600,15 +1610,15 @@ int Http2Upstream::error_reply(Downstream *downstream,
   auto content_length = util::make_string_ref_uint(balloc, html.size());
   auto date = make_string_ref(balloc, lgconf->tstamp->time_http);
 
-  auto nva = std::array<nghttp2_nv, 5>{
-      {http2::make_nv_ls_nocopy(":status", response_status),
-       http2::make_nv_ll("content-type", "text/html; charset=UTF-8"),
-       http2::make_nv_ls_nocopy("server", get_config()->http.server_name),
-       http2::make_nv_ls_nocopy("content-length", content_length),
-       http2::make_nv_ls_nocopy("date", date)}};
+  auto nva = std::to_array(
+      {http2::make_field(":status"_sr, response_status),
+       http2::make_field("content-type"_sr, "text/html; charset=UTF-8"_sr),
+       http2::make_field("server"_sr, get_config()->http.server_name),
+       http2::make_field("content-length"_sr, content_length),
+       http2::make_field("date"_sr, date)});
 
   rv = nghttp2_submit_response2(session_, downstream->get_stream_id(),
-                                nva.data(), nva.size(), &data_prd);
+                                nva.data(), nva.size(), data_prd_ptr);
   if (rv < NGHTTP2_ERR_FATAL) {
     ULOG(FATAL, this) << "nghttp2_submit_response2() failed: "
                       << nghttp2_strerror(rv);
@@ -1747,7 +1757,7 @@ int Http2Upstream::on_downstream_header_complete(Downstream *downstream) {
   if (downstream->get_non_final_response()) {
     auto response_status = http2::stringify_status(balloc, resp.http_status);
 
-    nva.push_back(http2::make_nv_ls_nocopy(":status", response_status));
+    nva.push_back(http2::make_field(":status"_sr, response_status));
 
     http2::copy_headers_to_nva_nocopy(nva, resp.fs.headers(),
                                       http2::HDOP_STRIP_ALL);
@@ -1780,16 +1790,16 @@ int Http2Upstream::on_downstream_header_complete(Downstream *downstream) {
     response_status = http2::stringify_status(balloc, resp.http_status);
   }
 
-  nva.push_back(http2::make_nv_ls_nocopy(":status", response_status));
+  nva.push_back(http2::make_field(":status"_sr, response_status));
 
   http2::copy_headers_to_nva_nocopy(nva, resp.fs.headers(), striphd_flags);
 
   if (!config->http2_proxy && !httpconf.no_server_rewrite) {
-    nva.push_back(http2::make_nv_ls_nocopy("server", httpconf.server_name));
+    nva.push_back(http2::make_field("server"_sr, httpconf.server_name));
   } else {
     auto server = resp.fs.header(http2::HD_SERVER);
     if (server) {
-      nva.push_back(http2::make_nv_ls_nocopy("server", (*server).value));
+      nva.push_back(http2::make_field("server"_sr, (*server).value));
     }
   }
 
@@ -1805,22 +1815,22 @@ int Http2Upstream::on_downstream_header_complete(Downstream *downstream) {
           http::require_cookie_secure_attribute(cookieconf.secure, req.scheme);
       auto cookie_str = http::create_affinity_cookie(
           balloc, cookieconf.name, affinity_cookie, cookieconf.path, secure);
-      nva.push_back(http2::make_nv_ls_nocopy("set-cookie", cookie_str));
+      nva.push_back(http2::make_field("set-cookie"_sr, cookie_str));
     }
   }
 
   if (!resp.fs.header(http2::HD_ALT_SVC)) {
     // We won't change or alter alt-svc from backend for now
     if (!httpconf.http2_altsvc_header_value.empty()) {
-      nva.push_back(http2::make_nv_ls_nocopy(
-          "alt-svc", httpconf.http2_altsvc_header_value));
+      nva.push_back(
+          http2::make_field("alt-svc"_sr, httpconf.http2_altsvc_header_value));
     }
   }
 
   auto via = resp.fs.header(http2::HD_VIA);
   if (httpconf.no_via) {
     if (via) {
-      nva.push_back(http2::make_nv_ls_nocopy("via", (*via).value));
+      nva.push_back(http2::make_field("via"_sr, (*via).value));
     }
   } else {
     // we don't create more than 16 bytes in
@@ -1831,7 +1841,7 @@ int Http2Upstream::on_downstream_header_complete(Downstream *downstream) {
     }
 
     auto iov = make_byte_ref(balloc, len + 1);
-    auto p = iov.base;
+    auto p = std::begin(iov);
     if (via) {
       p = std::copy(std::begin(via->value), std::end(via->value), p);
       p = util::copy_lit(p, ", ");
@@ -1839,17 +1849,18 @@ int Http2Upstream::on_downstream_header_complete(Downstream *downstream) {
     p = http::create_via_header_value(p, resp.http_major, resp.http_minor);
     *p = '\0';
 
-    nva.push_back(http2::make_nv_ls_nocopy("via", StringRef{iov.base, p}));
+    nva.push_back(
+        http2::make_field("via"_sr, StringRef{std::span{std::begin(iov), p}}));
   }
 
   for (auto &p : httpconf.add_response_headers) {
-    nva.push_back(http2::make_nv_nocopy(p.name, p.value));
+    nva.push_back(http2::make_field(p.name, p.value));
   }
 
   if (downstream->get_stream_id() % 2 == 0) {
     // This header field is basically for human on client side to
     // figure out that the resource is pushed.
-    nva.push_back(http2::make_nv_ll("x-http2-push", "1"));
+    nva.push_back(http2::make_field("x-http2-push"_sr, "1"_sr));
   }
 
   if (LOG_ENABLED(INFO)) {
@@ -1993,7 +2004,7 @@ int Http2Upstream::on_downstream_abort_request_with_https_redirect(
 
 int Http2Upstream::redirect_to_https(Downstream *downstream) {
   auto &req = downstream->request();
-  if (req.regular_connect_method() || req.scheme != "http") {
+  if (req.regular_connect_method() || req.scheme != "http"_sr) {
     return error_reply(downstream, 400);
   }
 
@@ -2007,19 +2018,16 @@ int Http2Upstream::redirect_to_https(Downstream *downstream) {
   auto &httpconf = config->http;
 
   StringRef loc;
-  if (httpconf.redirect_https_port == StringRef::from_lit("443")) {
-    loc = concat_string_ref(balloc, StringRef::from_lit("https://"), authority,
-                            req.path);
+  if (httpconf.redirect_https_port == "443"_sr) {
+    loc = concat_string_ref(balloc, "https://"_sr, authority, req.path);
   } else {
-    loc = concat_string_ref(balloc, StringRef::from_lit("https://"), authority,
-                            StringRef::from_lit(":"),
+    loc = concat_string_ref(balloc, "https://"_sr, authority, ":"_sr,
                             httpconf.redirect_https_port, req.path);
   }
 
   auto &resp = downstream->response();
   resp.http_status = 308;
-  resp.fs.add_header_token(StringRef::from_lit("location"), loc, false,
-                           http2::HD_LOCATION);
+  resp.fs.add_header_token("location"_sr, loc, false, http2::HD_LOCATION);
 
   return send_reply(downstream, nullptr, 0);
 }
@@ -2216,10 +2224,10 @@ int Http2Upstream::submit_push_promise(const StringRef &scheme,
   nva.reserve(4 + req.fs.headers().size());
 
   // just use "GET" for now
-  nva.push_back(http2::make_nv_ll(":method", "GET"));
-  nva.push_back(http2::make_nv_ls_nocopy(":scheme", scheme));
-  nva.push_back(http2::make_nv_ls_nocopy(":path", path));
-  nva.push_back(http2::make_nv_ls_nocopy(":authority", authority));
+  nva.push_back(http2::make_field(":method"_sr, "GET"_sr));
+  nva.push_back(http2::make_field(":scheme"_sr, scheme));
+  nva.push_back(http2::make_field(":path"_sr, path));
+  nva.push_back(http2::make_field(":authority"_sr, authority));
 
   for (auto &kv : req.fs.headers()) {
     switch (kv.token) {
@@ -2234,7 +2242,8 @@ int Http2Upstream::submit_push_promise(const StringRef &scheme,
     case http2::HD_CACHE_CONTROL:
     case http2::HD_HOST:
     case http2::HD_USER_AGENT:
-      nva.push_back(http2::make_nv_nocopy(kv.name, kv.value, kv.no_index));
+      nva.push_back(
+          http2::make_field(kv.name, kv.value, http2::no_index(kv.no_index)));
       break;
     }
   }
@@ -2378,7 +2387,8 @@ int Http2Upstream::on_downstream_push_promise_complete(
   nva.reserve(headers.size());
 
   for (auto &kv : headers) {
-    nva.push_back(http2::make_nv(kv.name, kv.value, kv.no_index));
+    nva.push_back(
+        http2::make_field_nv(kv.name, kv.value, http2::no_index(kv.no_index)));
   }
 
   auto promised_stream_id = nghttp2_submit_push_promise(
diff --git a/src/shrpx_http3_upstream.cc b/src/shrpx_http3_upstream.cc
index d12d2da..0be846d 100644
--- a/src/shrpx_http3_upstream.cc
+++ b/src/shrpx_http3_upstream.cc
@@ -120,6 +120,9 @@ Http3Upstream::Http3Upstream(ClientHandler *handler)
                         !get_config()->http2_proxy},
       tx_{
           .data = std::unique_ptr<uint8_t[]>(new uint8_t[64_k]),
+#ifndef UDP_SEGMENT
+          .no_gso = true,
+#endif // UDP_SEGMENT
       } {
   auto conn = handler_->get_connection();
   conn->conn_ref.get_conn = shrpx::get_conn;
@@ -273,7 +276,7 @@ int recv_stream_data(ngtcp2_conn *conn, uint32_t flags, int64_t stream_id,
                      void *user_data, void *stream_user_data) {
   auto upstream = static_cast<Http3Upstream *>(user_data);
 
-  if (upstream->recv_stream_data(flags, stream_id, data, datalen) != 0) {
+  if (upstream->recv_stream_data(flags, stream_id, {data, datalen}) != 0) {
     return NGTCP2_ERR_CALLBACK_FAILURE;
   }
 
@@ -282,11 +285,12 @@ int recv_stream_data(ngtcp2_conn *conn, uint32_t flags, int64_t stream_id,
 } // namespace
 
 int Http3Upstream::recv_stream_data(uint32_t flags, int64_t stream_id,
-                                    const uint8_t *data, size_t datalen) {
+                                    std::span<const uint8_t> data) {
   assert(httpconn_);
 
-  auto nconsumed = nghttp3_conn_read_stream(
-      httpconn_, stream_id, data, datalen, flags & NGTCP2_STREAM_DATA_FLAG_FIN);
+  auto nconsumed =
+      nghttp3_conn_read_stream(httpconn_, stream_id, data.data(), data.size(),
+                               flags & NGTCP2_STREAM_DATA_FLAG_FIN);
   if (nconsumed < 0) {
     ULOG(ERROR, this) << "nghttp3_conn_read_stream: "
                       << nghttp3_strerror(nconsumed);
@@ -506,25 +510,22 @@ int path_validation(ngtcp2_conn *conn, uint32_t flags, const ngtcp2_path *path,
 } // namespace
 
 int Http3Upstream::send_new_token(const ngtcp2_addr *remote_addr) {
-  std::array<uint8_t, NGTCP2_CRYPTO_MAX_REGULAR_TOKENLEN + 1> token;
-  size_t tokenlen;
-
   auto worker = handler_->get_worker();
   auto conn_handler = worker->get_connection_handler();
   auto &qkms = conn_handler->get_quic_keying_materials();
   auto &qkm = qkms->keying_materials.front();
 
-  if (generate_token(token.data(), tokenlen, remote_addr->addr,
-                     remote_addr->addrlen, qkm.secret.data(),
-                     qkm.secret.size()) != 0) {
+  std::array<uint8_t, NGTCP2_CRYPTO_MAX_REGULAR_TOKENLEN + 1> tokenbuf;
+
+  auto token = generate_token(tokenbuf, remote_addr->addr, remote_addr->addrlen,
+                              qkm.secret, qkm.id);
+  if (!token) {
     return -1;
   }
 
-  assert(tokenlen == NGTCP2_CRYPTO_MAX_REGULAR_TOKENLEN);
-
-  token[tokenlen++] = qkm.id;
+  assert(token->size() == NGTCP2_CRYPTO_MAX_REGULAR_TOKENLEN + 1);
 
-  auto rv = ngtcp2_conn_submit_new_token(conn_, token.data(), tokenlen);
+  auto rv = ngtcp2_conn_submit_new_token(conn_, token->data(), token->size());
   if (rv != 0) {
     ULOG(ERROR, this) << "ngtcp2_conn_submit_new_token: "
                       << ngtcp2_strerror(rv);
@@ -553,8 +554,8 @@ int recv_tx_key(ngtcp2_conn *conn, ngtcp2_encryption_level level,
 int Http3Upstream::init(const UpstreamAddr *faddr, const Address &remote_addr,
                         const Address &local_addr,
                         const ngtcp2_pkt_hd &initial_hd,
-                        const ngtcp2_cid *odcid, const uint8_t *token,
-                        size_t tokenlen, ngtcp2_token_type token_type) {
+                        const ngtcp2_cid *odcid, std::span<const uint8_t> token,
+                        ngtcp2_token_type token_type) {
   int rv;
 
   auto worker = handler_->get_worker();
@@ -637,8 +638,8 @@ int Http3Upstream::init(const UpstreamAddr *faddr, const Address &remote_addr,
   settings.max_window = http3conf.upstream.max_connection_window_size;
   settings.max_stream_window = http3conf.upstream.max_window_size;
   settings.rand_ctx.native_handle = &worker->get_randgen();
-  settings.token = token;
-  settings.tokenlen = tokenlen;
+  settings.token = token.data();
+  settings.tokenlen = token.size();
   settings.token_type = token_type;
   settings.initial_pkt_num = std::uniform_int_distribution<uint32_t>(
       0, std::numeric_limits<int32_t>::max())(worker->get_randgen());
@@ -779,17 +780,14 @@ int Http3Upstream::on_write() {
 int Http3Upstream::write_streams() {
   std::array<nghttp3_vec, 16> vec;
   auto max_udp_payload_size = ngtcp2_conn_get_max_tx_udp_payload_size(conn_);
-#ifdef UDP_SEGMENT
   auto path_max_udp_payload_size =
       ngtcp2_conn_get_path_max_tx_udp_payload_size(conn_);
-#endif // UDP_SEGMENT
-  auto max_pktcnt =
-      std::max(ngtcp2_conn_get_send_quantum(conn_) / max_udp_payload_size,
-               static_cast<size_t>(1));
   ngtcp2_pkt_info pi, prev_pi;
-  uint8_t *bufpos = tx_.data.get();
+  auto txbuf =
+      std::span{tx_.data.get(), std::max(ngtcp2_conn_get_send_quantum(conn_),
+                                         path_max_udp_payload_size)};
+  auto buf = txbuf;
   ngtcp2_path_storage ps, prev_ps;
-  size_t pktcnt = 0;
   int rv;
   size_t gso_size = 0;
   auto ts = quic_timestamp();
@@ -824,9 +822,12 @@ int Http3Upstream::write_streams() {
       flags |= NGTCP2_WRITE_STREAM_FLAG_FIN;
     }
 
+    auto buflen = buf.size() >= max_udp_payload_size
+                      ? max_udp_payload_size
+                      : path_max_udp_payload_size;
     auto nwrite = ngtcp2_conn_writev_stream(
-        conn_, &ps.path, &pi, bufpos, max_udp_payload_size, &ndatalen, flags,
-        stream_id, reinterpret_cast<const ngtcp2_vec *>(v), vcnt, ts);
+        conn_, &ps.path, &pi, buf.data(), buflen, &ndatalen, flags, stream_id,
+        reinterpret_cast<const ngtcp2_vec *>(v), vcnt, ts);
     if (nwrite < 0) {
       switch (nwrite) {
       case NGTCP2_ERR_STREAM_DATA_BLOCKED:
@@ -872,18 +873,17 @@ int Http3Upstream::write_streams() {
     }
 
     if (nwrite == 0) {
-      if (bufpos - tx_.data.get()) {
+      auto data = std::span{std::begin(txbuf), std::begin(buf)};
+      if (!data.empty()) {
         auto faddr = static_cast<UpstreamAddr *>(prev_ps.path.user_data);
-        auto data = tx_.data.get();
-        auto datalen = bufpos - data;
 
-        rv = send_packet(faddr, prev_ps.path.remote.addr,
-                         prev_ps.path.remote.addrlen, prev_ps.path.local.addr,
-                         prev_ps.path.local.addrlen, prev_pi, data, datalen,
-                         gso_size);
+        auto [rest, rv] =
+            send_packet(faddr, prev_ps.path.remote.addr,
+                        prev_ps.path.remote.addrlen, prev_ps.path.local.addr,
+                        prev_ps.path.local.addrlen, prev_pi, data, gso_size);
         if (rv == SHRPX_ERR_SEND_BLOCKED) {
           on_send_blocked(faddr, prev_ps.path.remote, prev_ps.path.local,
-                          prev_pi, data, datalen, gso_size);
+                          prev_pi, rest, gso_size);
 
           signal_write_upstream_addr(faddr);
         }
@@ -894,10 +894,11 @@ int Http3Upstream::write_streams() {
       return 0;
     }
 
-    bufpos += nwrite;
+    auto last_pkt = std::begin(buf);
+
+    buf = buf.subspan(nwrite);
 
-#ifdef UDP_SEGMENT
-    if (pktcnt == 0) {
+    if (last_pkt == std::begin(txbuf)) {
       ngtcp2_path_copy(&prev_ps.path, &ps.path);
       prev_pi = pi;
       gso_size = nwrite;
@@ -907,35 +908,36 @@ int Http3Upstream::write_streams() {
                (gso_size > path_max_udp_payload_size &&
                 static_cast<size_t>(nwrite) != gso_size)) {
       auto faddr = static_cast<UpstreamAddr *>(prev_ps.path.user_data);
-      auto data = tx_.data.get();
-      auto datalen = bufpos - data - nwrite;
+      auto data = std::span{std::begin(txbuf), last_pkt};
 
-      rv = send_packet(faddr, prev_ps.path.remote.addr,
-                       prev_ps.path.remote.addrlen, prev_ps.path.local.addr,
-                       prev_ps.path.local.addrlen, prev_pi, data, datalen,
-                       gso_size);
+      auto [rest, rv] =
+          send_packet(faddr, prev_ps.path.remote.addr,
+                      prev_ps.path.remote.addrlen, prev_ps.path.local.addr,
+                      prev_ps.path.local.addrlen, prev_pi, data, gso_size);
       switch (rv) {
       case SHRPX_ERR_SEND_BLOCKED:
         on_send_blocked(faddr, prev_ps.path.remote, prev_ps.path.local, prev_pi,
-                        data, datalen, gso_size);
+                        rest, gso_size);
 
+        data = std::span{last_pkt, std::begin(buf)};
         on_send_blocked(static_cast<UpstreamAddr *>(ps.path.user_data),
-                        ps.path.remote, ps.path.local, pi, bufpos - nwrite,
-                        nwrite, 0);
+                        ps.path.remote, ps.path.local, pi, data, data.size());
 
         signal_write_upstream_addr(faddr);
 
         break;
       default: {
         auto faddr = static_cast<UpstreamAddr *>(ps.path.user_data);
-        auto data = bufpos - nwrite;
+        auto data = std::span{last_pkt, std::begin(buf)};
 
-        rv = send_packet(faddr, ps.path.remote.addr, ps.path.remote.addrlen,
-                         ps.path.local.addr, ps.path.local.addrlen, pi, data,
-                         nwrite, 0);
+        auto [rest, rv] = send_packet(
+            faddr, ps.path.remote.addr, ps.path.remote.addrlen,
+            ps.path.local.addr, ps.path.local.addrlen, pi, data, data.size());
         if (rv == SHRPX_ERR_SEND_BLOCKED) {
-          on_send_blocked(faddr, ps.path.remote, ps.path.local, pi, data,
-                          nwrite, 0);
+          assert(rest.size() == data.size());
+
+          on_send_blocked(faddr, ps.path.remote, ps.path.local, pi, rest,
+                          rest.size());
 
           signal_write_upstream_addr(faddr);
         }
@@ -947,16 +949,16 @@ int Http3Upstream::write_streams() {
       return 0;
     }
 
-    if (++pktcnt == max_pktcnt || static_cast<size_t>(nwrite) < gso_size) {
+    if (buf.size() < path_max_udp_payload_size ||
+        static_cast<size_t>(nwrite) < gso_size) {
       auto faddr = static_cast<UpstreamAddr *>(ps.path.user_data);
-      auto data = tx_.data.get();
-      auto datalen = bufpos - data;
+      auto data = std::span{std::begin(txbuf), std::begin(buf)};
 
-      rv = send_packet(faddr, ps.path.remote.addr, ps.path.remote.addrlen,
-                       ps.path.local.addr, ps.path.local.addrlen, pi, data,
-                       datalen, gso_size);
+      auto [rest, rv] = send_packet(faddr, ps.path.remote.addr,
+                                    ps.path.remote.addrlen, ps.path.local.addr,
+                                    ps.path.local.addrlen, pi, data, gso_size);
       if (rv == SHRPX_ERR_SEND_BLOCKED) {
-        on_send_blocked(faddr, ps.path.remote, ps.path.local, pi, data, datalen,
+        on_send_blocked(faddr, ps.path.remote, ps.path.local, pi, rest,
                         gso_size);
 
         signal_write_upstream_addr(faddr);
@@ -966,33 +968,6 @@ int Http3Upstream::write_streams() {
 
       return 0;
     }
-#else  // !UDP_SEGMENT
-    auto faddr = static_cast<UpstreamAddr *>(ps.path.user_data);
-    auto data = tx_.data.get();
-    auto datalen = bufpos - data;
-
-    rv = send_packet(faddr, ps.path.remote.addr, ps.path.remote.addrlen,
-                     ps.path.local.addr, ps.path.local.addrlen, pi, data,
-                     datalen, 0);
-    if (rv == SHRPX_ERR_SEND_BLOCKED) {
-      on_send_blocked(faddr, ps.path.remote, ps.path.local, pi, data, datalen,
-                      0);
-
-      ngtcp2_conn_update_pkt_tx_time(conn_, ts);
-
-      signal_write_upstream_addr(faddr);
-
-      return 0;
-    }
-
-    if (++pktcnt == max_pktcnt) {
-      ngtcp2_conn_update_pkt_tx_time(conn_, ts);
-
-      return 0;
-    }
-
-    bufpos = tx_.data.get();
-#endif // !UDP_SEGMENT
   }
 
   return 0;
@@ -1329,7 +1304,7 @@ int Http3Upstream::on_downstream_header_complete(Downstream *downstream) {
   if (downstream->get_non_final_response()) {
     auto response_status = http2::stringify_status(balloc, resp.http_status);
 
-    nva.push_back(http3::make_nv_ls_nocopy(":status", response_status));
+    nva.push_back(http3::make_field(":status"_sr, response_status));
 
     http3::copy_headers_to_nva_nocopy(nva, resp.fs.headers(),
                                       http2::HDOP_STRIP_ALL);
@@ -1361,16 +1336,16 @@ int Http3Upstream::on_downstream_header_complete(Downstream *downstream) {
     response_status = http2::stringify_status(balloc, resp.http_status);
   }
 
-  nva.push_back(http3::make_nv_ls_nocopy(":status", response_status));
+  nva.push_back(http3::make_field(":status"_sr, response_status));
 
   http3::copy_headers_to_nva_nocopy(nva, resp.fs.headers(), striphd_flags);
 
   if (!config->http2_proxy && !httpconf.no_server_rewrite) {
-    nva.push_back(http3::make_nv_ls_nocopy("server", httpconf.server_name));
+    nva.push_back(http3::make_field("server"_sr, httpconf.server_name));
   } else {
     auto server = resp.fs.header(http2::HD_SERVER);
     if (server) {
-      nva.push_back(http3::make_nv_ls_nocopy("server", (*server).value));
+      nva.push_back(http3::make_field("server"_sr, (*server).value));
     }
   }
 
@@ -1386,14 +1361,14 @@ int Http3Upstream::on_downstream_header_complete(Downstream *downstream) {
           http::require_cookie_secure_attribute(cookieconf.secure, req.scheme);
       auto cookie_str = http::create_affinity_cookie(
           balloc, cookieconf.name, affinity_cookie, cookieconf.path, secure);
-      nva.push_back(http3::make_nv_ls_nocopy("set-cookie", cookie_str));
+      nva.push_back(http3::make_field("set-cookie"_sr, cookie_str));
     }
   }
 
   auto via = resp.fs.header(http2::HD_VIA);
   if (httpconf.no_via) {
     if (via) {
-      nva.push_back(http3::make_nv_ls_nocopy("via", (*via).value));
+      nva.push_back(http3::make_field("via"_sr, (*via).value));
     }
   } else {
     // we don't create more than 16 bytes in
@@ -1404,7 +1379,7 @@ int Http3Upstream::on_downstream_header_complete(Downstream *downstream) {
     }
 
     auto iov = make_byte_ref(balloc, len + 1);
-    auto p = iov.base;
+    auto p = std::begin(iov);
     if (via) {
       p = std::copy(std::begin(via->value), std::end(via->value), p);
       p = util::copy_lit(p, ", ");
@@ -1412,11 +1387,12 @@ int Http3Upstream::on_downstream_header_complete(Downstream *downstream) {
     p = http::create_via_header_value(p, resp.http_major, resp.http_minor);
     *p = '\0';
 
-    nva.push_back(http3::make_nv_ls_nocopy("via", StringRef{iov.base, p}));
+    nva.push_back(
+        http3::make_field("via"_sr, StringRef{std::span{std::begin(iov), p}}));
   }
 
   for (auto &p : httpconf.add_response_headers) {
-    nva.push_back(http3::make_nv_nocopy(p.name, p.value));
+    nva.push_back(http3::make_field(p.name, p.value));
   }
 
   if (LOG_ENABLED(INFO)) {
@@ -1582,7 +1558,7 @@ void Http3Upstream::on_handler_delete() {
 
     send_packet(static_cast<UpstreamAddr *>(ps.path.user_data),
                 ps.path.remote.addr, ps.path.remote.addrlen, ps.path.local.addr,
-                ps.path.local.addrlen, pi, conn_close_.data(), nwrite, 0);
+                ps.path.local.addrlen, pi, conn_close_, conn_close_.size());
   }
 
   auto d =
@@ -1700,9 +1676,15 @@ int Http3Upstream::send_reply(Downstream *downstream, const uint8_t *body,
 
   nghttp3_data_reader data_read, *data_read_ptr = nullptr;
 
-  if (bodylen) {
+  const auto &req = downstream->request();
+
+  if (req.method != HTTP_HEAD && bodylen) {
     data_read.read_data = downstream_read_data_callback;
     data_read_ptr = &data_read;
+
+    auto buf = downstream->get_response_buf();
+
+    buf->append(body, bodylen);
   }
 
   const auto &resp = downstream->response();
@@ -1718,7 +1700,7 @@ int Http3Upstream::send_reply(Downstream *downstream, const uint8_t *body,
 
   auto response_status = http2::stringify_status(balloc, resp.http_status);
 
-  nva.push_back(http3::make_nv_ls_nocopy(":status", response_status));
+  nva.push_back(http3::make_field(":status"_sr, response_status));
 
   for (auto &kv : headers) {
     if (kv.name.empty() || kv.name[0] == ':') {
@@ -1733,15 +1715,16 @@ int Http3Upstream::send_reply(Downstream *downstream, const uint8_t *body,
     case http2::HD_UPGRADE:
       continue;
     }
-    nva.push_back(http3::make_nv_nocopy(kv.name, kv.value, kv.no_index));
+    nva.push_back(
+        http3::make_field(kv.name, kv.value, http3::never_index(kv.no_index)));
   }
 
   if (!resp.fs.header(http2::HD_SERVER)) {
-    nva.push_back(http3::make_nv_ls_nocopy("server", config->http.server_name));
+    nva.push_back(http3::make_field("server"_sr, config->http.server_name));
   }
 
   for (auto &p : httpconf.add_response_headers) {
-    nva.push_back(http3::make_nv_nocopy(p.name, p.value));
+    nva.push_back(http3::make_field(p.name, p.value));
   }
 
   rv = nghttp3_conn_submit_response(httpconn_, downstream->get_stream_id(),
@@ -1752,10 +1735,6 @@ int Http3Upstream::send_reply(Downstream *downstream, const uint8_t *body,
     return -1;
   }
 
-  auto buf = downstream->get_response_buf();
-
-  buf->append(body, bodylen);
-
   downstream->set_response_state(DownstreamState::MSG_COMPLETE);
 
   if (data_read_ptr) {
@@ -1801,7 +1780,7 @@ void Http3Upstream::cancel_premature_downstream(
 int Http3Upstream::on_read(const UpstreamAddr *faddr,
                            const Address &remote_addr,
                            const Address &local_addr, const ngtcp2_pkt_info &pi,
-                           const uint8_t *data, size_t datalen) {
+                           std::span<const uint8_t> data) {
   int rv;
 
   auto path = ngtcp2_path{
@@ -1816,7 +1795,8 @@ int Http3Upstream::on_read(const UpstreamAddr *faddr,
       const_cast<UpstreamAddr *>(faddr),
   };
 
-  rv = ngtcp2_conn_read_pkt(conn_, &path, &pi, data, datalen, quic_timestamp());
+  rv = ngtcp2_conn_read_pkt(conn_, &path, &pi, data.data(), data.size(),
+                            quic_timestamp());
   if (rv != 0) {
     switch (rv) {
     case NGTCP2_ERR_DRAINING:
@@ -1834,8 +1814,8 @@ int Http3Upstream::on_read(const UpstreamAddr *faddr,
 
       ngtcp2_version_cid vc;
 
-      rv =
-          ngtcp2_pkt_decode_version_cid(&vc, data, datalen, SHRPX_QUIC_SCIDLEN);
+      rv = ngtcp2_pkt_decode_version_cid(&vc, data.data(), data.size(),
+                                         SHRPX_QUIC_SCIDLEN);
       if (rv != 0) {
         return -1;
       }
@@ -1843,9 +1823,9 @@ int Http3Upstream::on_read(const UpstreamAddr *faddr,
       // Overwrite error if any is set
       ngtcp2_ccerr_set_liberr(&last_error_, rv, nullptr, 0);
 
-      quic_conn_handler->send_retry(handler_->get_upstream_addr(), vc.version,
-                                    vc.dcid, vc.dcidlen, vc.scid, vc.scidlen,
-                                    remote_addr, local_addr, datalen * 3);
+      quic_conn_handler->send_retry(
+          handler_->get_upstream_addr(), vc.version, {vc.dcid, vc.dcidlen},
+          {vc.scid, vc.scidlen}, remote_addr, local_addr, data.size() * 3);
 
       return -1;
     }
@@ -1874,16 +1854,40 @@ int Http3Upstream::on_read(const UpstreamAddr *faddr,
   return 0;
 }
 
-int Http3Upstream::send_packet(const UpstreamAddr *faddr,
-                               const sockaddr *remote_sa, size_t remote_salen,
-                               const sockaddr *local_sa, size_t local_salen,
-                               const ngtcp2_pkt_info &pi, const uint8_t *data,
-                               size_t datalen, size_t gso_size) {
+std::pair<std::span<const uint8_t>, int>
+Http3Upstream::send_packet(const UpstreamAddr *faddr, const sockaddr *remote_sa,
+                           size_t remote_salen, const sockaddr *local_sa,
+                           size_t local_salen, const ngtcp2_pkt_info &pi,
+                           std::span<const uint8_t> data, size_t gso_size) {
+  if (tx_.no_gso) {
+    for (; !data.empty();) {
+      auto len = std::min(gso_size, data.size());
+      auto rv =
+          quic_send_packet(faddr, remote_sa, remote_salen, local_sa,
+                           local_salen, pi, {std::begin(data), len}, gso_size);
+      if (rv != 0) {
+        switch (rv) {
+        case -EAGAIN:
+#if EAGAIN != EWOULDBLOCK
+        case -EWOULDBLOCK:
+#endif // EAGAIN != EWOULDBLOCK
+          return {data, SHRPX_ERR_SEND_BLOCKED};
+        default:
+          return {data, -1};
+        }
+      }
+
+      data = data.subspan(len);
+    }
+
+    return {{}, 0};
+  }
+
   auto rv = quic_send_packet(faddr, remote_sa, remote_salen, local_sa,
-                             local_salen, pi, data, datalen, gso_size);
+                             local_salen, pi, data, gso_size);
   switch (rv) {
   case 0:
-    return 0;
+    return {{}, 0};
     // With GSO, sendmsg may fail with EINVAL if UDP payload is too
     // large.
   case -EINVAL:
@@ -1894,22 +1898,32 @@ int Http3Upstream::send_packet(const UpstreamAddr *faddr,
 #if EAGAIN != EWOULDBLOCK
   case -EWOULDBLOCK:
 #endif // EAGAIN != EWOULDBLOCK
-    return SHRPX_ERR_SEND_BLOCKED;
+    return {data, SHRPX_ERR_SEND_BLOCKED};
+  case -EIO:
+    if (tx_.no_gso) {
+      break;
+    }
+
+    tx_.no_gso = true;
+
+    return send_packet(faddr, remote_sa, remote_salen, local_sa, local_salen,
+                       pi, data, gso_size);
   default:
     break;
   }
 
-  return -1;
+  return {{}, -1};
 }
 
 void Http3Upstream::on_send_blocked(const UpstreamAddr *faddr,
                                     const ngtcp2_addr &remote_addr,
                                     const ngtcp2_addr &local_addr,
                                     const ngtcp2_pkt_info &pi,
-                                    const uint8_t *data, size_t datalen,
+                                    std::span<const uint8_t> data,
                                     size_t gso_size) {
   assert(tx_.num_blocked || !tx_.send_blocked);
   assert(tx_.num_blocked < 2);
+  assert(gso_size);
 
   tx_.send_blocked = true;
 
@@ -1923,22 +1937,21 @@ void Http3Upstream::on_send_blocked(const UpstreamAddr *faddr,
   p.faddr = faddr;
   p.pi = pi;
   p.data = data;
-  p.datalen = datalen;
   p.gso_size = gso_size;
 }
 
 int Http3Upstream::send_blocked_packet() {
-  int rv;
-
   assert(tx_.send_blocked);
 
   for (; tx_.num_blocked_sent < tx_.num_blocked; ++tx_.num_blocked_sent) {
     auto &p = tx_.blocked[tx_.num_blocked_sent];
 
-    rv = send_packet(p.faddr, &p.remote_addr.su.sa, p.remote_addr.len,
-                     &p.local_addr.su.sa, p.local_addr.len, p.pi, p.data,
-                     p.datalen, p.gso_size);
+    auto [rest, rv] = send_packet(p.faddr, &p.remote_addr.su.sa,
+                                  p.remote_addr.len, &p.local_addr.su.sa,
+                                  p.local_addr.len, p.pi, p.data, p.gso_size);
     if (rv == SHRPX_ERR_SEND_BLOCKED) {
+      p.data = rest;
+
       signal_write_upstream_addr(p.faddr);
 
       return 0;
@@ -1998,7 +2011,7 @@ int Http3Upstream::handle_error() {
 
   send_packet(static_cast<UpstreamAddr *>(ps.path.user_data),
               ps.path.remote.addr, ps.path.remote.addrlen, ps.path.local.addr,
-              ps.path.local.addrlen, pi, conn_close_.data(), nwrite, 0);
+              ps.path.local.addrlen, pi, conn_close_, conn_close_.size());
 
   return -1;
 }
@@ -2185,22 +2198,20 @@ int Http3Upstream::http_recv_request_header(Downstream *downstream,
     return 0;
   }
 
-  auto token = http2::lookup_token(namebuf.base, namebuf.len);
+  auto nameref = StringRef{namebuf.base, namebuf.len};
+  auto valueref = StringRef{valuebuf.base, valuebuf.len};
+  auto token = http2::lookup_token(nameref);
   auto no_index = flags & NGHTTP3_NV_FLAG_NEVER_INDEX;
 
   downstream->add_rcbuf(name);
   downstream->add_rcbuf(value);
 
   if (trailer) {
-    req.fs.add_trailer_token(StringRef{namebuf.base, namebuf.len},
-                             StringRef{valuebuf.base, valuebuf.len}, no_index,
-                             token);
+    req.fs.add_trailer_token(nameref, valueref, no_index, token);
     return 0;
   }
 
-  req.fs.add_header_token(StringRef{namebuf.base, namebuf.len},
-                          StringRef{valuebuf.base, valuebuf.len}, no_index,
-                          token);
+  req.fs.add_header_token(nameref, valueref, no_index, token);
   return 0;
 }
 
@@ -2240,7 +2251,7 @@ int Http3Upstream::http_end_request_headers(Downstream *downstream, int fin) {
   if (LOG_ENABLED(INFO)) {
     std::stringstream ss;
     for (auto &nv : nva) {
-      if (nv.name == "authorization") {
+      if (nv.name == "authorization"_sr) {
         ss << TTY_HTTP_HD << nv.name << TTY_RST << ": <redacted>\n";
         continue;
       }
@@ -2254,7 +2265,8 @@ int Http3Upstream::http_end_request_headers(Downstream *downstream, int fin) {
   auto content_length = req.fs.header(http2::HD_CONTENT_LENGTH);
   if (content_length) {
     // libnghttp3 guarantees this can be parsed
-    req.fs.content_length = util::parse_uint(content_length->value);
+    req.fs.content_length =
+        util::parse_uint(content_length->value).value_or(-1);
   }
 
   // presence of mandatory header fields are guaranteed by libnghttp3.
@@ -2298,8 +2310,7 @@ int Http3Upstream::http_end_request_headers(Downstream *downstream, int fin) {
   }
 
   if (path) {
-    if (method_token == HTTP_OPTIONS &&
-        path->value == StringRef::from_lit("*")) {
+    if (method_token == HTTP_OPTIONS && path->value == "*"_sr) {
       // Server-wide OPTIONS request.  Path is empty.
     } else if (config->http2_proxy &&
                faddr->alt_mode == UpstreamAltMode::NONE) {
@@ -2312,7 +2323,7 @@ int Http3Upstream::http_end_request_headers(Downstream *downstream, int fin) {
 
   auto connect_proto = req.fs.header(http2::HD__PROTOCOL);
   if (connect_proto) {
-    if (connect_proto->value != "websocket") {
+    if (connect_proto->value != "websocket"_sr) {
       if (error_reply(downstream, 400) != 0) {
         return -1;
       }
@@ -2452,7 +2463,7 @@ int http_recv_data(nghttp3_conn *conn, int64_t stream_id, const uint8_t *data,
   auto upstream = static_cast<Http3Upstream *>(user_data);
   auto downstream = static_cast<Downstream *>(stream_user_data);
 
-  if (upstream->http_recv_data(downstream, data, datalen) != 0) {
+  if (upstream->http_recv_data(downstream, {data, datalen}) != 0) {
     return NGHTTP3_ERR_CALLBACK_FAILURE;
   }
 
@@ -2460,16 +2471,16 @@ int http_recv_data(nghttp3_conn *conn, int64_t stream_id, const uint8_t *data,
 }
 } // namespace
 
-int Http3Upstream::http_recv_data(Downstream *downstream, const uint8_t *data,
-                                  size_t datalen) {
+int Http3Upstream::http_recv_data(Downstream *downstream,
+                                  std::span<const uint8_t> data) {
   downstream->reset_upstream_rtimer();
 
-  if (downstream->push_upload_data_chunk(data, datalen) != 0) {
+  if (downstream->push_upload_data_chunk(data.data(), data.size()) != 0) {
     if (downstream->get_response_state() != DownstreamState::MSG_COMPLETE) {
       shutdown_stream(downstream, NGHTTP3_H3_INTERNAL_ERROR);
     }
 
-    consume(downstream->get_stream_id(), datalen);
+    consume(downstream->get_stream_id(), data.size());
 
     return 0;
   }
@@ -2724,12 +2735,21 @@ int Http3Upstream::error_reply(Downstream *downstream,
 
   auto html = http::create_error_html(balloc, status_code);
   resp.http_status = status_code;
-  auto body = downstream->get_response_buf();
-  body->append(html);
-  downstream->set_response_state(DownstreamState::MSG_COMPLETE);
 
-  nghttp3_data_reader data_read;
-  data_read.read_data = downstream_read_data_callback;
+  nghttp3_data_reader data_read, *data_read_ptr = nullptr;
+
+  const auto &req = downstream->request();
+
+  if (req.method != HTTP_HEAD) {
+    data_read.read_data = downstream_read_data_callback;
+    data_read_ptr = &data_read;
+
+    auto body = downstream->get_response_buf();
+
+    body->append(html);
+  }
+
+  downstream->set_response_state(DownstreamState::MSG_COMPLETE);
 
   auto lgconf = log_config();
   lgconf->update_tstamp(std::chrono::system_clock::now());
@@ -2738,15 +2758,15 @@ int Http3Upstream::error_reply(Downstream *downstream,
   auto content_length = util::make_string_ref_uint(balloc, html.size());
   auto date = make_string_ref(balloc, lgconf->tstamp->time_http);
 
-  auto nva = std::array<nghttp3_nv, 5>{
-      {http3::make_nv_ls_nocopy(":status", response_status),
-       http3::make_nv_ll("content-type", "text/html; charset=UTF-8"),
-       http3::make_nv_ls_nocopy("server", get_config()->http.server_name),
-       http3::make_nv_ls_nocopy("content-length", content_length),
-       http3::make_nv_ls_nocopy("date", date)}};
+  auto nva = std::to_array(
+      {http3::make_field(":status"_sr, response_status),
+       http3::make_field("content-type"_sr, "text/html; charset=UTF-8"_sr),
+       http3::make_field("server"_sr, get_config()->http.server_name),
+       http3::make_field("content-length"_sr, content_length),
+       http3::make_field("date"_sr, date)});
 
   rv = nghttp3_conn_submit_response(httpconn_, downstream->get_stream_id(),
-                                    nva.data(), nva.size(), &data_read);
+                                    nva.data(), nva.size(), data_read_ptr);
   if (nghttp3_err_is_fatal(rv)) {
     ULOG(FATAL, this) << "nghttp3_conn_submit_response() failed: "
                       << nghttp3_strerror(rv);
@@ -2891,12 +2911,12 @@ int Http3Upstream::open_qlog_file(const StringRef &dir,
                                   const ngtcp2_cid &scid) const {
   std::array<char, sizeof("20141115T125824.741+0900")> buf;
 
-  auto path = dir.str();
+  auto path = std::string{dir};
   path += '/';
   path +=
       util::format_iso8601_basic(buf.data(), std::chrono::system_clock::now());
   path += '-';
-  path += util::format_hex(scid.data, scid.datalen);
+  path += util::format_hex(std::span{scid.data, scid.datalen});
   path += ".sqlog";
 
   int fd;
diff --git a/src/shrpx_http3_upstream.h b/src/shrpx_http3_upstream.h
index 53c73ae..ef0fcb4 100644
--- a/src/shrpx_http3_upstream.h
+++ b/src/shrpx_http3_upstream.h
@@ -89,12 +89,12 @@ public:
 
   int init(const UpstreamAddr *faddr, const Address &remote_addr,
            const Address &local_addr, const ngtcp2_pkt_hd &initial_hd,
-           const ngtcp2_cid *odcid, const uint8_t *token, size_t tokenlen,
+           const ngtcp2_cid *odcid, std::span<const uint8_t> token,
            ngtcp2_token_type token_type);
 
   int on_read(const UpstreamAddr *faddr, const Address &remote_addr,
               const Address &local_addr, const ngtcp2_pkt_info &pi,
-              const uint8_t *data, size_t datalen);
+              std::span<const uint8_t> data);
 
   int write_streams();
 
@@ -105,8 +105,8 @@ public:
 
   int setup_httpconn();
   void add_pending_downstream(std::unique_ptr<Downstream> downstream);
-  int recv_stream_data(uint32_t flags, int64_t stream_id, const uint8_t *data,
-                       size_t datalen);
+  int recv_stream_data(uint32_t flags, int64_t stream_id,
+                       std::span<const uint8_t> data);
   int acked_stream_data_offset(int64_t stream_id, uint64_t datalen);
   int extend_max_stream_data(int64_t stream_id);
   void extend_max_remote_streams_bidi(uint64_t max_streams);
@@ -131,16 +131,16 @@ public:
   int http_shutdown_stream_read(int64_t stream_id);
   int http_reset_stream(int64_t stream_id, uint64_t app_error_code);
   int http_stop_sending(int64_t stream_id, uint64_t app_error_code);
-  int http_recv_data(Downstream *downstream, const uint8_t *data,
-                     size_t datalen);
+  int http_recv_data(Downstream *downstream, std::span<const uint8_t> data);
   int handshake_completed();
   int check_shutdown();
   int start_graceful_shutdown();
   int submit_goaway();
-  int send_packet(const UpstreamAddr *faddr, const sockaddr *remote_sa,
-                  size_t remote_salen, const sockaddr *local_sa,
-                  size_t local_salen, const ngtcp2_pkt_info &pi,
-                  const uint8_t *data, size_t datalen, size_t gso_size);
+  std::pair<std::span<const uint8_t>, int>
+  send_packet(const UpstreamAddr *faddr, const sockaddr *remote_sa,
+              size_t remote_salen, const sockaddr *local_sa, size_t local_salen,
+              const ngtcp2_pkt_info &pi, std::span<const uint8_t> data,
+              size_t gso_size);
 
   void qlog_write(const void *data, size_t datalen, bool fin);
   int open_qlog_file(const StringRef &dir, const ngtcp2_cid &scid) const;
@@ -148,7 +148,7 @@ public:
   void on_send_blocked(const UpstreamAddr *faddr,
                        const ngtcp2_addr &remote_addr,
                        const ngtcp2_addr &local_addr, const ngtcp2_pkt_info &pi,
-                       const uint8_t *data, size_t datalen, size_t gso_size);
+                       std::span<const uint8_t> data, size_t gso_size);
   int send_blocked_packet();
   void signal_write_upstream_addr(const UpstreamAddr *faddr);
 
@@ -179,11 +179,11 @@ private:
       Address local_addr;
       Address remote_addr;
       ngtcp2_pkt_info pi;
-      const uint8_t *data;
-      size_t datalen;
+      std::span<const uint8_t> data;
       size_t gso_size;
     } blocked[2];
     std::unique_ptr<uint8_t[]> data;
+    bool no_gso;
   } tx_;
 };
 
diff --git a/src/shrpx_http_downstream_connection.cc b/src/shrpx_http_downstream_connection.cc
index 4164b8b..8031098 100644
--- a/src/shrpx_http_downstream_connection.cc
+++ b/src/shrpx_http_downstream_connection.cc
@@ -425,8 +425,8 @@ int HttpDownstreamConnection::initiate_connection() {
 
       auto sni_name =
           addr_->sni.empty() ? StringRef{addr_->host} : StringRef{addr_->sni};
-      if (!util::numeric_host(sni_name.c_str())) {
-        SSL_set_tlsext_host_name(conn_.tls.ssl, sni_name.c_str());
+      if (!util::numeric_host(sni_name.data())) {
+        SSL_set_tlsext_host_name(conn_.tls.ssl, sni_name.data());
       }
 
       auto session = tls::reuse_tls_session(addr_->tls_session_cache);
@@ -564,9 +564,10 @@ int HttpDownstreamConnection::push_request_headers() {
         return -1;
       }
       auto iov = make_byte_ref(balloc, base64::encode_length(nonce.size()) + 1);
-      auto p = base64::encode(std::begin(nonce), std::end(nonce), iov.base);
+      auto p =
+          base64::encode(std::begin(nonce), std::end(nonce), std::begin(iov));
       *p = '\0';
-      auto key = StringRef{iov.base, p};
+      auto key = StringRef{std::span{std::begin(iov), p}};
       downstream_->set_ws_key(key);
 
       buf->append("Sec-Websocket-Key: ");
diff --git a/src/shrpx_http_test.cc b/src/shrpx_http_test.cc
index f753ec8..8bc3e2e 100644
--- a/src/shrpx_http_test.cc
+++ b/src/shrpx_http_test.cc
@@ -36,6 +36,8 @@
 #include "shrpx_config.h"
 #include "shrpx_log.h"
 
+using namespace std::literals;
+
 namespace shrpx {
 
 namespace {
@@ -56,47 +58,34 @@ const MunitSuite http_suite{
 void test_shrpx_http_create_forwarded(void) {
   BlockAllocator balloc(1024, 1024);
 
-  assert_stdstring_equal(
+  assert_stdsv_equal(
       "by=\"example.com:3000\";for=\"[::1]\";host=\"www.example.com\";"
-      "proto=https",
+      "proto=https"sv,
       http::create_forwarded(
           balloc,
           FORWARDED_BY | FORWARDED_FOR | FORWARDED_HOST | FORWARDED_PROTO,
-          StringRef::from_lit("example.com:3000"), StringRef::from_lit("[::1]"),
-          StringRef::from_lit("www.example.com"), StringRef::from_lit("https"))
-          .str());
-
-  assert_stdstring_equal(
-      "for=192.168.0.1",
-      http::create_forwarded(
-          balloc, FORWARDED_FOR, StringRef::from_lit("alpha"),
-          StringRef::from_lit("192.168.0.1"), StringRef::from_lit("bravo"),
-          StringRef::from_lit("charlie"))
-          .str());
-
-  assert_stdstring_equal(
-      "by=_hidden;for=\"[::1]\"",
-      http::create_forwarded(balloc, FORWARDED_BY | FORWARDED_FOR,
-                             StringRef::from_lit("_hidden"),
-                             StringRef::from_lit("[::1]"),
-                             StringRef::from_lit(""), StringRef::from_lit(""))
-          .str());
-
-  assert_stdstring_equal(
-      "by=\"[::1]\";for=_hidden",
-      http::create_forwarded(balloc, FORWARDED_BY | FORWARDED_FOR,
-                             StringRef::from_lit("[::1]"),
-                             StringRef::from_lit("_hidden"),
-                             StringRef::from_lit(""), StringRef::from_lit(""))
-          .str());
-
-  assert_stdstring_equal(
-      "", http::create_forwarded(
-              balloc,
-              FORWARDED_BY | FORWARDED_FOR | FORWARDED_HOST | FORWARDED_PROTO,
-              StringRef::from_lit(""), StringRef::from_lit(""),
-              StringRef::from_lit(""), StringRef::from_lit(""))
-              .str());
+          "example.com:3000"_sr, "[::1]"_sr, "www.example.com"_sr, "https"_sr));
+
+  assert_stdsv_equal("for=192.168.0.1"sv,
+                     http::create_forwarded(balloc, FORWARDED_FOR, "alpha"_sr,
+                                            "192.168.0.1"_sr, "bravo"_sr,
+                                            "charlie"_sr));
+
+  assert_stdsv_equal(
+      "by=_hidden;for=\"[::1]\""sv,
+      http::create_forwarded(balloc, FORWARDED_BY | FORWARDED_FOR, "_hidden"_sr,
+                             "[::1]"_sr, ""_sr, ""_sr));
+
+  assert_stdsv_equal(
+      "by=\"[::1]\";for=_hidden"sv,
+      http::create_forwarded(balloc, FORWARDED_BY | FORWARDED_FOR, "[::1]"_sr,
+                             "_hidden"_sr, ""_sr, ""_sr));
+
+  assert_stdsv_equal(""sv, http::create_forwarded(balloc,
+                                                  FORWARDED_BY | FORWARDED_FOR |
+                                                      FORWARDED_HOST |
+                                                      FORWARDED_PROTO,
+                                                  ""_sr, ""_sr, ""_sr, ""_sr));
 }
 
 void test_shrpx_http_create_via_header_value(void) {
@@ -117,27 +106,25 @@ void test_shrpx_http_create_affinity_cookie(void) {
   BlockAllocator balloc(1024, 1024);
   StringRef c;
 
-  c = http::create_affinity_cookie(balloc, StringRef::from_lit("cookie-val"),
-                                   0xf1e2d3c4u, StringRef{}, false);
+  c = http::create_affinity_cookie(balloc, "cookie-val"_sr, 0xf1e2d3c4u,
+                                   StringRef{}, false);
 
-  assert_stdstring_equal("cookie-val=f1e2d3c4", c.str());
+  assert_stdsv_equal("cookie-val=f1e2d3c4"sv, c);
 
-  c = http::create_affinity_cookie(balloc, StringRef::from_lit("alpha"),
-                                   0x00000000u, StringRef{}, true);
+  c = http::create_affinity_cookie(balloc, "alpha"_sr, 0x00000000u, StringRef{},
+                                   true);
 
-  assert_stdstring_equal("alpha=00000000; Secure", c.str());
+  assert_stdsv_equal("alpha=00000000; Secure"sv, c);
 
-  c = http::create_affinity_cookie(balloc, StringRef::from_lit("bravo"),
-                                   0x01111111u, StringRef::from_lit("bar"),
+  c = http::create_affinity_cookie(balloc, "bravo"_sr, 0x01111111u, "bar"_sr,
                                    false);
 
-  assert_stdstring_equal("bravo=01111111; Path=bar", c.str());
+  assert_stdsv_equal("bravo=01111111; Path=bar"sv, c);
 
-  c = http::create_affinity_cookie(balloc, StringRef::from_lit("charlie"),
-                                   0x01111111u, StringRef::from_lit("bar"),
+  c = http::create_affinity_cookie(balloc, "charlie"_sr, 0x01111111u, "bar"_sr,
                                    true);
 
-  assert_stdstring_equal("charlie=01111111; Path=bar; Secure", c.str());
+  assert_stdsv_equal("charlie=01111111; Path=bar; Secure"sv, c);
 }
 
 void test_shrpx_http_create_altsvc_header_value(void) {
@@ -145,46 +132,44 @@ void test_shrpx_http_create_altsvc_header_value(void) {
     BlockAllocator balloc(1024, 1024);
     std::vector<AltSvc> altsvcs{
         AltSvc{
-            .protocol_id = StringRef::from_lit("h3"),
-            .host = StringRef::from_lit("127.0.0.1"),
-            .service = StringRef::from_lit("443"),
-            .params = StringRef::from_lit("ma=3600"),
+            .protocol_id = "h3"_sr,
+            .host = "127.0.0.1"_sr,
+            .service = "443"_sr,
+            .params = "ma=3600"_sr,
         },
     };
 
-    assert_stdstring_equal(
-        R"(h3="127.0.0.1:443"; ma=3600)",
-        http::create_altsvc_header_value(balloc, altsvcs).str());
+    assert_stdsv_equal(R"(h3="127.0.0.1:443"; ma=3600)"sv,
+                       http::create_altsvc_header_value(balloc, altsvcs));
   }
 
   {
     BlockAllocator balloc(1024, 1024);
     std::vector<AltSvc> altsvcs{
         AltSvc{
-            .protocol_id = StringRef::from_lit("h3"),
-            .service = StringRef::from_lit("443"),
-            .params = StringRef::from_lit("ma=3600"),
+            .protocol_id = "h3"_sr,
+            .service = "443"_sr,
+            .params = "ma=3600"_sr,
         },
         AltSvc{
-            .protocol_id = StringRef::from_lit("h3%"),
-            .host = StringRef::from_lit("\"foo\""),
-            .service = StringRef::from_lit("4433"),
+            .protocol_id = "h3%"_sr,
+            .host = "\"foo\""_sr,
+            .service = "4433"_sr,
         },
     };
 
-    assert_stdstring_equal(
-        R"(h3=":443"; ma=3600, h3%25="\"foo\":4433")",
-        http::create_altsvc_header_value(balloc, altsvcs).str());
+    assert_stdsv_equal(R"(h3=":443"; ma=3600, h3%25="\"foo\":4433")"sv,
+                       http::create_altsvc_header_value(balloc, altsvcs));
   }
 }
 
 void test_shrpx_http_check_http_scheme(void) {
-  assert_true(http::check_http_scheme(StringRef::from_lit("https"), true));
-  assert_false(http::check_http_scheme(StringRef::from_lit("https"), false));
-  assert_false(http::check_http_scheme(StringRef::from_lit("http"), true));
-  assert_true(http::check_http_scheme(StringRef::from_lit("http"), false));
-  assert_false(http::check_http_scheme(StringRef::from_lit("foo"), true));
-  assert_false(http::check_http_scheme(StringRef::from_lit("foo"), false));
+  assert_true(http::check_http_scheme("https"_sr, true));
+  assert_false(http::check_http_scheme("https"_sr, false));
+  assert_false(http::check_http_scheme("http"_sr, true));
+  assert_true(http::check_http_scheme("http"_sr, false));
+  assert_false(http::check_http_scheme("foo"_sr, true));
+  assert_false(http::check_http_scheme("foo"_sr, false));
   assert_false(http::check_http_scheme(StringRef{}, true));
   assert_false(http::check_http_scheme(StringRef{}, false));
 }
diff --git a/src/shrpx_https_upstream.cc b/src/shrpx_https_upstream.cc
index 0412384..aa54eb9 100644
--- a/src/shrpx_https_upstream.cc
+++ b/src/shrpx_https_upstream.cc
@@ -258,7 +258,7 @@ void rewrite_request_host_path_from_uri(BlockAllocator &balloc, Request &req,
 
   // As per https://tools.ietf.org/html/rfc7230#section-5.4, we
   // rewrite host header field with authority component.
-  auto authority = util::get_uri_field(uri.c_str(), u, UF_HOST);
+  auto authority = util::get_uri_field(uri.data(), u, UF_HOST);
   // TODO properly check IPv6 numeric address
   auto ipv6 = std::find(std::begin(authority), std::end(authority), ':') !=
               std::end(authority);
@@ -271,7 +271,7 @@ void rewrite_request_host_path_from_uri(BlockAllocator &balloc, Request &req,
   }
   if (authoritylen > authority.size()) {
     auto iovec = make_byte_ref(balloc, authoritylen + 1);
-    auto p = iovec.base;
+    auto p = std::begin(iovec);
     if (ipv6) {
       *p++ = '[';
     }
@@ -286,16 +286,16 @@ void rewrite_request_host_path_from_uri(BlockAllocator &balloc, Request &req,
     }
     *p = '\0';
 
-    req.authority = StringRef{iovec.base, p};
+    req.authority = StringRef{std::span{std::begin(iovec), p}};
   } else {
     req.authority = authority;
   }
 
-  req.scheme = util::get_uri_field(uri.c_str(), u, UF_SCHEMA);
+  req.scheme = util::get_uri_field(uri.data(), u, UF_SCHEMA);
 
   StringRef path;
   if (u.field_set & (1 << UF_PATH)) {
-    path = util::get_uri_field(uri.c_str(), u, UF_PATH);
+    path = util::get_uri_field(uri.data(), u, UF_PATH);
   } else if (req.method == HTTP_OPTIONS) {
     // Server-wide OPTIONS takes following form in proxy request:
     //
@@ -303,21 +303,21 @@ void rewrite_request_host_path_from_uri(BlockAllocator &balloc, Request &req,
     //
     // Notice that no slash after authority. See
     // http://tools.ietf.org/html/rfc7230#section-5.3.4
-    req.path = StringRef::from_lit("");
+    req.path = ""_sr;
     // we ignore query component here
     return;
   } else {
-    path = StringRef::from_lit("/");
+    path = "/"_sr;
   }
 
   if (u.field_set & (1 << UF_QUERY)) {
     auto &fdata = u.field_data[UF_QUERY];
 
     if (u.field_set & (1 << UF_PATH)) {
-      auto q = util::get_uri_field(uri.c_str(), u, UF_QUERY);
+      auto q = util::get_uri_field(uri.data(), u, UF_QUERY);
       path = StringRef{std::begin(path), std::end(q)};
     } else {
-      path = concat_string_ref(balloc, path, StringRef::from_lit("?"),
+      path = concat_string_ref(balloc, path, "?"_sr,
                                StringRef{&uri[fdata.off], fdata.len});
     }
   }
@@ -369,7 +369,7 @@ int htp_hdrs_completecb(llhttp_t *htp) {
        << "HTTP/" << req.http_major << "." << req.http_minor << "\n";
 
     for (const auto &kv : req.fs.headers()) {
-      if (kv.name == "authorization") {
+      if (kv.name == "authorization"_sr) {
         ss << TTY_HTTP_HD << kv.name << TTY_RST << ": <redacted>\n";
         continue;
       }
@@ -431,7 +431,7 @@ int htp_hdrs_completecb(llhttp_t *htp) {
 
   if (method != HTTP_CONNECT) {
     http_parser_url u{};
-    rv = http_parser_parse_url(req.path.c_str(), req.path.size(), 0, &u);
+    rv = http_parser_parse_url(req.path.data(), req.path.size(), 0, &u);
     if (rv != 0) {
       // Expect to respond with 400 bad request
       return -1;
@@ -440,7 +440,7 @@ int htp_hdrs_completecb(llhttp_t *htp) {
     if (!(u.field_set & (1 << UF_SCHEMA)) || !(u.field_set & (1 << UF_HOST))) {
       req.no_authority = true;
 
-      if (method == HTTP_OPTIONS && req.path == StringRef::from_lit("*")) {
+      if (method == HTTP_OPTIONS && req.path == "*"_sr) {
         req.path = StringRef{};
       } else {
         req.path = http2::rewrite_clean_path(balloc, req.path);
@@ -451,9 +451,9 @@ int htp_hdrs_completecb(llhttp_t *htp) {
       }
 
       if (handler->get_ssl()) {
-        req.scheme = StringRef::from_lit("https");
+        req.scheme = "https"_sr;
       } else {
-        req.scheme = StringRef::from_lit("http");
+        req.scheme = "http"_sr;
       }
     } else {
       rewrite_request_host_path_from_uri(balloc, req, req.path, u);
@@ -544,7 +544,7 @@ int htp_hdrs_completecb(llhttp_t *htp) {
     // Continue here to make the client happy.
     if (downstream->get_expect_100_continue()) {
       auto output = downstream->get_response_buf();
-      constexpr auto res = StringRef::from_lit("HTTP/1.1 100 Continue\r\n\r\n");
+      constexpr auto res = "HTTP/1.1 100 Continue\r\n\r\n"_sr;
       output->append(res);
       handler->signal_write();
     }
@@ -982,8 +982,7 @@ int HttpsUpstream::send_reply(Downstream *downstream, const uint8_t *body,
 
   if (httpconf.max_requests <= num_requests_ ||
       worker->get_graceful_shutdown()) {
-    resp.fs.add_header_token(StringRef::from_lit("connection"),
-                             StringRef::from_lit("close"), false,
+    resp.fs.add_header_token("connection"_sr, "close"_sr, false,
                              http2::HD_CONNECTION);
     connection_close = true;
   } else if (req.http_major <= 0 ||
@@ -991,7 +990,7 @@ int HttpsUpstream::send_reply(Downstream *downstream, const uint8_t *body,
     connection_close = true;
   } else {
     auto c = resp.fs.header(http2::HD_CONNECTION);
-    if (c && util::strieq_l("close", c->value)) {
+    if (c && util::strieq("close"_sr, c->value)) {
       connection_close = true;
     }
   }
@@ -1034,9 +1033,12 @@ int HttpsUpstream::send_reply(Downstream *downstream, const uint8_t *body,
 
   output->append("\r\n");
 
-  output->append(body, bodylen);
+  if (req.method != HTTP_HEAD) {
+    output->append(body, bodylen);
+
+    downstream->response_sent_body_length += bodylen;
+  }
 
-  downstream->response_sent_body_length += bodylen;
   downstream->set_response_state(DownstreamState::MSG_COMPLETE);
 
   return 0;
@@ -1071,7 +1073,7 @@ void HttpsUpstream::error_reply(unsigned int status_code) {
   output->append("\r\nServer: ");
   output->append(get_config()->http.server_name);
   output->append("\r\nContent-Length: ");
-  std::array<uint8_t, NGHTTP2_MAX_UINT64_DIGITS> intbuf;
+  std::array<char, NGHTTP2_MAX_UINT64_DIGITS> intbuf;
   output->append(StringRef{std::begin(intbuf),
                            util::utos(std::begin(intbuf), html.size())});
   output->append("\r\nDate: ");
@@ -1080,9 +1082,15 @@ void HttpsUpstream::error_reply(unsigned int status_code) {
   output->append(lgconf->tstamp->time_http);
   output->append("\r\nContent-Type: text/html; "
                  "charset=UTF-8\r\nConnection: close\r\n\r\n");
-  output->append(html);
 
-  downstream->response_sent_body_length += html.size();
+  const auto &req = downstream->request();
+
+  if (req.method != HTTP_HEAD) {
+    output->append(html);
+
+    downstream->response_sent_body_length += html.size();
+  }
+
   downstream->set_response_state(DownstreamState::MSG_COMPLETE);
 }
 
@@ -1403,7 +1411,7 @@ int HttpsUpstream::on_downstream_abort_request_with_https_redirect(
 
 int HttpsUpstream::redirect_to_https(Downstream *downstream) {
   auto &req = downstream->request();
-  if (req.method == HTTP_CONNECT || req.scheme != "http" ||
+  if (req.method == HTTP_CONNECT || req.scheme != "http"_sr ||
       req.authority.empty()) {
     error_reply(400);
     return 0;
@@ -1420,21 +1428,17 @@ int HttpsUpstream::redirect_to_https(Downstream *downstream) {
   auto &httpconf = config->http;
 
   StringRef loc;
-  if (httpconf.redirect_https_port == StringRef::from_lit("443")) {
-    loc = concat_string_ref(balloc, StringRef::from_lit("https://"), authority,
-                            req.path);
+  if (httpconf.redirect_https_port == "443"_sr) {
+    loc = concat_string_ref(balloc, "https://"_sr, authority, req.path);
   } else {
-    loc = concat_string_ref(balloc, StringRef::from_lit("https://"), authority,
-                            StringRef::from_lit(":"),
+    loc = concat_string_ref(balloc, "https://"_sr, authority, ":"_sr,
                             httpconf.redirect_https_port, req.path);
   }
 
   auto &resp = downstream->response();
   resp.http_status = 308;
-  resp.fs.add_header_token(StringRef::from_lit("location"), loc, false,
-                           http2::HD_LOCATION);
-  resp.fs.add_header_token(StringRef::from_lit("connection"),
-                           StringRef::from_lit("close"), false,
+  resp.fs.add_header_token("location"_sr, loc, false, http2::HD_LOCATION);
+  resp.fs.add_header_token("connection"_sr, "close"_sr, false,
                            http2::HD_CONNECTION);
 
   return send_reply(downstream, nullptr, 0);
diff --git a/src/shrpx_live_check.cc b/src/shrpx_live_check.cc
index 8e8d316..e59df5a 100644
--- a/src/shrpx_live_check.cc
+++ b/src/shrpx_live_check.cc
@@ -299,8 +299,8 @@ int LiveCheck::initiate_connection() {
   if (addr_->tls) {
     auto sni_name =
         addr_->sni.empty() ? StringRef{addr_->host} : StringRef{addr_->sni};
-    if (!util::numeric_host(sni_name.c_str())) {
-      SSL_set_tlsext_host_name(conn_.tls.ssl, sni_name.c_str());
+    if (!util::numeric_host(sni_name.data())) {
+      SSL_set_tlsext_host_name(conn_.tls.ssl, sni_name.data());
     }
 
     auto session = tls::reuse_tls_session(addr_->tls_session_cache);
@@ -411,7 +411,7 @@ int LiveCheck::tls_handshake() {
 
   switch (addr_->proto) {
   case Proto::HTTP1:
-    if (proto.empty() || proto == StringRef::from_lit("http/1.1")) {
+    if (proto.empty() || proto == "http/1.1"_sr) {
       break;
     }
     return -1;
diff --git a/src/shrpx_log.cc b/src/shrpx_log.cc
index de5e09f..386b33f 100644
--- a/src/shrpx_log.cc
+++ b/src/shrpx_log.cc
@@ -58,10 +58,8 @@ using namespace nghttp2;
 namespace shrpx {
 
 namespace {
-constexpr StringRef SEVERITY_STR[] = {
-    StringRef::from_lit("INFO"), StringRef::from_lit("NOTICE"),
-    StringRef::from_lit("WARN"), StringRef::from_lit("ERROR"),
-    StringRef::from_lit("FATAL")};
+constexpr StringRef SEVERITY_STR[] = {"INFO"_sr, "NOTICE"_sr, "WARN"_sr,
+                                      "ERROR"_sr, "FATAL"_sr};
 } // namespace
 
 namespace {
@@ -173,11 +171,10 @@ Log::~Log() {
   if (errorconf.syslog) {
     if (severity_ == NOTICE) {
       syslog(severity_to_syslog_level(severity_), "[%s] %.*s",
-             SEVERITY_STR[severity_].c_str(), static_cast<int>(rleft()),
-             begin_);
+             SEVERITY_STR[severity_].data(), static_cast<int>(rleft()), begin_);
     } else {
       syslog(severity_to_syslog_level(severity_), "[%s] %.*s (%s:%d)",
-             SEVERITY_STR[severity_].c_str(), static_cast<int>(rleft()), begin_,
+             SEVERITY_STR[severity_].data(), static_cast<int>(rleft()), begin_,
              filename_, linenum_);
     }
 
@@ -192,10 +189,10 @@ Log::~Log() {
   // Error log format: <datetime> <main-pid> <current-pid>
   // <thread-id> <level> (<filename>:<line>) <msg>
   rv = snprintf(buf, sizeof(buf), "%s %d %d %s %s%s%s (%s:%d) %.*s\n",
-                lgconf->tstamp->time_iso8601.c_str(), config->pid, lgconf->pid,
+                lgconf->tstamp->time_iso8601.data(), config->pid, lgconf->pid,
                 lgconf->thread_id.c_str(), tty ? SEVERITY_COLOR[severity_] : "",
-                SEVERITY_STR[severity_].c_str(), tty ? "\033[0m" : "",
-                filename_, linenum_, static_cast<int>(rleft()), begin_);
+                SEVERITY_STR[severity_].data(), tty ? "\033[0m" : "", filename_,
+                linenum_, static_cast<int>(rleft()), begin_);
 
   if (rv < 0) {
     return;
@@ -380,7 +377,7 @@ namespace {
 template <typename OutputIterator>
 std::pair<OutputIterator, OutputIterator>
 copy(const StringRef &src, OutputIterator d_first, OutputIterator d_last) {
-  return copy(src.c_str(), src.size(), d_first, d_last);
+  return copy(src.data(), src.size(), d_first, d_last);
 }
 } // namespace
 
@@ -531,7 +528,7 @@ template <typename OutputIterator>
 std::pair<OutputIterator, OutputIterator> copy_escape(const StringRef &src,
                                                       OutputIterator d_first,
                                                       OutputIterator d_last) {
-  return copy_escape(src.c_str(), src.size(), d_first, d_last);
+  return copy_escape(src.data(), src.size(), d_first, d_last);
 }
 } // namespace
 
@@ -555,7 +552,7 @@ StringRef construct_absolute_request_uri(BlockAllocator &balloc,
   }
 
   auto iov = make_byte_ref(balloc, len + 1);
-  auto p = iov.base;
+  auto p = std::begin(iov);
 
   if (req.scheme.empty()) {
     // We may have to log the request which lacks scheme (e.g.,
@@ -569,7 +566,7 @@ StringRef construct_absolute_request_uri(BlockAllocator &balloc,
   p = std::copy(std::begin(req.path), std::end(req.path), p);
   *p = '\0';
 
-  return StringRef{iov.base, p};
+  return StringRef{std::span{std::begin(iov), p}};
 }
 } // namespace
 
@@ -593,14 +590,13 @@ void upstream_accesslog(const std::vector<LogFragment> &lfv,
   auto &balloc = downstream->get_block_allocator();
 
   auto downstream_addr = downstream->get_addr();
-  auto method = req.method == -1 ? StringRef::from_lit("<unknown>")
-                                 : http2::to_method_string(req.method);
-  auto path =
-      req.method == HTTP_CONNECT ? req.authority
-      : config->http2_proxy      ? construct_absolute_request_uri(balloc, req)
-      : req.path.empty() ? req.method == HTTP_OPTIONS ? StringRef::from_lit("*")
-                                                      : StringRef::from_lit("-")
-                         : req.path;
+  auto method =
+      req.method == -1 ? "<unknown>"_sr : http2::to_method_string(req.method);
+  auto path = req.method == HTTP_CONNECT ? req.authority
+              : config->http2_proxy
+                  ? construct_absolute_request_uri(balloc, req)
+              : req.path.empty() ? req.method == HTTP_OPTIONS ? "*"_sr : "-"_sr
+                                 : req.path;
   auto path_without_query =
       req.method == HTTP_CONNECT
           ? path
@@ -880,7 +876,7 @@ int reopen_log_files(const LoggingConfig &loggingconf) {
   auto &errorconf = loggingconf.error;
 
   if (!accessconf.syslog && !accessconf.file.empty()) {
-    new_accesslog_fd = open_log_file(accessconf.file.c_str());
+    new_accesslog_fd = open_log_file(accessconf.file.data());
 
     if (new_accesslog_fd == -1) {
       LOG(ERROR) << "Failed to open accesslog file " << accessconf.file;
@@ -889,7 +885,7 @@ int reopen_log_files(const LoggingConfig &loggingconf) {
   }
 
   if (!errorconf.syslog && !errorconf.file.empty()) {
-    new_errorlog_fd = open_log_file(errorconf.file.c_str());
+    new_errorlog_fd = open_log_file(errorconf.file.data());
 
     if (new_errorlog_fd == -1) {
       if (lgconf->errorlog_fd != -1) {
diff --git a/src/shrpx_log.h b/src/shrpx_log.h
index bc30097..7a334ca 100644
--- a/src/shrpx_log.h
+++ b/src/shrpx_log.h
@@ -33,7 +33,6 @@
 #include <vector>
 #include <chrono>
 
-#include "shrpx_config.h"
 #include "shrpx_log_config.h"
 #include "tls.h"
 #include "template.h"
@@ -97,6 +96,7 @@ namespace shrpx {
 
 class Downstream;
 struct DownstreamAddr;
+struct LoggingConfig;
 
 enum SeverityLevel { INFO, NOTICE, WARN, ERROR, FATAL };
 
@@ -266,7 +266,7 @@ enum class LogFragmentType {
 };
 
 struct LogFragment {
-  LogFragment(LogFragmentType type, StringRef value = StringRef::from_lit(""))
+  LogFragment(LogFragmentType type, StringRef value = ""_sr)
       : type(type), value(std::move(value)) {}
   LogFragmentType type;
   StringRef value;
diff --git a/src/shrpx_log_config.cc b/src/shrpx_log_config.cc
index 92eb055..9d066f2 100644
--- a/src/shrpx_log_config.cc
+++ b/src/shrpx_log_config.cc
@@ -50,10 +50,8 @@ LogConfig::LogConfig()
       errorlog_tty(false) {
   auto tid = std::this_thread::get_id();
   auto tid_hash =
-      util::hash32(StringRef{reinterpret_cast<uint8_t *>(&tid),
-                             reinterpret_cast<uint8_t *>(&tid) + sizeof(tid)});
-  thread_id = util::format_hex(reinterpret_cast<uint8_t *>(&tid_hash),
-                               sizeof(tid_hash));
+      util::hash32(StringRef{reinterpret_cast<char *>(&tid), sizeof(tid)});
+  thread_id = util::format_hex(std::span{&tid_hash, 1});
 }
 
 #ifndef NOTHREADS
diff --git a/src/shrpx_memcached_connection.cc b/src/shrpx_memcached_connection.cc
index f72cb11..472df43 100644
--- a/src/shrpx_memcached_connection.cc
+++ b/src/shrpx_memcached_connection.cc
@@ -182,8 +182,8 @@ int MemcachedConnection::initiate_connection() {
   }
 
   if (ssl_ctx_) {
-    if (!util::numeric_host(sni_name_.c_str())) {
-      SSL_set_tlsext_host_name(conn_.tls.ssl, sni_name_.c_str());
+    if (!util::numeric_host(sni_name_.data())) {
+      SSL_set_tlsext_host_name(conn_.tls.ssl, sni_name_.data());
     }
 
     auto session = tls::reuse_tls_session(tls_session_cache_);
diff --git a/src/shrpx_mruby.cc b/src/shrpx_mruby.cc
index 4d412ef..cfa10fd 100644
--- a/src/shrpx_mruby.cc
+++ b/src/shrpx_mruby.cc
@@ -144,7 +144,7 @@ RProc *compile(mrb_state *mrb, const StringRef &filename) {
     return nullptr;
   }
 
-  auto infile = fopen(filename.c_str(), "rb");
+  auto infile = fopen(filename.data(), "rb");
   if (infile == nullptr) {
     LOG(ERROR) << "Could not open mruby file " << filename;
     return nullptr;
diff --git a/src/shrpx_mruby_module.cc b/src/shrpx_mruby_module.cc
index 27b7769..0159ba2 100644
--- a/src/shrpx_mruby_module.cc
+++ b/src/shrpx_mruby_module.cc
@@ -94,13 +94,13 @@ mrb_value create_headers_hash(mrb_state *mrb, const HeaderRefs &headers) {
     }
     auto ai = mrb_gc_arena_save(mrb);
 
-    auto key = mrb_str_new(mrb, hd.name.c_str(), hd.name.size());
+    auto key = mrb_str_new(mrb, hd.name.data(), hd.name.size());
     auto ary = mrb_hash_get(mrb, hash, key);
     if (mrb_nil_p(ary)) {
       ary = mrb_ary_new(mrb);
       mrb_hash_set(mrb, hash, key, ary);
     }
-    mrb_ary_push(mrb, ary, mrb_str_new(mrb, hd.value.c_str(), hd.value.size()));
+    mrb_ary_push(mrb, ary, mrb_str_new(mrb, hd.value.data(), hd.value.size()));
 
     mrb_gc_arena_restore(mrb, ai);
   }
diff --git a/src/shrpx_mruby_module_env.cc b/src/shrpx_mruby_module_env.cc
index 5ebd9c0..9b63c51 100644
--- a/src/shrpx_mruby_module_env.cc
+++ b/src/shrpx_mruby_module_env.cc
@@ -90,7 +90,7 @@ mrb_value env_get_remote_addr(mrb_state *mrb, mrb_value self) {
 
   auto &ipaddr = handler->get_ipaddr();
 
-  return mrb_str_new(mrb, ipaddr.c_str(), ipaddr.size());
+  return mrb_str_new(mrb, ipaddr.data(), ipaddr.size());
 }
 } // namespace
 
@@ -114,7 +114,7 @@ mrb_value env_get_server_addr(mrb_state *mrb, mrb_value self) {
   auto handler = upstream->get_client_handler();
   auto faddr = handler->get_upstream_addr();
 
-  return mrb_str_new(mrb, faddr->host.c_str(), faddr->host.size());
+  return mrb_str_new(mrb, faddr->host.data(), faddr->host.size());
 }
 } // namespace
 
@@ -137,7 +137,7 @@ mrb_value env_get_tls_sni(mrb_state *mrb, mrb_value self) {
   auto handler = upstream->get_client_handler();
   auto sni = handler->get_tls_sni();
 
-  return mrb_str_new(mrb, sni.c_str(), sni.size());
+  return mrb_str_new(mrb, sni.data(), sni.size());
 }
 } // namespace
 
@@ -172,11 +172,10 @@ mrb_value env_get_tls_client_fingerprint_md(mrb_state *mrb, const EVP_MD *md) {
     mrb_raise(mrb, E_RUNTIME_ERROR, "could not compute client fingerprint");
   }
 
-  // TODO Use template version of format_hex
   auto &balloc = downstream->get_block_allocator();
   auto f = util::format_hex(balloc,
-                            StringRef{std::begin(buf), std::begin(buf) + slen});
-  return mrb_str_new(mrb, f.c_str(), f.size());
+                            std::span{buf.data(), static_cast<size_t>(slen)});
+  return mrb_str_new(mrb, f.data(), f.size());
 }
 } // namespace
 
@@ -219,7 +218,7 @@ mrb_value env_get_tls_client_subject_name(mrb_state *mrb, mrb_value self) {
 #if !OPENSSL_3_0_0_API
   X509_free(x);
 #endif // !OPENSSL_3_0_0_API
-  return mrb_str_new(mrb, name.c_str(), name.size());
+  return mrb_str_new(mrb, name.data(), name.size());
 }
 } // namespace
 
@@ -249,7 +248,7 @@ mrb_value env_get_tls_client_issuer_name(mrb_state *mrb, mrb_value self) {
 #if !OPENSSL_3_0_0_API
   X509_free(x);
 #endif // !OPENSSL_3_0_0_API
-  return mrb_str_new(mrb, name.c_str(), name.size());
+  return mrb_str_new(mrb, name.data(), name.size());
 }
 } // namespace
 
@@ -279,7 +278,7 @@ mrb_value env_get_tls_client_serial(mrb_state *mrb, mrb_value self) {
 #if !OPENSSL_3_0_0_API
   X509_free(x);
 #endif // !OPENSSL_3_0_0_API
-  return mrb_str_new(mrb, sn.c_str(), sn.size());
+  return mrb_str_new(mrb, sn.data(), sn.size());
 }
 } // namespace
 
@@ -403,10 +402,9 @@ mrb_value env_get_tls_session_id(mrb_state *mrb, mrb_value self) {
   unsigned int session_id_length = 0;
   auto session_id = SSL_SESSION_get_id(session, &session_id_length);
 
-  // TODO Use template version of util::format_hex.
   auto &balloc = downstream->get_block_allocator();
-  auto id = util::format_hex(balloc, StringRef{session_id, session_id_length});
-  return mrb_str_new(mrb, id.c_str(), id.size());
+  auto id = util::format_hex(balloc, std::span{session_id, session_id_length});
+  return mrb_str_new(mrb, id.data(), id.size());
 }
 } // namespace
 
@@ -433,7 +431,7 @@ mrb_value env_get_alpn(mrb_state *mrb, mrb_value self) {
   auto upstream = downstream->get_upstream();
   auto handler = upstream->get_client_handler();
   auto alpn = handler->get_alpn();
-  return mrb_str_new(mrb, alpn.c_str(), alpn.size());
+  return mrb_str_new(mrb, alpn.data(), alpn.size());
 }
 } // namespace
 
diff --git a/src/shrpx_mruby_module_request.cc b/src/shrpx_mruby_module_request.cc
index 1ed3aa9..84b39fa 100644
--- a/src/shrpx_mruby_module_request.cc
+++ b/src/shrpx_mruby_module_request.cc
@@ -71,7 +71,7 @@ mrb_value request_get_method(mrb_state *mrb, mrb_value self) {
   const auto &req = downstream->request();
   auto method = http2::to_method_string(req.method);
 
-  return mrb_str_new(mrb, method.c_str(), method.size());
+  return mrb_str_new(mrb, method.data(), method.size());
 }
 } // namespace
 
@@ -90,7 +90,7 @@ mrb_value request_set_method(mrb_state *mrb, mrb_value self) {
     mrb_raise(mrb, E_RUNTIME_ERROR, "method must not be empty string");
   }
   auto token =
-      http2::lookup_method_token(reinterpret_cast<const uint8_t *>(method), n);
+      http2::lookup_method_token(StringRef{method, static_cast<size_t>(n)});
   if (token == -1) {
     mrb_raise(mrb, E_RUNTIME_ERROR, "method not supported");
   }
@@ -107,7 +107,7 @@ mrb_value request_get_authority(mrb_state *mrb, mrb_value self) {
   auto downstream = data->downstream;
   const auto &req = downstream->request();
 
-  return mrb_str_new(mrb, req.authority.c_str(), req.authority.size());
+  return mrb_str_new(mrb, req.authority.data(), req.authority.size());
 }
 } // namespace
 
@@ -141,7 +141,7 @@ mrb_value request_get_scheme(mrb_state *mrb, mrb_value self) {
   auto downstream = data->downstream;
   const auto &req = downstream->request();
 
-  return mrb_str_new(mrb, req.scheme.c_str(), req.scheme.size());
+  return mrb_str_new(mrb, req.scheme.data(), req.scheme.size());
 }
 } // namespace
 
@@ -175,7 +175,7 @@ mrb_value request_get_path(mrb_state *mrb, mrb_value self) {
   auto downstream = data->downstream;
   const auto &req = downstream->request();
 
-  return mrb_str_new(mrb, req.path.c_str(), req.path.size());
+  return mrb_str_new(mrb, req.path.data(), req.path.size());
 }
 } // namespace
 
@@ -235,7 +235,7 @@ mrb_value request_mod_header(mrb_state *mrb, mrb_value self, bool repl) {
 
   mrb_gc_arena_restore(mrb, ai);
 
-  auto token = http2::lookup_token(keyref.byte(), keyref.size());
+  auto token = http2::lookup_token(keyref);
 
   if (repl) {
     size_t p = 0;
diff --git a/src/shrpx_mruby_module_response.cc b/src/shrpx_mruby_module_response.cc
index 1de1d5f..5d02d83 100644
--- a/src/shrpx_mruby_module_response.cc
+++ b/src/shrpx_mruby_module_response.cc
@@ -127,7 +127,7 @@ mrb_value response_mod_header(mrb_state *mrb, mrb_value self, bool repl) {
 
   mrb_gc_arena_restore(mrb, ai);
 
-  auto token = http2::lookup_token(keyref.byte(), keyref.size());
+  auto token = http2::lookup_token(keyref);
 
   if (repl) {
     size_t p = 0;
@@ -245,8 +245,8 @@ mrb_value response_return(mrb_state *mrb, mrb_value self) {
     if (cl) {
       cl->value = content_length;
     } else {
-      resp.fs.add_header_token(StringRef::from_lit("content-length"),
-                               content_length, false, http2::HD_CONTENT_LENGTH);
+      resp.fs.add_header_token("content-length"_sr, content_length, false,
+                               http2::HD_CONTENT_LENGTH);
     }
 
     resp.fs.content_length = vallen;
@@ -256,7 +256,7 @@ mrb_value response_return(mrb_state *mrb, mrb_value self) {
   if (!date) {
     auto lgconf = log_config();
     lgconf->update_tstamp(std::chrono::system_clock::now());
-    resp.fs.add_header_token(StringRef::from_lit("date"),
+    resp.fs.add_header_token("date"_sr,
                              make_string_ref(balloc, lgconf->tstamp->time_http),
                              false, http2::HD_DATE);
   }
@@ -319,7 +319,7 @@ mrb_value response_send_info(mrb_state *mrb, mrb_value self) {
 
     mrb_gc_arena_restore(mrb, ai);
 
-    auto token = http2::lookup_token(keyref.byte(), keyref.size());
+    auto token = http2::lookup_token(keyref);
 
     if (mrb_array_p(values)) {
       auto n = RARRAY_LEN(values);
diff --git a/src/shrpx_quic.cc b/src/shrpx_quic.cc
index c52eee4..1ffd217 100644
--- a/src/shrpx_quic.cc
+++ b/src/shrpx_quic.cc
@@ -58,8 +58,10 @@ ngtcp2_tstamp quic_timestamp() {
 int quic_send_packet(const UpstreamAddr *faddr, const sockaddr *remote_sa,
                      size_t remote_salen, const sockaddr *local_sa,
                      size_t local_salen, const ngtcp2_pkt_info &pi,
-                     const uint8_t *data, size_t datalen, size_t gso_size) {
-  iovec msg_iov = {const_cast<uint8_t *>(data), datalen};
+                     std::span<const uint8_t> data, size_t gso_size) {
+  assert(gso_size);
+
+  iovec msg_iov = {const_cast<uint8_t *>(data.data()), data.size()};
   msghdr msg{};
   msg.msg_name = const_cast<sockaddr *>(remote_sa);
   msg.msg_namelen = remote_salen;
@@ -113,7 +115,7 @@ int quic_send_packet(const UpstreamAddr *faddr, const sockaddr *remote_sa,
   }
 
 #ifdef UDP_SEGMENT
-  if (gso_size && datalen > gso_size) {
+  if (data.size() > gso_size) {
     controllen += CMSG_SPACE(sizeof(uint16_t));
     cm = CMSG_NXTHDR(&msg, cm);
     cm->cmsg_level = SOL_UDP;
@@ -170,6 +172,8 @@ int quic_send_packet(const UpstreamAddr *faddr, const sockaddr *remote_sa,
               << " bytes";
   }
 
+  assert(static_cast<size_t>(nwrite) == data.size());
+
   return 0;
 }
 
@@ -267,87 +271,90 @@ int generate_quic_stateless_reset_token(uint8_t *token, const ngtcp2_cid &cid,
   return 0;
 }
 
-int generate_retry_token(uint8_t *token, size_t &tokenlen, uint32_t version,
-                         const sockaddr *sa, socklen_t salen,
-                         const ngtcp2_cid &retry_scid, const ngtcp2_cid &odcid,
-                         const uint8_t *secret, size_t secretlen) {
+std::optional<std::span<const uint8_t>>
+generate_retry_token(std::span<uint8_t> token, uint32_t version,
+                     const sockaddr *sa, socklen_t salen,
+                     const ngtcp2_cid &retry_scid, const ngtcp2_cid &odcid,
+                     std::span<const uint8_t> secret) {
   auto t = std::chrono::duration_cast<std::chrono::nanoseconds>(
                std::chrono::system_clock::now().time_since_epoch())
                .count();
 
-  auto stokenlen = ngtcp2_crypto_generate_retry_token(
-      token, secret, secretlen, version, sa, salen, &retry_scid, &odcid, t);
-  if (stokenlen < 0) {
-    return -1;
+  auto tokenlen = ngtcp2_crypto_generate_retry_token(
+      token.data(), secret.data(), secret.size(), version, sa, salen,
+      &retry_scid, &odcid, t);
+  if (tokenlen < 0) {
+    return {};
   }
 
-  tokenlen = stokenlen;
-
-  return 0;
+  return {{std::begin(token), static_cast<size_t>(tokenlen)}};
 }
 
-int verify_retry_token(ngtcp2_cid &odcid, const uint8_t *token, size_t tokenlen,
+int verify_retry_token(ngtcp2_cid &odcid, std::span<const uint8_t> token,
                        uint32_t version, const ngtcp2_cid &dcid,
                        const sockaddr *sa, socklen_t salen,
-                       const uint8_t *secret, size_t secretlen) {
-
+                       std::span<const uint8_t> secret) {
   auto t = std::chrono::duration_cast<std::chrono::nanoseconds>(
                std::chrono::system_clock::now().time_since_epoch())
                .count();
 
-  if (ngtcp2_crypto_verify_retry_token(&odcid, token, tokenlen, secret,
-                                       secretlen, version, sa, salen, &dcid,
-                                       10 * NGTCP2_SECONDS, t) != 0) {
+  if (ngtcp2_crypto_verify_retry_token(
+          &odcid, token.data(), token.size(), secret.data(), secret.size(),
+          version, sa, salen, &dcid, 10 * NGTCP2_SECONDS, t) != 0) {
     return -1;
   }
 
   return 0;
 }
 
-int generate_token(uint8_t *token, size_t &tokenlen, const sockaddr *sa,
-                   size_t salen, const uint8_t *secret, size_t secretlen) {
+std::optional<std::span<const uint8_t>>
+generate_token(std::span<uint8_t> token, const sockaddr *sa, size_t salen,
+               std::span<const uint8_t> secret, uint8_t km_id) {
   auto t = std::chrono::duration_cast<std::chrono::nanoseconds>(
                std::chrono::system_clock::now().time_since_epoch())
                .count();
 
-  auto stokenlen = ngtcp2_crypto_generate_regular_token(
-      token, secret, secretlen, sa, salen, t);
-  if (stokenlen < 0) {
-    return -1;
+  auto tokenlen = ngtcp2_crypto_generate_regular_token(
+      token.data(), secret.data(), secret.size(), sa, salen, t);
+  if (tokenlen < 0) {
+    return {};
   }
 
-  tokenlen = stokenlen;
+  token[tokenlen++] = km_id;
 
-  return 0;
+  return {{std::begin(token), static_cast<size_t>(tokenlen)}};
 }
 
-int verify_token(const uint8_t *token, size_t tokenlen, const sockaddr *sa,
-                 socklen_t salen, const uint8_t *secret, size_t secretlen) {
+int verify_token(std::span<const uint8_t> token, const sockaddr *sa,
+                 socklen_t salen, std::span<const uint8_t> secret) {
+  if (token.empty()) {
+    return -1;
+  }
+
   auto t = std::chrono::duration_cast<std::chrono::nanoseconds>(
                std::chrono::system_clock::now().time_since_epoch())
                .count();
 
-  if (ngtcp2_crypto_verify_regular_token(token, tokenlen, secret, secretlen, sa,
-                                         salen, 3600 * NGTCP2_SECONDS,
-                                         t) != 0) {
+  if (ngtcp2_crypto_verify_regular_token(
+          token.data(), token.size() - 1, secret.data(), secret.size(), sa,
+          salen, 3600 * NGTCP2_SECONDS, t) != 0) {
     return -1;
   }
 
   return 0;
 }
 
-int generate_quic_connection_id_encryption_key(uint8_t *key, size_t keylen,
-                                               const uint8_t *secret,
-                                               size_t secretlen,
-                                               const uint8_t *salt,
-                                               size_t saltlen) {
+int generate_quic_connection_id_encryption_key(std::span<uint8_t> key,
+                                               std::span<const uint8_t> secret,
+                                               std::span<const uint8_t> salt) {
   constexpr uint8_t info[] = "connection id encryption key";
   ngtcp2_crypto_md sha256;
   ngtcp2_crypto_md_init(
       &sha256, reinterpret_cast<void *>(const_cast<EVP_MD *>(EVP_sha256())));
 
-  if (ngtcp2_crypto_hkdf(key, keylen, &sha256, secret, secretlen, salt, saltlen,
-                         info, str_size(info)) != 0) {
+  if (ngtcp2_crypto_hkdf(key.data(), key.size(), &sha256, secret.data(),
+                         secret.size(), salt.data(), salt.size(), info,
+                         str_size(info)) != 0) {
     return -1;
   }
 
diff --git a/src/shrpx_quic.h b/src/shrpx_quic.h
index dae6e31..bc7f729 100644
--- a/src/shrpx_quic.h
+++ b/src/shrpx_quic.h
@@ -30,6 +30,8 @@
 #include <stdint.h>
 
 #include <functional>
+#include <optional>
+#include <span>
 
 #include <openssl/evp.h>
 
@@ -115,7 +117,7 @@ ngtcp2_tstamp quic_timestamp();
 int quic_send_packet(const UpstreamAddr *faddr, const sockaddr *remote_sa,
                      size_t remote_salen, const sockaddr *local_sa,
                      size_t local_salen, const ngtcp2_pkt_info &pi,
-                     const uint8_t *data, size_t datalen, size_t gso_size);
+                     std::span<const uint8_t> data, size_t gso_size);
 
 int generate_quic_retry_connection_id(ngtcp2_cid &cid, uint32_t server_id,
                                       uint8_t km_id, EVP_CIPHER_CTX *ctx);
@@ -138,27 +140,27 @@ int generate_quic_stateless_reset_token(uint8_t *token, const ngtcp2_cid &cid,
                                         const uint8_t *secret,
                                         size_t secretlen);
 
-int generate_retry_token(uint8_t *token, size_t &tokenlen, uint32_t version,
-                         const sockaddr *sa, socklen_t salen,
-                         const ngtcp2_cid &retry_scid, const ngtcp2_cid &odcid,
-                         const uint8_t *secret, size_t secretlen);
+std::optional<std::span<const uint8_t>>
+generate_retry_token(std::span<uint8_t> token, uint32_t version,
+                     const sockaddr *sa, socklen_t salen,
+                     const ngtcp2_cid &retry_scid, const ngtcp2_cid &odcid,
+                     std::span<const uint8_t> secret);
 
-int verify_retry_token(ngtcp2_cid &odcid, const uint8_t *token, size_t tokenlen,
+int verify_retry_token(ngtcp2_cid &odcid, std::span<const uint8_t> token,
                        uint32_t version, const ngtcp2_cid &dcid,
                        const sockaddr *sa, socklen_t salen,
-                       const uint8_t *secret, size_t secretlen);
+                       std::span<const uint8_t> secret);
 
-int generate_token(uint8_t *token, size_t &tokenlen, const sockaddr *sa,
-                   size_t salen, const uint8_t *secret, size_t secretlen);
+std::optional<std::span<const uint8_t>>
+generate_token(std::span<uint8_t> token, const sockaddr *sa, size_t salen,
+               std::span<const uint8_t> secret, uint8_t km_id);
 
-int verify_token(const uint8_t *token, size_t tokenlen, const sockaddr *sa,
-                 socklen_t salen, const uint8_t *secret, size_t secretlen);
+int verify_token(std::span<const uint8_t> token, const sockaddr *sa,
+                 socklen_t salen, std::span<const uint8_t> secret);
 
-int generate_quic_connection_id_encryption_key(uint8_t *key, size_t keylen,
-                                               const uint8_t *secret,
-                                               size_t secretlen,
-                                               const uint8_t *salt,
-                                               size_t saltlen);
+int generate_quic_connection_id_encryption_key(std::span<uint8_t> key,
+                                               std::span<const uint8_t> secret,
+                                               std::span<const uint8_t> salt);
 
 const QUICKeyingMaterial *
 select_quic_keying_material(const QUICKeyingMaterials &qkms, uint8_t km_id);
diff --git a/src/shrpx_quic_connection_handler.cc b/src/shrpx_quic_connection_handler.cc
index b810aa6..f10cc83 100644
--- a/src/shrpx_quic_connection_handler.cc
+++ b/src/shrpx_quic_connection_handler.cc
@@ -63,17 +63,18 @@ int QUICConnectionHandler::handle_packet(const UpstreamAddr *faddr,
                                          const Address &remote_addr,
                                          const Address &local_addr,
                                          const ngtcp2_pkt_info &pi,
-                                         const uint8_t *data, size_t datalen) {
+                                         std::span<const uint8_t> data) {
   int rv;
   ngtcp2_version_cid vc;
 
-  rv = ngtcp2_pkt_decode_version_cid(&vc, data, datalen, SHRPX_QUIC_SCIDLEN);
+  rv = ngtcp2_pkt_decode_version_cid(&vc, data.data(), data.size(),
+                                     SHRPX_QUIC_SCIDLEN);
   switch (rv) {
   case 0:
     break;
   case NGTCP2_ERR_VERSION_NEGOTIATION:
-    send_version_negotiation(faddr, vc.version, vc.dcid, vc.dcidlen, vc.scid,
-                             vc.scidlen, remote_addr, local_addr);
+    send_version_negotiation(faddr, vc.version, {vc.dcid, vc.dcidlen},
+                             {vc.scid, vc.scidlen}, remote_addr, local_addr);
 
     return 0;
   default:
@@ -97,7 +98,7 @@ int QUICConnectionHandler::handle_packet(const UpstreamAddr *faddr,
     if (cwit != std::end(close_waits_)) {
       auto cw = (*cwit).second;
 
-      cw->handle_packet(faddr, remote_addr, local_addr, pi, data, datalen);
+      cw->handle_packet(faddr, remote_addr, local_addr, pi, data);
 
       return 0;
     }
@@ -114,7 +115,7 @@ int QUICConnectionHandler::handle_packet(const UpstreamAddr *faddr,
         if (cwit != std::end(close_waits_)) {
           auto cw = (*cwit).second;
 
-          cw->handle_packet(faddr, remote_addr, local_addr, pi, data, datalen);
+          cw->handle_packet(faddr, remote_addr, local_addr, pi, data);
 
           return 0;
         }
@@ -145,7 +146,7 @@ int QUICConnectionHandler::handle_packet(const UpstreamAddr *faddr,
                 decrypted_dcid.worker);
         if (quic_lwp) {
           if (conn_handler->forward_quic_packet_to_lingering_worker_process(
-                  quic_lwp, remote_addr, local_addr, pi, data, datalen) == 0) {
+                  quic_lwp, remote_addr, local_addr, pi, data) == 0) {
             return 0;
           }
 
@@ -169,11 +170,10 @@ int QUICConnectionHandler::handle_packet(const UpstreamAddr *faddr,
 
     ngtcp2_pkt_hd hd;
     ngtcp2_cid odcid, *podcid = nullptr;
-    const uint8_t *token = nullptr;
-    size_t tokenlen = 0;
+    std::span<const uint8_t> token;
     ngtcp2_token_type token_type = NGTCP2_TOKEN_TYPE_UNKNOWN;
 
-    switch (ngtcp2_accept(&hd, data, datalen)) {
+    switch (ngtcp2_accept(&hd, data.data(), data.size())) {
     case 0: {
       // If we get Initial and it has the Worker ID of this worker, it
       // is likely that client is intentionally use the prefix.  Just
@@ -197,14 +197,15 @@ int QUICConnectionHandler::handle_packet(const UpstreamAddr *faddr,
       if (worker_->get_graceful_shutdown()) {
         send_connection_close(faddr, hd.version, hd.dcid, hd.scid, remote_addr,
                               local_addr, NGTCP2_CONNECTION_REFUSED,
-                              datalen * 3);
+                              data.size() * 3);
         return 0;
       }
 
       if (hd.tokenlen == 0) {
         if (quicconf.upstream.require_token) {
-          send_retry(faddr, vc.version, vc.dcid, vc.dcidlen, vc.scid,
-                     vc.scidlen, remote_addr, local_addr, datalen * 3);
+          send_retry(faddr, vc.version, {vc.dcid, vc.dcidlen},
+                     {vc.scid, vc.scidlen}, remote_addr, local_addr,
+                     data.size() * 3);
 
           return 0;
         }
@@ -223,9 +224,9 @@ int QUICConnectionHandler::handle_packet(const UpstreamAddr *faddr,
         auto qkm = select_quic_keying_material(
             *qkms.get(), vc.dcid[0] & SHRPX_QUIC_DCID_KM_ID_MASK);
 
-        if (verify_retry_token(odcid, hd.token, hd.tokenlen, hd.version,
+        if (verify_retry_token(odcid, {hd.token, hd.tokenlen}, hd.version,
                                hd.dcid, &remote_addr.su.sa, remote_addr.len,
-                               qkm->secret.data(), qkm->secret.size()) != 0) {
+                               qkm->secret) != 0) {
           if (LOG_ENABLED(INFO)) {
             LOG(INFO) << "Failed to validate Retry token from remote="
                       << util::to_numeric_addr(&remote_addr);
@@ -235,7 +236,7 @@ int QUICConnectionHandler::handle_packet(const UpstreamAddr *faddr,
           // with INVALID_TOKEN.
           send_connection_close(faddr, hd.version, hd.dcid, hd.scid,
                                 remote_addr, local_addr, NGTCP2_INVALID_TOKEN,
-                                datalen * 3);
+                                data.size() * 3);
           return 0;
         }
 
@@ -245,8 +246,7 @@ int QUICConnectionHandler::handle_packet(const UpstreamAddr *faddr,
         }
 
         podcid = &odcid;
-        token = hd.token;
-        tokenlen = hd.tokenlen;
+        token = {hd.token, hd.tokenlen};
         token_type = NGTCP2_TOKEN_TYPE_RETRY;
 
         break;
@@ -265,8 +265,9 @@ int QUICConnectionHandler::handle_packet(const UpstreamAddr *faddr,
           }
 
           if (quicconf.upstream.require_token) {
-            send_retry(faddr, vc.version, vc.dcid, vc.dcidlen, vc.scid,
-                       vc.scidlen, remote_addr, local_addr, datalen * 3);
+            send_retry(faddr, vc.version, {vc.dcid, vc.dcidlen},
+                       {vc.scid, vc.scidlen}, remote_addr, local_addr,
+                       data.size() * 3);
 
             return 0;
           }
@@ -277,17 +278,17 @@ int QUICConnectionHandler::handle_packet(const UpstreamAddr *faddr,
         auto qkm = select_quic_keying_material(
             *qkms.get(), hd.token[NGTCP2_CRYPTO_MAX_REGULAR_TOKENLEN]);
 
-        if (verify_token(hd.token, hd.tokenlen - 1, &remote_addr.su.sa,
-                         remote_addr.len, qkm->secret.data(),
-                         qkm->secret.size()) != 0) {
+        if (verify_token({hd.token, hd.tokenlen}, &remote_addr.su.sa,
+                         remote_addr.len, qkm->secret) != 0) {
           if (LOG_ENABLED(INFO)) {
             LOG(INFO) << "Failed to validate token from remote="
                       << util::to_numeric_addr(&remote_addr);
           }
 
           if (quicconf.upstream.require_token) {
-            send_retry(faddr, vc.version, vc.dcid, vc.dcidlen, vc.scid,
-                       vc.scidlen, remote_addr, local_addr, datalen * 3);
+            send_retry(faddr, vc.version, {vc.dcid, vc.dcidlen},
+                       {vc.scid, vc.scidlen}, remote_addr, local_addr,
+                       data.size() * 3);
 
             return 0;
           }
@@ -300,16 +301,16 @@ int QUICConnectionHandler::handle_packet(const UpstreamAddr *faddr,
                     << util::to_numeric_addr(&remote_addr);
         }
 
-        token = hd.token;
-        tokenlen = hd.tokenlen;
+        token = {hd.token, hd.tokenlen};
         token_type = NGTCP2_TOKEN_TYPE_NEW_TOKEN;
 
         break;
       }
       default:
         if (quicconf.upstream.require_token) {
-          send_retry(faddr, vc.version, vc.dcid, vc.dcidlen, vc.scid,
-                     vc.scidlen, remote_addr, local_addr, datalen * 3);
+          send_retry(faddr, vc.version, {vc.dcid, vc.dcidlen},
+                     {vc.scid, vc.scidlen}, remote_addr, local_addr,
+                     data.size() * 3);
 
           return 0;
         }
@@ -322,16 +323,15 @@ int QUICConnectionHandler::handle_packet(const UpstreamAddr *faddr,
     default:
       if (!(data[0] & 0x80) && vc.dcidlen == SHRPX_QUIC_SCIDLEN &&
           decrypted_dcid.worker != worker_->get_worker_id()) {
-        if (!config->single_thread &&
-            conn_handler->forward_quic_packet(faddr, remote_addr, local_addr,
-                                              pi, decrypted_dcid.worker, data,
-                                              datalen) == 0) {
+        if (!config->single_thread && conn_handler->forward_quic_packet(
+                                          faddr, remote_addr, local_addr, pi,
+                                          decrypted_dcid.worker, data) == 0) {
           return 0;
         }
 
-        if (datalen >= SHRPX_QUIC_SCIDLEN + 22) {
-          send_stateless_reset(faddr, datalen, vc.dcid, vc.dcidlen, remote_addr,
-                               local_addr);
+        if (data.size() >= SHRPX_QUIC_SCIDLEN + 22) {
+          send_stateless_reset(faddr, data.size(), {vc.dcid, vc.dcidlen},
+                               remote_addr, local_addr);
         }
       }
 
@@ -339,7 +339,7 @@ int QUICConnectionHandler::handle_packet(const UpstreamAddr *faddr,
     }
 
     handler = handle_new_connection(faddr, remote_addr, local_addr, hd, podcid,
-                                    token, tokenlen, token_type);
+                                    token, token_type);
     if (handler == nullptr) {
       return 0;
     }
@@ -347,8 +347,7 @@ int QUICConnectionHandler::handle_packet(const UpstreamAddr *faddr,
     handler = (*it).second;
   }
 
-  if (handler->read_quic(faddr, remote_addr, local_addr, pi, data, datalen) !=
-      0) {
+  if (handler->read_quic(faddr, remote_addr, local_addr, pi, data) != 0) {
     delete handler;
     return 0;
   }
@@ -361,7 +360,7 @@ int QUICConnectionHandler::handle_packet(const UpstreamAddr *faddr,
 ClientHandler *QUICConnectionHandler::handle_new_connection(
     const UpstreamAddr *faddr, const Address &remote_addr,
     const Address &local_addr, const ngtcp2_pkt_hd &hd, const ngtcp2_cid *odcid,
-    const uint8_t *token, size_t tokenlen, ngtcp2_token_type token_type) {
+    std::span<const uint8_t> token, ngtcp2_token_type token_type) {
   std::array<char, NI_MAXHOST> host;
   std::array<char, NI_MAXSERV> service;
   int rv;
@@ -412,7 +411,7 @@ ClientHandler *QUICConnectionHandler::handle_new_connection(
       StringRef{service.data()}, remote_addr.su.sa.sa_family, faddr);
 
   auto upstream = std::make_unique<Http3Upstream>(handler.get());
-  if (upstream->init(faddr, remote_addr, local_addr, hd, odcid, token, tokenlen,
+  if (upstream->init(faddr, remote_addr, local_addr, hd, odcid, token,
                      token_type) != 0) {
     return nullptr;
   }
@@ -450,8 +449,8 @@ uint32_t generate_reserved_version(const Address &addr, uint32_t version) {
 } // namespace
 
 int QUICConnectionHandler::send_retry(
-    const UpstreamAddr *faddr, uint32_t version, const uint8_t *ini_dcid,
-    size_t ini_dcidlen, const uint8_t *ini_scid, size_t ini_scidlen,
+    const UpstreamAddr *faddr, uint32_t version,
+    std::span<const uint8_t> ini_dcid, std::span<const uint8_t> ini_scid,
     const Address &remote_addr, const Address &local_addr, size_t max_pktlen) {
   std::array<char, NI_MAXHOST> host;
   std::array<char, NI_MAXSERV> port;
@@ -476,25 +475,25 @@ int QUICConnectionHandler::send_retry(
     return -1;
   }
 
-  std::array<uint8_t, NGTCP2_CRYPTO_MAX_RETRY_TOKENLEN> token;
-  size_t tokenlen;
-
   ngtcp2_cid idcid, iscid;
-  ngtcp2_cid_init(&idcid, ini_dcid, ini_dcidlen);
-  ngtcp2_cid_init(&iscid, ini_scid, ini_scidlen);
+  ngtcp2_cid_init(&idcid, ini_dcid.data(), ini_dcid.size());
+  ngtcp2_cid_init(&iscid, ini_scid.data(), ini_scid.size());
+
+  std::array<uint8_t, NGTCP2_CRYPTO_MAX_RETRY_TOKENLEN> tokenbuf;
 
-  if (generate_retry_token(token.data(), tokenlen, version, &remote_addr.su.sa,
-                           remote_addr.len, retry_scid, idcid,
-                           qkm.secret.data(), qkm.secret.size()) != 0) {
+  auto token =
+      generate_retry_token(tokenbuf, version, &remote_addr.su.sa,
+                           remote_addr.len, retry_scid, idcid, qkm.secret);
+  if (!token) {
     return -1;
   }
 
   std::vector<uint8_t> buf;
   buf.resize(std::min(max_pktlen, static_cast<size_t>(256)));
 
-  auto nwrite =
-      ngtcp2_crypto_write_retry(buf.data(), buf.size(), version, &iscid,
-                                &retry_scid, &idcid, token.data(), tokenlen);
+  auto nwrite = ngtcp2_crypto_write_retry(buf.data(), buf.size(), version,
+                                          &iscid, &retry_scid, &idcid,
+                                          token->data(), token->size());
   if (nwrite < 0) {
     LOG(ERROR) << "ngtcp2_crypto_write_retry: " << ngtcp2_strerror(nwrite);
     return -1;
@@ -503,8 +502,8 @@ int QUICConnectionHandler::send_retry(
   buf.resize(nwrite);
 
   quic_send_packet(faddr, &remote_addr.su.sa, remote_addr.len,
-                   &local_addr.su.sa, local_addr.len, ngtcp2_pkt_info{},
-                   buf.data(), buf.size(), 0);
+                   &local_addr.su.sa, local_addr.len, ngtcp2_pkt_info{}, buf,
+                   buf.size());
 
   if (generate_quic_hashed_connection_id(idcid, remote_addr, local_addr,
                                          idcid) != 0) {
@@ -528,13 +527,13 @@ int QUICConnectionHandler::send_retry(
 }
 
 int QUICConnectionHandler::send_version_negotiation(
-    const UpstreamAddr *faddr, uint32_t version, const uint8_t *ini_dcid,
-    size_t ini_dcidlen, const uint8_t *ini_scid, size_t ini_scidlen,
+    const UpstreamAddr *faddr, uint32_t version,
+    std::span<const uint8_t> ini_dcid, std::span<const uint8_t> ini_scid,
     const Address &remote_addr, const Address &local_addr) {
-  std::array<uint32_t, 2> sv{
+  auto sv = std::to_array({
       generate_reserved_version(remote_addr, version),
       NGTCP2_PROTO_VER_V1,
-  };
+  });
 
   std::array<uint8_t, NGTCP2_MAX_UDP_PAYLOAD_SIZE> buf;
 
@@ -542,22 +541,25 @@ int QUICConnectionHandler::send_version_negotiation(
   util::random_bytes(&rand_byte, &rand_byte + 1, worker_->get_randgen());
 
   auto nwrite = ngtcp2_pkt_write_version_negotiation(
-      buf.data(), buf.size(), rand_byte, ini_scid, ini_scidlen, ini_dcid,
-      ini_dcidlen, sv.data(), sv.size());
+      buf.data(), buf.size(), rand_byte, ini_scid.data(), ini_scid.size(),
+      ini_dcid.data(), ini_dcid.size(), sv.data(), sv.size());
   if (nwrite < 0) {
     LOG(ERROR) << "ngtcp2_pkt_write_version_negotiation: "
                << ngtcp2_strerror(nwrite);
     return -1;
   }
 
+  auto pkt = std::span{std::begin(buf), static_cast<size_t>(nwrite)};
   return quic_send_packet(faddr, &remote_addr.su.sa, remote_addr.len,
                           &local_addr.su.sa, local_addr.len, ngtcp2_pkt_info{},
-                          buf.data(), nwrite, 0);
+                          pkt, pkt.size());
 }
 
-int QUICConnectionHandler::send_stateless_reset(
-    const UpstreamAddr *faddr, size_t pktlen, const uint8_t *dcid,
-    size_t dcidlen, const Address &remote_addr, const Address &local_addr) {
+int QUICConnectionHandler::send_stateless_reset(const UpstreamAddr *faddr,
+                                                size_t pktlen,
+                                                std::span<const uint8_t> dcid,
+                                                const Address &remote_addr,
+                                                const Address &local_addr) {
   if (stateless_reset_bucket_ == 0) {
     if (LOG_ENABLED(INFO)) {
       LOG(INFO) << "Stateless Reset bucket has been depleted";
@@ -572,25 +574,24 @@ int QUICConnectionHandler::send_stateless_reset(
     ev_timer_again(worker_->get_loop(), &stateless_reset_bucket_regen_timer_);
   }
 
-  int rv;
   std::array<uint8_t, NGTCP2_STATELESS_RESET_TOKENLEN> token;
   ngtcp2_cid cid;
 
-  ngtcp2_cid_init(&cid, dcid, dcidlen);
+  ngtcp2_cid_init(&cid, dcid.data(), dcid.size());
 
   auto conn_handler = worker_->get_connection_handler();
   auto &qkms = conn_handler->get_quic_keying_materials();
   auto &qkm = qkms->keying_materials.front();
 
-  rv = generate_quic_stateless_reset_token(token.data(), cid, qkm.secret.data(),
-                                           qkm.secret.size());
-  if (rv != 0) {
+  if (auto rv = generate_quic_stateless_reset_token(
+          token.data(), cid, qkm.secret.data(), qkm.secret.size());
+      rv != 0) {
     return -1;
   }
 
   // SCID + minimum expansion - NGTCP2_STATELESS_RESET_TOKENLEN
   constexpr size_t max_rand_byteslen =
-      SHRPX_QUIC_SCIDLEN + 22 - NGTCP2_STATELESS_RESET_TOKENLEN;
+      NGTCP2_MAX_CIDLEN + 22 - NGTCP2_STATELESS_RESET_TOKENLEN;
 
   size_t rand_byteslen;
 
@@ -621,12 +622,13 @@ int QUICConnectionHandler::send_stateless_reset(
   if (LOG_ENABLED(INFO)) {
     LOG(INFO) << "Send stateless_reset to remote="
               << util::to_numeric_addr(&remote_addr)
-              << " dcid=" << util::format_hex(dcid, dcidlen);
+              << " dcid=" << util::format_hex(dcid);
   }
 
+  auto pkt = std::span{std::begin(buf), static_cast<size_t>(nwrite)};
   return quic_send_packet(faddr, &remote_addr.su.sa, remote_addr.len,
                           &local_addr.su.sa, local_addr.len, ngtcp2_pkt_info{},
-                          buf.data(), nwrite, 0);
+                          pkt, pkt.size());
 }
 
 int QUICConnectionHandler::send_connection_close(
@@ -649,13 +651,16 @@ int QUICConnectionHandler::send_connection_close(
     LOG(INFO) << "Send Initial CONNECTION_CLOSE with error_code=" << log::hex
               << error_code << log::dec
               << " to remote=" << util::to_numeric_addr(&remote_addr)
-              << " dcid=" << util::format_hex(ini_scid.data, ini_scid.datalen)
-              << " scid=" << util::format_hex(ini_dcid.data, ini_dcid.datalen);
+              << " dcid="
+              << util::format_hex(std::span{ini_scid.data, ini_scid.datalen})
+              << " scid="
+              << util::format_hex(std::span{ini_dcid.data, ini_dcid.datalen});
   }
 
+  auto pkt = std::span{std::begin(buf), static_cast<size_t>(nwrite)};
   return quic_send_packet(faddr, &remote_addr.su.sa, remote_addr.len,
                           &local_addr.su.sa, local_addr.len, ngtcp2_pkt_info{},
-                          buf.data(), nwrite, 0);
+                          pkt, pkt.size());
 }
 
 void QUICConnectionHandler::add_connection_id(const ngtcp2_cid &cid,
@@ -735,23 +740,24 @@ CloseWait::~CloseWait() {
 int CloseWait::handle_packet(const UpstreamAddr *faddr,
                              const Address &remote_addr,
                              const Address &local_addr,
-                             const ngtcp2_pkt_info &pi, const uint8_t *data,
-                             size_t datalen) {
+                             const ngtcp2_pkt_info &pi,
+                             std::span<const uint8_t> data) {
   if (pkt.empty()) {
     return 0;
   }
 
   ++num_pkts_recv;
-  bytes_recv += datalen;
+  bytes_recv += data.size();
 
   if (bytes_sent + pkt.size() > 3 * bytes_recv ||
       next_pkts_recv > num_pkts_recv) {
     return 0;
   }
 
-  if (quic_send_packet(faddr, &remote_addr.su.sa, remote_addr.len,
-                       &local_addr.su.sa, local_addr.len, ngtcp2_pkt_info{},
-                       pkt.data(), pkt.size(), 0) != 0) {
+  auto rv = quic_send_packet(faddr, &remote_addr.su.sa, remote_addr.len,
+                             &local_addr.su.sa, local_addr.len,
+                             ngtcp2_pkt_info{}, pkt, pkt.size());
+  if (rv != 0) {
     return -1;
   }
 
diff --git a/src/shrpx_quic_connection_handler.h b/src/shrpx_quic_connection_handler.h
index 7f65370..374d84b 100644
--- a/src/shrpx_quic_connection_handler.h
+++ b/src/shrpx_quic_connection_handler.h
@@ -56,7 +56,7 @@ struct CloseWait {
 
   int handle_packet(const UpstreamAddr *faddr, const Address &remote_addr,
                     const Address &local_addr, const ngtcp2_pkt_info &pi,
-                    const uint8_t *data, size_t datalen);
+                    std::span<const uint8_t> data);
 
   Worker *worker;
   // Source Connection IDs of the connection.
@@ -83,28 +83,25 @@ public:
   ~QUICConnectionHandler();
   int handle_packet(const UpstreamAddr *faddr, const Address &remote_addr,
                     const Address &local_addr, const ngtcp2_pkt_info &pi,
-                    const uint8_t *data, size_t datalen);
+                    std::span<const uint8_t> data);
   // Send Retry packet.  |ini_dcid| is the destination Connection ID
-  // which appeared in Client Initial packet and its length is
-  // |dcidlen|.  |ini_scid| is the source Connection ID which appeared
-  // in Client Initial packet and its length is |scidlen|.
+  // which appeared in Client Initial packet.  |ini_scid| is the
+  // source Connection ID which appeared in Client Initial packet.
   int send_retry(const UpstreamAddr *faddr, uint32_t version,
-                 const uint8_t *ini_dcid, size_t ini_dcidlen,
-                 const uint8_t *ini_scid, size_t ini_scidlen,
-                 const Address &remote_addr, const Address &local_addr,
-                 size_t max_pktlen);
+                 std::span<const uint8_t> ini_dcid,
+                 std::span<const uint8_t> ini_scid, const Address &remote_addr,
+                 const Address &local_addr, size_t max_pktlen);
   // Send Version Negotiation packet.  |ini_dcid| is the destination
-  // Connection ID which appeared in Client Initial packet and its
-  // length is |dcidlen|.  |ini_scid| is the source Connection ID
-  // which appeared in Client Initial packet and its length is
-  // |scidlen|.
+  // Connection ID which appeared in Client Initial packet.
+  // |ini_scid| is the source Connection ID which appeared in Client
+  // Initial packet.
   int send_version_negotiation(const UpstreamAddr *faddr, uint32_t version,
-                               const uint8_t *ini_dcid, size_t ini_dcidlen,
-                               const uint8_t *ini_scid, size_t ini_scidlen,
+                               std::span<const uint8_t> ini_dcid,
+                               std::span<const uint8_t> ini_scid,
                                const Address &remote_addr,
                                const Address &local_addr);
   int send_stateless_reset(const UpstreamAddr *faddr, size_t pktlen,
-                           const uint8_t *dcid, size_t dcidlen,
+                           std::span<const uint8_t> dcid,
                            const Address &remote_addr,
                            const Address &local_addr);
   // Send Initial CONNECTION_CLOSE.  |ini_dcid| is the destination
@@ -120,8 +117,8 @@ public:
   ClientHandler *
   handle_new_connection(const UpstreamAddr *faddr, const Address &remote_addr,
                         const Address &local_addr, const ngtcp2_pkt_hd &hd,
-                        const ngtcp2_cid *odcid, const uint8_t *token,
-                        size_t tokenlen, ngtcp2_token_type token_type);
+                        const ngtcp2_cid *odcid, std::span<const uint8_t> token,
+                        ngtcp2_token_type token_type);
   void add_connection_id(const ngtcp2_cid &cid, ClientHandler *handler);
   void remove_connection_id(const ngtcp2_cid &cid);
 
diff --git a/src/shrpx_quic_listener.cc b/src/shrpx_quic_listener.cc
index 681f605..cf15e2f 100644
--- a/src/shrpx_quic_listener.cc
+++ b/src/shrpx_quic_listener.cc
@@ -106,10 +106,10 @@ void QUICListener::on_read() {
       gso_size = static_cast<size_t>(nread);
     }
 
-    auto data = buf.data();
+    auto data = std::span{std::begin(buf), static_cast<size_t>(nread)};
 
     for (;;) {
-      auto datalen = std::min(static_cast<size_t>(nread), gso_size);
+      auto datalen = std::min(data.size(), gso_size);
 
       ++pktcnt;
 
@@ -131,14 +131,12 @@ void QUICListener::on_read() {
       remote_addr.len = msg.msg_namelen;
 
       quic_conn_handler->handle_packet(faddr_, remote_addr, local_addr, pi,
-                                       data, datalen);
+                                       {std::begin(data), datalen});
 
-      nread -= datalen;
-      if (nread == 0) {
+      data = data.subspan(datalen);
+      if (data.empty()) {
         break;
       }
-
-      data += datalen;
     }
   }
 }
diff --git a/src/shrpx_router.cc b/src/shrpx_router.cc
index d3565db..559b236 100644
--- a/src/shrpx_router.cc
+++ b/src/shrpx_router.cc
@@ -67,7 +67,7 @@ void Router::add_node(RNode *node, const char *pattern, size_t patlen,
                       ssize_t index, ssize_t wildcard_index) {
   auto pat = make_string_ref(balloc_, StringRef{pattern, patlen});
   auto new_node =
-      std::make_unique<RNode>(pat.c_str(), pat.size(), index, wildcard_index);
+      std::make_unique<RNode>(pat.data(), pat.size(), index, wildcard_index);
   add_next_node(node, std::move(new_node));
 }
 
@@ -85,7 +85,7 @@ size_t Router::add_route(const StringRef &pattern, size_t idx, bool wildcard) {
   for (;;) {
     auto next_node = find_next_node(node, pattern[i]);
     if (next_node == nullptr) {
-      add_node(node, pattern.c_str() + i, pattern.size() - i, index,
+      add_node(node, pattern.data() + i, pattern.size() - i, index,
                wildcard_index);
       return idx;
     }
@@ -93,7 +93,7 @@ size_t Router::add_route(const StringRef &pattern, size_t idx, bool wildcard) {
     node = next_node;
 
     auto slen = pattern.size() - i;
-    auto s = pattern.c_str() + i;
+    auto s = pattern.data() + i;
     auto n = std::min(node->len, slen);
     size_t j;
     for (j = 0; j < n && node->s[j] == s[j]; ++j)
@@ -151,7 +151,7 @@ size_t Router::add_route(const StringRef &pattern, size_t idx, bool wildcard) {
     i += j;
 
     assert(pattern.size() > i);
-    add_node(node, pattern.c_str() + i, pattern.size() - i, index,
+    add_node(node, pattern.data() + i, pattern.size() - i, index,
              wildcard_index);
 
     return idx;
diff --git a/src/shrpx_router_test.cc b/src/shrpx_router_test.cc
index a9625a0..0fc4a3a 100644
--- a/src/shrpx_router_test.cc
+++ b/src/shrpx_router_test.cc
@@ -51,16 +51,16 @@ struct Pattern {
 
 void test_shrpx_router_match(void) {
   auto patterns = std::vector<Pattern>{
-      {StringRef::from_lit("nghttp2.org/"), 0},
-      {StringRef::from_lit("nghttp2.org/alpha"), 1},
-      {StringRef::from_lit("nghttp2.org/alpha/"), 2},
-      {StringRef::from_lit("nghttp2.org/alpha/bravo/"), 3},
-      {StringRef::from_lit("www.nghttp2.org/alpha/"), 4},
-      {StringRef::from_lit("/alpha"), 5},
-      {StringRef::from_lit("example.com/alpha/"), 6},
-      {StringRef::from_lit("nghttp2.org/alpha/bravo2/"), 7},
-      {StringRef::from_lit("www2.nghttp2.org/alpha/"), 8},
-      {StringRef::from_lit("www2.nghttp2.org/alpha2/"), 9},
+      {"nghttp2.org/"_sr, 0},
+      {"nghttp2.org/alpha"_sr, 1},
+      {"nghttp2.org/alpha/"_sr, 2},
+      {"nghttp2.org/alpha/bravo/"_sr, 3},
+      {"www.nghttp2.org/alpha/"_sr, 4},
+      {"/alpha"_sr, 5},
+      {"example.com/alpha/"_sr, 6},
+      {"nghttp2.org/alpha/bravo2/"_sr, 7},
+      {"www2.nghttp2.org/alpha/"_sr, 8},
+      {"www2.nghttp2.org/alpha2/"_sr, 9},
   };
 
   Router router;
@@ -71,56 +71,49 @@ void test_shrpx_router_match(void) {
 
   ssize_t idx;
 
-  idx = router.match(StringRef::from_lit("nghttp2.org"),
-                     StringRef::from_lit("/"));
+  idx = router.match("nghttp2.org"_sr, "/"_sr);
 
   assert_ssize(0, ==, idx);
 
-  idx = router.match(StringRef::from_lit("nghttp2.org"),
-                     StringRef::from_lit("/alpha"));
+  idx = router.match("nghttp2.org"_sr, "/alpha"_sr);
 
   assert_ssize(1, ==, idx);
 
-  idx = router.match(StringRef::from_lit("nghttp2.org"),
-                     StringRef::from_lit("/alpha/"));
+  idx = router.match("nghttp2.org"_sr, "/alpha/"_sr);
 
   assert_ssize(2, ==, idx);
 
-  idx = router.match(StringRef::from_lit("nghttp2.org"),
-                     StringRef::from_lit("/alpha/charlie"));
+  idx = router.match("nghttp2.org"_sr, "/alpha/charlie"_sr);
 
   assert_ssize(2, ==, idx);
 
-  idx = router.match(StringRef::from_lit("nghttp2.org"),
-                     StringRef::from_lit("/alpha/bravo/"));
+  idx = router.match("nghttp2.org"_sr, "/alpha/bravo/"_sr);
 
   assert_ssize(3, ==, idx);
 
   // matches pattern when last '/' is missing in path
-  idx = router.match(StringRef::from_lit("nghttp2.org"),
-                     StringRef::from_lit("/alpha/bravo"));
+  idx = router.match("nghttp2.org"_sr, "/alpha/bravo"_sr);
 
   assert_ssize(3, ==, idx);
 
-  idx = router.match(StringRef::from_lit("www2.nghttp2.org"),
-                     StringRef::from_lit("/alpha"));
+  idx = router.match("www2.nghttp2.org"_sr, "/alpha"_sr);
 
   assert_ssize(8, ==, idx);
 
-  idx = router.match(StringRef{}, StringRef::from_lit("/alpha"));
+  idx = router.match(StringRef{}, "/alpha"_sr);
 
   assert_ssize(5, ==, idx);
 }
 
 void test_shrpx_router_match_wildcard(void) {
-  constexpr auto patterns = std::array<Pattern, 6>{{
-      {StringRef::from_lit("nghttp2.org/"), 0},
-      {StringRef::from_lit("nghttp2.org/"), 1, true},
-      {StringRef::from_lit("nghttp2.org/alpha/"), 2},
-      {StringRef::from_lit("nghttp2.org/alpha/"), 3, true},
-      {StringRef::from_lit("nghttp2.org/bravo"), 4},
-      {StringRef::from_lit("nghttp2.org/bravo"), 5, true},
-  }};
+  constexpr auto patterns = std::to_array<Pattern>({
+      {"nghttp2.org/"_sr, 0},
+      {"nghttp2.org/"_sr, 1, true},
+      {"nghttp2.org/alpha/"_sr, 2},
+      {"nghttp2.org/alpha/"_sr, 3, true},
+      {"nghttp2.org/bravo"_sr, 4},
+      {"nghttp2.org/bravo"_sr, 5, true},
+  });
 
   Router router;
 
@@ -128,49 +121,31 @@ void test_shrpx_router_match_wildcard(void) {
     router.add_route(p.pattern, p.idx, p.wildcard);
   }
 
-  assert_ssize(0, ==,
-               router.match(StringRef::from_lit("nghttp2.org"),
-                            StringRef::from_lit("/")));
+  assert_ssize(0, ==, router.match("nghttp2.org"_sr, "/"_sr));
 
-  assert_ssize(1, ==,
-               router.match(StringRef::from_lit("nghttp2.org"),
-                            StringRef::from_lit("/a")));
+  assert_ssize(1, ==, router.match("nghttp2.org"_sr, "/a"_sr));
 
-  assert_ssize(1, ==,
-               router.match(StringRef::from_lit("nghttp2.org"),
-                            StringRef::from_lit("/charlie")));
+  assert_ssize(1, ==, router.match("nghttp2.org"_sr, "/charlie"_sr));
 
-  assert_ssize(2, ==,
-               router.match(StringRef::from_lit("nghttp2.org"),
-                            StringRef::from_lit("/alpha")));
+  assert_ssize(2, ==, router.match("nghttp2.org"_sr, "/alpha"_sr));
 
-  assert_ssize(2, ==,
-               router.match(StringRef::from_lit("nghttp2.org"),
-                            StringRef::from_lit("/alpha/")));
+  assert_ssize(2, ==, router.match("nghttp2.org"_sr, "/alpha/"_sr));
 
-  assert_ssize(3, ==,
-               router.match(StringRef::from_lit("nghttp2.org"),
-                            StringRef::from_lit("/alpha/b")));
+  assert_ssize(3, ==, router.match("nghttp2.org"_sr, "/alpha/b"_sr));
 
-  assert_ssize(4, ==,
-               router.match(StringRef::from_lit("nghttp2.org"),
-                            StringRef::from_lit("/bravo")));
+  assert_ssize(4, ==, router.match("nghttp2.org"_sr, "/bravo"_sr));
 
-  assert_ssize(5, ==,
-               router.match(StringRef::from_lit("nghttp2.org"),
-                            StringRef::from_lit("/bravocharlie")));
+  assert_ssize(5, ==, router.match("nghttp2.org"_sr, "/bravocharlie"_sr));
 
-  assert_ssize(5, ==,
-               router.match(StringRef::from_lit("nghttp2.org"),
-                            StringRef::from_lit("/bravo/")));
+  assert_ssize(5, ==, router.match("nghttp2.org"_sr, "/bravo/"_sr));
 }
 
 void test_shrpx_router_match_prefix(void) {
   auto patterns = std::vector<Pattern>{
-      {StringRef::from_lit("gro.2ptthgn."), 0},
-      {StringRef::from_lit("gro.2ptthgn.www."), 1},
-      {StringRef::from_lit("gro.2ptthgn.gmi."), 2},
-      {StringRef::from_lit("gro.2ptthgn.gmi.ahpla."), 3},
+      {"gro.2ptthgn."_sr, 0},
+      {"gro.2ptthgn.www."_sr, 1},
+      {"gro.2ptthgn.gmi."_sr, 2},
+      {"gro.2ptthgn.gmi.ahpla."_sr, 3},
   };
 
   Router router;
@@ -185,19 +160,17 @@ void test_shrpx_router_match_prefix(void) {
 
   node = nullptr;
 
-  idx = router.match_prefix(&nread, &node,
-                            StringRef::from_lit("gro.2ptthgn.gmi.ahpla.ovarb"));
+  idx = router.match_prefix(&nread, &node, "gro.2ptthgn.gmi.ahpla.ovarb"_sr);
 
   assert_ssize(0, ==, idx);
   assert_size(12, ==, nread);
 
-  idx = router.match_prefix(&nread, &node,
-                            StringRef::from_lit("gmi.ahpla.ovarb"));
+  idx = router.match_prefix(&nread, &node, "gmi.ahpla.ovarb"_sr);
 
   assert_ssize(2, ==, idx);
   assert_size(4, ==, nread);
 
-  idx = router.match_prefix(&nread, &node, StringRef::from_lit("ahpla.ovarb"));
+  idx = router.match_prefix(&nread, &node, "ahpla.ovarb"_sr);
 
   assert_ssize(3, ==, idx);
   assert_ssize(6, ==, nread);
diff --git a/src/shrpx_signal.cc b/src/shrpx_signal.cc
index 63fcc07..cfc4fc1 100644
--- a/src/shrpx_signal.cc
+++ b/src/shrpx_signal.cc
@@ -110,13 +110,13 @@ int signal_set_handler(void (*handler)(int), Signals &&sigs) {
 } // namespace
 
 namespace {
-constexpr auto main_proc_ign_signals = std::array<int, 1>{SIGPIPE};
+constexpr auto main_proc_ign_signals = std::to_array({SIGPIPE});
 } // namespace
 
 namespace {
 constexpr auto worker_proc_ign_signals =
-    std::array<int, 5>{REOPEN_LOG_SIGNAL, EXEC_BINARY_SIGNAL,
-                       GRACEFUL_SHUTDOWN_SIGNAL, RELOAD_SIGNAL, SIGPIPE};
+    std::to_array({REOPEN_LOG_SIGNAL, EXEC_BINARY_SIGNAL,
+                   GRACEFUL_SHUTDOWN_SIGNAL, RELOAD_SIGNAL, SIGPIPE});
 } // namespace
 
 int shrpx_signal_set_main_proc_ign_handler() {
diff --git a/src/shrpx_tls.cc b/src/shrpx_tls.cc
index 10bbbf2..00cf1ca 100644
--- a/src/shrpx_tls.cc
+++ b/src/shrpx_tls.cc
@@ -157,7 +157,7 @@ int ssl_pem_passwd_cb(char *buf, int size, int rwflag, void *user_data) {
     return 0;
   }
   // Copy string including last '\0'.
-  memcpy(buf, config->tls.private_key_passwd.c_str(), len + 1);
+  memcpy(buf, config->tls.private_key_passwd.data(), len + 1);
   return len;
 }
 } // namespace
@@ -166,8 +166,7 @@ namespace {
 std::shared_ptr<std::vector<uint8_t>>
 get_ocsp_data(TLSContextData *tls_ctx_data) {
 #ifdef HAVE_ATOMIC_STD_SHARED_PTR
-  return std::atomic_load_explicit(&tls_ctx_data->ocsp_data,
-                                   std::memory_order_acquire);
+  return tls_ctx_data->ocsp_data.load(std::memory_order_acquire);
 #else  // !HAVE_ATOMIC_STD_SHARED_PTR
   std::lock_guard<std::mutex> g(tls_ctx_data->mu);
   return tls_ctx_data->ocsp_data;
@@ -214,7 +213,7 @@ int servername_callback(SSL *ssl, int *al, void *arg) {
     return SSL_TLSEXT_ERR_NOACK;
   }
 
-  std::array<uint8_t, NI_MAXHOST> buf;
+  std::array<char, NI_MAXHOST> buf;
 
   auto end_buf = std::copy_n(rawhost, len, std::begin(buf));
 
@@ -366,7 +365,7 @@ int ocsp_resp_cb(SSL *ssl, void *arg) {
 #endif // NGHTTP2_OPENSSL_IS_BORINGSSL
 
 constexpr auto MEMCACHED_SESSION_CACHE_KEY_PREFIX =
-    StringRef::from_lit("nghttpx:tls-session-cache:");
+    "nghttpx:tls-session-cache:"_sr;
 
 namespace {
 int tls_session_client_new_cb(SSL *ssl, SSL_SESSION *session) {
@@ -402,14 +401,15 @@ int tls_session_new_cb(SSL *ssl, SSL_SESSION *session) {
   id = SSL_SESSION_get_id(session, &idlen);
 
   if (LOG_ENABLED(INFO)) {
-    LOG(INFO) << "Memcached: cache session, id=" << util::format_hex(id, idlen);
+    LOG(INFO) << "Memcached: cache session, id="
+              << util::format_hex(std::span{id, idlen});
   }
 
   auto req = std::make_unique<MemcachedRequest>();
   req->op = MemcachedOp::ADD;
-  req->key = MEMCACHED_SESSION_CACHE_KEY_PREFIX.str();
+  req->key = MEMCACHED_SESSION_CACHE_KEY_PREFIX;
   req->key +=
-      util::format_hex(balloc, StringRef{id, static_cast<size_t>(idlen)});
+      util::format_hex(balloc, std::span{id, static_cast<size_t>(idlen)});
 
   auto sessionlen = i2d_SSL_SESSION(session, nullptr);
   req->value.resize(sessionlen);
@@ -454,7 +454,7 @@ SSL_SESSION *tls_session_get_cb(SSL *ssl, const unsigned char *id, int idlen,
   if (conn->tls.cached_session) {
     if (LOG_ENABLED(INFO)) {
       LOG(INFO) << "Memcached: found cached session, id="
-                << util::format_hex(id, idlen);
+                << util::format_hex(std::span{id, static_cast<size_t>(idlen)});
     }
 
     // This is required, without this, memory leak occurs.
@@ -467,14 +467,14 @@ SSL_SESSION *tls_session_get_cb(SSL *ssl, const unsigned char *id, int idlen,
 
   if (LOG_ENABLED(INFO)) {
     LOG(INFO) << "Memcached: get cached session, id="
-              << util::format_hex(id, idlen);
+              << util::format_hex(std::span{id, static_cast<size_t>(idlen)});
   }
 
   auto req = std::make_unique<MemcachedRequest>();
   req->op = MemcachedOp::GET;
-  req->key = MEMCACHED_SESSION_CACHE_KEY_PREFIX.str();
+  req->key = MEMCACHED_SESSION_CACHE_KEY_PREFIX;
   req->key +=
-      util::format_hex(balloc, StringRef{id, static_cast<size_t>(idlen)});
+      util::format_hex(balloc, std::span{id, static_cast<size_t>(idlen)});
   req->cb = [conn](MemcachedRequest *, MemcachedResult res) {
     if (LOG_ENABLED(INFO)) {
       LOG(INFO) << "Memcached: returned status code "
@@ -560,14 +560,14 @@ int ticket_key_cb(SSL *ssl, unsigned char *key_name, unsigned char *iv,
     EVP_EncryptInit_ex(ctx, get_config()->tls.ticket.cipher, nullptr,
                        key.data.enc_key.data(), iv);
 #if OPENSSL_3_0_0_API
-    std::array<OSSL_PARAM, 3> params{
+    auto params = std::to_array({
         OSSL_PARAM_construct_octet_string(
             OSSL_MAC_PARAM_KEY, key.data.hmac_key.data(), key.hmac_keylen),
         OSSL_PARAM_construct_utf8_string(
             OSSL_MAC_PARAM_DIGEST,
             const_cast<char *>(EVP_MD_get0_name(key.hmac)), 0),
         OSSL_PARAM_construct_end(),
-    };
+    });
     if (!EVP_MAC_CTX_set_params(hctx, params.data())) {
       if (LOG_ENABLED(INFO)) {
         CLOG(INFO, handler) << "EVP_MAC_CTX_set_params failed";
@@ -593,26 +593,27 @@ int ticket_key_cb(SSL *ssl, unsigned char *key_name, unsigned char *iv,
   if (i == keys.size()) {
     if (LOG_ENABLED(INFO)) {
       CLOG(INFO, handler) << "session ticket key "
-                          << util::format_hex(key_name, 16) << " not found";
+                          << util::format_hex(std::span{key_name, 16})
+                          << " not found";
     }
     return 0;
   }
 
   if (LOG_ENABLED(INFO)) {
     CLOG(INFO, handler) << "decrypt session ticket key: "
-                        << util::format_hex(key_name, 16);
+                        << util::format_hex(std::span{key_name, 16});
   }
 
   auto &key = keys[i];
 #if OPENSSL_3_0_0_API
-  std::array<OSSL_PARAM, 3> params{
+  auto params = std::to_array({
       OSSL_PARAM_construct_octet_string(
           OSSL_MAC_PARAM_KEY, key.data.hmac_key.data(), key.hmac_keylen),
       OSSL_PARAM_construct_utf8_string(
           OSSL_MAC_PARAM_DIGEST, const_cast<char *>(EVP_MD_get0_name(key.hmac)),
           0),
       OSSL_PARAM_construct_end(),
-  };
+  });
   if (!EVP_MAC_CTX_set_params(hctx, params.data())) {
     if (LOG_ENABLED(INFO)) {
       CLOG(INFO, handler) << "EVP_MAC_CTX_set_params failed";
@@ -676,7 +677,7 @@ int alpn_select_proto_cb(SSL *ssl, const unsigned char **out,
       auto proto_len = *p;
 
       if (proto_id + proto_len <= end &&
-          util::streq(target_proto_id, StringRef{proto_id, proto_len})) {
+          target_proto_id == StringRef{proto_id, proto_len}) {
 
         *out = reinterpret_cast<const unsigned char *>(proto_id);
         *outlen = proto_len;
@@ -698,8 +699,8 @@ int quic_alpn_select_proto_cb(SSL *ssl, const unsigned char **out,
                               unsigned char *outlen, const unsigned char *in,
                               unsigned int inlen, void *arg) {
   constexpr StringRef alpnlist[] = {
-      StringRef::from_lit("h3"),
-      StringRef::from_lit("h3-29"),
+      "h3"_sr,
+      "h3-29"_sr,
   };
 
   for (auto &alpn : alpnlist) {
@@ -929,9 +930,9 @@ struct TLSProtocol {
 };
 
 constexpr TLSProtocol TLS_PROTOS[] = {
-    TLSProtocol{StringRef::from_lit("TLSv1.2"), SSL_OP_NO_TLSv1_2},
-    TLSProtocol{StringRef::from_lit("TLSv1.1"), SSL_OP_NO_TLSv1_1},
-    TLSProtocol{StringRef::from_lit("TLSv1.0"), SSL_OP_NO_TLSv1}};
+    TLSProtocol{"TLSv1.2"_sr, SSL_OP_NO_TLSv1_2},
+    TLSProtocol{"TLSv1.1"_sr, SSL_OP_NO_TLSv1_1},
+    TLSProtocol{"TLSv1.0"_sr, SSL_OP_NO_TLSv1}};
 
 long int create_tls_proto_mask(const std::vector<StringRef> &tls_proto_list) {
   long int res = 0;
@@ -1008,14 +1009,14 @@ SSL_CTX *create_ssl_context(const char *private_key_file, const char *cert_file,
 
   SSL_CTX_set_timeout(ssl_ctx, tlsconf.session_timeout.count());
 
-  if (SSL_CTX_set_cipher_list(ssl_ctx, tlsconf.ciphers.c_str()) == 0) {
+  if (SSL_CTX_set_cipher_list(ssl_ctx, tlsconf.ciphers.data()) == 0) {
     LOG(FATAL) << "SSL_CTX_set_cipher_list " << tlsconf.ciphers
                << " failed: " << ERR_error_string(ERR_get_error(), nullptr);
     DIE();
   }
 
 #if defined(NGHTTP2_GENUINE_OPENSSL) || defined(NGHTTP2_OPENSSL_IS_LIBRESSL)
-  if (SSL_CTX_set_ciphersuites(ssl_ctx, tlsconf.tls13_ciphers.c_str()) == 0) {
+  if (SSL_CTX_set_ciphersuites(ssl_ctx, tlsconf.tls13_ciphers.data()) == 0) {
     LOG(FATAL) << "SSL_CTX_set_ciphersuites " << tlsconf.tls13_ciphers
                << " failed: " << ERR_error_string(ERR_get_error(), nullptr);
     DIE();
@@ -1023,7 +1024,7 @@ SSL_CTX *create_ssl_context(const char *private_key_file, const char *cert_file,
 #endif // NGHTTP2_GENUINE_OPENSSL || NGHTTP2_OPENSSL_IS_LIBRESSL
 
 #ifndef OPENSSL_NO_EC
-  if (SSL_CTX_set1_curves_list(ssl_ctx, tlsconf.ecdh_curves.c_str()) != 1) {
+  if (SSL_CTX_set1_curves_list(ssl_ctx, tlsconf.ecdh_curves.data()) != 1) {
     LOG(FATAL) << "SSL_CTX_set1_curves_list " << tlsconf.ecdh_curves
                << " failed";
     DIE();
@@ -1032,7 +1033,7 @@ SSL_CTX *create_ssl_context(const char *private_key_file, const char *cert_file,
 
   if (!tlsconf.dh_param_file.empty()) {
     // Read DH parameters from file
-    auto bio = BIO_new_file(tlsconf.dh_param_file.c_str(), "rb");
+    auto bio = BIO_new_file(tlsconf.dh_param_file.data(), "rb");
     if (bio == nullptr) {
       LOG(FATAL) << "BIO_new_file() failed: "
                  << ERR_error_string(ERR_get_error(), nullptr);
@@ -1076,7 +1077,7 @@ SSL_CTX *create_ssl_context(const char *private_key_file, const char *cert_file,
   }
 
   if (!tlsconf.cacert.empty()) {
-    if (SSL_CTX_load_verify_locations(ssl_ctx, tlsconf.cacert.c_str(),
+    if (SSL_CTX_load_verify_locations(ssl_ctx, tlsconf.cacert.data(),
                                       nullptr) != 1) {
       LOG(FATAL) << "Could not load trusted ca certificates from "
                  << tlsconf.cacert << ": "
@@ -1119,7 +1120,7 @@ SSL_CTX *create_ssl_context(const char *private_key_file, const char *cert_file,
   if (tlsconf.client_verify.enabled) {
     if (!tlsconf.client_verify.cacert.empty()) {
       if (SSL_CTX_load_verify_locations(
-              ssl_ctx, tlsconf.client_verify.cacert.c_str(), nullptr) != 1) {
+              ssl_ctx, tlsconf.client_verify.cacert.data(), nullptr) != 1) {
 
         LOG(FATAL) << "Could not load trusted ca certificates from "
                    << tlsconf.client_verify.cacert << ": "
@@ -1130,7 +1131,7 @@ SSL_CTX *create_ssl_context(const char *private_key_file, const char *cert_file,
       // error even though it returns success. See
       // http://forum.nginx.org/read.php?29,242540
       ERR_clear_error();
-      auto list = SSL_load_client_CA_file(tlsconf.client_verify.cacert.c_str());
+      auto list = SSL_load_client_CA_file(tlsconf.client_verify.cacert.data());
       if (!list) {
         LOG(FATAL) << "Could not load ca certificates from "
                    << tlsconf.client_verify.cacert << ": "
@@ -1282,14 +1283,14 @@ SSL_CTX *create_quic_ssl_context(const char *private_key_file,
 
   SSL_CTX_set_timeout(ssl_ctx, tlsconf.session_timeout.count());
 
-  if (SSL_CTX_set_cipher_list(ssl_ctx, tlsconf.ciphers.c_str()) == 0) {
+  if (SSL_CTX_set_cipher_list(ssl_ctx, tlsconf.ciphers.data()) == 0) {
     LOG(FATAL) << "SSL_CTX_set_cipher_list " << tlsconf.ciphers
                << " failed: " << ERR_error_string(ERR_get_error(), nullptr);
     DIE();
   }
 
 #  if defined(NGHTTP2_GENUINE_OPENSSL) || defined(NGHTTP2_OPENSSL_IS_LIBRESSL)
-  if (SSL_CTX_set_ciphersuites(ssl_ctx, tlsconf.tls13_ciphers.c_str()) == 0) {
+  if (SSL_CTX_set_ciphersuites(ssl_ctx, tlsconf.tls13_ciphers.data()) == 0) {
     LOG(FATAL) << "SSL_CTX_set_ciphersuites " << tlsconf.tls13_ciphers
                << " failed: " << ERR_error_string(ERR_get_error(), nullptr);
     DIE();
@@ -1297,7 +1298,7 @@ SSL_CTX *create_quic_ssl_context(const char *private_key_file,
 #  endif // NGHTTP2_GENUINE_OPENSSL || NGHTTP2_OPENSSL_IS_LIBRESSL
 
 #  ifndef OPENSSL_NO_EC
-  if (SSL_CTX_set1_curves_list(ssl_ctx, tlsconf.ecdh_curves.c_str()) != 1) {
+  if (SSL_CTX_set1_curves_list(ssl_ctx, tlsconf.ecdh_curves.data()) != 1) {
     LOG(FATAL) << "SSL_CTX_set1_curves_list " << tlsconf.ecdh_curves
                << " failed";
     DIE();
@@ -1306,7 +1307,7 @@ SSL_CTX *create_quic_ssl_context(const char *private_key_file,
 
   if (!tlsconf.dh_param_file.empty()) {
     // Read DH parameters from file
-    auto bio = BIO_new_file(tlsconf.dh_param_file.c_str(), "rb");
+    auto bio = BIO_new_file(tlsconf.dh_param_file.data(), "rb");
     if (bio == nullptr) {
       LOG(FATAL) << "BIO_new_file() failed: "
                  << ERR_error_string(ERR_get_error(), nullptr);
@@ -1350,7 +1351,7 @@ SSL_CTX *create_quic_ssl_context(const char *private_key_file,
   }
 
   if (!tlsconf.cacert.empty()) {
-    if (SSL_CTX_load_verify_locations(ssl_ctx, tlsconf.cacert.c_str(),
+    if (SSL_CTX_load_verify_locations(ssl_ctx, tlsconf.cacert.data(),
                                       nullptr) != 1) {
       LOG(FATAL) << "Could not load trusted ca certificates from "
                  << tlsconf.cacert << ": "
@@ -1393,7 +1394,7 @@ SSL_CTX *create_quic_ssl_context(const char *private_key_file,
   if (tlsconf.client_verify.enabled) {
     if (!tlsconf.client_verify.cacert.empty()) {
       if (SSL_CTX_load_verify_locations(
-              ssl_ctx, tlsconf.client_verify.cacert.c_str(), nullptr) != 1) {
+              ssl_ctx, tlsconf.client_verify.cacert.data(), nullptr) != 1) {
 
         LOG(FATAL) << "Could not load trusted ca certificates from "
                    << tlsconf.client_verify.cacert << ": "
@@ -1404,7 +1405,7 @@ SSL_CTX *create_quic_ssl_context(const char *private_key_file,
       // error even though it returns success. See
       // http://forum.nginx.org/read.php?29,242540
       ERR_clear_error();
-      auto list = SSL_load_client_CA_file(tlsconf.client_verify.cacert.c_str());
+      auto list = SSL_load_client_CA_file(tlsconf.client_verify.cacert.data());
       if (!list) {
         LOG(FATAL) << "Could not load ca certificates from "
                    << tlsconf.client_verify.cacert << ": "
@@ -1533,14 +1534,14 @@ SSL_CTX *create_ssl_client_context(
     DIE();
   }
 
-  if (SSL_CTX_set_cipher_list(ssl_ctx, tlsconf.client.ciphers.c_str()) == 0) {
+  if (SSL_CTX_set_cipher_list(ssl_ctx, tlsconf.client.ciphers.data()) == 0) {
     LOG(FATAL) << "SSL_CTX_set_cipher_list " << tlsconf.client.ciphers
                << " failed: " << ERR_error_string(ERR_get_error(), nullptr);
     DIE();
   }
 
 #if defined(NGHTTP2_GENUINE_OPENSSL) || defined(NGHTTP2_OPENSSL_IS_LIBRESSL)
-  if (SSL_CTX_set_ciphersuites(ssl_ctx, tlsconf.client.tls13_ciphers.c_str()) ==
+  if (SSL_CTX_set_ciphersuites(ssl_ctx, tlsconf.client.tls13_ciphers.data()) ==
       0) {
     LOG(FATAL) << "SSL_CTX_set_ciphersuites " << tlsconf.client.tls13_ciphers
                << " failed: " << ERR_error_string(ERR_get_error(), nullptr);
@@ -1556,7 +1557,7 @@ SSL_CTX *create_ssl_client_context(
   }
 
   if (!cacert.empty()) {
-    if (SSL_CTX_load_verify_locations(ssl_ctx, cacert.c_str(), nullptr) != 1) {
+    if (SSL_CTX_load_verify_locations(ssl_ctx, cacert.data(), nullptr) != 1) {
 
       LOG(FATAL) << "Could not load trusted ca certificates from " << cacert
                  << ": " << ERR_error_string(ERR_get_error(), nullptr);
@@ -1569,7 +1570,7 @@ SSL_CTX *create_ssl_client_context(
   }
 
   if (!cert_file.empty()) {
-    if (SSL_CTX_use_certificate_chain_file(ssl_ctx, cert_file.c_str()) != 1) {
+    if (SSL_CTX_use_certificate_chain_file(ssl_ctx, cert_file.data()) != 1) {
 
       LOG(FATAL) << "Could not load client certificate from " << cert_file
                  << ": " << ERR_error_string(ERR_get_error(), nullptr);
@@ -1579,7 +1580,7 @@ SSL_CTX *create_ssl_client_context(
 
   if (!private_key_file.empty()) {
 #ifndef HAVE_NEVERBLEED
-    if (SSL_CTX_use_PrivateKey_file(ssl_ctx, private_key_file.c_str(),
+    if (SSL_CTX_use_PrivateKey_file(ssl_ctx, private_key_file.data(),
                                     SSL_FILETYPE_PEM) != 1) {
       LOG(FATAL) << "Could not load client private key from "
                  << private_key_file << ": "
@@ -1588,7 +1589,7 @@ SSL_CTX *create_ssl_client_context(
     }
 #else  // HAVE_NEVERBLEED
     std::array<char, NEVERBLEED_ERRBUF_SIZE> errbuf;
-    if (neverbleed_load_private_key_file(nb, ssl_ctx, private_key_file.c_str(),
+    if (neverbleed_load_private_key_file(nb, ssl_ctx, private_key_file.data(),
                                          errbuf.data()) != 1) {
       LOG(FATAL) << "neverbleed_load_private_key_file: could not load client "
                     "private key from "
@@ -1684,7 +1685,7 @@ bool tls_hostname_match(const StringRef &pattern, const StringRef &hostname) {
   if (ptLeftLabelEnd == std::end(pattern) ||
       std::find(ptLeftLabelEnd + 1, std::end(pattern), '.') ==
           std::end(pattern) ||
-      ptLeftLabelEnd < ptWildcard || util::istarts_with_l(pattern, "xn--")) {
+      ptLeftLabelEnd < ptWildcard || util::istarts_with(pattern, "xn--"_sr)) {
     wildcardEnabled = false;
   }
 
@@ -1801,8 +1802,8 @@ int verify_numeric_hostname(X509 *cert, const StringRef &hostname,
   }
 
   // cn is not NULL terminated
-  auto rv = util::streq(hostname, cn);
-  OPENSSL_free(const_cast<char *>(cn.c_str()));
+  auto rv = hostname == cn;
+  OPENSSL_free(const_cast<char *>(cn.data()));
 
   if (rv) {
     return 0;
@@ -1867,15 +1868,15 @@ int verify_dns_hostname(X509 *cert, const StringRef &hostname) {
 
   if (cn[cn.size() - 1] == '.') {
     if (cn.size() == 1) {
-      OPENSSL_free(const_cast<char *>(cn.c_str()));
+      OPENSSL_free(const_cast<char *>(cn.data()));
 
       return -1;
     }
-    cn = StringRef{cn.c_str(), cn.size() - 1};
+    cn = StringRef{cn.data(), cn.size() - 1};
   }
 
   auto rv = tls_hostname_match(cn, hostname);
-  OPENSSL_free(const_cast<char *>(cn.c_str()));
+  OPENSSL_free(const_cast<char *>(cn.data()));
 
   return rv ? 0 : -1;
 }
@@ -1883,7 +1884,7 @@ int verify_dns_hostname(X509 *cert, const StringRef &hostname) {
 namespace {
 int verify_hostname(X509 *cert, const StringRef &hostname,
                     const Address *addr) {
-  if (util::numeric_host(hostname.c_str())) {
+  if (util::numeric_host(hostname.data())) {
     return verify_numeric_hostname(cert, hostname, addr);
   }
 
@@ -1923,7 +1924,7 @@ int check_cert(SSL *ssl, const DownstreamAddr *addr, const Address *raddr) {
 CertLookupTree::CertLookupTree() {}
 
 ssize_t CertLookupTree::add_cert(const StringRef &hostname, size_t idx) {
-  std::array<uint8_t, NI_MAXHOST> buf;
+  std::array<char, NI_MAXHOST> buf;
 
   // NI_MAXHOST includes terminal NULL byte
   if (hostname.empty() || hostname.size() + 1 > buf.size()) {
@@ -1975,7 +1976,7 @@ ssize_t CertLookupTree::add_cert(const StringRef &hostname, size_t idx) {
 }
 
 ssize_t CertLookupTree::lookup(const StringRef &hostname) {
-  std::array<uint8_t, NI_MAXHOST> buf;
+  std::array<char, NI_MAXHOST> buf;
 
   // NI_MAXHOST includes terminal NULL byte
   if (hostname.empty() || hostname.size() + 1 > buf.size()) {
@@ -2024,9 +2025,7 @@ ssize_t CertLookupTree::lookup(const StringRef &hostname) {
         continue;
       }
 
-      auto prefixlen =
-          wprefix.prefix.size() +
-          (reinterpret_cast<const uint8_t *>(&rev_host[0]) - &buf[0]);
+      auto prefixlen = wprefix.prefix.size() + (&rev_host[0] - &buf[0]);
 
       // Breaking a tie with longer suffix
       if (prefixlen < best_prefixlen) {
@@ -2049,7 +2048,7 @@ void CertLookupTree::dump() const {
 int cert_lookup_tree_add_ssl_ctx(
     CertLookupTree *lt, std::vector<std::vector<SSL_CTX *>> &indexed_ssl_ctx,
     SSL_CTX *ssl_ctx) {
-  std::array<uint8_t, NI_MAXHOST> buf;
+  std::array<char, NI_MAXHOST> buf;
 
   auto cert = SSL_CTX_get0_certificate(ssl_ctx);
   auto altnames = static_cast<GENERAL_NAMES *>(
@@ -2121,17 +2120,17 @@ int cert_lookup_tree_add_ssl_ctx(
 
   if (cn[cn.size() - 1] == '.') {
     if (cn.size() == 1) {
-      OPENSSL_free(const_cast<char *>(cn.c_str()));
+      OPENSSL_free(const_cast<char *>(cn.data()));
 
       return 0;
     }
 
-    cn = StringRef{cn.c_str(), cn.size() - 1};
+    cn = StringRef{cn.data(), cn.size() - 1};
   }
 
   auto end_buf = std::copy(std::begin(cn), std::end(cn), std::begin(buf));
 
-  OPENSSL_free(const_cast<char *>(cn.c_str()));
+  OPENSSL_free(const_cast<char *>(cn.data()));
 
   util::inp_strlower(std::begin(buf), end_buf);
 
@@ -2154,7 +2153,7 @@ int cert_lookup_tree_add_ssl_ctx(
 bool in_proto_list(const std::vector<StringRef> &protos,
                    const StringRef &needle) {
   for (auto &proto : protos) {
-    if (util::streq(proto, needle)) {
+    if (proto == needle) {
       return true;
     }
   }
@@ -2210,8 +2209,8 @@ setup_server_ssl_context(std::vector<SSL_CTX *> &all_ssl_ctx,
 
   auto &tlsconf = config->tls;
 
-  auto ssl_ctx = create_ssl_context(tlsconf.private_key_file.c_str(),
-                                    tlsconf.cert_file.c_str(), tlsconf.sct_data
+  auto ssl_ctx = create_ssl_context(tlsconf.private_key_file.data(),
+                                    tlsconf.cert_file.data(), tlsconf.sct_data
 #ifdef HAVE_NEVERBLEED
                                     ,
                                     nb
@@ -2228,8 +2227,8 @@ setup_server_ssl_context(std::vector<SSL_CTX *> &all_ssl_ctx,
   }
 
   for (auto &c : tlsconf.subcerts) {
-    auto ssl_ctx = create_ssl_context(c.private_key_file.c_str(),
-                                      c.cert_file.c_str(), c.sct_data
+    auto ssl_ctx = create_ssl_context(c.private_key_file.data(),
+                                      c.cert_file.data(), c.sct_data
 #ifdef HAVE_NEVERBLEED
                                       ,
                                       nb
@@ -2266,8 +2265,8 @@ SSL_CTX *setup_quic_server_ssl_context(
   auto &tlsconf = config->tls;
 
   auto ssl_ctx =
-      create_quic_ssl_context(tlsconf.private_key_file.c_str(),
-                              tlsconf.cert_file.c_str(), tlsconf.sct_data
+      create_quic_ssl_context(tlsconf.private_key_file.data(),
+                              tlsconf.cert_file.data(), tlsconf.sct_data
 #  ifdef HAVE_NEVERBLEED
                               ,
                               nb
@@ -2284,8 +2283,8 @@ SSL_CTX *setup_quic_server_ssl_context(
   }
 
   for (auto &c : tlsconf.subcerts) {
-    auto ssl_ctx = create_quic_ssl_context(c.private_key_file.c_str(),
-                                           c.cert_file.c_str(), c.sct_data
+    auto ssl_ctx = create_quic_ssl_context(c.private_key_file.data(),
+                                           c.cert_file.data(), c.sct_data
 #  ifdef HAVE_NEVERBLEED
                                            ,
                                            nb
@@ -2378,17 +2377,17 @@ SSL_SESSION *reuse_tls_session(const TLSSessionCache &cache) {
 
 int proto_version_from_string(const StringRef &v) {
 #ifdef TLS1_3_VERSION
-  if (util::strieq_l("TLSv1.3", v)) {
+  if (util::strieq("TLSv1.3"_sr, v)) {
     return TLS1_3_VERSION;
   }
 #endif // TLS1_3_VERSION
-  if (util::strieq_l("TLSv1.2", v)) {
+  if (util::strieq("TLSv1.2"_sr, v)) {
     return TLS1_2_VERSION;
   }
-  if (util::strieq_l("TLSv1.1", v)) {
+  if (util::strieq("TLSv1.1"_sr, v)) {
     return TLS1_1_VERSION;
   }
-  if (util::strieq_l("TLSv1.0", v)) {
+  if (util::strieq("TLSv1.0"_sr, v)) {
     return TLS1_VERSION;
   }
   return -1;
@@ -2500,9 +2499,9 @@ StringRef get_x509_name(BlockAllocator &balloc, X509_NAME *nm) {
   }
 
   auto iov = make_byte_ref(balloc, slen + 1);
-  BIO_read(b, iov.base, slen);
-  iov.base[slen] = '\0';
-  return StringRef{iov.base, static_cast<size_t>(slen)};
+  BIO_read(b, iov.data(), slen);
+  iov[slen] = '\0';
+  return StringRef{iov.data(), static_cast<size_t>(slen)};
 }
 } // namespace
 
@@ -2526,7 +2525,7 @@ StringRef get_x509_serial(BlockAllocator &balloc, X509 *x) {
   auto n = BN_bn2bin(bn, b.data());
   assert(n <= 20);
 
-  return util::format_hex(balloc, StringRef{b.data(), static_cast<size_t>(n)});
+  return util::format_hex(balloc, std::span{b.data(), static_cast<size_t>(n)});
 }
 
 namespace {
diff --git a/src/shrpx_tls.h b/src/shrpx_tls.h
index f740507..8ca165c 100644
--- a/src/shrpx_tls.h
+++ b/src/shrpx_tls.h
@@ -72,7 +72,11 @@ struct TLSContextData {
   std::mutex mu;
 #endif // !HAVE_ATOMIC_STD_SHARED_PTR
   // OCSP response
+#ifdef HAVE_ATOMIC_STD_SHARED_PTR
+  std::atomic<std::shared_ptr<std::vector<uint8_t>>> ocsp_data;
+#else  // !HAVE_ATOMIC_STD_SHARED_PTR
   std::shared_ptr<std::vector<uint8_t>> ocsp_data;
+#endif // !HAVE_ATOMIC_STD_SHARED_PTR
 
   // Path to certificate file
   const char *cert_file;
diff --git a/src/shrpx_tls_test.cc b/src/shrpx_tls_test.cc
index 04d16da..013c347 100644
--- a/src/shrpx_tls_test.cc
+++ b/src/shrpx_tls_test.cc
@@ -54,16 +54,16 @@ void test_shrpx_tls_create_lookup_tree(void) {
   auto tree = std::make_unique<tls::CertLookupTree>();
 
   constexpr StringRef hostnames[] = {
-      StringRef::from_lit("example.com"),             // 0
-      StringRef::from_lit("www.example.org"),         // 1
-      StringRef::from_lit("*www.example.org"),        // 2
-      StringRef::from_lit("xy*.host.domain"),         // 3
-      StringRef::from_lit("*yy.host.domain"),         // 4
-      StringRef::from_lit("nghttp2.sourceforge.net"), // 5
-      StringRef::from_lit("sourceforge.net"),         // 6
-      StringRef::from_lit("sourceforge.net"),         // 7, duplicate
-      StringRef::from_lit("*.foo.bar"), // 8, oo.bar is suffix of *.foo.bar
-      StringRef::from_lit("oo.bar")     // 9
+      "example.com"_sr,             // 0
+      "www.example.org"_sr,         // 1
+      "*www.example.org"_sr,        // 2
+      "xy*.host.domain"_sr,         // 3
+      "*yy.host.domain"_sr,         // 4
+      "nghttp2.sourceforge.net"_sr, // 5
+      "sourceforge.net"_sr,         // 6
+      "sourceforge.net"_sr,         // 7, duplicate
+      "*.foo.bar"_sr,               // 8, oo.bar is suffix of *.foo.bar
+      "oo.bar"_sr                   // 9
   };
   auto num = array_size(hostnames);
 
@@ -75,13 +75,13 @@ void test_shrpx_tls_create_lookup_tree(void) {
 
   assert_ssize(0, ==, tree->lookup(hostnames[0]));
   assert_ssize(1, ==, tree->lookup(hostnames[1]));
-  assert_ssize(2, ==, tree->lookup(StringRef::from_lit("2www.example.org")));
-  assert_ssize(-1, ==, tree->lookup(StringRef::from_lit("www2.example.org")));
-  assert_ssize(3, ==, tree->lookup(StringRef::from_lit("xy1.host.domain")));
+  assert_ssize(2, ==, tree->lookup("2www.example.org"_sr));
+  assert_ssize(-1, ==, tree->lookup("www2.example.org"_sr));
+  assert_ssize(3, ==, tree->lookup("xy1.host.domain"_sr));
   // Does not match *yy.host.domain, because * must match at least 1
   // character.
-  assert_ssize(-1, ==, tree->lookup(StringRef::from_lit("yy.host.domain")));
-  assert_ssize(4, ==, tree->lookup(StringRef::from_lit("xyy.host.domain")));
+  assert_ssize(-1, ==, tree->lookup("yy.host.domain"_sr));
+  assert_ssize(4, ==, tree->lookup("xyy.host.domain"_sr));
   assert_ssize(-1, ==, tree->lookup(StringRef{}));
   assert_ssize(5, ==, tree->lookup(hostnames[5]));
   assert_ssize(6, ==, tree->lookup(hostnames[6]));
@@ -89,14 +89,14 @@ void test_shrpx_tls_create_lookup_tree(void) {
   for (int i = 0; i < 7; ++i) {
     assert_ssize(-1, ==, tree->lookup(StringRef{h6 + i, str_size(h6) - i}));
   }
-  assert_ssize(8, ==, tree->lookup(StringRef::from_lit("x.foo.bar")));
+  assert_ssize(8, ==, tree->lookup("x.foo.bar"_sr));
   assert_ssize(9, ==, tree->lookup(hostnames[9]));
 
   constexpr StringRef names[] = {
-      StringRef::from_lit("rab"),  // 1
-      StringRef::from_lit("zab"),  // 2
-      StringRef::from_lit("zzub"), // 3
-      StringRef::from_lit("ab")    // 4
+      "rab"_sr,  // 1
+      "zab"_sr,  // 2
+      "zzub"_sr, // 3
+      "ab"_sr    // 4
   };
   num = array_size(names);
 
@@ -169,12 +169,11 @@ void test_shrpx_tls_cert_lookup_tree_add_ssl_ctx(void) {
 
   assert_int(0, ==, rv);
 
-  assert_ssize(-1, ==,
-               tree.lookup(StringRef::from_lit("not-used.nghttp2.org")));
-  assert_ssize(0, ==, tree.lookup(StringRef::from_lit("test.nghttp2.org")));
-  assert_ssize(1, ==, tree.lookup(StringRef::from_lit("w.test.nghttp2.org")));
-  assert_ssize(2, ==, tree.lookup(StringRef::from_lit("www.test.nghttp2.org")));
-  assert_ssize(3, ==, tree.lookup(StringRef::from_lit("test.example.com")));
+  assert_ssize(-1, ==, tree.lookup("not-used.nghttp2.org"_sr));
+  assert_ssize(0, ==, tree.lookup("test.nghttp2.org"_sr));
+  assert_ssize(1, ==, tree.lookup("w.test.nghttp2.org"_sr));
+  assert_ssize(2, ==, tree.lookup("www.test.nghttp2.org"_sr));
+  assert_ssize(3, ==, tree.lookup("test.example.com"_sr));
 }
 
 template <size_t N, size_t M>
@@ -249,11 +248,10 @@ static Address parse_addr(const char *ipaddr) {
 void test_shrpx_tls_verify_numeric_hostname(void) {
   {
     // Successful IPv4 address match in SAN
-    static constexpr char ipaddr[] = "127.0.0.1";
+    static constexpr auto ipaddr = "127.0.0.1"_sr;
     auto cert = load_cert(NGHTTP2_SRC_DIR "/testdata/verify_hostname.crt");
-    auto addr = parse_addr(ipaddr);
-    auto rv =
-        tls::verify_numeric_hostname(cert, StringRef::from_lit(ipaddr), &addr);
+    auto addr = parse_addr(ipaddr.data());
+    auto rv = tls::verify_numeric_hostname(cert, ipaddr, &addr);
 
     assert_int(0, ==, rv);
 
@@ -262,11 +260,10 @@ void test_shrpx_tls_verify_numeric_hostname(void) {
 
   {
     // Successful IPv6 address match in SAN
-    static constexpr char ipaddr[] = "::1";
+    static constexpr auto ipaddr = "::1"_sr;
     auto cert = load_cert(NGHTTP2_SRC_DIR "/testdata/verify_hostname.crt");
-    auto addr = parse_addr(ipaddr);
-    auto rv =
-        tls::verify_numeric_hostname(cert, StringRef::from_lit(ipaddr), &addr);
+    auto addr = parse_addr(ipaddr.data());
+    auto rv = tls::verify_numeric_hostname(cert, ipaddr, &addr);
 
     assert_int(0, ==, rv);
 
@@ -275,11 +272,10 @@ void test_shrpx_tls_verify_numeric_hostname(void) {
 
   {
     // Unsuccessful IPv4 address match in SAN
-    static constexpr char ipaddr[] = "192.168.0.127";
+    static constexpr auto ipaddr = "192.168.0.127"_sr;
     auto cert = load_cert(NGHTTP2_SRC_DIR "/testdata/verify_hostname.crt");
-    auto addr = parse_addr(ipaddr);
-    auto rv =
-        tls::verify_numeric_hostname(cert, StringRef::from_lit(ipaddr), &addr);
+    auto addr = parse_addr(ipaddr.data());
+    auto rv = tls::verify_numeric_hostname(cert, ipaddr, &addr);
 
     assert_int(-1, ==, rv);
 
@@ -288,11 +284,10 @@ void test_shrpx_tls_verify_numeric_hostname(void) {
 
   {
     // CommonName is not used if SAN is available
-    static constexpr char ipaddr[] = "192.168.0.1";
+    static constexpr auto ipaddr = "192.168.0.1"_sr;
     auto cert = load_cert(NGHTTP2_SRC_DIR "/testdata/ipaddr.crt");
-    auto addr = parse_addr(ipaddr);
-    auto rv =
-        tls::verify_numeric_hostname(cert, StringRef::from_lit(ipaddr), &addr);
+    auto addr = parse_addr(ipaddr.data());
+    auto rv = tls::verify_numeric_hostname(cert, ipaddr, &addr);
 
     assert_int(-1, ==, rv);
 
@@ -301,11 +296,10 @@ void test_shrpx_tls_verify_numeric_hostname(void) {
 
   {
     // Successful IPv4 address match in CommonName
-    static constexpr char ipaddr[] = "127.0.0.1";
+    static constexpr auto ipaddr = "127.0.0.1"_sr;
     auto cert = load_cert(NGHTTP2_SRC_DIR "/testdata/nosan_ip.crt");
-    auto addr = parse_addr(ipaddr);
-    auto rv =
-        tls::verify_numeric_hostname(cert, StringRef::from_lit(ipaddr), &addr);
+    auto addr = parse_addr(ipaddr.data());
+    auto rv = tls::verify_numeric_hostname(cert, ipaddr, &addr);
 
     assert_int(0, ==, rv);
 
@@ -317,8 +311,7 @@ void test_shrpx_tls_verify_dns_hostname(void) {
   {
     // Successful exact DNS name match in SAN
     auto cert = load_cert(NGHTTP2_SRC_DIR "/testdata/verify_hostname.crt");
-    auto rv = tls::verify_dns_hostname(
-        cert, StringRef::from_lit("nghttp2.example.com"));
+    auto rv = tls::verify_dns_hostname(cert, "nghttp2.example.com"_sr);
 
     assert_int(0, ==, rv);
 
@@ -328,8 +321,7 @@ void test_shrpx_tls_verify_dns_hostname(void) {
   {
     // Successful wildcard DNS name match in SAN
     auto cert = load_cert(NGHTTP2_SRC_DIR "/testdata/verify_hostname.crt");
-    auto rv = tls::verify_dns_hostname(
-        cert, StringRef::from_lit("www.nghttp2.example.com"));
+    auto rv = tls::verify_dns_hostname(cert, "www.nghttp2.example.com"_sr);
 
     assert_int(0, ==, rv);
 
@@ -339,7 +331,7 @@ void test_shrpx_tls_verify_dns_hostname(void) {
   {
     // CommonName is not used if SAN is available.
     auto cert = load_cert(NGHTTP2_SRC_DIR "/testdata/verify_hostname.crt");
-    auto rv = tls::verify_dns_hostname(cert, StringRef::from_lit("localhost"));
+    auto rv = tls::verify_dns_hostname(cert, "localhost"_sr);
 
     assert_int(-1, ==, rv);
 
@@ -349,7 +341,7 @@ void test_shrpx_tls_verify_dns_hostname(void) {
   {
     // Successful DNS name match in CommonName
     auto cert = load_cert(NGHTTP2_SRC_DIR "/testdata/nosan.crt");
-    auto rv = tls::verify_dns_hostname(cert, StringRef::from_lit("localhost"));
+    auto rv = tls::verify_dns_hostname(cert, "localhost"_sr);
 
     assert_int(0, ==, rv);
 
diff --git a/src/shrpx_worker.cc b/src/shrpx_worker.cc
index 9f5911f..3a585f6 100644
--- a/src/shrpx_worker.cc
+++ b/src/shrpx_worker.cc
@@ -555,9 +555,9 @@ void Worker::process_events() {
       faddr = &quic_upstream_addrs_[wev.quic_pkt->upstream_addr_index];
     }
 
-    quic_conn_handler_.handle_packet(
-        faddr, wev.quic_pkt->remote_addr, wev.quic_pkt->local_addr,
-        wev.quic_pkt->pi, wev.quic_pkt->data.data(), wev.quic_pkt->data.size());
+    quic_conn_handler_.handle_packet(faddr, wev.quic_pkt->remote_addr,
+                                     wev.quic_pkt->local_addr, wev.quic_pkt->pi,
+                                     wev.quic_pkt->data);
 
     break;
   }
@@ -579,7 +579,7 @@ tls::CertLookupTree *Worker::get_quic_cert_lookup_tree() const {
 
 std::shared_ptr<TicketKeys> Worker::get_ticket_keys() {
 #ifdef HAVE_ATOMIC_STD_SHARED_PTR
-  return std::atomic_load_explicit(&ticket_keys_, std::memory_order_acquire);
+  return ticket_keys_.load(std::memory_order_acquire);
 #else  // !HAVE_ATOMIC_STD_SHARED_PTR
   std::lock_guard<std::mutex> g(ticket_keys_m_);
   return ticket_keys_;
@@ -589,8 +589,7 @@ std::shared_ptr<TicketKeys> Worker::get_ticket_keys() {
 void Worker::set_ticket_keys(std::shared_ptr<TicketKeys> ticket_keys) {
 #ifdef HAVE_ATOMIC_STD_SHARED_PTR
   // This is single writer
-  std::atomic_store_explicit(&ticket_keys_, std::move(ticket_keys),
-                             std::memory_order_release);
+  ticket_keys_.store(std::move(ticket_keys), std::memory_order_release);
 #else  // !HAVE_ATOMIC_STD_SHARED_PTR
   std::lock_guard<std::mutex> g(ticket_keys_m_);
   ticket_keys_ = std::move(ticket_keys);
@@ -855,8 +854,7 @@ int Worker::create_quic_server_socket(UpstreamAddr &faddr) {
   hints.ai_flags |= AI_ADDRCONFIG;
 #  endif // AI_ADDRCONFIG
 
-  auto node =
-      faddr.host == StringRef::from_lit("*") ? nullptr : faddr.host.c_str();
+  auto node = faddr.host == "*"_sr ? nullptr : faddr.host.data();
 
   addrinfo *res, *rp;
   rv = getaddrinfo(node, service.c_str(), &hints, &res);
@@ -1027,7 +1025,7 @@ int Worker::create_quic_server_socket(UpstreamAddr &faddr) {
     if (should_attach_bpf()) {
       auto &bpfconf = config->quic.bpf;
 
-      auto obj = bpf_object__open_file(bpfconf.prog_file.c_str(), nullptr);
+      auto obj = bpf_object__open_file(bpfconf.prog_file.data(), nullptr);
       if (!obj) {
         auto error = errno;
         LOG(FATAL) << "Failed to open bpf object file: "
@@ -1231,13 +1229,13 @@ const UpstreamAddr *Worker::find_quic_upstream_addr(const Address &local_addr) {
     if (faddr.port == 443 || faddr.port == 80) {
       switch (faddr.family) {
       case AF_INET:
-        if (util::streq(faddr.hostport, StringRef::from_lit("0.0.0.0"))) {
+        if (faddr.hostport == "0.0.0.0"_sr) {
           fallback_faddr = &faddr;
         }
 
         break;
       case AF_INET6:
-        if (util::streq(faddr.hostport, StringRef::from_lit("[::]"))) {
+        if (faddr.hostport == "[::]"_sr) {
           fallback_faddr = &faddr;
         }
 
@@ -1248,14 +1246,13 @@ const UpstreamAddr *Worker::find_quic_upstream_addr(const Address &local_addr) {
     } else {
       switch (faddr.family) {
       case AF_INET:
-        if (util::starts_with(faddr.hostport,
-                              StringRef::from_lit("0.0.0.0:"))) {
+        if (util::starts_with(faddr.hostport, "0.0.0.0:"_sr)) {
           fallback_faddr = &faddr;
         }
 
         break;
       case AF_INET6:
-        if (util::starts_with(faddr.hostport, StringRef::from_lit("[::]:"))) {
+        if (util::starts_with(faddr.hostport, "[::]:"_sr)) {
           fallback_faddr = &faddr;
         }
 
@@ -1297,10 +1294,10 @@ size_t match_downstream_addr_group_host(
 
   if (!wildcard_patterns.empty() && !host.empty()) {
     auto rev_host_src = make_byte_ref(balloc, host.size() - 1);
-    auto ep =
-        std::copy(std::begin(host) + 1, std::end(host), rev_host_src.base);
-    std::reverse(rev_host_src.base, ep);
-    auto rev_host = StringRef{rev_host_src.base, ep};
+    auto ep = std::copy(std::begin(host) + 1, std::end(host),
+                        std::begin(rev_host_src));
+    std::reverse(std::begin(rev_host_src), ep);
+    auto rev_host = StringRef{std::span{std::begin(rev_host_src), ep}};
 
     ssize_t best_group = -1;
     const RNode *last_node = nullptr;
@@ -1334,7 +1331,7 @@ size_t match_downstream_addr_group_host(
     }
   }
 
-  group = router.match(StringRef::from_lit(""), path);
+  group = router.match(""_sr, path);
   if (group != -1) {
     if (LOG_ENABLED(INFO)) {
       LOG(INFO) << "Found pattern with query " << path
@@ -1367,7 +1364,7 @@ size_t match_downstream_addr_group(
   auto path = StringRef{std::begin(raw_path), query};
 
   if (path.empty() || path[0] != '/') {
-    path = StringRef::from_lit("/");
+    path = "/"_sr;
   }
 
   if (hostport.empty()) {
@@ -1398,10 +1395,10 @@ size_t match_downstream_addr_group(
         return 'A' <= c || c <= 'Z';
       }) != std::end(host)) {
     auto low_host = make_byte_ref(balloc, host.size() + 1);
-    auto ep = std::copy(std::begin(host), std::end(host), low_host.base);
+    auto ep = std::copy(std::begin(host), std::end(host), std::begin(low_host));
     *ep = '\0';
-    util::inp_strlower(low_host.base, ep);
-    host = StringRef{low_host.base, ep};
+    util::inp_strlower(std::begin(low_host), ep);
+    host = StringRef{std::span{std::begin(low_host), ep}};
   }
   return match_downstream_addr_group_host(routerconf, host, path, groups,
                                           catch_all, balloc);
diff --git a/src/shrpx_worker.h b/src/shrpx_worker.h
index f8a2d84..346e764 100644
--- a/src/shrpx_worker.h
+++ b/src/shrpx_worker.h
@@ -265,12 +265,12 @@ struct WorkerStat {
 struct QUICPacket {
   QUICPacket(size_t upstream_addr_index, const Address &remote_addr,
              const Address &local_addr, const ngtcp2_pkt_info &pi,
-             const uint8_t *data, size_t datalen)
+             std::span<const uint8_t> data)
       : upstream_addr_index{upstream_addr_index},
         remote_addr{remote_addr},
         local_addr{local_addr},
         pi{pi},
-        data{data, data + datalen} {}
+        data{std::begin(data), std::end(data)} {}
   QUICPacket() : upstream_addr_index{}, remote_addr{}, local_addr{}, pi{} {}
   size_t upstream_addr_index;
   Address remote_addr;
@@ -439,10 +439,12 @@ private:
   QUICConnectionHandler quic_conn_handler_;
 #endif // ENABLE_HTTP3
 
-#ifndef HAVE_ATOMIC_STD_SHARED_PTR
+#ifdef HAVE_ATOMIC_STD_SHARED_PTR
+  std::atomic<std::shared_ptr<TicketKeys>> ticket_keys_;
+#else  // !HAVE_ATOMIC_STD_SHARED_PTR
   std::mutex ticket_keys_m_;
-#endif // !HAVE_ATOMIC_STD_SHARED_PTR
   std::shared_ptr<TicketKeys> ticket_keys_;
+#endif // !HAVE_ATOMIC_STD_SHARED_PTR
   std::vector<std::shared_ptr<DownstreamAddrGroup>> downstream_addr_groups_;
   // Worker level blocker for downstream connection.  For example,
   // this is used when file descriptor is exhausted.
diff --git a/src/shrpx_worker_process.cc b/src/shrpx_worker_process.cc
index 6591e9b..14040b4 100644
--- a/src/shrpx_worker_process.cc
+++ b/src/shrpx_worker_process.cc
@@ -74,11 +74,11 @@ void drop_privileges(
   if (getuid() == 0 && config->uid != 0) {
 #ifdef HAVE_NEVERBLEED
     if (nb) {
-      neverbleed_setuidgid(nb, config->user.c_str(), 1);
+      neverbleed_setuidgid(nb, config->user.data(), 1);
     }
 #endif // HAVE_NEVERBLEED
 
-    if (initgroups(config->user.c_str(), config->gid) != 0) {
+    if (initgroups(config->user.data(), config->gid) != 0) {
       auto error = errno;
       LOG(FATAL) << "Could not change supplementary groups: "
                  << xsi_strerror(error, errbuf.data(), errbuf.size());
@@ -576,10 +576,8 @@ int worker_process_event_loop(WorkerProcessConfig *wpconf) {
   }
 
   for (auto &qkm : qkms->keying_materials) {
-    if (generate_quic_connection_id_encryption_key(
-            qkm.cid_encryption_key.data(), qkm.cid_encryption_key.size(),
-            qkm.secret.data(), qkm.secret.size(), qkm.salt.data(),
-            qkm.salt.size()) != 0) {
+    if (generate_quic_connection_id_encryption_key(qkm.cid_encryption_key,
+                                                   qkm.secret, qkm.salt) != 0) {
       LOG(ERROR) << "Failed to generate QUIC Connection ID encryption key";
       return -1;
     }
diff --git a/src/shrpx_worker_test.cc b/src/shrpx_worker_test.cc
index 4b4b7a6..9372a2c 100644
--- a/src/shrpx_worker_test.cc
+++ b/src/shrpx_worker_test.cc
@@ -74,154 +74,134 @@ void test_shrpx_worker_match_downstream_addr_group(void) {
   }
 
   assert_size(0, ==,
-              match_downstream_addr_group(
-                  routerconf, StringRef::from_lit("nghttp2.org"),
-                  StringRef::from_lit("/"), groups, 255, balloc));
+              match_downstream_addr_group(routerconf, "nghttp2.org"_sr, "/"_sr,
+                                          groups, 255, balloc));
 
   // port is removed
   assert_size(0, ==,
-              match_downstream_addr_group(
-                  routerconf, StringRef::from_lit("nghttp2.org:8080"),
-                  StringRef::from_lit("/"), groups, 255, balloc));
+              match_downstream_addr_group(routerconf, "nghttp2.org:8080"_sr,
+                                          "/"_sr, groups, 255, balloc));
 
   // host is case-insensitive
   assert_size(4, ==,
-              match_downstream_addr_group(
-                  routerconf, StringRef::from_lit("WWW.nghttp2.org"),
-                  StringRef::from_lit("/alpha"), groups, 255, balloc));
+              match_downstream_addr_group(routerconf, "WWW.nghttp2.org"_sr,
+                                          "/alpha"_sr, groups, 255, balloc));
 
   assert_size(1, ==,
-              match_downstream_addr_group(
-                  routerconf, StringRef::from_lit("nghttp2.org"),
-                  StringRef::from_lit("/alpha/bravo/"), groups, 255, balloc));
+              match_downstream_addr_group(routerconf, "nghttp2.org"_sr,
+                                          "/alpha/bravo/"_sr, groups, 255,
+                                          balloc));
 
   // /alpha/bravo also matches /alpha/bravo/
   assert_size(1, ==,
-              match_downstream_addr_group(
-                  routerconf, StringRef::from_lit("nghttp2.org"),
-                  StringRef::from_lit("/alpha/bravo"), groups, 255, balloc));
+              match_downstream_addr_group(routerconf, "nghttp2.org"_sr,
+                                          "/alpha/bravo"_sr, groups, 255,
+                                          balloc));
 
   // path part is case-sensitive
   assert_size(0, ==,
-              match_downstream_addr_group(
-                  routerconf, StringRef::from_lit("nghttp2.org"),
-                  StringRef::from_lit("/Alpha/bravo"), groups, 255, balloc));
+              match_downstream_addr_group(routerconf, "nghttp2.org"_sr,
+                                          "/Alpha/bravo"_sr, groups, 255,
+                                          balloc));
 
   assert_size(1, ==,
-              match_downstream_addr_group(
-                  routerconf, StringRef::from_lit("nghttp2.org"),
-                  StringRef::from_lit("/alpha/bravo/charlie"), groups, 255,
-                  balloc));
+              match_downstream_addr_group(routerconf, "nghttp2.org"_sr,
+                                          "/alpha/bravo/charlie"_sr, groups,
+                                          255, balloc));
 
   assert_size(2, ==,
-              match_downstream_addr_group(
-                  routerconf, StringRef::from_lit("nghttp2.org"),
-                  StringRef::from_lit("/alpha/charlie"), groups, 255, balloc));
+              match_downstream_addr_group(routerconf, "nghttp2.org"_sr,
+                                          "/alpha/charlie"_sr, groups, 255,
+                                          balloc));
 
   // pattern which does not end with '/' must match its entirely.  So
   // this matches to group 0, not group 2.
   assert_size(0, ==,
-              match_downstream_addr_group(
-                  routerconf, StringRef::from_lit("nghttp2.org"),
-                  StringRef::from_lit("/alpha/charlie/"), groups, 255, balloc));
+              match_downstream_addr_group(routerconf, "nghttp2.org"_sr,
+                                          "/alpha/charlie/"_sr, groups, 255,
+                                          balloc));
 
   assert_size(255, ==,
-              match_downstream_addr_group(
-                  routerconf, StringRef::from_lit("example.org"),
-                  StringRef::from_lit("/"), groups, 255, balloc));
+              match_downstream_addr_group(routerconf, "example.org"_sr, "/"_sr,
+                                          groups, 255, balloc));
 
   assert_size(255, ==,
-              match_downstream_addr_group(routerconf, StringRef::from_lit(""),
-                                          StringRef::from_lit("/"), groups, 255,
-                                          balloc));
+              match_downstream_addr_group(routerconf, ""_sr, "/"_sr, groups,
+                                          255, balloc));
 
   assert_size(255, ==,
-              match_downstream_addr_group(routerconf, StringRef::from_lit(""),
-                                          StringRef::from_lit("alpha"), groups,
+              match_downstream_addr_group(routerconf, ""_sr, "alpha"_sr, groups,
                                           255, balloc));
 
   assert_size(255, ==,
-              match_downstream_addr_group(
-                  routerconf, StringRef::from_lit("foo/bar"),
-                  StringRef::from_lit("/"), groups, 255, balloc));
+              match_downstream_addr_group(routerconf, "foo/bar"_sr, "/"_sr,
+                                          groups, 255, balloc));
 
-  // If path is StringRef::from_lit("*", only match with host + "/").
+  // If path is "*", only match with host + "/").
   assert_size(0, ==,
-              match_downstream_addr_group(
-                  routerconf, StringRef::from_lit("nghttp2.org"),
-                  StringRef::from_lit("*"), groups, 255, balloc));
+              match_downstream_addr_group(routerconf, "nghttp2.org"_sr, "*"_sr,
+                                          groups, 255, balloc));
 
   assert_size(5, ==,
-              match_downstream_addr_group(
-                  routerconf, StringRef::from_lit("[::1]"),
-                  StringRef::from_lit("/"), groups, 255, balloc));
+              match_downstream_addr_group(routerconf, "[::1]"_sr, "/"_sr,
+                                          groups, 255, balloc));
   assert_size(5, ==,
-              match_downstream_addr_group(
-                  routerconf, StringRef::from_lit("[::1]:8080"),
-                  StringRef::from_lit("/"), groups, 255, balloc));
+              match_downstream_addr_group(routerconf, "[::1]:8080"_sr, "/"_sr,
+                                          groups, 255, balloc));
   assert_size(255, ==,
-              match_downstream_addr_group(
-                  routerconf, StringRef::from_lit("[::1"),
-                  StringRef::from_lit("/"), groups, 255, balloc));
+              match_downstream_addr_group(routerconf, "[::1"_sr, "/"_sr, groups,
+                                          255, balloc));
   assert_size(255, ==,
-              match_downstream_addr_group(
-                  routerconf, StringRef::from_lit("[::1]8000"),
-                  StringRef::from_lit("/"), groups, 255, balloc));
+              match_downstream_addr_group(routerconf, "[::1]8000"_sr, "/"_sr,
+                                          groups, 255, balloc));
 
   // Check the case where adding route extends tree
   assert_size(6, ==,
-              match_downstream_addr_group(
-                  routerconf, StringRef::from_lit("nghttp2.org"),
-                  StringRef::from_lit("/alpha/bravo/delta"), groups, 255,
-                  balloc));
+              match_downstream_addr_group(routerconf, "nghttp2.org"_sr,
+                                          "/alpha/bravo/delta"_sr, groups, 255,
+                                          balloc));
 
   assert_size(1, ==,
-              match_downstream_addr_group(
-                  routerconf, StringRef::from_lit("nghttp2.org"),
-                  StringRef::from_lit("/alpha/bravo/delta/"), groups, 255,
-                  balloc));
+              match_downstream_addr_group(routerconf, "nghttp2.org"_sr,
+                                          "/alpha/bravo/delta/"_sr, groups, 255,
+                                          balloc));
 
   // Check the case where query is done in a single node
   assert_size(7, ==,
-              match_downstream_addr_group(
-                  routerconf, StringRef::from_lit("example.com"),
-                  StringRef::from_lit("/alpha/bravo"), groups, 255, balloc));
+              match_downstream_addr_group(routerconf, "example.com"_sr,
+                                          "/alpha/bravo"_sr, groups, 255,
+                                          balloc));
 
   assert_size(255, ==,
-              match_downstream_addr_group(
-                  routerconf, StringRef::from_lit("example.com"),
-                  StringRef::from_lit("/alpha/bravo/"), groups, 255, balloc));
+              match_downstream_addr_group(routerconf, "example.com"_sr,
+                                          "/alpha/bravo/"_sr, groups, 255,
+                                          balloc));
 
   assert_size(255, ==,
-              match_downstream_addr_group(
-                  routerconf, StringRef::from_lit("example.com"),
-                  StringRef::from_lit("/alpha"), groups, 255, balloc));
+              match_downstream_addr_group(routerconf, "example.com"_sr,
+                                          "/alpha"_sr, groups, 255, balloc));
 
   // Check the case where quey is done in a single node
   assert_size(8, ==,
-              match_downstream_addr_group(
-                  routerconf, StringRef::from_lit("192.168.0.1"),
-                  StringRef::from_lit("/alpha"), groups, 255, balloc));
+              match_downstream_addr_group(routerconf, "192.168.0.1"_sr,
+                                          "/alpha"_sr, groups, 255, balloc));
 
   assert_size(8, ==,
-              match_downstream_addr_group(
-                  routerconf, StringRef::from_lit("192.168.0.1"),
-                  StringRef::from_lit("/alpha/"), groups, 255, balloc));
+              match_downstream_addr_group(routerconf, "192.168.0.1"_sr,
+                                          "/alpha/"_sr, groups, 255, balloc));
 
   assert_size(8, ==,
-              match_downstream_addr_group(
-                  routerconf, StringRef::from_lit("192.168.0.1"),
-                  StringRef::from_lit("/alpha/bravo"), groups, 255, balloc));
+              match_downstream_addr_group(routerconf, "192.168.0.1"_sr,
+                                          "/alpha/bravo"_sr, groups, 255,
+                                          balloc));
 
   assert_size(255, ==,
-              match_downstream_addr_group(
-                  routerconf, StringRef::from_lit("192.168.0.1"),
-                  StringRef::from_lit("/alph"), groups, 255, balloc));
+              match_downstream_addr_group(routerconf, "192.168.0.1"_sr,
+                                          "/alph"_sr, groups, 255, balloc));
 
   assert_size(255, ==,
-              match_downstream_addr_group(
-                  routerconf, StringRef::from_lit("192.168.0.1"),
-                  StringRef::from_lit("/"), groups, 255, balloc));
+              match_downstream_addr_group(routerconf, "192.168.0.1"_sr, "/"_sr,
+                                          groups, 255, balloc));
 
   // Test for wildcard hosts
   auto g1 = std::make_shared<DownstreamAddrGroup>();
@@ -236,52 +216,46 @@ void test_shrpx_worker_match_downstream_addr_group(void) {
   g3->pattern = ImmutableString::from_lit(".local");
   groups.push_back(std::move(g3));
 
-  wp.emplace_back(StringRef::from_lit("git.nghttp2.org"));
-  wcrouter.add_route(StringRef::from_lit("gro.2ptthgn.tig"), 0);
-  wp.back().router.add_route(StringRef::from_lit("/echo/"), 10);
+  wp.emplace_back("git.nghttp2.org"_sr);
+  wcrouter.add_route("gro.2ptthgn.tig"_sr, 0);
+  wp.back().router.add_route("/echo/"_sr, 10);
 
-  wp.emplace_back(StringRef::from_lit(".nghttp2.org"));
-  wcrouter.add_route(StringRef::from_lit("gro.2ptthgn."), 1);
-  wp.back().router.add_route(StringRef::from_lit("/echo/"), 11);
-  wp.back().router.add_route(StringRef::from_lit("/echo/foxtrot"), 12);
+  wp.emplace_back(".nghttp2.org"_sr);
+  wcrouter.add_route("gro.2ptthgn."_sr, 1);
+  wp.back().router.add_route("/echo/"_sr, 11);
+  wp.back().router.add_route("/echo/foxtrot"_sr, 12);
 
-  wp.emplace_back(StringRef::from_lit(".local"));
-  wcrouter.add_route(StringRef::from_lit("lacol."), 2);
-  wp.back().router.add_route(StringRef::from_lit("/"), 13);
+  wp.emplace_back(".local"_sr);
+  wcrouter.add_route("lacol."_sr, 2);
+  wp.back().router.add_route("/"_sr, 13);
 
   assert_size(11, ==,
-              match_downstream_addr_group(
-                  routerconf, StringRef::from_lit("git.nghttp2.org"),
-                  StringRef::from_lit("/echo"), groups, 255, balloc));
+              match_downstream_addr_group(routerconf, "git.nghttp2.org"_sr,
+                                          "/echo"_sr, groups, 255, balloc));
 
   assert_size(10, ==,
-              match_downstream_addr_group(
-                  routerconf, StringRef::from_lit("0git.nghttp2.org"),
-                  StringRef::from_lit("/echo"), groups, 255, balloc));
+              match_downstream_addr_group(routerconf, "0git.nghttp2.org"_sr,
+                                          "/echo"_sr, groups, 255, balloc));
 
   assert_size(11, ==,
-              match_downstream_addr_group(
-                  routerconf, StringRef::from_lit("it.nghttp2.org"),
-                  StringRef::from_lit("/echo"), groups, 255, balloc));
+              match_downstream_addr_group(routerconf, "it.nghttp2.org"_sr,
+                                          "/echo"_sr, groups, 255, balloc));
 
   assert_size(255, ==,
-              match_downstream_addr_group(
-                  routerconf, StringRef::from_lit(".nghttp2.org"),
-                  StringRef::from_lit("/echo/foxtrot"), groups, 255, balloc));
+              match_downstream_addr_group(routerconf, ".nghttp2.org"_sr,
+                                          "/echo/foxtrot"_sr, groups, 255,
+                                          balloc));
 
   assert_size(9, ==,
-              match_downstream_addr_group(
-                  routerconf, StringRef::from_lit("alpha.nghttp2.org"),
-                  StringRef::from_lit("/golf"), groups, 255, balloc));
+              match_downstream_addr_group(routerconf, "alpha.nghttp2.org"_sr,
+                                          "/golf"_sr, groups, 255, balloc));
 
   assert_size(0, ==,
-              match_downstream_addr_group(
-                  routerconf, StringRef::from_lit("nghttp2.org"),
-                  StringRef::from_lit("/echo"), groups, 255, balloc));
+              match_downstream_addr_group(routerconf, "nghttp2.org"_sr,
+                                          "/echo"_sr, groups, 255, balloc));
 
   assert_size(13, ==,
-              match_downstream_addr_group(routerconf,
-                                          StringRef::from_lit("test.local"),
+              match_downstream_addr_group(routerconf, "test.local"_sr,
                                           StringRef{}, groups, 255, balloc));
 }
 
diff --git a/src/template.h b/src/template.h
index 530a1d1..3ab3677 100644
--- a/src/template.h
+++ b/src/template.h
@@ -37,20 +37,11 @@
 #include <algorithm>
 #include <ostream>
 #include <utility>
+#include <span>
+#include <string_view>
 
 namespace nghttp2 {
 
-// std::forward is constexpr since C++14
-template <typename... T>
-constexpr std::array<
-    typename std::decay<typename std::common_type<T...>::type>::type,
-    sizeof...(T)>
-make_array(T &&...t) {
-  return std::array<
-      typename std::decay<typename std::common_type<T...>::type>::type,
-      sizeof...(T)>{{std::forward<T>(t)...}};
-}
-
 template <typename T, size_t N> constexpr size_t array_size(T (&)[N]) {
   return N;
 }
@@ -67,8 +58,7 @@ template <typename F, typename... T> struct Defer {
   Defer(Defer &&o) noexcept : f(std::move(o.f)) {}
   ~Defer() { f(); }
 
-  using ResultType = typename std::result_of<typename std::decay<F>::type(
-      typename std::decay<T>::type...)>::type;
+  using ResultType = std::invoke_result_t<F, T...>;
   std::function<ResultType()> f;
 };
 
@@ -234,27 +224,27 @@ public:
   using const_iterator = const_pointer;
   using const_reverse_iterator = std::reverse_iterator<const_iterator>;
 
-  ImmutableString() : len(0), base("") {}
-  ImmutableString(const char *s, size_t slen)
+  constexpr ImmutableString() : len(0), base("") {}
+  constexpr ImmutableString(const char *s, size_t slen)
       : len(slen), base(copystr(s, s + len)) {}
-  explicit ImmutableString(const char *s)
-      : len(strlen(s)), base(copystr(s, s + len)) {}
-  explicit ImmutableString(const std::string &s)
+  constexpr explicit ImmutableString(const char *s)
+      : len(traits_type::length(s)), base(copystr(s, s + len)) {}
+  constexpr explicit ImmutableString(const std::string &s)
       : len(s.size()), base(copystr(std::begin(s), std::end(s))) {}
   template <typename InputIt>
-  ImmutableString(InputIt first, InputIt last)
+  constexpr ImmutableString(InputIt first, InputIt last)
       : len(std::distance(first, last)), base(copystr(first, last)) {}
-  ImmutableString(const ImmutableString &other)
+  constexpr ImmutableString(const ImmutableString &other)
       : len(other.len), base(copystr(std::begin(other), std::end(other))) {}
-  ImmutableString(ImmutableString &&other) noexcept
+  constexpr ImmutableString(ImmutableString &&other) noexcept
       : len{std::exchange(other.len, 0)}, base{std::exchange(other.base, "")} {}
-  ~ImmutableString() {
+  constexpr ~ImmutableString() {
     if (len) {
       delete[] base;
     }
   }
 
-  ImmutableString &operator=(const ImmutableString &other) {
+  constexpr ImmutableString &operator=(const ImmutableString &other) {
     if (this == &other) {
       return *this;
     }
@@ -265,7 +255,7 @@ public:
     base = copystr(std::begin(other), std::end(other));
     return *this;
   }
-  ImmutableString &operator=(ImmutableString &&other) noexcept {
+  constexpr ImmutableString &operator=(ImmutableString &&other) noexcept {
     if (this == &other) {
       return *this;
     }
@@ -277,33 +267,41 @@ public:
     return *this;
   }
 
-  template <size_t N> static ImmutableString from_lit(const char (&s)[N]) {
+  template <size_t N>
+  static constexpr ImmutableString from_lit(const char (&s)[N]) {
     return ImmutableString(s, N - 1);
   }
 
-  const_iterator begin() const { return base; };
-  const_iterator cbegin() const { return base; };
+  constexpr const_iterator begin() const noexcept { return base; };
+  constexpr const_iterator cbegin() const noexcept { return base; };
 
-  const_iterator end() const { return base + len; };
-  const_iterator cend() const { return base + len; };
+  constexpr const_iterator end() const noexcept { return base + len; };
+  constexpr const_iterator cend() const noexcept { return base + len; };
 
-  const_reverse_iterator rbegin() const {
+  constexpr const_reverse_iterator rbegin() const noexcept {
     return const_reverse_iterator{base + len};
   }
-  const_reverse_iterator crbegin() const {
+  constexpr const_reverse_iterator crbegin() const noexcept {
     return const_reverse_iterator{base + len};
   }
 
-  const_reverse_iterator rend() const { return const_reverse_iterator{base}; }
-  const_reverse_iterator crend() const { return const_reverse_iterator{base}; }
+  constexpr const_reverse_iterator rend() const noexcept {
+    return const_reverse_iterator{base};
+  }
+  constexpr const_reverse_iterator crend() const noexcept {
+    return const_reverse_iterator{base};
+  }
 
-  const char *c_str() const { return base; }
-  size_type size() const { return len; }
-  bool empty() const { return len == 0; }
-  const_reference operator[](size_type pos) const { return *(base + pos); }
+  constexpr const char *c_str() const noexcept { return base; }
+  constexpr size_type size() const noexcept { return len; }
+  constexpr bool empty() const noexcept { return len == 0; }
+  constexpr const_reference operator[](size_type pos) const noexcept {
+    return *(base + pos);
+  }
 
 private:
-  template <typename InputIt> const char *copystr(InputIt first, InputIt last) {
+  template <typename InputIt>
+  constexpr const char *copystr(InputIt first, InputIt last) {
     if (first == last) {
       return "";
     }
@@ -316,49 +314,23 @@ private:
   const char *base;
 };
 
-inline bool operator==(const ImmutableString &lhs, const ImmutableString &rhs) {
+inline constexpr bool operator==(const ImmutableString &lhs,
+                                 const ImmutableString &rhs) {
   return lhs.size() == rhs.size() &&
          std::equal(std::begin(lhs), std::end(lhs), std::begin(rhs));
 }
 
-inline bool operator==(const ImmutableString &lhs, const std::string &rhs) {
+inline constexpr bool operator==(const ImmutableString &lhs,
+                                 const std::string &rhs) {
   return lhs.size() == rhs.size() &&
          std::equal(std::begin(lhs), std::end(lhs), std::begin(rhs));
 }
 
-inline bool operator==(const std::string &lhs, const ImmutableString &rhs) {
-  return rhs == lhs;
-}
-
-inline bool operator==(const ImmutableString &lhs, const char *rhs) {
-  return lhs.size() == strlen(rhs) &&
+inline constexpr bool operator==(const ImmutableString &lhs, const char *rhs) {
+  return lhs.size() == std::char_traits<char>::length(rhs) &&
          std::equal(std::begin(lhs), std::end(lhs), rhs);
 }
 
-inline bool operator==(const char *lhs, const ImmutableString &rhs) {
-  return rhs == lhs;
-}
-
-inline bool operator!=(const ImmutableString &lhs, const ImmutableString &rhs) {
-  return !(lhs == rhs);
-}
-
-inline bool operator!=(const ImmutableString &lhs, const std::string &rhs) {
-  return !(lhs == rhs);
-}
-
-inline bool operator!=(const std::string &lhs, const ImmutableString &rhs) {
-  return !(rhs == lhs);
-}
-
-inline bool operator!=(const ImmutableString &lhs, const char *rhs) {
-  return !(lhs == rhs);
-}
-
-inline bool operator!=(const char *lhs, const ImmutableString &rhs) {
-  return !(rhs == lhs);
-}
-
 inline std::ostream &operator<<(std::ostream &o, const ImmutableString &s) {
   return o.write(s.c_str(), s.size());
 }
@@ -371,8 +343,7 @@ inline std::string &operator+=(std::string &lhs, const ImmutableString &rhs) {
 // StringRef is a reference to a string owned by something else.  So
 // it behaves like simple string, but it does not own pointer.  When
 // it is default constructed, it has empty string.  You can freely
-// copy or move around this struct, but never free its pointer.  str()
-// function can be used to export the content as std::string.
+// copy or move around this struct, but never free its pointer.
 class StringRef {
 public:
   using traits_type = std::char_traits<char>;
@@ -386,28 +357,28 @@ public:
   using const_iterator = const_pointer;
   using const_reverse_iterator = std::reverse_iterator<const_iterator>;
 
-  constexpr StringRef() : base(""), len(0) {}
-  explicit StringRef(const std::string &s) : base(s.c_str()), len(s.size()) {}
-  explicit StringRef(const ImmutableString &s)
+  constexpr StringRef() noexcept : base(""), len(0) {}
+  constexpr StringRef(const StringRef &other) noexcept = default;
+  constexpr StringRef(std::nullptr_t) = delete;
+  constexpr StringRef(const std::string &s) : base(s.c_str()), len(s.size()) {}
+  constexpr explicit StringRef(const std::string_view &s)
+      : base(s.data()), len(s.size()) {}
+  constexpr explicit StringRef(const ImmutableString &s)
       : base(s.c_str()), len(s.size()) {}
-  explicit StringRef(const char *s) : base(s), len(strlen(s)) {}
+  constexpr StringRef(const char *s) : base(s), len(traits_type::length(s)) {}
   constexpr StringRef(const char *s, size_t n) : base(s), len(n) {}
-  template <typename CharT>
-  constexpr StringRef(const CharT *s, size_t n)
+  explicit StringRef(const uint8_t *s, size_t n)
       : base(reinterpret_cast<const char *>(s)), len(n) {}
-  template <typename InputIt>
-  StringRef(InputIt first, InputIt last)
-      : base(reinterpret_cast<const char *>(&*first)),
-        len(std::distance(first, last)) {}
-  template <typename InputIt>
-  StringRef(InputIt *first, InputIt *last)
-      : base(reinterpret_cast<const char *>(first)),
-        len(std::distance(first, last)) {}
-  template <typename CharT, size_t N>
-  constexpr static StringRef from_lit(const CharT (&s)[N]) {
-    return StringRef{s, N - 1};
-  }
-  static StringRef from_maybe_nullptr(const char *s) {
+  template <std::contiguous_iterator InputIt,
+            typename = std::enable_if_t<
+                std::is_same_v<std::iter_value_t<InputIt>, char>>>
+  constexpr StringRef(InputIt first, InputIt last)
+      : base(std::to_address(first)), len(std::distance(first, last)) {}
+  constexpr StringRef(std::span<const char> s)
+      : base(s.data()), len(s.size_bytes()) {}
+  explicit StringRef(std::span<const uint8_t> s)
+      : base(reinterpret_cast<const char *>(s.data())), len(s.size_bytes()) {}
+  static constexpr StringRef from_maybe_nullptr(const char *s) noexcept {
     if (s == nullptr) {
       return StringRef();
     }
@@ -415,105 +386,103 @@ public:
     return StringRef(s);
   }
 
-  constexpr const_iterator begin() const { return base; };
-  constexpr const_iterator cbegin() const { return base; };
+  constexpr StringRef &operator=(const StringRef &other) noexcept = default;
+
+  constexpr const_iterator begin() const noexcept { return base; };
+  constexpr const_iterator cbegin() const noexcept { return base; };
 
-  constexpr const_iterator end() const { return base + len; };
-  constexpr const_iterator cend() const { return base + len; };
+  constexpr const_iterator end() const noexcept { return base + len; };
+  constexpr const_iterator cend() const noexcept { return base + len; };
 
-  const_reverse_iterator rbegin() const {
+  constexpr const_reverse_iterator rbegin() const noexcept {
     return const_reverse_iterator{base + len};
   }
-  const_reverse_iterator crbegin() const {
+  constexpr const_reverse_iterator crbegin() const noexcept {
     return const_reverse_iterator{base + len};
   }
 
-  const_reverse_iterator rend() const { return const_reverse_iterator{base}; }
-  const_reverse_iterator crend() const { return const_reverse_iterator{base}; }
+  constexpr const_reverse_iterator rend() const noexcept {
+    return const_reverse_iterator{base};
+  }
+  constexpr const_reverse_iterator crend() const noexcept {
+    return const_reverse_iterator{base};
+  }
 
-  constexpr const char *c_str() const { return base; }
-  constexpr size_type size() const { return len; }
-  constexpr bool empty() const { return len == 0; }
+  constexpr const_pointer data() const noexcept { return base; }
+  constexpr size_type size() const noexcept { return len; }
+  [[nodiscard]] constexpr bool empty() const noexcept { return len == 0; }
   constexpr const_reference operator[](size_type pos) const {
     return *(base + pos);
   }
 
-  std::string str() const { return std::string(base, len); }
   const uint8_t *byte() const {
     return reinterpret_cast<const uint8_t *>(base);
   }
 
+  constexpr operator std::string_view() const noexcept { return {base, len}; }
+
+  static constexpr size_type npos = size_type(-1);
+
+  constexpr StringRef substr(size_type pos = 0, size_type count = npos) const {
+    return {base + pos, std::min(count, len - pos)};
+  }
+
 private:
   const char *base;
   size_type len;
 };
 
-inline bool operator==(const StringRef &lhs, const StringRef &rhs) {
+inline constexpr bool operator==(const StringRef &lhs,
+                                 const StringRef &rhs) noexcept {
   return lhs.size() == rhs.size() &&
          std::equal(std::begin(lhs), std::end(lhs), std::begin(rhs));
 }
 
-inline bool operator==(const StringRef &lhs, const std::string &rhs) {
+inline constexpr bool operator==(const StringRef &lhs,
+                                 const ImmutableString &rhs) noexcept {
   return lhs.size() == rhs.size() &&
          std::equal(std::begin(lhs), std::end(lhs), std::begin(rhs));
 }
 
-inline bool operator==(const std::string &lhs, const StringRef &rhs) {
-  return rhs == lhs;
-}
-
-inline bool operator==(const StringRef &lhs, const char *rhs) {
-  return lhs.size() == strlen(rhs) &&
-         std::equal(std::begin(lhs), std::end(lhs), rhs);
-}
-
-inline bool operator==(const StringRef &lhs, const ImmutableString &rhs) {
-  return lhs.size() == rhs.size() &&
-         std::equal(std::begin(lhs), std::end(lhs), std::begin(rhs));
+#ifndef __APPLE__
+inline constexpr std::strong_ordering
+operator<=>(const StringRef &lhs, const StringRef &rhs) noexcept {
+  return std::lexicographical_compare_three_way(std::begin(lhs), std::end(lhs),
+                                                std::begin(rhs), std::end(rhs));
 }
-
-inline bool operator==(const ImmutableString &lhs, const StringRef &rhs) {
-  return rhs == lhs;
-}
-
-inline bool operator==(const char *lhs, const StringRef &rhs) {
-  return rhs == lhs;
-}
-
-inline bool operator!=(const StringRef &lhs, const StringRef &rhs) {
-  return !(lhs == rhs);
-}
-
-inline bool operator!=(const StringRef &lhs, const std::string &rhs) {
-  return !(lhs == rhs);
-}
-
-inline bool operator!=(const std::string &lhs, const StringRef &rhs) {
-  return !(rhs == lhs);
-}
-
-inline bool operator!=(const StringRef &lhs, const char *rhs) {
-  return !(lhs == rhs);
-}
-
-inline bool operator!=(const char *lhs, const StringRef &rhs) {
-  return !(rhs == lhs);
-}
-
-inline bool operator<(const StringRef &lhs, const StringRef &rhs) {
+#else  // __APPLE__
+inline constexpr bool operator<(const StringRef &lhs,
+                                const StringRef &rhs) noexcept {
   return std::lexicographical_compare(std::begin(lhs), std::end(lhs),
                                       std::begin(rhs), std::end(rhs));
 }
+#endif // __APPLE__
 
 inline std::ostream &operator<<(std::ostream &o, const StringRef &s) {
-  return o.write(s.c_str(), s.size());
+  return o.write(s.data(), s.size());
 }
 
 inline std::string &operator+=(std::string &lhs, const StringRef &rhs) {
-  lhs.append(rhs.c_str(), rhs.size());
+  lhs.append(rhs.data(), rhs.size());
   return lhs;
 }
 
+constexpr StringRef operator""_sr(const char *str, size_t len) noexcept {
+  return {str, len};
+}
+
+template <typename T, std::size_t N>
+[[nodiscard]] std::span<const uint8_t, N == std::dynamic_extent
+                                           ? std::dynamic_extent
+                                           : N * sizeof(T)>
+as_uint8_span(std::span<T, N> s) noexcept {
+  return std::span < const uint8_t,
+         N == std::dynamic_extent
+             ? std::dynamic_extent
+             : N * sizeof(T) > {reinterpret_cast<const uint8_t *>(s.data()),
+                                s.size_bytes()};
+}
+
 inline int run_app(std::function<int(int, char **)> app, int argc,
                    char **argv) {
   try {
diff --git a/src/template_test.cc b/src/template_test.cc
index db212d1..99b193b 100644
--- a/src/template_test.cc
+++ b/src/template_test.cc
@@ -32,12 +32,15 @@
 
 #include "template.h"
 
+using namespace std::literals;
+
 namespace nghttp2 {
 
 namespace {
 const MunitTest tests[]{
     munit_void_test(test_template_immutable_string),
     munit_void_test(test_template_string_ref),
+    munit_void_test(test_template_as_uint8_span),
     munit_test_end(),
 };
 } // namespace
@@ -147,7 +150,7 @@ void test_template_immutable_string(void) {
 void test_template_string_ref(void) {
   StringRef empty;
 
-  assert_stdstring_equal("", empty.str());
+  assert_stdsv_equal(""sv, empty);
   assert_size(0, ==, empty.size());
 
   // from std::string
@@ -162,9 +165,9 @@ void test_template_string_ref(void) {
   assert_size(5, ==, ref.size());
 
   // from string literal
-  auto from_lit = StringRef::from_lit("alpha");
+  auto from_lit = "alpha"_sr;
 
-  assert_stdstring_equal("alpha", from_lit.str());
+  assert_stdsv_equal("alpha"sv, from_lit);
   assert_size(5, ==, from_lit.size());
 
   // from ImmutableString
@@ -172,19 +175,19 @@ void test_template_string_ref(void) {
 
   StringRef imref(im);
 
-  assert_stdstring_equal("bravo", imref.str());
+  assert_stdsv_equal("bravo"sv, imref);
   assert_size(5, ==, imref.size());
 
   // from C-string
   StringRef cstrref("charlie");
 
-  assert_stdstring_equal("charlie", cstrref.str());
+  assert_stdsv_equal("charlie"sv, cstrref);
   assert_size(7, ==, cstrref.size());
 
   // from C-string and its length
   StringRef cstrnref("delta", 5);
 
-  assert_stdstring_equal("delta", cstrnref.str());
+  assert_stdsv_equal("delta"sv, cstrnref);
   assert_size(5, ==, cstrnref.size());
 
   // operator[]
@@ -213,4 +216,24 @@ void test_template_string_ref(void) {
   }
 }
 
+void test_template_as_uint8_span(void) {
+  uint32_t a[2];
+
+  memcpy(&a, "\xc0\xc1\xc2\xc3\xf0\xf1\xf2\xf3", sizeof(a));
+
+  // dynamic extent
+  auto s = as_uint8_span(std::span{a, 2});
+
+  assert_size(sizeof(a), ==, s.size());
+  assert_size(std::dynamic_extent, ==, s.extent);
+  assert_memory_equal(s.size(), &a, s.data());
+
+  // non-dynamic extent
+  auto t = as_uint8_span(std::span<uint32_t, 2>{a, 2});
+
+  assert_size(sizeof(a), ==, t.size());
+  assert_size(sizeof(a), ==, t.extent);
+  assert_memory_equal(t.size(), &a, t.data());
+}
+
 } // namespace nghttp2
diff --git a/src/template_test.h b/src/template_test.h
index df39de9..d52bd26 100644
--- a/src/template_test.h
+++ b/src/template_test.h
@@ -39,6 +39,7 @@ extern const MunitSuite template_suite;
 
 munit_void_test_decl(test_template_immutable_string);
 munit_void_test_decl(test_template_string_ref);
+munit_void_test_decl(test_template_as_uint8_span);
 
 } // namespace nghttp2
 
diff --git a/src/tls.h b/src/tls.h
index c5fda32..b969af7 100644
--- a/src/tls.h
+++ b/src/tls.h
@@ -28,11 +28,14 @@
 #include "nghttp2_config.h"
 
 #include <cinttypes>
+#include <string_view>
 
 #include <openssl/ssl.h>
 
 #include "ssl_compat.h"
 
+using namespace std::literals;
+
 namespace nghttp2 {
 
 namespace tls {
@@ -41,19 +44,20 @@ namespace tls {
 // suites for TLSv1.2 by mozilla.
 //
 // https://wiki.mozilla.org/Security/Server_Side_TLS
-constexpr char DEFAULT_CIPHER_LIST[] =
+constexpr auto DEFAULT_CIPHER_LIST =
     "ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-"
     "AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-"
     "POLY1305:ECDHE-RSA-CHACHA20-POLY1305:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-"
-    "AES256-GCM-SHA384";
+    "AES256-GCM-SHA384"sv;
 
 // Recommended general purpose "Modern compatibility" cipher suites
 // for TLSv1.3 by mozilla.
 //
 // https://wiki.mozilla.org/Security/Server_Side_TLS
-constexpr char DEFAULT_TLS13_CIPHER_LIST[] =
+constexpr auto DEFAULT_TLS13_CIPHER_LIST =
 #if defined(NGHTTP2_GENUINE_OPENSSL) || defined(NGHTTP2_OPENSSL_IS_LIBRESSL)
-    "TLS_AES_128_GCM_SHA256:TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256"
+    "TLS_AES_128_GCM_SHA256:TLS_AES_256_GCM_SHA384:"
+    "TLS_CHACHA20_POLY1305_SHA256"sv
 #else  // !NGHTTP2_GENUINE_OPENSSL && !NGHTTP2_OPENSSL_IS_LIBRESSL
     ""
 #endif // !NGHTTP2_GENUINE_OPENSSL && !NGHTTP2_OPENSSL_IS_LIBRESSL
diff --git a/src/util.cc b/src/util.cc
index 47151b2..e6c4214 100644
--- a/src/util.cc
+++ b/src/util.cc
@@ -191,11 +191,11 @@ bool in_attr_char(char c) {
 StringRef percent_encode_token(BlockAllocator &balloc,
                                const StringRef &target) {
   auto iov = make_byte_ref(balloc, target.size() * 3 + 1);
-  auto p = percent_encode_token(iov.base, target);
+  auto p = percent_encode_token(std::begin(iov), target);
 
   *p = '\0';
 
-  return StringRef{iov.base, p};
+  return StringRef{std::span{std::begin(iov), p}};
 }
 
 size_t percent_encode_tokenlen(const StringRef &target) {
@@ -237,11 +237,11 @@ StringRef quote_string(BlockAllocator &balloc, const StringRef &target) {
   }
 
   auto iov = make_byte_ref(balloc, target.size() + cnt + 1);
-  auto p = quote_string(iov.base, target);
+  auto p = quote_string(std::begin(iov), target);
 
   *p = '\0';
 
-  return StringRef{iov.base, p};
+  return StringRef{std::span{std::begin(iov), p}};
 }
 
 size_t quote_stringlen(const StringRef &target) {
@@ -465,13 +465,13 @@ time_t parse_http_date(const StringRef &s) {
   tm tm{};
 #ifdef _WIN32
   // there is no strptime - use std::get_time
-  std::stringstream sstr(s.str());
+  std::stringstream sstr(s.data());
   sstr >> std::get_time(&tm, "%a, %d %b %Y %H:%M:%S GMT");
   if (sstr.fail()) {
     return 0;
   }
 #else  // !_WIN32
-  char *r = strptime(s.c_str(), "%a, %d %b %Y %H:%M:%S GMT", &tm);
+  char *r = strptime(s.data(), "%a, %d %b %Y %H:%M:%S GMT", &tm);
   if (r == 0) {
     return 0;
   }
@@ -481,7 +481,7 @@ time_t parse_http_date(const StringRef &s) {
 
 time_t parse_openssl_asn1_time_print(const StringRef &s) {
   tm tm{};
-  auto r = strptime(s.c_str(), "%b %d %H:%M:%S %Y GMT", &tm);
+  auto r = strptime(s.data(), "%b %d %H:%M:%S %Y GMT", &tm);
   if (r == nullptr) {
     return 0;
   }
@@ -496,32 +496,22 @@ char upcase(char c) {
   }
 }
 
-std::string format_hex(const unsigned char *s, size_t len) {
+std::string format_hex(std::span<const uint8_t> s) {
   std::string res;
-  res.resize(len * 2);
+  res.resize(s.size() * 2);
 
-  for (size_t i = 0; i < len; ++i) {
-    unsigned char c = s[i];
+  format_hex(std::begin(res), s);
 
-    res[i * 2] = LOWER_XDIGITS[c >> 4];
-    res[i * 2 + 1] = LOWER_XDIGITS[c & 0x0f];
-  }
   return res;
 }
 
-StringRef format_hex(BlockAllocator &balloc, const StringRef &s) {
+StringRef format_hex(BlockAllocator &balloc, std::span<const uint8_t> s) {
   auto iov = make_byte_ref(balloc, s.size() * 2 + 1);
-  auto p = iov.base;
-
-  for (auto cc : s) {
-    uint8_t c = cc;
-    *p++ = LOWER_XDIGITS[c >> 4];
-    *p++ = LOWER_XDIGITS[c & 0xf];
-  }
+  auto p = format_hex(std::begin(iov), s);
 
   *p = '\0';
 
-  return StringRef{iov.base, p};
+  return StringRef{std::span{std::begin(iov), p}};
 }
 
 void to_token68(std::string &base64str) {
@@ -544,19 +534,18 @@ StringRef to_base64(BlockAllocator &balloc, const StringRef &token68str) {
   // At most 3 padding '='
   auto len = token68str.size() + 3;
   auto iov = make_byte_ref(balloc, len + 1);
-  auto p = iov.base;
-
-  p = std::transform(std::begin(token68str), std::end(token68str), p,
-                     [](char c) {
-                       switch (c) {
-                       case '-':
-                         return '+';
-                       case '_':
-                         return '/';
-                       default:
-                         return c;
-                       }
-                     });
+
+  auto p = std::transform(std::begin(token68str), std::end(token68str),
+                          std::begin(iov), [](char c) {
+                            switch (c) {
+                            case '-':
+                              return '+';
+                            case '_':
+                              return '/';
+                            default:
+                              return c;
+                            }
+                          });
 
   auto rem = token68str.size() & 0x3;
   if (rem) {
@@ -565,7 +554,7 @@ StringRef to_base64(BlockAllocator &balloc, const StringRef &token68str) {
 
   *p = '\0';
 
-  return StringRef{iov.base, p};
+  return StringRef{std::span{std::begin(iov), p}};
 }
 
 namespace {
@@ -878,7 +867,7 @@ bool check_path(const std::string &path) {
          path.find('\\') == std::string::npos &&
          path.find("/../") == std::string::npos &&
          path.find("/./") == std::string::npos &&
-         !util::ends_with_l(path, "/..") && !util::ends_with_l(path, "/.");
+         !util::ends_with(path, "/.."_sr) && !util::ends_with(path, "/."_sr);
 }
 
 int64_t to_time64(const timeval &tv) {
@@ -886,8 +875,8 @@ int64_t to_time64(const timeval &tv) {
 }
 
 bool check_h2_is_selected(const StringRef &proto) {
-  return streq(NGHTTP2_H2, proto) || streq(NGHTTP2_H2_16, proto) ||
-         streq(NGHTTP2_H2_14, proto);
+  return NGHTTP2_H2 == proto || NGHTTP2_H2_16 == proto ||
+         NGHTTP2_H2_14 == proto;
 }
 
 namespace {
@@ -1148,58 +1137,63 @@ bool ipv6_numeric_addr(const char *host) {
 }
 
 namespace {
-std::pair<int64_t, size_t> parse_uint_digits(const void *ss, size_t len) {
-  const uint8_t *s = static_cast<const uint8_t *>(ss);
-  int64_t n = 0;
-  size_t i;
-  if (len == 0) {
-    return {-1, 0};
+std::optional<std::pair<int64_t, StringRef>>
+parse_uint_digits(const StringRef &s) {
+  if (s.empty()) {
+    return {};
   }
+
   constexpr int64_t max = std::numeric_limits<int64_t>::max();
-  for (i = 0; i < len; ++i) {
-    if ('0' <= s[i] && s[i] <= '9') {
-      if (n > max / 10) {
-        return {-1, 0};
-      }
-      n *= 10;
-      if (n > max - (s[i] - '0')) {
-        return {-1, 0};
-      }
-      n += s[i] - '0';
-      continue;
+
+  int64_t n = 0;
+  size_t i = 0;
+
+  for (auto c : s) {
+    if ('0' > c || c > '9') {
+      break;
     }
-    break;
+
+    if (n > max / 10) {
+      return {};
+    }
+
+    n *= 10;
+
+    if (n > max - (c - '0')) {
+      return {};
+    }
+
+    n += c - '0';
+
+    ++i;
   }
+
   if (i == 0) {
-    return {-1, 0};
+    return {};
   }
-  return {n, i};
+
+  return std::pair{n, s.substr(i)};
 }
 } // namespace
 
-int64_t parse_uint_with_unit(const char *s) {
-  return parse_uint_with_unit(reinterpret_cast<const uint8_t *>(s), strlen(s));
-}
+std::optional<int64_t> parse_uint_with_unit(const StringRef &s) {
+  auto r = parse_uint_digits(s);
+  if (!r) {
+    return {};
+  }
 
-int64_t parse_uint_with_unit(const StringRef &s) {
-  return parse_uint_with_unit(s.byte(), s.size());
-}
+  auto [n, rest] = *r;
 
-int64_t parse_uint_with_unit(const uint8_t *s, size_t len) {
-  int64_t n;
-  size_t i;
-  std::tie(n, i) = parse_uint_digits(s, len);
-  if (n == -1) {
-    return -1;
-  }
-  if (i == len) {
+  if (rest.empty()) {
     return n;
   }
-  if (i + 1 != len) {
-    return -1;
+
+  if (rest.size() != 1) {
+    return {};
   }
+
   int mul = 1;
-  switch (s[i]) {
+  switch (rest[0]) {
   case 'K':
   case 'k':
     mul = 1 << 10;
@@ -1213,94 +1207,81 @@ int64_t parse_uint_with_unit(const uint8_t *s, size_t len) {
     mul = 1 << 30;
     break;
   default:
-    return -1;
+    return {};
   }
+
   constexpr int64_t max = std::numeric_limits<int64_t>::max();
   if (n > max / mul) {
-    return -1;
+    return {};
   }
-  return n * mul;
-}
 
-int64_t parse_uint(const char *s) {
-  return parse_uint(reinterpret_cast<const uint8_t *>(s), strlen(s));
-}
-
-int64_t parse_uint(const std::string &s) {
-  return parse_uint(reinterpret_cast<const uint8_t *>(s.c_str()), s.size());
-}
-
-int64_t parse_uint(const StringRef &s) {
-  return parse_uint(s.byte(), s.size());
+  return n * mul;
 }
 
-int64_t parse_uint(const uint8_t *s, size_t len) {
-  int64_t n;
-  size_t i;
-  std::tie(n, i) = parse_uint_digits(s, len);
-  if (n == -1 || i != len) {
-    return -1;
+std::optional<int64_t> parse_uint(const StringRef &s) {
+  auto r = parse_uint_digits(s);
+  if (!r || !(*r).second.empty()) {
+    return {};
   }
-  return n;
-}
-
-double parse_duration_with_unit(const char *s) {
-  return parse_duration_with_unit(reinterpret_cast<const uint8_t *>(s),
-                                  strlen(s));
-}
 
-double parse_duration_with_unit(const StringRef &s) {
-  return parse_duration_with_unit(s.byte(), s.size());
+  return (*r).first;
 }
 
-double parse_duration_with_unit(const uint8_t *s, size_t len) {
+std::optional<double> parse_duration_with_unit(const StringRef &s) {
   constexpr auto max = std::numeric_limits<int64_t>::max();
-  int64_t n;
-  size_t i;
 
-  std::tie(n, i) = parse_uint_digits(s, len);
-  if (n == -1) {
-    goto fail;
+  auto r = parse_uint_digits(s);
+  if (!r) {
+    return {};
   }
-  if (i == len) {
+
+  auto [n, rest] = *r;
+
+  if (rest.empty()) {
     return static_cast<double>(n);
   }
-  switch (s[i]) {
+
+  switch (rest[0]) {
   case 'S':
   case 's':
     // seconds
-    if (i + 1 != len) {
-      goto fail;
+    if (rest.size() != 1) {
+      return {};
     }
+
     return static_cast<double>(n);
   case 'M':
   case 'm':
-    if (i + 1 == len) {
+    if (rest.size() == 1) {
       // minutes
       if (n > max / 60) {
-        goto fail;
+        return {};
       }
+
       return static_cast<double>(n) * 60;
     }
 
-    if (i + 2 != len || (s[i + 1] != 's' && s[i + 1] != 'S')) {
-      goto fail;
+    if (rest.size() != 2 || (rest[1] != 's' && rest[1] != 'S')) {
+      return {};
     }
+
     // milliseconds
     return static_cast<double>(n) / 1000.;
   case 'H':
   case 'h':
     // hours
-    if (i + 1 != len) {
-      goto fail;
+    if (rest.size() != 1) {
+      return {};
     }
+
     if (n > max / 3600) {
-      goto fail;
+      return {};
     }
+
     return static_cast<double>(n) * 3600;
+  default:
+    return {};
   }
-fail:
-  return std::numeric_limits<double>::infinity();
 }
 
 std::string duration_str(double t) {
@@ -1362,13 +1343,13 @@ std::string dtos(double n) {
 StringRef make_http_hostport(BlockAllocator &balloc, const StringRef &host,
                              uint16_t port) {
   auto iov = make_byte_ref(balloc, host.size() + 2 + 1 + 5 + 1);
-  return make_http_hostport(iov.base, host, port);
+  return make_http_hostport(std::begin(iov), host, port);
 }
 
 StringRef make_hostport(BlockAllocator &balloc, const StringRef &host,
                         uint16_t port) {
   auto iov = make_byte_ref(balloc, host.size() + 2 + 1 + 5 + 1);
-  return make_hostport(iov.base, host, port);
+  return make_hostport(std::begin(iov), host, port);
 }
 
 namespace {
@@ -1611,7 +1592,7 @@ int read_mime_types(std::map<std::string, std::string> &res,
 
 StringRef percent_decode(BlockAllocator &balloc, const StringRef &src) {
   auto iov = make_byte_ref(balloc, src.size() * 3 + 1);
-  auto p = iov.base;
+  auto p = std::begin(iov);
   for (auto first = std::begin(src); first != std::end(src); ++first) {
     if (*first != '%') {
       *p++ = *first;
@@ -1628,7 +1609,7 @@ StringRef percent_decode(BlockAllocator &balloc, const StringRef &src) {
     *p++ = *first;
   }
   *p = '\0';
-  return StringRef{iov.base, p};
+  return StringRef{std::span{std::begin(iov), p}};
 }
 
 // Returns x**y
@@ -1669,7 +1650,7 @@ int message_digest(uint8_t *res, const EVP_MD *meth, const StringRef &s) {
     return -1;
   }
 
-  rv = EVP_DigestUpdate(ctx, s.c_str(), s.size());
+  rv = EVP_DigestUpdate(ctx, s.data(), s.size());
   if (rv != 1) {
     return -1;
   }
@@ -1707,11 +1688,12 @@ bool is_hex_string(const StringRef &s) {
   return true;
 }
 
-StringRef decode_hex(BlockAllocator &balloc, const StringRef &s) {
+std::span<const uint8_t> decode_hex(BlockAllocator &balloc,
+                                    const StringRef &s) {
   auto iov = make_byte_ref(balloc, s.size() + 1);
-  auto p = decode_hex(iov.base, s);
+  auto p = decode_hex(std::begin(iov), s);
   *p = '\0';
-  return StringRef{iov.base, p};
+  return {std::begin(iov), p};
 }
 
 StringRef extract_host(const StringRef &hostport) {
@@ -1824,7 +1806,7 @@ StringRef rstrip(BlockAllocator &balloc, const StringRef &s) {
     return s;
   }
 
-  return make_string_ref(balloc, StringRef{s.c_str(), s.size() - len});
+  return make_string_ref(balloc, StringRef{s.data(), s.size() - len});
 }
 
 #ifdef ENABLE_HTTP3
diff --git a/src/util.h b/src/util.h
index e1c0d81..4f8ae25 100644
--- a/src/util.h
+++ b/src/util.h
@@ -46,6 +46,7 @@
 #include <chrono>
 #include <map>
 #include <random>
+#include <optional>
 
 #ifdef HAVE_LIBEV
 #  include <ev.h>
@@ -59,20 +60,20 @@
 
 namespace nghttp2 {
 
-constexpr auto NGHTTP2_H2_ALPN = StringRef::from_lit("\x2h2");
-constexpr auto NGHTTP2_H2 = StringRef::from_lit("h2");
+constexpr auto NGHTTP2_H2_ALPN = "\x2h2"_sr;
+constexpr auto NGHTTP2_H2 = "h2"_sr;
 
 // The additional HTTP/2 protocol ALPN protocol identifier we also
 // supports for our applications to make smooth migration into final
 // h2 ALPN ID.
-constexpr auto NGHTTP2_H2_16_ALPN = StringRef::from_lit("\x5h2-16");
-constexpr auto NGHTTP2_H2_16 = StringRef::from_lit("h2-16");
+constexpr auto NGHTTP2_H2_16_ALPN = "\x5h2-16"_sr;
+constexpr auto NGHTTP2_H2_16 = "h2-16"_sr;
 
-constexpr auto NGHTTP2_H2_14_ALPN = StringRef::from_lit("\x5h2-14");
-constexpr auto NGHTTP2_H2_14 = StringRef::from_lit("h2-14");
+constexpr auto NGHTTP2_H2_14_ALPN = "\x5h2-14"_sr;
+constexpr auto NGHTTP2_H2_14 = "h2-14"_sr;
 
-constexpr auto NGHTTP2_H1_1_ALPN = StringRef::from_lit("\x8http/1.1");
-constexpr auto NGHTTP2_H1_1 = StringRef::from_lit("http/1.1");
+constexpr auto NGHTTP2_H1_1_ALPN = "\x8http/1.1"_sr;
+constexpr auto NGHTTP2_H1_1 = "http/1.1"_sr;
 
 constexpr size_t NGHTTP2_MAX_UINT64_DIGITS = str_size("18446744073709551615");
 
@@ -185,35 +186,42 @@ OutputIt quote_string(OutputIt it, const StringRef &target) {
 // NUL byte.
 size_t quote_stringlen(const StringRef &target);
 
-std::string format_hex(const unsigned char *s, size_t len);
+static constexpr char LOWER_XDIGITS[] = "0123456789abcdef";
+
+template <std::weakly_incrementable OutputIt>
+OutputIt format_hex(OutputIt it, std::span<const uint8_t> s) {
+  for (auto c : s) {
+    *it++ = LOWER_XDIGITS[c >> 4];
+    *it++ = LOWER_XDIGITS[c & 0xf];
+  }
 
-template <size_t N> std::string format_hex(const unsigned char (&s)[N]) {
-  return format_hex(s, N);
+  return it;
 }
 
-template <size_t N> std::string format_hex(const std::array<uint8_t, N> &s) {
-  return format_hex(s.data(), s.size());
+template <typename T, size_t N = std::dynamic_extent,
+          std::weakly_incrementable OutputIt>
+OutputIt format_hex(OutputIt it, std::span<T, N> s) {
+  return format_hex(it, std::span<const uint8_t>{as_uint8_span(s)});
 }
 
-StringRef format_hex(BlockAllocator &balloc, const StringRef &s);
+std::string format_hex(std::span<const uint8_t> s);
 
-static constexpr char LOWER_XDIGITS[] = "0123456789abcdef";
+template <typename T, size_t N = std::dynamic_extent>
+std::string format_hex(std::span<T, N> s) {
+  return format_hex(std::span<const uint8_t>{as_uint8_span(s)});
+}
 
-template <typename OutputIt>
-OutputIt format_hex(OutputIt it, const StringRef &s) {
-  for (auto cc : s) {
-    uint8_t c = cc;
-    *it++ = LOWER_XDIGITS[c >> 4];
-    *it++ = LOWER_XDIGITS[c & 0xf];
-  }
+StringRef format_hex(BlockAllocator &balloc, std::span<const uint8_t> s);
 
-  return it;
+template <typename T, size_t N = std::dynamic_extent>
+StringRef format_hex(BlockAllocator &balloc, std::span<T, N> s) {
+  return format_hex(balloc, std::span<const uint8_t>{as_uint8_span(s)});
 }
 
 // decode_hex decodes hex string |s|, returns the decoded byte string.
 // This function assumes |s| is hex string, that is is_hex_string(s)
 // == true.
-StringRef decode_hex(BlockAllocator &balloc, const StringRef &s);
+std::span<const uint8_t> decode_hex(BlockAllocator &balloc, const StringRef &s);
 
 template <typename OutputIt>
 OutputIt decode_hex(OutputIt d_first, const StringRef &s) {
@@ -289,14 +297,12 @@ inline char lowcase(char c) {
 template <typename InputIterator1, typename InputIterator2>
 bool starts_with(InputIterator1 first1, InputIterator1 last1,
                  InputIterator2 first2, InputIterator2 last2) {
-  if (last1 - first1 < last2 - first2) {
-    return false;
-  }
-  return std::equal(first2, last2, first1);
+  return std::distance(first1, last1) >= std::distance(first2, last2) &&
+         std::equal(first2, last2, first1);
 }
 
 template <typename S, typename T> bool starts_with(const S &a, const T &b) {
-  return starts_with(a.begin(), a.end(), b.begin(), b.end());
+  return starts_with(std::begin(a), std::end(a), std::begin(b), std::end(b));
 }
 
 struct CaseCmp {
@@ -308,107 +314,60 @@ struct CaseCmp {
 template <typename InputIterator1, typename InputIterator2>
 bool istarts_with(InputIterator1 first1, InputIterator1 last1,
                   InputIterator2 first2, InputIterator2 last2) {
-  if (last1 - first1 < last2 - first2) {
-    return false;
-  }
-  return std::equal(first2, last2, first1, CaseCmp());
+  return std::distance(first1, last1) >= std::distance(first2, last2) &&
+         std::equal(first2, last2, first1, CaseCmp());
 }
 
 template <typename S, typename T> bool istarts_with(const S &a, const T &b) {
-  return istarts_with(a.begin(), a.end(), b.begin(), b.end());
-}
-
-template <typename T, typename CharT, size_t N>
-bool istarts_with_l(const T &a, const CharT (&b)[N]) {
-  return istarts_with(a.begin(), a.end(), b, b + N - 1);
+  return istarts_with(std::begin(a), std::end(a), std::begin(b), std::end(b));
 }
 
 template <typename InputIterator1, typename InputIterator2>
 bool ends_with(InputIterator1 first1, InputIterator1 last1,
                InputIterator2 first2, InputIterator2 last2) {
-  if (last1 - first1 < last2 - first2) {
-    return false;
-  }
-  return std::equal(first2, last2, last1 - (last2 - first2));
-}
+  auto len1 = std::distance(first1, last1);
+  auto len2 = std::distance(first2, last2);
 
-template <typename T, typename S> bool ends_with(const T &a, const S &b) {
-  return ends_with(a.begin(), a.end(), b.begin(), b.end());
+  return len1 >= len2 && std::equal(first2, last2, first1 + (len1 - len2));
 }
 
-template <typename T, typename CharT, size_t N>
-bool ends_with_l(const T &a, const CharT (&b)[N]) {
-  return ends_with(a.begin(), a.end(), b, b + N - 1);
+template <typename T, typename S> bool ends_with(const T &a, const S &b) {
+  return ends_with(std::begin(a), std::end(a), std::begin(b), std::end(b));
 }
 
 template <typename InputIterator1, typename InputIterator2>
 bool iends_with(InputIterator1 first1, InputIterator1 last1,
                 InputIterator2 first2, InputIterator2 last2) {
-  if (last1 - first1 < last2 - first2) {
-    return false;
-  }
-  return std::equal(first2, last2, last1 - (last2 - first2), CaseCmp());
-}
+  auto len1 = std::distance(first1, last1);
+  auto len2 = std::distance(first2, last2);
 
-template <typename T, typename S> bool iends_with(const T &a, const S &b) {
-  return iends_with(a.begin(), a.end(), b.begin(), b.end());
+  return len1 >= len2 &&
+         std::equal(first2, last2, first1 + (len1 - len2), CaseCmp());
 }
 
-template <typename T, typename CharT, size_t N>
-bool iends_with_l(const T &a, const CharT (&b)[N]) {
-  return iends_with(a.begin(), a.end(), b, b + N - 1);
+template <typename T, typename S> bool iends_with(const T &a, const S &b) {
+  return iends_with(std::begin(a), std::end(a), std::begin(b), std::end(b));
 }
 
 template <typename InputIt1, typename InputIt2>
 bool strieq(InputIt1 first1, InputIt1 last1, InputIt2 first2, InputIt2 last2) {
-  if (std::distance(first1, last1) != std::distance(first2, last2)) {
-    return false;
-  }
-
-  return std::equal(first1, last1, first2, CaseCmp());
+  return std::equal(first1, last1, first2, last2, CaseCmp());
 }
 
 template <typename T, typename S> bool strieq(const T &a, const S &b) {
-  return strieq(a.begin(), a.end(), b.begin(), b.end());
-}
-
-template <typename CharT, typename InputIt, size_t N>
-bool strieq_l(const CharT (&a)[N], InputIt b, size_t blen) {
-  return strieq(a, a + (N - 1), b, b + blen);
-}
-
-template <typename CharT, size_t N, typename T>
-bool strieq_l(const CharT (&a)[N], const T &b) {
-  return strieq(a, a + (N - 1), b.begin(), b.end());
-}
-
-template <typename InputIt1, typename InputIt2>
-bool streq(InputIt1 first1, InputIt1 last1, InputIt2 first2, InputIt2 last2) {
-  if (std::distance(first1, last1) != std::distance(first2, last2)) {
-    return false;
-  }
-  return std::equal(first1, last1, first2);
-}
-
-template <typename T, typename S> bool streq(const T &a, const S &b) {
-  return streq(a.begin(), a.end(), b.begin(), b.end());
+  return strieq(std::begin(a), std::end(a), std::begin(b), std::end(b));
 }
 
-template <typename CharT, typename InputIt, size_t N>
-bool streq_l(const CharT (&a)[N], InputIt b, size_t blen) {
-  return streq(a, a + (N - 1), b, b + blen);
+template <typename T, typename S>
+bool strieq(const T &a, const S &b, size_t blen) {
+  return std::equal(std::begin(a), std::end(a), std::begin(b),
+                    std::next(std::begin(b), blen), CaseCmp());
 }
 
-template <typename CharT, size_t N, typename T>
-bool streq_l(const CharT (&a)[N], const T &b) {
-  return streq(a, a + (N - 1), b.begin(), b.end());
-}
-
-// Returns true if |a| contains |b|.  If both |a| and |b| are empty,
-// this function returns false.
-template <typename S, typename T> bool strifind(const S &a, const T &b) {
-  return std::search(a.begin(), a.end(), b.begin(), b.end(), CaseCmp()) !=
-         a.end();
+template <typename T, typename S>
+bool streq(const T &a, const S &b, size_t blen) {
+  return std::equal(std::begin(a), std::end(a), std::begin(b),
+                    std::next(std::begin(b), blen));
 }
 
 template <typename InputIt> void inp_strlower(InputIt first, InputIt last) {
@@ -458,10 +417,10 @@ template <typename T, typename OutputIt> OutputIt utos(OutputIt dst, T n) {
 template <typename T>
 StringRef make_string_ref_uint(BlockAllocator &balloc, T n) {
   auto iov = make_byte_ref(balloc, NGHTTP2_MAX_UINT64_DIGITS + 1);
-  auto p = iov.base;
+  auto p = std::begin(iov);
   p = util::utos(p, n);
   *p = '\0';
-  return StringRef{iov.base, p};
+  return StringRef{std::span{std::begin(iov), p}};
 }
 
 template <typename T> std::string utos_unit(T n) {
@@ -735,35 +694,22 @@ int get_socket_error(int fd);
 // Returns true if |host| is IPv6 numeric address (e.g., ::1)
 bool ipv6_numeric_addr(const char *host);
 
-// Parses NULL terminated string |s| as unsigned integer and returns
-// the parsed integer.  Additionally, if |s| ends with 'k', 'm', 'g'
-// and its upper case characters, multiply the integer by 1024, 1024 *
-// 1024 and 1024 * 1024 respectively.  If there is an error, returns
-// -1.
-int64_t parse_uint_with_unit(const char *s);
-// The following overload does not require |s| is NULL terminated.
-int64_t parse_uint_with_unit(const uint8_t *s, size_t len);
-int64_t parse_uint_with_unit(const StringRef &s);
-
-// Parses NULL terminated string |s| as unsigned integer and returns
-// the parsed integer.  If there is an error, returns -1.
-int64_t parse_uint(const char *s);
-// The following overload does not require |s| is NULL terminated.
-int64_t parse_uint(const uint8_t *s, size_t len);
-int64_t parse_uint(const std::string &s);
-int64_t parse_uint(const StringRef &s);
-
-// Parses NULL terminated string |s| as unsigned integer and returns
-// the parsed integer casted to double.  If |s| ends with "s", the
-// parsed value's unit is a second.  If |s| ends with "ms", the unit
-// is millisecond.  Similarly, it also supports 'm' and 'h' for
-// minutes and hours respectively.  If none of them are given, the
-// unit is second.  This function returns
-// std::numeric_limits<double>::infinity() if error occurs.
-double parse_duration_with_unit(const char *s);
-// The following overload does not require |s| is NULL terminated.
-double parse_duration_with_unit(const uint8_t *s, size_t len);
-double parse_duration_with_unit(const StringRef &s);
+// Parses |s| as unsigned integer and returns the parsed integer.
+// Additionally, if |s| ends with 'k', 'm', 'g' and its upper case
+// characters, multiply the integer by 1024, 1024 * 1024 and 1024 *
+// 1024 respectively.  If there is an error, returns no value.
+std::optional<int64_t> parse_uint_with_unit(const StringRef &s);
+
+// Parses |s| as unsigned integer and returns the parsed integer..
+std::optional<int64_t> parse_uint(const StringRef &s);
+
+// Parses |s| as unsigned integer and returns the parsed integer
+// casted to double.  If |s| ends with "s", the parsed value's unit is
+// a second.  If |s| ends with "ms", the unit is millisecond.
+// Similarly, it also supports 'm' and 'h' for minutes and hours
+// respectively.  If none of them are given, the unit is second.  This
+// function returns no value if error occurs.
+std::optional<double> parse_duration_with_unit(const StringRef &s);
 
 // Returns string representation of time duration |t|.  If t has
 // fractional part (at least more than or equal to 1e-3), |t| is
@@ -792,7 +738,7 @@ StringRef make_hostport(BlockAllocator &balloc, const StringRef &host,
 
 template <typename OutputIt>
 StringRef make_hostport(OutputIt first, const StringRef &host, uint16_t port) {
-  auto ipv6 = ipv6_numeric_addr(host.c_str());
+  auto ipv6 = ipv6_numeric_addr(host.data());
   auto serv = utos(port);
   auto p = first;
 
@@ -812,7 +758,7 @@ StringRef make_hostport(OutputIt first, const StringRef &host, uint16_t port) {
 
   *p = '\0';
 
-  return StringRef{first, p};
+  return StringRef{std::span{first, p}};
 }
 
 // Creates "host:port" string using given |host| and |port|.  If
@@ -828,7 +774,7 @@ StringRef make_http_hostport(OutputIt first, const StringRef &host,
     return make_hostport(first, host, port);
   }
 
-  auto ipv6 = ipv6_numeric_addr(host.c_str());
+  auto ipv6 = ipv6_numeric_addr(host.data());
   auto p = first;
 
   if (ipv6) {
@@ -843,7 +789,7 @@ StringRef make_http_hostport(OutputIt first, const StringRef &host,
 
   *p = '\0';
 
-  return StringRef{first, p};
+  return StringRef{std::span{first, p}};
 }
 
 // hexdump dumps |data| of length |datalen| in the format similar to
@@ -909,13 +855,13 @@ void shuffle(RandomIt first, RandomIt last, Generator &&gen, SwapFun fun) {
     return;
   }
 
-  for (unsigned int i = 0; i < static_cast<unsigned int>(len - 1); ++i) {
-    auto dis = std::uniform_int_distribution<unsigned int>(i, len - 1);
-    auto j = dis(gen);
-    if (i == j) {
-      continue;
-    }
-    fun(first + i, first + j);
+  using dist_type = std::uniform_int_distribution<size_t>;
+  using param_type = dist_type::param_type;
+
+  dist_type d;
+
+  for (decltype(len) i = 0; i < len - 1; ++i) {
+    fun(first + i, first + d(gen, param_type(i, len - 1)));
   }
 }
 
diff --git a/src/util_test.cc b/src/util_test.cc
index 2e01e9d..e65c3a8 100644
--- a/src/util_test.cc
+++ b/src/util_test.cc
@@ -36,6 +36,7 @@
 #include "template.h"
 
 using namespace nghttp2;
+using namespace std::literals;
 
 namespace shrpx {
 
@@ -70,7 +71,6 @@ const MunitTest tests[]{
     munit_void_test(test_util_parse_config_str_list),
     munit_void_test(test_util_make_http_hostport),
     munit_void_test(test_util_make_hostport),
-    munit_void_test(test_util_strifind),
     munit_void_test(test_util_random_alpha_digit),
     munit_void_test(test_util_format_hex),
     munit_void_test(test_util_is_hex_string),
@@ -88,33 +88,14 @@ const MunitSuite util_suite{
 };
 
 void test_util_streq(void) {
-  assert_true(
-      util::streq(StringRef::from_lit("alpha"), StringRef::from_lit("alpha")));
-  assert_false(util::streq(StringRef::from_lit("alpha"),
-                           StringRef::from_lit("alphabravo")));
-  assert_false(util::streq(StringRef::from_lit("alphabravo"),
-                           StringRef::from_lit("alpha")));
-  assert_false(
-      util::streq(StringRef::from_lit("alpha"), StringRef::from_lit("alphA")));
-  assert_false(util::streq(StringRef{}, StringRef::from_lit("a")));
-  assert_true(util::streq(StringRef{}, StringRef{}));
-  assert_false(util::streq(StringRef::from_lit("alpha"), StringRef{}));
-
-  assert_false(
-      util::streq(StringRef::from_lit("alph"), StringRef::from_lit("alpha")));
-  assert_false(
-      util::streq(StringRef::from_lit("alpha"), StringRef::from_lit("alph")));
-  assert_false(
-      util::streq(StringRef::from_lit("alpha"), StringRef::from_lit("alphA")));
-
-  assert_true(util::streq_l("alpha", "alpha", 5));
-  assert_true(util::streq_l("alpha", "alphabravo", 5));
-  assert_false(util::streq_l("alpha", "alphabravo", 6));
-  assert_false(util::streq_l("alphabravo", "alpha", 5));
-  assert_false(util::streq_l("alpha", "alphA", 5));
-  assert_false(util::streq_l("", "a", 1));
-  assert_true(util::streq_l("", "", 0));
-  assert_false(util::streq_l("alpha", "", 0));
+  assert_true(util::streq("alpha"_sr, "alpha"_sr, 5));
+  assert_true(util::streq("alpha"_sr, "alphabravo"_sr, 5));
+  assert_false(util::streq("alpha"_sr, "alphabravo"_sr, 6));
+  assert_false(util::streq("alphabravo"_sr, "alpha"_sr, 5));
+  assert_false(util::streq("alpha"_sr, "alphA"_sr, 5));
+  assert_false(util::streq(""_sr, "a"_sr, 1));
+  assert_true(util::streq(""_sr, ""_sr, 0));
+  assert_false(util::streq("alpha"_sr, ""_sr, 0));
 }
 
 void test_util_strieq(void) {
@@ -124,27 +105,16 @@ void test_util_strieq(void) {
   assert_false(util::strieq(std::string("alpha"), std::string("AlPhA ")));
   assert_false(util::strieq(std::string(), std::string("AlPhA ")));
 
-  assert_true(
-      util::strieq(StringRef::from_lit("alpha"), StringRef::from_lit("alpha")));
-  assert_true(
-      util::strieq(StringRef::from_lit("alpha"), StringRef::from_lit("AlPhA")));
+  assert_true(util::strieq("alpha"_sr, "alpha"_sr));
+  assert_true(util::strieq("alpha"_sr, "AlPhA"_sr));
   assert_true(util::strieq(StringRef{}, StringRef{}));
-  assert_false(util::strieq(StringRef::from_lit("alpha"),
-                            StringRef::from_lit("AlPhA ")));
-  assert_false(
-      util::strieq(StringRef::from_lit(""), StringRef::from_lit("AlPhA ")));
+  assert_false(util::strieq("alpha"_sr, "AlPhA "_sr));
+  assert_false(util::strieq(""_sr, "AlPhA "_sr));
 
-  assert_true(util::strieq_l("alpha", "alpha", 5));
-  assert_true(util::strieq_l("alpha", "AlPhA", 5));
-  assert_true(util::strieq_l("", static_cast<const char *>(nullptr), 0));
-  assert_false(util::strieq_l("alpha", "AlPhA ", 6));
-  assert_false(util::strieq_l("", "AlPhA ", 6));
-
-  assert_true(util::strieq_l("alpha", StringRef::from_lit("alpha")));
-  assert_true(util::strieq_l("alpha", StringRef::from_lit("AlPhA")));
-  assert_true(util::strieq_l("", StringRef{}));
-  assert_false(util::strieq_l("alpha", StringRef::from_lit("AlPhA ")));
-  assert_false(util::strieq_l("", StringRef::from_lit("AlPhA ")));
+  assert_true(util::strieq("alpha"_sr, "alpha"_sr, 5));
+  assert_true(util::strieq("alpha"_sr, "AlPhA"_sr, 5));
+  assert_false(util::strieq("alpha"_sr, "AlPhA "_sr, 6));
+  assert_false(util::strieq(""_sr, "AlPhA "_sr, 6));
 }
 
 void test_util_inp_strlower(void) {
@@ -164,12 +134,8 @@ void test_util_inp_strlower(void) {
 void test_util_to_base64(void) {
   BlockAllocator balloc(4096, 4096);
 
-  assert_stdstring_equal(
-      "AAA++B/=",
-      util::to_base64(balloc, StringRef::from_lit("AAA--B_")).str());
-  assert_stdstring_equal(
-      "AAA++B/B",
-      util::to_base64(balloc, StringRef::from_lit("AAA--B_B")).str());
+  assert_stdsv_equal("AAA++B/="sv, util::to_base64(balloc, "AAA--B_"_sr));
+  assert_stdsv_equal("AAA++B/B"sv, util::to_base64(balloc, "AAA--B_B"_sr));
 }
 
 void test_util_to_token68(void) {
@@ -184,18 +150,11 @@ void test_util_to_token68(void) {
 
 void test_util_percent_encode_token(void) {
   BlockAllocator balloc(4096, 4096);
-  assert_stdstring_equal(
-      "h2",
-      util::percent_encode_token(balloc, StringRef::from_lit("h2")).str());
-  assert_stdstring_equal(
-      "h3~",
-      util::percent_encode_token(balloc, StringRef::from_lit("h3~")).str());
-  assert_stdstring_equal(
-      "100%25",
-      util::percent_encode_token(balloc, StringRef::from_lit("100%")).str());
-  assert_stdstring_equal(
-      "http%202",
-      util::percent_encode_token(balloc, StringRef::from_lit("http 2")).str());
+  assert_stdsv_equal("h2"sv, util::percent_encode_token(balloc, "h2"_sr));
+  assert_stdsv_equal("h3~"sv, util::percent_encode_token(balloc, "h3~"_sr));
+  assert_stdsv_equal("100%25"sv, util::percent_encode_token(balloc, "100%"_sr));
+  assert_stdsv_equal("http%202"sv,
+                     util::percent_encode_token(balloc, "http 2"_sr));
 }
 
 void test_util_percent_decode(void) {
@@ -216,27 +175,20 @@ void test_util_percent_decode(void) {
   }
   BlockAllocator balloc(1024, 1024);
 
-  assert_stdstring_equal(
-      "foobar",
-      util::percent_decode(balloc, StringRef::from_lit("%66%6F%6f%62%61%72"))
-          .str());
+  assert_stdsv_equal("foobar"sv,
+                     util::percent_decode(balloc, "%66%6F%6f%62%61%72"_sr));
 
-  assert_stdstring_equal(
-      "f%6", util::percent_decode(balloc, StringRef::from_lit("%66%6")).str());
+  assert_stdsv_equal("f%6"sv, util::percent_decode(balloc, "%66%6"_sr));
 
-  assert_stdstring_equal(
-      "f%", util::percent_decode(balloc, StringRef::from_lit("%66%")).str());
+  assert_stdsv_equal("f%"sv, util::percent_decode(balloc, "%66%"_sr));
 }
 
 void test_util_quote_string(void) {
   BlockAllocator balloc(4096, 4096);
-  assert_stdstring_equal(
-      "alpha", util::quote_string(balloc, StringRef::from_lit("alpha")).str());
-  assert_stdstring_equal(
-      "", util::quote_string(balloc, StringRef::from_lit("")).str());
-  assert_stdstring_equal(
-      "\\\"alpha\\\"",
-      util::quote_string(balloc, StringRef::from_lit("\"alpha\"")).str());
+  assert_stdsv_equal("alpha"sv, util::quote_string(balloc, "alpha"_sr));
+  assert_stdsv_equal(""sv, util::quote_string(balloc, ""_sr));
+  assert_stdsv_equal("\\\"alpha\\\""sv,
+                     util::quote_string(balloc, "\"alpha\""_sr));
 }
 
 void test_util_utox(void) {
@@ -255,17 +207,15 @@ void test_util_http_date(void) {
 
   std::array<char, 30> http_buf;
 
-  assert_stdstring_equal(
-      "Thu, 01 Jan 1970 00:00:00 GMT",
+  assert_stdsv_equal(
+      "Thu, 01 Jan 1970 00:00:00 GMT"sv,
       util::format_http_date(http_buf.data(),
-                             std::chrono::system_clock::time_point())
-          .str());
-  assert_stdstring_equal(
-      "Wed, 29 Feb 2012 09:15:16 GMT",
+                             std::chrono::system_clock::time_point()));
+  assert_stdsv_equal(
+      "Wed, 29 Feb 2012 09:15:16 GMT"sv,
       util::format_http_date(http_buf.data(),
                              std::chrono::system_clock::time_point(
-                                 std::chrono::seconds(1330506916)))
-          .str());
+                                 std::chrono::seconds(1330506916))));
 }
 
 void test_util_select_h2(void) {
@@ -310,7 +260,7 @@ void test_util_select_h2(void) {
   // picked up because it has precedence over the other.
   const unsigned char t6[] = "\x5h2-14\x5h2-16";
   assert_true(util::select_h2(&out, &outlen, t6, sizeof(t6) - 1));
-  assert_true(util::streq(NGHTTP2_H2_16, StringRef{out, outlen}));
+  assert_stdsv_equal(NGHTTP2_H2_16, (StringRef{out, outlen}));
 }
 
 void test_util_ipv6_numeric_addr(void) {
@@ -336,11 +286,11 @@ void test_util_utos(void) {
 void test_util_make_string_ref_uint(void) {
   BlockAllocator balloc(1024, 1024);
 
-  assert_stdstring_equal("0", util::make_string_ref_uint(balloc, 0).str());
-  assert_stdstring_equal("123", util::make_string_ref_uint(balloc, 123).str());
-  assert_stdstring_equal(
-      "18446744073709551615",
-      util::make_string_ref_uint(balloc, 18446744073709551615ULL).str());
+  assert_stdsv_equal("0"sv, util::make_string_ref_uint(balloc, 0));
+  assert_stdsv_equal("123"sv, util::make_string_ref_uint(balloc, 123));
+  assert_stdsv_equal(
+      "18446744073709551615"sv,
+      util::make_string_ref_uint(balloc, 18446744073709551615ULL));
 }
 
 void test_util_utos_unit(void) {
@@ -369,65 +319,69 @@ void test_util_utos_funit(void) {
 }
 
 void test_util_parse_uint_with_unit(void) {
-  assert_int64(0, ==, util::parse_uint_with_unit("0"));
-  assert_int64(1023, ==, util::parse_uint_with_unit("1023"));
-  assert_int64(1024, ==, util::parse_uint_with_unit("1k"));
-  assert_int64(2048, ==, util::parse_uint_with_unit("2K"));
-  assert_int64(1 << 20, ==, util::parse_uint_with_unit("1m"));
-  assert_int64(1 << 21, ==, util::parse_uint_with_unit("2M"));
-  assert_int64(1 << 30, ==, util::parse_uint_with_unit("1g"));
-  assert_int64(1LL << 31, ==, util::parse_uint_with_unit("2G"));
+  assert_int64(0, ==, util::parse_uint_with_unit("0").value_or(-1));
+  assert_int64(1023, ==, util::parse_uint_with_unit("1023").value_or(-1));
+  assert_int64(1024, ==, util::parse_uint_with_unit("1k").value_or(-1));
+  assert_int64(2048, ==, util::parse_uint_with_unit("2K").value_or(-1));
+  assert_int64(1 << 20, ==, util::parse_uint_with_unit("1m").value_or(-1));
+  assert_int64(1 << 21, ==, util::parse_uint_with_unit("2M").value_or(-1));
+  assert_int64(1 << 30, ==, util::parse_uint_with_unit("1g").value_or(-1));
+  assert_int64(1LL << 31, ==, util::parse_uint_with_unit("2G").value_or(-1));
   assert_int64(9223372036854775807LL, ==,
-               util::parse_uint_with_unit("9223372036854775807"));
+               util::parse_uint_with_unit("9223372036854775807").value_or(-1));
   // check overflow case
-  assert_int64(-1, ==, util::parse_uint_with_unit("9223372036854775808"));
-  assert_int64(-1, ==, util::parse_uint_with_unit("10000000000000000000"));
-  assert_int64(-1, ==, util::parse_uint_with_unit("9223372036854775807G"));
+  assert_false(util::parse_uint_with_unit("9223372036854775808"));
+  assert_false(util::parse_uint_with_unit("10000000000000000000"));
+  assert_false(util::parse_uint_with_unit("9223372036854775807G"));
   // bad characters
-  assert_int64(-1, ==, util::parse_uint_with_unit("1.1"));
-  assert_int64(-1, ==, util::parse_uint_with_unit("1a"));
-  assert_int64(-1, ==, util::parse_uint_with_unit("a1"));
-  assert_int64(-1, ==, util::parse_uint_with_unit("1T"));
-  assert_int64(-1, ==, util::parse_uint_with_unit(""));
+  assert_false(util::parse_uint_with_unit("1.1"));
+  assert_false(util::parse_uint_with_unit("1a"));
+  assert_false(util::parse_uint_with_unit("a1"));
+  assert_false(util::parse_uint_with_unit("1T"));
+  assert_false(util::parse_uint_with_unit(""));
 }
 
 void test_util_parse_uint(void) {
-  assert_int64(0, ==, util::parse_uint("0"));
-  assert_int64(1023, ==, util::parse_uint("1023"));
-  assert_int64(-1, ==, util::parse_uint("1k"));
+  assert_int64(0, ==, util::parse_uint("0").value_or(-1));
+  assert_int64(1023, ==, util::parse_uint("1023").value_or(-1));
+  assert_false(util::parse_uint("1k"));
   assert_int64(9223372036854775807LL, ==,
-               util::parse_uint("9223372036854775807"));
+               util::parse_uint("9223372036854775807").value_or(-1));
   // check overflow case
-  assert_int64(-1, ==, util::parse_uint("9223372036854775808"));
-  assert_int64(-1, ==, util::parse_uint("10000000000000000000"));
+  assert_false(util::parse_uint("9223372036854775808"));
+  assert_false(util::parse_uint("10000000000000000000"));
   // bad characters
-  assert_int64(-1, ==, util::parse_uint("1.1"));
-  assert_int64(-1, ==, util::parse_uint("1a"));
-  assert_int64(-1, ==, util::parse_uint("a1"));
-  assert_int64(-1, ==, util::parse_uint("1T"));
-  assert_int64(-1, ==, util::parse_uint(""));
+  assert_false(util::parse_uint("1.1"));
+  assert_false(util::parse_uint("1a"));
+  assert_false(util::parse_uint("a1"));
+  assert_false(util::parse_uint("1T"));
+  assert_false(util::parse_uint(""));
 }
 
 void test_util_parse_duration_with_unit(void) {
-  assert_double(0., ==, util::parse_duration_with_unit("0"));
-  assert_double(123., ==, util::parse_duration_with_unit("123"));
-  assert_double(123., ==, util::parse_duration_with_unit("123s"));
-  assert_double(0.500, ==, util::parse_duration_with_unit("500ms"));
-  assert_double(123., ==, util::parse_duration_with_unit("123S"));
-  assert_double(0.500, ==, util::parse_duration_with_unit("500MS"));
-  assert_double(180, ==, util::parse_duration_with_unit("3m"));
-  assert_double(3600 * 5, ==, util::parse_duration_with_unit("5h"));
-
-  auto err = std::numeric_limits<double>::infinity();
+  auto inf = std::numeric_limits<double>::infinity();
+
+  assert_double(0., ==, util::parse_duration_with_unit("0").value_or(inf));
+  assert_double(123., ==, util::parse_duration_with_unit("123").value_or(inf));
+  assert_double(123., ==, util::parse_duration_with_unit("123s").value_or(inf));
+  assert_double(0.500, ==,
+                util::parse_duration_with_unit("500ms").value_or(inf));
+  assert_double(123., ==, util::parse_duration_with_unit("123S").value_or(inf));
+  assert_double(0.500, ==,
+                util::parse_duration_with_unit("500MS").value_or(inf));
+  assert_double(180, ==, util::parse_duration_with_unit("3m").value_or(inf));
+  assert_double(3600 * 5, ==,
+                util::parse_duration_with_unit("5h").value_or(inf));
+
   // check overflow case
-  assert_double(err, ==, util::parse_duration_with_unit("9223372036854775808"));
+  assert_false(util::parse_duration_with_unit("9223372036854775808"));
   // bad characters
-  assert_double(err, ==, util::parse_duration_with_unit("0u"));
-  assert_double(err, ==, util::parse_duration_with_unit("0xs"));
-  assert_double(err, ==, util::parse_duration_with_unit("0mt"));
-  assert_double(err, ==, util::parse_duration_with_unit("0mss"));
-  assert_double(err, ==, util::parse_duration_with_unit("s"));
-  assert_double(err, ==, util::parse_duration_with_unit("ms"));
+  assert_false(util::parse_duration_with_unit("0u"));
+  assert_false(util::parse_duration_with_unit("0xs"));
+  assert_false(util::parse_duration_with_unit("0mt"));
+  assert_false(util::parse_duration_with_unit("0mss"));
+  assert_false(util::parse_duration_with_unit("s"));
+  assert_false(util::parse_duration_with_unit("ms"));
 }
 
 void test_util_duration_str(void) {
@@ -469,51 +423,32 @@ void test_util_format_duration(void) {
 }
 
 void test_util_starts_with(void) {
-  assert_true(util::starts_with(StringRef::from_lit("foo"),
-                                StringRef::from_lit("foo")));
-  assert_true(util::starts_with(StringRef::from_lit("fooo"),
-                                StringRef::from_lit("foo")));
-  assert_true(util::starts_with(StringRef::from_lit("ofoo"), StringRef{}));
-  assert_false(util::starts_with(StringRef::from_lit("ofoo"),
-                                 StringRef::from_lit("foo")));
-
-  assert_true(util::istarts_with(StringRef::from_lit("FOO"),
-                                 StringRef::from_lit("fOO")));
-  assert_true(util::istarts_with(StringRef::from_lit("ofoo"), StringRef{}));
-  assert_true(util::istarts_with(StringRef::from_lit("fOOo"),
-                                 StringRef::from_lit("Foo")));
-  assert_false(util::istarts_with(StringRef::from_lit("ofoo"),
-                                  StringRef::from_lit("foo")));
-
-  assert_true(util::istarts_with_l(StringRef::from_lit("fOOo"), "Foo"));
-  assert_false(util::istarts_with_l(StringRef::from_lit("ofoo"), "foo"));
+  assert_true(util::starts_with("foo"_sr, "foo"_sr));
+  assert_true(util::starts_with("fooo"_sr, "foo"_sr));
+  assert_true(util::starts_with("ofoo"_sr, StringRef{}));
+  assert_false(util::starts_with("ofoo"_sr, "foo"_sr));
+
+  assert_true(util::istarts_with("FOO"_sr, "fOO"_sr));
+  assert_true(util::istarts_with("ofoo"_sr, StringRef{}));
+  assert_true(util::istarts_with("fOOo"_sr, "Foo"_sr));
+  assert_false(util::istarts_with("ofoo"_sr, "foo"_sr));
 }
 
 void test_util_ends_with(void) {
-  assert_true(
-      util::ends_with(StringRef::from_lit("foo"), StringRef::from_lit("foo")));
-  assert_true(util::ends_with(StringRef::from_lit("foo"), StringRef{}));
-  assert_true(
-      util::ends_with(StringRef::from_lit("ofoo"), StringRef::from_lit("foo")));
-  assert_false(
-      util::ends_with(StringRef::from_lit("ofoo"), StringRef::from_lit("fo")));
-
-  assert_true(
-      util::iends_with(StringRef::from_lit("fOo"), StringRef::from_lit("Foo")));
-  assert_true(util::iends_with(StringRef::from_lit("foo"), StringRef{}));
-  assert_true(util::iends_with(StringRef::from_lit("oFoo"),
-                               StringRef::from_lit("fOO")));
-  assert_false(
-      util::iends_with(StringRef::from_lit("ofoo"), StringRef::from_lit("fo")));
+  assert_true(util::ends_with("foo"_sr, "foo"_sr));
+  assert_true(util::ends_with("foo"_sr, StringRef{}));
+  assert_true(util::ends_with("ofoo"_sr, "foo"_sr));
+  assert_false(util::ends_with("ofoo"_sr, "fo"_sr));
 
-  assert_true(util::iends_with_l(StringRef::from_lit("oFoo"), "fOO"));
-  assert_false(util::iends_with_l(StringRef::from_lit("ofoo"), "fo"));
+  assert_true(util::iends_with("fOo"_sr, "Foo"_sr));
+  assert_true(util::iends_with("foo"_sr, StringRef{}));
+  assert_true(util::iends_with("oFoo"_sr, "fOO"_sr));
+  assert_false(util::iends_with("ofoo"_sr, "fo"_sr));
 }
 
 void test_util_parse_http_date(void) {
   assert_int64(1001939696, ==,
-               util::parse_http_date(
-                   StringRef::from_lit("Mon, 1 Oct 2001 12:34:56 GMT")));
+               util::parse_http_date("Mon, 1 Oct 2001 12:34:56 GMT"_sr));
 }
 
 void test_util_localtime_date(void) {
@@ -535,21 +470,19 @@ void test_util_localtime_date(void) {
 
   std::array<char, 27> common_buf;
 
-  assert_stdstring_equal(
-      "02/Oct/2001:00:34:56 +1200",
+  assert_stdsv_equal(
+      "02/Oct/2001:00:34:56 +1200"sv,
       util::format_common_log(common_buf.data(),
                               std::chrono::system_clock::time_point(
-                                  std::chrono::seconds(1001939696)))
-          .str());
+                                  std::chrono::seconds(1001939696))));
 
   std::array<char, 30> iso8601_buf;
 
-  assert_stdstring_equal(
-      "2001-10-02T00:34:56.123+12:00",
+  assert_stdsv_equal(
+      "2001-10-02T00:34:56.123+12:00"sv,
       util::format_iso8601(iso8601_buf.data(),
                            std::chrono::system_clock::time_point(
-                               std::chrono::milliseconds(1001939696123LL)))
-          .str());
+                               std::chrono::milliseconds(1001939696123LL))));
 
   if (tz) {
     setenv("TZ", tz, 1);
@@ -562,16 +495,16 @@ void test_util_localtime_date(void) {
 
 void test_util_get_uint64(void) {
   {
-    auto v = std::array<unsigned char, 8>{
-        {0x01, 0x12, 0x34, 0x56, 0xff, 0x9a, 0xab, 0xbc}};
+    auto v = std::to_array<unsigned char>(
+        {0x01, 0x12, 0x34, 0x56, 0xff, 0x9a, 0xab, 0xbc});
 
     auto n = util::get_uint64(v.data());
 
     assert_uint64(0x01123456ff9aabbcULL, ==, n);
   }
   {
-    auto v = std::array<unsigned char, 8>{
-        {0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff}};
+    auto v = std::to_array<unsigned char>(
+        {0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff});
 
     auto n = util::get_uint64(v.data());
 
@@ -580,16 +513,16 @@ void test_util_get_uint64(void) {
 }
 
 void test_util_parse_config_str_list(void) {
-  auto res = util::parse_config_str_list(StringRef::from_lit("a"));
+  auto res = util::parse_config_str_list("a"_sr);
   assert_size(1, ==, res.size());
   assert_stdstring_equal("a", res[0]);
 
-  res = util::parse_config_str_list(StringRef::from_lit("a,"));
+  res = util::parse_config_str_list("a,"_sr);
   assert_size(2, ==, res.size());
   assert_stdstring_equal("a", res[0]);
   assert_stdstring_equal("", res[1]);
 
-  res = util::parse_config_str_list(StringRef::from_lit(":a::"), ':');
+  res = util::parse_config_str_list(":a::"_sr, ':');
   assert_size(4, ==, res.size());
   assert_stdstring_equal("", res[0]);
   assert_stdstring_equal("a", res[1]);
@@ -600,7 +533,7 @@ void test_util_parse_config_str_list(void) {
   assert_size(1, ==, res.size());
   assert_stdstring_equal("", res[0]);
 
-  res = util::parse_config_str_list(StringRef::from_lit("alpha,bravo,charlie"));
+  res = util::parse_config_str_list("alpha,bravo,charlie"_sr);
   assert_size(3, ==, res.size());
   assert_stdstring_equal("alpha", res[0]);
   assert_stdstring_equal("bravo", res[1]);
@@ -610,56 +543,27 @@ void test_util_parse_config_str_list(void) {
 void test_util_make_http_hostport(void) {
   BlockAllocator balloc(4096, 4096);
 
-  assert_stdstring_equal(
-      "localhost",
-      util::make_http_hostport(balloc, StringRef::from_lit("localhost"), 80)
-          .str());
-  assert_stdstring_equal(
-      "[::1]",
-      util::make_http_hostport(balloc, StringRef::from_lit("::1"), 443).str());
-  assert_stdstring_equal(
-      "localhost:3000",
-      util::make_http_hostport(balloc, StringRef::from_lit("localhost"), 3000)
-          .str());
+  assert_stdsv_equal("localhost"sv,
+                     util::make_http_hostport(balloc, "localhost"_sr, 80));
+  assert_stdsv_equal("[::1]"sv,
+                     util::make_http_hostport(balloc, "::1"_sr, 443));
+  assert_stdsv_equal("localhost:3000"sv,
+                     util::make_http_hostport(balloc, "localhost"_sr, 3000));
 }
 
 void test_util_make_hostport(void) {
   std::array<char, util::max_hostport> hostport_buf;
-  assert_stdstring_equal(
-      "localhost:80", util::make_hostport(std::begin(hostport_buf),
-                                          StringRef::from_lit("localhost"), 80)
-                          .str());
-  assert_stdstring_equal("[::1]:443",
-                         util::make_hostport(std::begin(hostport_buf),
-                                             StringRef::from_lit("::1"), 443)
-                             .str());
+  assert_stdsv_equal(
+      "localhost:80"sv,
+      util::make_hostport(std::begin(hostport_buf), "localhost"_sr, 80));
+  assert_stdsv_equal(
+      "[::1]:443"sv,
+      util::make_hostport(std::begin(hostport_buf), "::1"_sr, 443));
 
   BlockAllocator balloc(4096, 4096);
-  assert_stdstring_equal(
-      "localhost:80",
-      util::make_hostport(balloc, StringRef::from_lit("localhost"), 80).str());
-  assert_stdstring_equal(
-      "[::1]:443",
-      util::make_hostport(balloc, StringRef::from_lit("::1"), 443).str());
-}
-
-void test_util_strifind(void) {
-  assert_true(util::strifind(StringRef::from_lit("gzip, deflate, bzip2"),
-                             StringRef::from_lit("gzip")));
-
-  assert_true(util::strifind(StringRef::from_lit("gzip, deflate, bzip2"),
-                             StringRef::from_lit("dEflate")));
-
-  assert_true(util::strifind(StringRef::from_lit("gzip, deflate, bzip2"),
-                             StringRef::from_lit("BZIP2")));
-
-  assert_true(util::strifind(StringRef::from_lit("nghttp2"), StringRef{}));
-
-  // Be aware this fact
-  assert_false(util::strifind(StringRef{}, StringRef{}));
-
-  assert_false(util::strifind(StringRef::from_lit("nghttp2"),
-                              StringRef::from_lit("http1")));
+  assert_stdsv_equal("localhost:80"sv,
+                     util::make_hostport(balloc, "localhost"_sr, 80));
+  assert_stdsv_equal("[::1]:443"sv, util::make_hostport(balloc, "::1"_sr, 443));
 }
 
 void test_util_random_alpha_digit(void) {
@@ -680,123 +584,121 @@ void test_util_random_alpha_digit(void) {
 void test_util_format_hex(void) {
   BlockAllocator balloc(4096, 4096);
 
-  assert_stdstring_equal(
-      "0ff0", util::format_hex(balloc, StringRef::from_lit("\x0f\xf0")).str());
-  assert_stdstring_equal(
-      "", util::format_hex(balloc, StringRef::from_lit("")).str());
+  assert_stdsv_equal("0ff0"sv,
+                     util::format_hex(balloc, std::span{"\x0f\xf0"_sr}));
+  assert_stdsv_equal(""sv,
+                     util::format_hex(balloc, std::span<const uint8_t>{}));
+
+  union T {
+    uint16_t x;
+    uint8_t y[2];
+  };
+
+  auto t = T{.y = {0xbe, 0xef}};
+
+  assert_stdstring_equal("beef", util::format_hex(std::span{&t.x, 1}));
+
+  std::string o;
+  o.resize(4);
+
+  assert_true(std::end(o) ==
+              util::format_hex(std::begin(o), std::span{&t.x, 1}));
+  assert_stdstring_equal("beef", o);
+
+  struct S {
+    uint8_t x[8];
+  };
+
+  auto s = S{{0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0xf8}};
+
+  assert_stdstring_equal("01020304050607f8", util::format_hex(s.x));
 }
 
 void test_util_is_hex_string(void) {
   assert_true(util::is_hex_string(StringRef{}));
-  assert_true(util::is_hex_string(StringRef::from_lit("0123456789abcdef")));
-  assert_true(util::is_hex_string(StringRef::from_lit("0123456789ABCDEF")));
-  assert_false(util::is_hex_string(StringRef::from_lit("000")));
-  assert_false(util::is_hex_string(StringRef::from_lit("XX")));
+  assert_true(util::is_hex_string("0123456789abcdef"_sr));
+  assert_true(util::is_hex_string("0123456789ABCDEF"_sr));
+  assert_false(util::is_hex_string("000"_sr));
+  assert_false(util::is_hex_string("XX"_sr));
 }
 
 void test_util_decode_hex(void) {
   BlockAllocator balloc(4096, 4096);
 
-  assert_stdstring_equal(
-      "\x0f\xf0", util::decode_hex(balloc, StringRef::from_lit("0ff0")).str());
-  assert_stdstring_equal("", util::decode_hex(balloc, StringRef{}).str());
+  assert_stdsv_equal("\x0f\xf0"sv,
+                     StringRef{util::decode_hex(balloc, "0ff0"_sr)});
+  assert_stdsv_equal(""sv, StringRef{util::decode_hex(balloc, StringRef{})});
 }
 
 void test_util_extract_host(void) {
-  assert_stdstring_equal("foo",
-                         util::extract_host(StringRef::from_lit("foo")).str());
-  assert_stdstring_equal("foo",
-                         util::extract_host(StringRef::from_lit("foo:")).str());
-  assert_stdstring_equal(
-      "foo", util::extract_host(StringRef::from_lit("foo:0")).str());
-  assert_stdstring_equal(
-      "[::1]", util::extract_host(StringRef::from_lit("[::1]")).str());
-  assert_stdstring_equal(
-      "[::1]", util::extract_host(StringRef::from_lit("[::1]:")).str());
-
-  assert_true(util::extract_host(StringRef::from_lit(":foo")).empty());
-  assert_true(util::extract_host(StringRef::from_lit("[::1")).empty());
-  assert_true(util::extract_host(StringRef::from_lit("[::1]0")).empty());
+  assert_stdsv_equal("foo"sv, util::extract_host("foo"_sr));
+  assert_stdsv_equal("foo"sv, util::extract_host("foo:"_sr));
+  assert_stdsv_equal("foo"sv, util::extract_host("foo:0"_sr));
+  assert_stdsv_equal("[::1]"sv, util::extract_host("[::1]"_sr));
+  assert_stdsv_equal("[::1]"sv, util::extract_host("[::1]:"_sr));
+
+  assert_true(util::extract_host(":foo"_sr).empty());
+  assert_true(util::extract_host("[::1"_sr).empty());
+  assert_true(util::extract_host("[::1]0"_sr).empty());
   assert_true(util::extract_host(StringRef{}).empty());
 }
 
 void test_util_split_hostport(void) {
-  assert_true(std::make_pair(StringRef::from_lit("foo"), StringRef{}) ==
-              util::split_hostport(StringRef::from_lit("foo")));
-  assert_true(
-      std::make_pair(StringRef::from_lit("foo"), StringRef::from_lit("80")) ==
-      util::split_hostport(StringRef::from_lit("foo:80")));
-  assert_true(
-      std::make_pair(StringRef::from_lit("::1"), StringRef::from_lit("80")) ==
-      util::split_hostport(StringRef::from_lit("[::1]:80")));
-  assert_true(std::make_pair(StringRef::from_lit("::1"), StringRef{}) ==
-              util::split_hostport(StringRef::from_lit("[::1]")));
+  assert_true(std::make_pair("foo"_sr, StringRef{}) ==
+              util::split_hostport("foo"_sr));
+  assert_true(std::make_pair("foo"_sr, "80"_sr) ==
+              util::split_hostport("foo:80"_sr));
+  assert_true(std::make_pair("::1"_sr, "80"_sr) ==
+              util::split_hostport("[::1]:80"_sr));
+  assert_true(std::make_pair("::1"_sr, StringRef{}) ==
+              util::split_hostport("[::1]"_sr));
 
   assert_true(std::make_pair(StringRef{}, StringRef{}) ==
               util::split_hostport(StringRef{}));
   assert_true(std::make_pair(StringRef{}, StringRef{}) ==
-              util::split_hostport(StringRef::from_lit("[::1]:")));
+              util::split_hostport("[::1]:"_sr));
   assert_true(std::make_pair(StringRef{}, StringRef{}) ==
-              util::split_hostport(StringRef::from_lit("foo:")));
+              util::split_hostport("foo:"_sr));
   assert_true(std::make_pair(StringRef{}, StringRef{}) ==
-              util::split_hostport(StringRef::from_lit("[::1:")));
+              util::split_hostport("[::1:"_sr));
   assert_true(std::make_pair(StringRef{}, StringRef{}) ==
-              util::split_hostport(StringRef::from_lit("[::1]80")));
+              util::split_hostport("[::1]80"_sr));
 }
 
 void test_util_split_str(void) {
-  assert_true(std::vector<StringRef>{StringRef::from_lit("")} ==
-              util::split_str(StringRef::from_lit(""), ','));
-  assert_true(std::vector<StringRef>{StringRef::from_lit("alpha")} ==
-              util::split_str(StringRef::from_lit("alpha"), ','));
-  assert_true((std::vector<StringRef>{StringRef::from_lit("alpha"),
-                                      StringRef::from_lit("")}) ==
-              util::split_str(StringRef::from_lit("alpha,"), ','));
-  assert_true((std::vector<StringRef>{StringRef::from_lit("alpha"),
-                                      StringRef::from_lit("bravo")}) ==
-              util::split_str(StringRef::from_lit("alpha,bravo"), ','));
-  assert_true((std::vector<StringRef>{StringRef::from_lit("alpha"),
-                                      StringRef::from_lit("bravo"),
-                                      StringRef::from_lit("charlie")}) ==
-              util::split_str(StringRef::from_lit("alpha,bravo,charlie"), ','));
-  assert_true(
-      (std::vector<StringRef>{StringRef::from_lit("alpha"),
-                              StringRef::from_lit("bravo"),
-                              StringRef::from_lit("charlie")}) ==
-      util::split_str(StringRef::from_lit("alpha,bravo,charlie"), ',', 0));
-  assert_true(std::vector<StringRef>{StringRef::from_lit("")} ==
-              util::split_str(StringRef::from_lit(""), ',', 1));
-  assert_true(std::vector<StringRef>{StringRef::from_lit("")} ==
-              util::split_str(StringRef::from_lit(""), ',', 2));
-  assert_true(
-      (std::vector<StringRef>{StringRef::from_lit("alpha"),
-                              StringRef::from_lit("bravo,charlie")}) ==
-      util::split_str(StringRef::from_lit("alpha,bravo,charlie"), ',', 2));
-  assert_true(std::vector<StringRef>{StringRef::from_lit("alpha")} ==
-              util::split_str(StringRef::from_lit("alpha"), ',', 2));
-  assert_true((std::vector<StringRef>{StringRef::from_lit("alpha"),
-                                      StringRef::from_lit("")}) ==
-              util::split_str(StringRef::from_lit("alpha,"), ',', 2));
-  assert_true(std::vector<StringRef>{StringRef::from_lit("alpha")} ==
-              util::split_str(StringRef::from_lit("alpha"), ',', 0));
-  assert_true(
-      std::vector<StringRef>{StringRef::from_lit("alpha,bravo,charlie")} ==
-      util::split_str(StringRef::from_lit("alpha,bravo,charlie"), ',', 1));
+  assert_true(std::vector<StringRef>{""_sr} == util::split_str(""_sr, ','));
+  assert_true(std::vector<StringRef>{"alpha"_sr} ==
+              util::split_str("alpha"_sr, ','));
+  assert_true((std::vector<StringRef>{"alpha"_sr, ""_sr}) ==
+              util::split_str("alpha,"_sr, ','));
+  assert_true((std::vector<StringRef>{"alpha"_sr, "bravo"_sr}) ==
+              util::split_str("alpha,bravo"_sr, ','));
+  assert_true((std::vector<StringRef>{"alpha"_sr, "bravo"_sr, "charlie"_sr}) ==
+              util::split_str("alpha,bravo,charlie"_sr, ','));
+  assert_true((std::vector<StringRef>{"alpha"_sr, "bravo"_sr, "charlie"_sr}) ==
+              util::split_str("alpha,bravo,charlie"_sr, ',', 0));
+  assert_true(std::vector<StringRef>{""_sr} == util::split_str(""_sr, ',', 1));
+  assert_true(std::vector<StringRef>{""_sr} == util::split_str(""_sr, ',', 2));
+  assert_true((std::vector<StringRef>{"alpha"_sr, "bravo,charlie"_sr}) ==
+              util::split_str("alpha,bravo,charlie"_sr, ',', 2));
+  assert_true(std::vector<StringRef>{"alpha"_sr} ==
+              util::split_str("alpha"_sr, ',', 2));
+  assert_true((std::vector<StringRef>{"alpha"_sr, ""_sr}) ==
+              util::split_str("alpha,"_sr, ',', 2));
+  assert_true(std::vector<StringRef>{"alpha"_sr} ==
+              util::split_str("alpha"_sr, ',', 0));
+  assert_true(std::vector<StringRef>{"alpha,bravo,charlie"_sr} ==
+              util::split_str("alpha,bravo,charlie"_sr, ',', 1));
 }
 
 void test_util_rstrip(void) {
   BlockAllocator balloc(4096, 4096);
 
-  assert_stdstring_equal(
-      "alpha", util::rstrip(balloc, StringRef::from_lit("alpha")).str());
-  assert_stdstring_equal(
-      "alpha", util::rstrip(balloc, StringRef::from_lit("alpha ")).str());
-  assert_stdstring_equal(
-      "alpha", util::rstrip(balloc, StringRef::from_lit("alpha \t")).str());
-  assert_stdstring_equal("",
-                         util::rstrip(balloc, StringRef::from_lit("")).str());
-  assert_stdstring_equal(
-      "", util::rstrip(balloc, StringRef::from_lit("\t\t\t   ")).str());
+  assert_stdsv_equal("alpha"sv, util::rstrip(balloc, "alpha"_sr));
+  assert_stdsv_equal("alpha"sv, util::rstrip(balloc, "alpha "_sr));
+  assert_stdsv_equal("alpha"sv, util::rstrip(balloc, "alpha \t"_sr));
+  assert_stdsv_equal(""sv, util::rstrip(balloc, ""_sr));
+  assert_stdsv_equal(""sv, util::rstrip(balloc, "\t\t\t   "_sr));
 }
 
 } // namespace shrpx
diff --git a/src/util_test.h b/src/util_test.h
index 8b9608b..39d6167 100644
--- a/src/util_test.h
+++ b/src/util_test.h
@@ -66,7 +66,6 @@ munit_void_test_decl(test_util_get_uint64);
 munit_void_test_decl(test_util_parse_config_str_list);
 munit_void_test_decl(test_util_make_http_hostport);
 munit_void_test_decl(test_util_make_hostport);
-munit_void_test_decl(test_util_strifind);
 munit_void_test_decl(test_util_random_alpha_digit);
 munit_void_test_decl(test_util_format_hex);
 munit_void_test_decl(test_util_is_hex_string);