Merging upstream version 1.60.0.

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

14 files changed, 1691 insertions, 351 deletions

diff --git a/lib/CMakeLists.txt b/lib/CMakeLists.txt
index 4180748..211c8e4 100644
--- a/lib/CMakeLists.txt
+++ b/lib/CMakeLists.txt
@@ -31,6 +31,8 @@ set(NGHTTP2_SOURCES
 )
 
 set(NGHTTP2_RES "")
+set(STATIC_LIB "nghttp2_static")
+set(SHARED_LIB "nghttp2")
 
 if(WIN32)
   configure_file(
@@ -41,40 +43,61 @@ if(WIN32)
   set(NGHTTP2_RES ${CMAKE_CURRENT_BINARY_DIR}/version.rc)
 endif()
 
+set(EXPORT_SET "${PROJECT_NAME}-targets")
+
 # Public shared library
-if(ENABLE_SHARED_LIB)
-  add_library(nghttp2 SHARED ${NGHTTP2_SOURCES} ${NGHTTP2_RES})
-  set_target_properties(nghttp2 PROPERTIES
+if(BUILD_SHARED_LIBS)
+  add_library(${SHARED_LIB} SHARED ${NGHTTP2_SOURCES} ${NGHTTP2_RES})
+
+  set_target_properties(${SHARED_LIB} PROPERTIES
     COMPILE_FLAGS "${WARNCFLAGS}"
     VERSION ${LT_VERSION} SOVERSION ${LT_SOVERSION}
     C_VISIBILITY_PRESET hidden
   )
-  target_include_directories(nghttp2 INTERFACE
-    "${CMAKE_CURRENT_BINARY_DIR}/includes"
-    "${CMAKE_CURRENT_SOURCE_DIR}/includes"
+
+  target_include_directories(${SHARED_LIB} INTERFACE
+    $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/includes>
+    $<BUILD_INTERFACE:${CMAKE_CURRENT_BINARY_DIR}/includes>
+    $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>
   )
 
-  install(TARGETS nghttp2
-    ARCHIVE DESTINATION "${CMAKE_INSTALL_LIBDIR}"
-    LIBRARY DESTINATION "${CMAKE_INSTALL_LIBDIR}"
-    RUNTIME DESTINATION "${CMAKE_INSTALL_BINDIR}")
+  install(TARGETS ${SHARED_LIB} EXPORT ${EXPORT_SET})
+  list(APPEND nghttp2_exports ${SHARED_LIB})
 endif()
 
-if(HAVE_CUNIT OR ENABLE_STATIC_LIB)
-  # Static library (for unittests because of symbol visibility)
-  add_library(nghttp2_static STATIC ${NGHTTP2_SOURCES})
-  set_target_properties(nghttp2_static PROPERTIES
-    COMPILE_FLAGS "${WARNCFLAGS}"
-    VERSION ${LT_VERSION} SOVERSION ${LT_SOVERSION}
-    ARCHIVE_OUTPUT_NAME nghttp2${STATIC_LIB_SUFFIX}
-  )
-  target_compile_definitions(nghttp2_static PUBLIC "-DNGHTTP2_STATICLIB")
-  if(ENABLE_STATIC_LIB)
-    install(TARGETS nghttp2_static
-      DESTINATION "${CMAKE_INSTALL_LIBDIR}")
-  endif()
+# Static library (for unittests because of symbol visibility)
+add_library(${STATIC_LIB} STATIC ${NGHTTP2_SOURCES})
+
+set_target_properties(${STATIC_LIB} PROPERTIES
+  COMPILE_FLAGS "${WARNCFLAGS}"
+  VERSION ${LT_VERSION} SOVERSION ${LT_SOVERSION}
+  ARCHIVE_OUTPUT_NAME nghttp2${STATIC_LIB_SUFFIX}
+)
+
+target_include_directories(${STATIC_LIB} INTERFACE
+  $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/includes>
+  $<BUILD_INTERFACE:${CMAKE_CURRENT_BINARY_DIR}/includes>
+  $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>
+)
+
+target_compile_definitions(${STATIC_LIB} PUBLIC "-DNGHTTP2_STATICLIB")
+
+if(BUILD_STATIC_LIBS)
+  install(TARGETS ${STATIC_LIB} EXPORT ${EXPORT_SET})
+  list(APPEND nghttp2_exports ${STATIC_LIB})
 endif()
 
+if(BUILD_SHARED_LIBS)
+  set(LIB_SELECTED ${SHARED_LIB})
+else()
+  set(LIB_SELECTED ${STATIC_LIB})
+endif()
+
+add_library(${PROJECT_NAME}::nghttp2 ALIAS ${LIB_SELECTED})
 
 install(FILES "${CMAKE_CURRENT_BINARY_DIR}/libnghttp2.pc"
   DESTINATION "${CMAKE_INSTALL_LIBDIR}/pkgconfig")
+
+install(EXPORT ${EXPORT_SET}
+  DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/${PROJECT_NAME}
+  NAMESPACE ${PROJECT_NAME}::)
diff --git a/lib/includes/nghttp2/nghttp2.h b/lib/includes/nghttp2/nghttp2.h
index 7910db2..8891760 100644
--- a/lib/includes/nghttp2/nghttp2.h
+++ b/lib/includes/nghttp2/nghttp2.h
@@ -51,6 +51,7 @@ extern "C" {
 #endif /* !defined(_MSC_VER) || (_MSC_VER >= 1800) */
 #include <sys/types.h>
 #include <stdarg.h>
+#include <stddef.h>
 
 #include <nghttp2/nghttp2ver.h>
 
@@ -72,6 +73,13 @@ extern "C" {
 #endif   /* !defined(WIN32) */
 
 /**
+ * @typedef
+ *
+ * :type:`nghttp2_ssize` is a signed counterpart of size_t.
+ */
+typedef ptrdiff_t nghttp2_ssize;
+
+/**
  * @macro
  *
  * The protocol version identification string of this library
@@ -168,6 +176,12 @@ typedef struct {
 /**
  * @macro
  *
+ * .. warning::
+ *
+ *   Deprecated.  :rfc:`7540` priorities are deprecated by
+ *   :rfc:`9113`.  Consider migrating to :rfc:`9218` extensible
+ *   prioritization scheme.
+ *
  * The default weight of stream dependency.
  */
 #define NGHTTP2_DEFAULT_WEIGHT 16
@@ -175,6 +189,12 @@ typedef struct {
 /**
  * @macro
  *
+ * .. warning::
+ *
+ *   Deprecated.  :rfc:`7540` priorities are deprecated by
+ *   :rfc:`9113`.  Consider migrating to :rfc:`9218` extensible
+ *   prioritization scheme.
+ *
  * The maximum weight of stream dependency.
  */
 #define NGHTTP2_MAX_WEIGHT 256
@@ -182,6 +202,12 @@ typedef struct {
 /**
  * @macro
  *
+ * .. warning::
+ *
+ *   Deprecated.  :rfc:`7540` priorities are deprecated by
+ *   :rfc:`9113`.  Consider migrating to :rfc:`9218` extensible
+ *   prioritization scheme.
+ *
  * The minimum weight of stream dependency.
  */
 #define NGHTTP2_MIN_WEIGHT 1
@@ -255,7 +281,7 @@ typedef enum {
    */
   NGHTTP2_ERR_UNSUPPORTED_VERSION = -503,
   /**
-   * Used as a return value from :type:`nghttp2_send_callback`,
+   * Used as a return value from :type:`nghttp2_send_callback2`,
    * :type:`nghttp2_recv_callback` and
    * :type:`nghttp2_send_data_callback` to indicate that the operation
    * would block.
@@ -275,9 +301,9 @@ typedef enum {
   NGHTTP2_ERR_EOF = -507,
   /**
    * Used as a return value from
-   * :func:`nghttp2_data_source_read_callback` to indicate that data
+   * :func:`nghttp2_data_source_read_callback2` to indicate that data
    * transfer is postponed.  See
-   * :func:`nghttp2_data_source_read_callback` for details.
+   * :func:`nghttp2_data_source_read_callback2` for details.
    */
   NGHTTP2_ERR_DEFERRED = -508,
   /**
@@ -830,7 +856,7 @@ typedef struct {
  * @union
  *
  * This union represents the some kind of data source passed to
- * :type:`nghttp2_data_source_read_callback`.
+ * :type:`nghttp2_data_source_read_callback2`.
  */
 typedef union {
   /**
@@ -847,7 +873,7 @@ typedef union {
  * @enum
  *
  * The flags used to set in |data_flags| output parameter in
- * :type:`nghttp2_data_source_read_callback`.
+ * :type:`nghttp2_data_source_read_callback2`.
  */
 typedef enum {
   /**
@@ -861,8 +887,8 @@ typedef enum {
   /**
    * Indicates that END_STREAM flag must not be set even if
    * NGHTTP2_DATA_FLAG_EOF is set.  Usually this flag is used to send
-   * trailer fields with `nghttp2_submit_request()` or
-   * `nghttp2_submit_response()`.
+   * trailer fields with `nghttp2_submit_request2()` or
+   * `nghttp2_submit_response2()`.
    */
   NGHTTP2_DATA_FLAG_NO_END_STREAM = 0x02,
   /**
@@ -872,9 +898,15 @@ typedef enum {
   NGHTTP2_DATA_FLAG_NO_COPY = 0x04
 } nghttp2_data_flag;
 
+#ifndef NGHTTP2_NO_SSIZE_T
 /**
  * @functypedef
  *
+ * .. warning::
+ *
+ *   Deprecated.  Use :type:`nghttp2_data_source_read_callback2`
+ *   instead.
+ *
  * Callback function invoked when the library wants to read data from
  * the |source|.  The read data is sent in the stream |stream_id|.
  * The implementation of this function must read at most |length|
@@ -939,9 +971,83 @@ typedef ssize_t (*nghttp2_data_source_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);
 
+#endif /* NGHTTP2_NO_SSIZE_T */
+
+/**
+ * @functypedef
+ *
+ * Callback function invoked when the library wants to read data from
+ * the |source|.  The read data is sent in the stream |stream_id|.
+ * The implementation of this function must read at most |length|
+ * bytes of data from |source| (or possibly other places) and store
+ * them in |buf| and return number of data stored in |buf|.  If EOF is
+ * reached, set :enum:`nghttp2_data_flag.NGHTTP2_DATA_FLAG_EOF` flag
+ * in |*data_flags|.
+ *
+ * Sometime it is desirable to avoid copying data into |buf| and let
+ * application to send data directly.  To achieve this, set
+ * :enum:`nghttp2_data_flag.NGHTTP2_DATA_FLAG_NO_COPY` to
+ * |*data_flags| (and possibly other flags, just like when we do
+ * copy), and return the number of bytes to send without copying data
+ * into |buf|.  The library, seeing
+ * :enum:`nghttp2_data_flag.NGHTTP2_DATA_FLAG_NO_COPY`, will invoke
+ * :type:`nghttp2_send_data_callback`.  The application must send
+ * complete DATA frame in that callback.
+ *
+ * If this callback is set by `nghttp2_submit_request2()`,
+ * `nghttp2_submit_response2()` or `nghttp2_submit_headers()` and
+ * `nghttp2_submit_data2()` with flag parameter
+ * :enum:`nghttp2_flag.NGHTTP2_FLAG_END_STREAM` set, and
+ * :enum:`nghttp2_data_flag.NGHTTP2_DATA_FLAG_EOF` flag is set to
+ * |*data_flags|, DATA frame will have END_STREAM flag set.  Usually,
+ * this is expected behaviour and all are fine.  One exception is send
+ * trailer fields.  You cannot send trailer fields after sending frame
+ * with END_STREAM set.  To avoid this problem, one can set
+ * :enum:`nghttp2_data_flag.NGHTTP2_DATA_FLAG_NO_END_STREAM` along
+ * with :enum:`nghttp2_data_flag.NGHTTP2_DATA_FLAG_EOF` to signal the
+ * library not to set END_STREAM in DATA frame.  Then application can
+ * use `nghttp2_submit_trailer()` to send trailer fields.
+ * `nghttp2_submit_trailer()` can be called inside this callback.
+ *
+ * If the application wants to postpone DATA frames (e.g.,
+ * asynchronous I/O, or reading data blocks for long time), it is
+ * achieved by returning :enum:`nghttp2_error.NGHTTP2_ERR_DEFERRED`
+ * without reading any data in this invocation.  The library removes
+ * DATA frame from the outgoing queue temporarily.  To move back
+ * deferred DATA frame to outgoing queue, call
+ * `nghttp2_session_resume_data()`.
+ *
+ * By default, |length| is limited to 16KiB at maximum.  If peer
+ * allows larger frames, application can enlarge transmission buffer
+ * size.  See :type:`nghttp2_data_source_read_length_callback` for
+ * more details.
+ *
+ * If the application just wants to return from
+ * `nghttp2_session_send()` or `nghttp2_session_mem_send2()` without
+ * sending anything, return :enum:`nghttp2_error.NGHTTP2_ERR_PAUSE`.
+ *
+ * In case of error, there are 2 choices. Returning
+ * :enum:`nghttp2_error.NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE` will
+ * close the stream by issuing RST_STREAM with
+ * :enum:`nghttp2_error_code.NGHTTP2_INTERNAL_ERROR`.  If a different
+ * error code is desirable, use `nghttp2_submit_rst_stream()` with a
+ * desired error code and then return
+ * :enum:`nghttp2_error.NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE`.
+ * Returning :enum:`nghttp2_error.NGHTTP2_ERR_CALLBACK_FAILURE` will
+ * signal the entire session failure.
+ */
+typedef nghttp2_ssize (*nghttp2_data_source_read_callback2)(
+    nghttp2_session *session, int32_t stream_id, uint8_t *buf, size_t length,
+    uint32_t *data_flags, nghttp2_data_source *source, void *user_data);
+
+#ifndef NGHTTP2_NO_SSIZE_T
 /**
  * @struct
  *
+ * .. warning::
+ *
+ *   Deprecated.  Use :type:`nghttp2_data_provider2` instead.
+ *
  * This struct represents the data source and the way to read a chunk
  * of data from it.
  */
@@ -956,6 +1062,25 @@ typedef struct {
   nghttp2_data_source_read_callback read_callback;
 } nghttp2_data_provider;
 
+#endif /* NGHTTP2_NO_SSIZE_T */
+
+/**
+ * @struct
+ *
+ * This struct represents the data source and the way to read a chunk
+ * of data from it.
+ */
+typedef struct {
+  /**
+   * The data source.
+   */
+  nghttp2_data_source source;
+  /**
+   * The callback function to read a chunk of data from the |source|.
+   */
+  nghttp2_data_source_read_callback2 read_callback;
+} nghttp2_data_provider2;
+
 /**
  * @struct
  *
@@ -1008,6 +1133,12 @@ typedef enum {
 /**
  * @struct
  *
+ * .. warning::
+ *
+ *   Deprecated.  :rfc:`7540` priorities are deprecated by
+ *   :rfc:`9113`.  Consider migrating to :rfc:`9218` extensible
+ *   prioritization scheme.
+ *
  * The structure to specify stream dependency.
  */
 typedef struct {
@@ -1042,6 +1173,12 @@ typedef struct {
    */
   size_t padlen;
   /**
+   * .. warning::
+   *
+   *   Deprecated.  :rfc:`7540` priorities are deprecated by
+   *   :rfc:`9113`.  Consider migrating to :rfc:`9218` extensible
+   *   prioritization scheme.
+   *
    * The priority specification
    */
   nghttp2_priority_spec pri_spec;
@@ -1062,6 +1199,12 @@ typedef struct {
 /**
  * @struct
  *
+ * .. warning::
+ *
+ *   Deprecated.  :rfc:`7540` priorities are deprecated by
+ *   :rfc:`9113`.  Consider migrating to :rfc:`9218` extensible
+ *   prioritization scheme.
+ *
  * The PRIORITY frame.  It has the following members:
  */
 typedef struct {
@@ -1305,9 +1448,14 @@ typedef union {
   nghttp2_extension ext;
 } nghttp2_frame;
 
+#ifndef NGHTTP2_NO_SSIZE_T
 /**
  * @functypedef
  *
+ * .. warning::
+ *
+ *   Deprecated.  Use :type:`nghttp2_send_callback2` instead.
+ *
  * Callback function invoked when |session| wants to send data to the
  * remote peer.  The implementation of this function must send at most
  * |length| bytes of data stored in |data|.  The |flags| is currently
@@ -1340,6 +1488,44 @@ typedef ssize_t (*nghttp2_send_callback)(nghttp2_session *session,
                                          const uint8_t *data, size_t length,
                                          int flags, void *user_data);
 
+#endif /* NGHTTP2_NO_SSIZE_T */
+
+/**
+ * @functypedef
+ *
+ * Callback function invoked when |session| wants to send data to the
+ * remote peer.  The implementation of this function must send at most
+ * |length| bytes of data stored in |data|.  The |flags| is currently
+ * not used and always 0. It must return the number of bytes sent if
+ * it succeeds.  If it cannot send any single byte without blocking,
+ * it must return :enum:`nghttp2_error.NGHTTP2_ERR_WOULDBLOCK`.  For
+ * other errors, it must return
+ * :enum:`nghttp2_error.NGHTTP2_ERR_CALLBACK_FAILURE`.  The
+ * |user_data| pointer is the third argument passed in to the call to
+ * `nghttp2_session_client_new()` or `nghttp2_session_server_new()`.
+ *
+ * This callback is required if the application uses
+ * `nghttp2_session_send()` to send data to the remote endpoint.  If
+ * the application uses solely `nghttp2_session_mem_send2()` instead,
+ * this callback function is unnecessary.
+ *
+ * To set this callback to :type:`nghttp2_session_callbacks`, use
+ * `nghttp2_session_callbacks_set_send_callback2()`.
+ *
+ * .. note::
+ *
+ *   The |length| may be very small.  If that is the case, and
+ *   application disables Nagle algorithm (``TCP_NODELAY``), then just
+ *   writing |data| to the network stack leads to very small packet,
+ *   and it is very inefficient.  An application should be responsible
+ *   to buffer up small chunks of data as necessary to avoid this
+ *   situation.
+ */
+typedef nghttp2_ssize (*nghttp2_send_callback2)(nghttp2_session *session,
+                                                const uint8_t *data,
+                                                size_t length, int flags,
+                                                void *user_data);
+
 /**
  * @functypedef
  *
@@ -1370,7 +1556,7 @@ typedef ssize_t (*nghttp2_send_callback)(nghttp2_session *session,
  * error; if partial frame data has already sent, it is impossible to
  * send another data in that state, and all we can do is tear down
  * connection).  When data is fully processed, but application wants
- * to make `nghttp2_session_mem_send()` or `nghttp2_session_send()`
+ * to make `nghttp2_session_mem_send2()` or `nghttp2_session_send()`
  * return immediately without processing next frames, return
  * :enum:`nghttp2_error.NGHTTP2_ERR_PAUSE`.  If application decided to
  * reset this stream, return
@@ -1387,9 +1573,14 @@ typedef int (*nghttp2_send_data_callback)(nghttp2_session *session,
                                           nghttp2_data_source *source,
                                           void *user_data);
 
+#ifndef NGHTTP2_NO_SSIZE_T
 /**
  * @functypedef
  *
+ * .. warning::
+ *
+ *   Deprecated.  Use :type:`nghttp2_recv_callback2` instead.
+ *
  * Callback function invoked when |session| wants to receive data from
  * the remote peer.  The implementation of this function must read at
  * most |length| bytes of data and store it in |buf|.  The |flags| is
@@ -1417,11 +1608,43 @@ typedef ssize_t (*nghttp2_recv_callback)(nghttp2_session *session, uint8_t *buf,
                                          size_t length, int flags,
                                          void *user_data);
 
+#endif /* NGHTTP2_NO_SSIZE_T */
+
+/**
+ * @functypedef
+ *
+ * Callback function invoked when |session| wants to receive data from
+ * the remote peer.  The implementation of this function must read at
+ * most |length| bytes of data and store it in |buf|.  The |flags| is
+ * currently not used and always 0.  It must return the number of
+ * bytes written in |buf| if it succeeds.  If it cannot read any
+ * single byte without blocking, it must return
+ * :enum:`nghttp2_error.NGHTTP2_ERR_WOULDBLOCK`.  If it gets EOF
+ * before it reads any single byte, it must return
+ * :enum:`nghttp2_error.NGHTTP2_ERR_EOF`.  For other errors, it must
+ * return :enum:`nghttp2_error.NGHTTP2_ERR_CALLBACK_FAILURE`.
+ * Returning 0 is treated as
+ * :enum:`nghttp2_error.NGHTTP2_ERR_WOULDBLOCK`.  The |user_data|
+ * pointer is the third argument passed in to the call to
+ * `nghttp2_session_client_new()` or `nghttp2_session_server_new()`.
+ *
+ * This callback is required if the application uses
+ * `nghttp2_session_recv()` to receive data from the remote endpoint.
+ * If the application uses solely `nghttp2_session_mem_recv2()`
+ * instead, this callback function is unnecessary.
+ *
+ * To set this callback to :type:`nghttp2_session_callbacks`, use
+ * `nghttp2_session_callbacks_set_recv_callback2()`.
+ */
+typedef nghttp2_ssize (*nghttp2_recv_callback2)(nghttp2_session *session,
+                                                uint8_t *buf, size_t length,
+                                                int flags, void *user_data);
+
 /**
  * @functypedef
  *
  * Callback function invoked by `nghttp2_session_recv()` and
- * `nghttp2_session_mem_recv()` when a frame is received.  The
+ * `nghttp2_session_mem_recv2()` when a frame is received.  The
  * |user_data| pointer is the third argument passed in to the call to
  * `nghttp2_session_client_new()` or `nghttp2_session_server_new()`.
  *
@@ -1439,8 +1662,8 @@ typedef ssize_t (*nghttp2_recv_callback)(nghttp2_session *session, uint8_t *buf,
  *
  * The implementation of this function must return 0 if it succeeds.
  * If nonzero value is returned, it is treated as fatal error and
- * `nghttp2_session_recv()` and `nghttp2_session_mem_recv()` functions
- * immediately return
+ * `nghttp2_session_recv()` and `nghttp2_session_mem_recv2()`
+ * functions immediately return
  * :enum:`nghttp2_error.NGHTTP2_ERR_CALLBACK_FAILURE`.
  *
  * To set this callback to :type:`nghttp2_session_callbacks`, use
@@ -1454,7 +1677,7 @@ typedef int (*nghttp2_on_frame_recv_callback)(nghttp2_session *session,
  * @functypedef
  *
  * Callback function invoked by `nghttp2_session_recv()` and
- * `nghttp2_session_mem_recv()` when an invalid non-DATA frame is
+ * `nghttp2_session_mem_recv2()` when an invalid non-DATA frame is
  * received.  The error is indicated by the |lib_error_code|, which is
  * one of the values defined in :type:`nghttp2_error`.  When this
  * callback function is invoked, the library automatically submits
@@ -1468,8 +1691,8 @@ typedef int (*nghttp2_on_frame_recv_callback)(nghttp2_session *session,
  *
  * The implementation of this function must return 0 if it succeeds.
  * If nonzero is returned, it is treated as fatal error and
- * `nghttp2_session_recv()` and `nghttp2_session_mem_recv()` functions
- * immediately return
+ * `nghttp2_session_recv()` and `nghttp2_session_mem_recv2()`
+ * functions immediately return
  * :enum:`nghttp2_error.NGHTTP2_ERR_CALLBACK_FAILURE`.
  *
  * To set this callback to :type:`nghttp2_session_callbacks`, use
@@ -1492,19 +1715,19 @@ typedef int (*nghttp2_on_invalid_frame_recv_callback)(
  * argument passed in to the call to `nghttp2_session_client_new()` or
  * `nghttp2_session_server_new()`.
  *
- * If the application uses `nghttp2_session_mem_recv()`, it can return
- * :enum:`nghttp2_error.NGHTTP2_ERR_PAUSE` to make
- * `nghttp2_session_mem_recv()` return without processing further
+ * If the application uses `nghttp2_session_mem_recv2()`, it can
+ * return :enum:`nghttp2_error.NGHTTP2_ERR_PAUSE` to make
+ * `nghttp2_session_mem_recv2()` return without processing further
  * input bytes.  The memory by pointed by the |data| is retained until
- * `nghttp2_session_mem_recv()` or `nghttp2_session_recv()` is called.
- * The application must retain the input bytes which was used to
- * produce the |data| parameter, because it may refer to the memory
+ * `nghttp2_session_mem_recv2()` or `nghttp2_session_recv()` is
+ * called.  The application must retain the input bytes which was used
+ * to produce the |data| parameter, because it may refer to the memory
  * region included in the input bytes.
  *
  * The implementation of this function must return 0 if it succeeds.
  * If nonzero is returned, it is treated as fatal error, and
- * `nghttp2_session_recv()` and `nghttp2_session_mem_recv()` functions
- * immediately return
+ * `nghttp2_session_recv()` and `nghttp2_session_mem_recv2()`
+ * functions immediately return
  * :enum:`nghttp2_error.NGHTTP2_ERR_CALLBACK_FAILURE`.
  *
  * To set this callback to :type:`nghttp2_session_callbacks`, use
@@ -1531,8 +1754,8 @@ typedef int (*nghttp2_on_data_chunk_recv_callback)(nghttp2_session *session,
  * If there is a fatal error while executing this callback, the
  * implementation should return
  * :enum:`nghttp2_error.NGHTTP2_ERR_CALLBACK_FAILURE`, which makes
- * `nghttp2_session_send()` and `nghttp2_session_mem_send()` functions
- * immediately return
+ * `nghttp2_session_send()` and `nghttp2_session_mem_send2()`
+ * functions immediately return
  * :enum:`nghttp2_error.NGHTTP2_ERR_CALLBACK_FAILURE`.
  *
  * If the other value is returned, it is treated as if
@@ -1556,8 +1779,8 @@ typedef int (*nghttp2_before_frame_send_callback)(nghttp2_session *session,
  *
  * The implementation of this function must return 0 if it succeeds.
  * If nonzero is returned, it is treated as fatal error and
- * `nghttp2_session_send()` and `nghttp2_session_mem_send()` functions
- * immediately return
+ * `nghttp2_session_send()` and `nghttp2_session_mem_send2()`
+ * functions immediately return
  * :enum:`nghttp2_error.NGHTTP2_ERR_CALLBACK_FAILURE`.
  *
  * To set this callback to :type:`nghttp2_session_callbacks`, use
@@ -1579,8 +1802,8 @@ typedef int (*nghttp2_on_frame_send_callback)(nghttp2_session *session,
  *
  * The implementation of this function must return 0 if it succeeds.
  * If nonzero is returned, it is treated as fatal error and
- * `nghttp2_session_send()` and `nghttp2_session_mem_send()` functions
- * immediately return
+ * `nghttp2_session_send()` and `nghttp2_session_mem_send2()`
+ * functions immediately return
  * :enum:`nghttp2_error.NGHTTP2_ERR_CALLBACK_FAILURE`.
  *
  * `nghttp2_session_get_stream_user_data()` can be used to get
@@ -1601,7 +1824,7 @@ typedef int (*nghttp2_on_frame_not_send_callback)(nghttp2_session *session,
  * The reason of closure is indicated by the |error_code|.  The
  * |error_code| is usually one of :enum:`nghttp2_error_code`, but that
  * is not guaranteed.  The stream_user_data, which was specified in
- * `nghttp2_submit_request()` or `nghttp2_submit_headers()`, is still
+ * `nghttp2_submit_request2()` or `nghttp2_submit_headers()`, is still
  * available in this function.  The |user_data| pointer is the third
  * argument passed in to the call to `nghttp2_session_client_new()` or
  * `nghttp2_session_server_new()`.
@@ -1610,8 +1833,8 @@ typedef int (*nghttp2_on_frame_not_send_callback)(nghttp2_session *session,
  *
  * The implementation of this function must return 0 if it succeeds.
  * If nonzero is returned, it is treated as fatal error and
- * `nghttp2_session_recv()`, `nghttp2_session_mem_recv()`,
- * `nghttp2_session_send()`, and `nghttp2_session_mem_send()`
+ * `nghttp2_session_recv()`, `nghttp2_session_mem_recv2()`,
+ * `nghttp2_session_send()`, and `nghttp2_session_mem_send2()`
  * functions immediately return
  * :enum:`nghttp2_error.NGHTTP2_ERR_CALLBACK_FAILURE`.
  *
@@ -1681,7 +1904,7 @@ typedef int (*nghttp2_on_stream_close_callback)(nghttp2_session *session,
  * value is returned, it is treated as if
  * :enum:`nghttp2_error.NGHTTP2_ERR_CALLBACK_FAILURE` is returned.  If
  * :enum:`nghttp2_error.NGHTTP2_ERR_CALLBACK_FAILURE` is returned,
- * `nghttp2_session_mem_recv()` function will immediately return
+ * `nghttp2_session_mem_recv2()` function will immediately return
  * :enum:`nghttp2_error.NGHTTP2_ERR_CALLBACK_FAILURE`.
  *
  * To set this callback to :type:`nghttp2_session_callbacks`, use
@@ -1726,11 +1949,11 @@ typedef int (*nghttp2_on_begin_headers_callback)(nghttp2_session *session,
  * performs validation based on HTTP Messaging rule, which is briefly
  * explained in :ref:`http-messaging` section.
  *
- * If the application uses `nghttp2_session_mem_recv()`, it can return
- * :enum:`nghttp2_error.NGHTTP2_ERR_PAUSE` to make
- * `nghttp2_session_mem_recv()` return without processing further
+ * If the application uses `nghttp2_session_mem_recv2()`, it can
+ * return :enum:`nghttp2_error.NGHTTP2_ERR_PAUSE` to make
+ * `nghttp2_session_mem_recv2()` return without processing further
  * input bytes.  The memory pointed by |frame|, |name| and |value|
- * parameters are retained until `nghttp2_session_mem_recv()` or
+ * parameters are retained until `nghttp2_session_mem_recv2()` or
  * `nghttp2_session_recv()` is called.  The application must retain
  * the input bytes which was used to produce these parameters, because
  * it may refer to the memory region included in the input bytes.
@@ -1757,8 +1980,8 @@ typedef int (*nghttp2_on_begin_headers_callback)(nghttp2_session *session,
  * nonzero value is returned, it is treated as
  * :enum:`nghttp2_error.NGHTTP2_ERR_CALLBACK_FAILURE`.  If
  * :enum:`nghttp2_error.NGHTTP2_ERR_CALLBACK_FAILURE` is returned,
- * `nghttp2_session_recv()` and `nghttp2_session_mem_recv()` functions
- * immediately return
+ * `nghttp2_session_recv()` and `nghttp2_session_mem_recv2()`
+ * functions immediately return
  * :enum:`nghttp2_error.NGHTTP2_ERR_CALLBACK_FAILURE`.
  *
  * To set this callback to :type:`nghttp2_session_callbacks`, use
@@ -1873,9 +2096,15 @@ typedef int (*nghttp2_on_invalid_header_callback2)(
     nghttp2_session *session, const nghttp2_frame *frame, nghttp2_rcbuf *name,
     nghttp2_rcbuf *value, uint8_t flags, void *user_data);
 
+#ifndef NGHTTP2_NO_SSIZE_T
 /**
  * @functypedef
  *
+ * .. warning::
+ *
+ *   Deprecated.  Use :type:`nghttp2_select_padding_callback2`
+ *   instead.
+ *
  * Callback function invoked when the library asks application how
  * many padding bytes are required for the transmission of the
  * |frame|.  The application must choose the total length of payload
@@ -1896,9 +2125,39 @@ typedef ssize_t (*nghttp2_select_padding_callback)(nghttp2_session *session,
                                                    size_t max_payloadlen,
                                                    void *user_data);
 
+#endif /* NGHTTP2_NO_SSIZE_T */
+
+/**
+ * @functypedef
+ *
+ * Callback function invoked when the library asks application how
+ * many padding bytes are required for the transmission of the
+ * |frame|.  The application must choose the total length of payload
+ * including padded bytes in range [frame->hd.length, max_payloadlen],
+ * inclusive.  Choosing number not in this range will be treated as
+ * :enum:`nghttp2_error.NGHTTP2_ERR_CALLBACK_FAILURE`.  Returning
+ * ``frame->hd.length`` means no padding is added.  Returning
+ * :enum:`nghttp2_error.NGHTTP2_ERR_CALLBACK_FAILURE` will make
+ * `nghttp2_session_send()` and `nghttp2_session_mem_send2()`
+ * functions immediately return
+ * :enum:`nghttp2_error.NGHTTP2_ERR_CALLBACK_FAILURE`.
+ *
+ * To set this callback to :type:`nghttp2_session_callbacks`, use
+ * `nghttp2_session_callbacks_set_select_padding_callback2()`.
+ */
+typedef nghttp2_ssize (*nghttp2_select_padding_callback2)(
+    nghttp2_session *session, const nghttp2_frame *frame, size_t max_payloadlen,
+    void *user_data);
+
+#ifndef NGHTTP2_NO_SSIZE_T
 /**
  * @functypedef
  *
+ * .. warning::
+ *
+ *   Deprecated.  Use
+ *   :type:`nghttp2_data_source_read_length_callback2` instead.
+ *
  * Callback function invoked when library wants to get max length of
  * data to send data to the remote peer.  The implementation of this
  * function should return a value in the following range.  [1,
@@ -1926,6 +2185,38 @@ typedef ssize_t (*nghttp2_data_source_read_length_callback)(
     int32_t session_remote_window_size, int32_t stream_remote_window_size,
     uint32_t remote_max_frame_size, void *user_data);
 
+#endif /* NGHTTP2_NO_SSIZE_T */
+
+/**
+ * @functypedef
+ *
+ * Callback function invoked when library wants to get max length of
+ * data to send data to the remote peer.  The implementation of this
+ * function should return a value in the following range.  [1,
+ * min(|session_remote_window_size|, |stream_remote_window_size|,
+ * |remote_max_frame_size|)].  If a value greater than this range is
+ * returned than the max allow value will be used.  Returning a value
+ * smaller than this range is treated as
+ * :enum:`nghttp2_error.NGHTTP2_ERR_CALLBACK_FAILURE`.  The
+ * |frame_type| is provided for future extensibility and identifies
+ * the type of frame (see :type:`nghttp2_frame_type`) for which to get
+ * the length for.  Currently supported frame types are:
+ * :enum:`nghttp2_frame_type.NGHTTP2_DATA`.
+ *
+ * This callback can be used to control the length in bytes for which
+ * :type:`nghttp2_data_source_read_callback` is allowed to send to the
+ * remote endpoint.  This callback is optional.  Returning
+ * :enum:`nghttp2_error.NGHTTP2_ERR_CALLBACK_FAILURE` will signal the
+ * entire session failure.
+ *
+ * To set this callback to :type:`nghttp2_session_callbacks`, use
+ * `nghttp2_session_callbacks_set_data_source_read_length_callback2()`.
+ */
+typedef nghttp2_ssize (*nghttp2_data_source_read_length_callback2)(
+    nghttp2_session *session, uint8_t frame_type, int32_t stream_id,
+    int32_t session_remote_window_size, int32_t stream_remote_window_size,
+    uint32_t remote_max_frame_size, void *user_data);
+
 /**
  * @functypedef
  *
@@ -1942,8 +2233,8 @@ typedef ssize_t (*nghttp2_data_source_read_length_callback)(
  *
  * The implementation of this function must return 0 if it succeeds.
  * If nonzero value is returned, it is treated as fatal error and
- * `nghttp2_session_recv()` and `nghttp2_session_mem_recv()` functions
- * immediately return
+ * `nghttp2_session_recv()` and `nghttp2_session_mem_recv2()`
+ * functions immediately return
  * :enum:`nghttp2_error.NGHTTP2_ERR_CALLBACK_FAILURE`.
  *
  * To set this callback to :type:`nghttp2_session_callbacks`, use
@@ -1967,8 +2258,8 @@ typedef int (*nghttp2_on_begin_frame_callback)(nghttp2_session *session,
  *
  * If fatal error occurred, application should return
  * :enum:`nghttp2_error.NGHTTP2_ERR_CALLBACK_FAILURE`.  In this case,
- * `nghttp2_session_recv()` and `nghttp2_session_mem_recv()` functions
- * immediately return
+ * `nghttp2_session_recv()` and `nghttp2_session_mem_recv2()`
+ * functions immediately return
  * :enum:`nghttp2_error.NGHTTP2_ERR_CALLBACK_FAILURE`.  If the other
  * values are returned, currently they are treated as
  * :enum:`nghttp2_error.NGHTTP2_ERR_CALLBACK_FAILURE`.
@@ -2005,8 +2296,8 @@ typedef int (*nghttp2_on_extension_chunk_recv_callback)(
  *
  * If fatal error occurred, application should return
  * :enum:`nghttp2_error.NGHTTP2_ERR_CALLBACK_FAILURE`.  In this case,
- * `nghttp2_session_recv()` and `nghttp2_session_mem_recv()` functions
- * immediately return
+ * `nghttp2_session_recv()` and `nghttp2_session_mem_recv2()`
+ * functions immediately return
  * :enum:`nghttp2_error.NGHTTP2_ERR_CALLBACK_FAILURE`.  If the other
  * values are returned, currently they are treated as
  * :enum:`nghttp2_error.NGHTTP2_ERR_CALLBACK_FAILURE`.
@@ -2016,9 +2307,15 @@ typedef int (*nghttp2_unpack_extension_callback)(nghttp2_session *session,
                                                  const nghttp2_frame_hd *hd,
                                                  void *user_data);
 
+#ifndef NGHTTP2_NO_SSIZE_T
 /**
  * @functypedef
  *
+ * .. warning::
+ *
+ *   Deprecated.  Use :type:`nghttp2_pack_extension_callback2`
+ *   instead.
+ *
  * Callback function invoked when library asks the application to pack
  * extension payload in its wire format.  The frame header will be
  * packed by library.  Application must pack payload only.
@@ -2049,18 +2346,53 @@ typedef ssize_t (*nghttp2_pack_extension_callback)(nghttp2_session *session,
                                                    const nghttp2_frame *frame,
                                                    void *user_data);
 
+#endif /* NGHTTP2_NO_SSIZE_T */
+
+/**
+ * @functypedef
+ *
+ * Callback function invoked when library asks the application to pack
+ * extension payload in its wire format.  The frame header will be
+ * packed by library.  Application must pack payload only.
+ * ``frame->ext.payload`` is the object passed to
+ * `nghttp2_submit_extension()` as payload parameter.  Application
+ * must pack extension payload to the |buf| of its capacity |len|
+ * bytes.  The |len| is at least 16KiB.
+ *
+ * The implementation of this function should return the number of
+ * bytes written into |buf| when it succeeds.
+ *
+ * To abort processing this extension frame, return
+ * :enum:`nghttp2_error.NGHTTP2_ERR_CANCEL`, and
+ * :type:`nghttp2_on_frame_not_send_callback` will be invoked.
+ *
+ * If fatal error occurred, application should return
+ * :enum:`nghttp2_error.NGHTTP2_ERR_CALLBACK_FAILURE`.  In this case,
+ * `nghttp2_session_send()` and `nghttp2_session_mem_send2()`
+ * functions immediately return
+ * :enum:`nghttp2_error.NGHTTP2_ERR_CALLBACK_FAILURE`.  If the other
+ * values are returned, currently they are treated as
+ * :enum:`nghttp2_error.NGHTTP2_ERR_CALLBACK_FAILURE`.  If the return
+ * value is strictly larger than |len|, it is treated as
+ * :enum:`nghttp2_error.NGHTTP2_ERR_CALLBACK_FAILURE`.
+ */
+typedef nghttp2_ssize (*nghttp2_pack_extension_callback2)(
+    nghttp2_session *session, uint8_t *buf, size_t len,
+    const nghttp2_frame *frame, void *user_data);
+
 /**
  * @functypedef
  *
+ * .. warning::
+ *
+ *   Deprecated.  Use :type:`nghttp2_error_callback2` instead.
+ *
  * Callback function invoked when library provides the error message
  * intended for human consumption.  This callback is solely for
  * debugging purpose.  The |msg| is typically NULL-terminated string
  * of length |len|.  |len| does not include the sentinel NULL
  * character.
  *
- * This function is deprecated.  The new application should use
- * :type:`nghttp2_error_callback2`.
- *
  * The format of error message may change between nghttp2 library
  * versions.  The application should not depend on the particular
  * format.
@@ -2143,9 +2475,15 @@ nghttp2_session_callbacks_new(nghttp2_session_callbacks **callbacks_ptr);
 NGHTTP2_EXTERN void
 nghttp2_session_callbacks_del(nghttp2_session_callbacks *callbacks);
 
+#ifndef NGHTTP2_NO_SSIZE_T
 /**
  * @function
  *
+ * .. warning::
+ *
+ *   Deprecated.  Use `nghttp2_session_callbacks_set_send_callback2()`
+ *   with :type:`nghttp2_send_callback2` instead.
+ *
  * Sets callback function invoked when a session wants to send data to
  * the remote peer.  This callback is not necessary if the application
  * uses solely `nghttp2_session_mem_send()` to serialize data to
@@ -2154,9 +2492,28 @@ nghttp2_session_callbacks_del(nghttp2_session_callbacks *callbacks);
 NGHTTP2_EXTERN void nghttp2_session_callbacks_set_send_callback(
     nghttp2_session_callbacks *cbs, nghttp2_send_callback send_callback);
 
+#endif /* NGHTTP2_NO_SSIZE_T */
+
+/**
+ * @function
+ *
+ * Sets callback function invoked when a session wants to send data to
+ * the remote peer.  This callback is not necessary if the application
+ * uses solely `nghttp2_session_mem_send2()` to serialize data to
+ * transmit.
+ */
+NGHTTP2_EXTERN void nghttp2_session_callbacks_set_send_callback2(
+    nghttp2_session_callbacks *cbs, nghttp2_send_callback2 send_callback);
+
+#ifndef NGHTTP2_NO_SSIZE_T
 /**
  * @function
  *
+ * .. warning::
+ *
+ *   Deprecated.  Use `nghttp2_session_callbacks_set_recv_callback2()`
+ *   with :type:`nghttp2_recv_callback2` instead.
+ *
  * Sets callback function invoked when the a session wants to receive
  * data from the remote peer.  This callback is not necessary if the
  * application uses solely `nghttp2_session_mem_recv()` to process
@@ -2165,11 +2522,24 @@ NGHTTP2_EXTERN void nghttp2_session_callbacks_set_send_callback(
 NGHTTP2_EXTERN void nghttp2_session_callbacks_set_recv_callback(
     nghttp2_session_callbacks *cbs, nghttp2_recv_callback recv_callback);
 
+#endif /* NGHTTP2_NO_SSIZE_T */
+
+/**
+ * @function
+ *
+ * Sets callback function invoked when the a session wants to receive
+ * data from the remote peer.  This callback is not necessary if the
+ * application uses solely `nghttp2_session_mem_recv2()` to process
+ * received data.
+ */
+NGHTTP2_EXTERN void nghttp2_session_callbacks_set_recv_callback2(
+    nghttp2_session_callbacks *cbs, nghttp2_recv_callback2 recv_callback);
+
 /**
  * @function
  *
  * Sets callback function invoked by `nghttp2_session_recv()` and
- * `nghttp2_session_mem_recv()` when a frame is received.
+ * `nghttp2_session_mem_recv2()` when a frame is received.
  */
 NGHTTP2_EXTERN void nghttp2_session_callbacks_set_on_frame_recv_callback(
     nghttp2_session_callbacks *cbs,
@@ -2179,7 +2549,7 @@ NGHTTP2_EXTERN void nghttp2_session_callbacks_set_on_frame_recv_callback(
  * @function
  *
  * Sets callback function invoked by `nghttp2_session_recv()` and
- * `nghttp2_session_mem_recv()` when an invalid non-DATA frame is
+ * `nghttp2_session_mem_recv2()` when an invalid non-DATA frame is
  * received.
  */
 NGHTTP2_EXTERN void
@@ -2290,9 +2660,16 @@ NGHTTP2_EXTERN void nghttp2_session_callbacks_set_on_invalid_header_callback2(
     nghttp2_session_callbacks *cbs,
     nghttp2_on_invalid_header_callback2 on_invalid_header_callback2);
 
+#ifndef NGHTTP2_NO_SSIZE_T
 /**
  * @function
  *
+ * .. warning::
+ *
+ *   Deprecated.  Use
+ *   `nghttp2_session_callbacks_set_select_padding_callback2()` with
+ *   :type:`nghttp2_select_padding_callback2` instead.
+ *
  * Sets callback function invoked when the library asks application
  * how many padding bytes are required for the transmission of the
  * given frame.
@@ -2301,9 +2678,29 @@ NGHTTP2_EXTERN void nghttp2_session_callbacks_set_select_padding_callback(
     nghttp2_session_callbacks *cbs,
     nghttp2_select_padding_callback select_padding_callback);
 
+#endif /* NGHTTP2_NO_SSIZE_T */
+
 /**
  * @function
  *
+ * Sets callback function invoked when the library asks application
+ * how many padding bytes are required for the transmission of the
+ * given frame.
+ */
+NGHTTP2_EXTERN void nghttp2_session_callbacks_set_select_padding_callback2(
+    nghttp2_session_callbacks *cbs,
+    nghttp2_select_padding_callback2 select_padding_callback);
+
+#ifndef NGHTTP2_NO_SSIZE_T
+/**
+ * @function
+ *
+ * .. warning::
+ *
+ *   Deprecated.  Use
+ *   `nghttp2_session_callbacks_set_data_source_read_length_callback2()`
+ *   with :type:`nghttp2_data_source_read_length_callback2` instead.
+ *
  * Sets callback function determine the length allowed in
  * :type:`nghttp2_data_source_read_callback`.
  */
@@ -2312,6 +2709,19 @@ nghttp2_session_callbacks_set_data_source_read_length_callback(
     nghttp2_session_callbacks *cbs,
     nghttp2_data_source_read_length_callback data_source_read_length_callback);
 
+#endif /* NGHTTP2_NO_SSIZE_T */
+
+/**
+ * @function
+ *
+ * Sets callback function determine the length allowed in
+ * :type:`nghttp2_data_source_read_callback2`.
+ */
+NGHTTP2_EXTERN void
+nghttp2_session_callbacks_set_data_source_read_length_callback2(
+    nghttp2_session_callbacks *cbs,
+    nghttp2_data_source_read_length_callback2 data_source_read_length_callback);
+
 /**
  * @function
  *
@@ -2326,15 +2736,22 @@ NGHTTP2_EXTERN void nghttp2_session_callbacks_set_on_begin_frame_callback(
  *
  * Sets callback function invoked when
  * :enum:`nghttp2_data_flag.NGHTTP2_DATA_FLAG_NO_COPY` is used in
- * :type:`nghttp2_data_source_read_callback` to avoid data copy.
+ * :type:`nghttp2_data_source_read_callback2` to avoid data copy.
  */
 NGHTTP2_EXTERN void nghttp2_session_callbacks_set_send_data_callback(
     nghttp2_session_callbacks *cbs,
     nghttp2_send_data_callback send_data_callback);
 
+#ifndef NGHTTP2_NO_SSIZE_T
 /**
  * @function
  *
+ * .. warning::
+ *
+ *   Deprecated.  Use
+ *   `nghttp2_session_callbacks_set_pack_extension_callback2()` with
+ *   :type:`nghttp2_pack_extension_callback2` instead.
+ *
  * Sets callback function invoked when the library asks the
  * application to pack extension frame payload in wire format.
  */
@@ -2342,6 +2759,18 @@ NGHTTP2_EXTERN void nghttp2_session_callbacks_set_pack_extension_callback(
     nghttp2_session_callbacks *cbs,
     nghttp2_pack_extension_callback pack_extension_callback);
 
+#endif /* NGHTTP2_NO_SSIZE_T */
+
+/**
+ * @function
+ *
+ * Sets callback function invoked when the library asks the
+ * application to pack extension frame payload in wire format.
+ */
+NGHTTP2_EXTERN void nghttp2_session_callbacks_set_pack_extension_callback2(
+    nghttp2_session_callbacks *cbs,
+    nghttp2_pack_extension_callback2 pack_extension_callback);
+
 /**
  * @function
  *
@@ -2366,12 +2795,15 @@ nghttp2_session_callbacks_set_on_extension_chunk_recv_callback(
 /**
  * @function
  *
+ * .. warning::
+ *
+ *   Deprecated.  Use
+ *   `nghttp2_session_callbacks_set_error_callback2()` with
+ *   :type:`nghttp2_error_callback2` instead.
+ *
  * Sets callback function invoked when library tells error message to
  * the application.
  *
- * This function is deprecated.  The new application should use
- * `nghttp2_session_callbacks_set_error_callback2()`.
- *
  * If both :type:`nghttp2_error_callback` and
  * :type:`nghttp2_error_callback2` are set, the latter takes
  * precedence.
@@ -2568,7 +3000,7 @@ nghttp2_option_set_peer_max_concurrent_streams(nghttp2_option *option,
  *
  * If this option is not used or used with zero value, if MAGIC does
  * not match :macro:`NGHTTP2_CLIENT_MAGIC`, `nghttp2_session_recv()`
- * and `nghttp2_session_mem_recv()` will return error
+ * and `nghttp2_session_mem_recv2()` will return error
  * :enum:`nghttp2_error.NGHTTP2_ERR_BAD_CLIENT_MAGIC`, which is fatal
  * error.
  */
@@ -2781,7 +3213,7 @@ nghttp2_option_set_stream_reset_rate_limit(nghttp2_option *option,
  * does not store |callbacks|.  The |user_data| is an arbitrary user
  * supplied data, which will be passed to the callback functions.
  *
- * The :type:`nghttp2_send_callback` must be specified.  If the
+ * The :type:`nghttp2_send_callback2` must be specified.  If the
  * application code uses `nghttp2_session_recv()`, the
  * :type:`nghttp2_recv_callback` must be specified.  The other members
  * of |callbacks| can be ``NULL``.
@@ -2807,7 +3239,7 @@ nghttp2_session_client_new(nghttp2_session **session_ptr,
  * does not store |callbacks|.  The |user_data| is an arbitrary user
  * supplied data, which will be passed to the callback functions.
  *
- * The :type:`nghttp2_send_callback` must be specified.  If the
+ * The :type:`nghttp2_send_callback2` must be specified.  If the
  * application code uses `nghttp2_session_recv()`, the
  * :type:`nghttp2_recv_callback` must be specified.  The other members
  * of |callbacks| can be ``NULL``.
@@ -2943,7 +3375,7 @@ NGHTTP2_EXTERN void nghttp2_session_del(nghttp2_session *session);
  * This function retrieves the highest prioritized frame from the
  * outbound queue and sends it to the remote peer.  It does this as
  * many times as possible until the user callback
- * :type:`nghttp2_send_callback` returns
+ * :type:`nghttp2_send_callback2` returns
  * :enum:`nghttp2_error.NGHTTP2_ERR_WOULDBLOCK`, the outbound queue
  * becomes empty or flow control is triggered (remote window size
  * becomes depleted or maximum number of concurrent streams is
@@ -2973,7 +3405,7 @@ NGHTTP2_EXTERN void nghttp2_session_del(nghttp2_session *session);
  *    :type:`nghttp2_on_frame_not_send_callback` is invoked.  Abort
  *    the following steps.
  *
- * 8. :type:`nghttp2_send_callback` is invoked one or more times to
+ * 8. :type:`nghttp2_send_callback2` is invoked one or more times to
  *    send the frame.
  *
  * 9. :type:`nghttp2_on_frame_send_callback` is invoked.
@@ -2992,9 +3424,14 @@ NGHTTP2_EXTERN void nghttp2_session_del(nghttp2_session *session);
  */
 NGHTTP2_EXTERN int nghttp2_session_send(nghttp2_session *session);
 
+#ifndef NGHTTP2_NO_SSIZE_T
 /**
  * @function
  *
+ * .. warning::
+ *
+ *   Deprecated.  Use `nghttp2_session_mem_send2()` instead.
+ *
  * Returns the serialized data to send.
  *
  * This function behaves like `nghttp2_session_send()` except that it
@@ -3034,6 +3471,50 @@ NGHTTP2_EXTERN int nghttp2_session_send(nghttp2_session *session);
 NGHTTP2_EXTERN ssize_t nghttp2_session_mem_send(nghttp2_session *session,
                                                 const uint8_t **data_ptr);
 
+#endif /* NGHTTP2_NO_SSIZE_T */
+
+/**
+ * @function
+ *
+ * Returns the serialized data to send.
+ *
+ * This function behaves like `nghttp2_session_send()` except that it
+ * does not use :type:`nghttp2_send_callback2` to transmit data.
+ * Instead, it assigns the pointer to the serialized data to the
+ * |*data_ptr| and returns its length.  The other callbacks are called
+ * in the same way as they are in `nghttp2_session_send()`.
+ *
+ * If no data is available to send, this function returns 0.
+ *
+ * This function may not return all serialized data in one invocation.
+ * To get all data, call this function repeatedly until it returns 0
+ * or one of negative error codes.
+ *
+ * The assigned |*data_ptr| is valid until the next call of
+ * `nghttp2_session_mem_send2()` or `nghttp2_session_send()`.
+ *
+ * The caller must send all data before sending the next chunk of
+ * data.
+ *
+ * This function returns the length of the data pointed by the
+ * |*data_ptr| if it succeeds, or one of the following negative error
+ * codes:
+ *
+ * :enum:`nghttp2_error.NGHTTP2_ERR_NOMEM`
+ *     Out of memory.
+ *
+ * .. note::
+ *
+ *   This function may produce very small byte string.  If that is the
+ *   case, and application disables Nagle algorithm (``TCP_NODELAY``),
+ *   then writing this small chunk leads to very small packet, and it
+ *   is very inefficient.  An application should be responsible to
+ *   buffer up small chunks of data as necessary to avoid this
+ *   situation.
+ */
+NGHTTP2_EXTERN nghttp2_ssize
+nghttp2_session_mem_send2(nghttp2_session *session, const uint8_t **data_ptr);
+
 /**
  * @function
  *
@@ -3104,9 +3585,14 @@ NGHTTP2_EXTERN ssize_t nghttp2_session_mem_send(nghttp2_session *session,
  */
 NGHTTP2_EXTERN int nghttp2_session_recv(nghttp2_session *session);
 
+#ifndef NGHTTP2_NO_SSIZE_T
 /**
  * @function
  *
+ * .. warning::
+ *
+ *   Deprecated.  Use `nghttp2_session_mem_recv2()` instead.
+ *
  * Processes data |in| as an input from the remote endpoint.  The
  * |inlen| indicates the number of bytes to receive in the |in|.
  *
@@ -3145,6 +3631,49 @@ NGHTTP2_EXTERN ssize_t nghttp2_session_mem_recv(nghttp2_session *session,
                                                 const uint8_t *in,
                                                 size_t inlen);
 
+#endif /* NGHTTP2_NO_SSIZE_T */
+
+/**
+ * @function
+ *
+ * Processes data |in| as an input from the remote endpoint.  The
+ * |inlen| indicates the number of bytes to receive in the |in|.
+ *
+ * This function behaves like `nghttp2_session_recv()` except that it
+ * does not use :type:`nghttp2_recv_callback` to receive data; the
+ * |in| is the only data for the invocation of this function.  If all
+ * bytes are processed, this function returns.  The other callbacks
+ * are called in the same way as they are in `nghttp2_session_recv()`.
+ *
+ * In the current implementation, this function always tries to
+ * processes |inlen| bytes of input data unless either an error occurs or
+ * :enum:`nghttp2_error.NGHTTP2_ERR_PAUSE` is returned from
+ * :type:`nghttp2_on_header_callback` or
+ * :type:`nghttp2_on_data_chunk_recv_callback`.  If
+ * :enum:`nghttp2_error.NGHTTP2_ERR_PAUSE` is used, the return value
+ * includes the number of bytes which was used to produce the data or
+ * frame for the callback.
+ *
+ * This function returns the number of processed bytes, or one of the
+ * following negative error codes:
+ *
+ * :enum:`nghttp2_error.NGHTTP2_ERR_NOMEM`
+ *     Out of memory.
+ * :enum:`nghttp2_error.NGHTTP2_ERR_CALLBACK_FAILURE`
+ *     The callback function failed.
+ * :enum:`nghttp2_error.NGHTTP2_ERR_BAD_CLIENT_MAGIC`
+ *     Invalid client magic was detected.  This error only returns
+ *     when |session| was configured as server and
+ *     `nghttp2_option_set_no_recv_client_magic()` is not used with
+ *     nonzero value.
+ * :enum:`nghttp2_error.NGHTTP2_ERR_FLOODED`
+ *     Flooding was detected in this HTTP/2 session, and it must be
+ *     closed.  This is most likely caused by misbehaviour of peer.
+ */
+NGHTTP2_EXTERN nghttp2_ssize nghttp2_session_mem_recv2(nghttp2_session *session,
+                                                       const uint8_t *in,
+                                                       size_t inlen);
+
 /**
  * @function
  *
@@ -3190,7 +3719,7 @@ NGHTTP2_EXTERN int nghttp2_session_want_write(nghttp2_session *session);
  * @function
  *
  * Returns stream_user_data for the stream |stream_id|.  The
- * stream_user_data is provided by `nghttp2_submit_request()`,
+ * stream_user_data is provided by `nghttp2_submit_request2()`,
  * `nghttp2_submit_headers()` or
  * `nghttp2_session_set_stream_user_data()`.  Unless it is set using
  * `nghttp2_session_set_stream_user_data()`, if the stream is
@@ -3626,6 +4155,13 @@ NGHTTP2_EXTERN int nghttp2_session_consume_stream(nghttp2_session *session,
 /**
  * @function
  *
+ * .. warning::
+ *
+ *   Deprecated.  :rfc:`7540` priorities are deprecated by
+ *   :rfc:`9113`.  Consider migrating to :rfc:`9218` extensible
+ *   prioritization scheme.  In the future release after the end of
+ *   2024, this function will always return 0 without doing anything.
+ *
  * Changes priority of existing stream denoted by |stream_id|.  The
  * new priority specification is |pri_spec|.
  *
@@ -3665,6 +4201,13 @@ nghttp2_session_change_stream_priority(nghttp2_session *session,
 /**
  * @function
  *
+ * .. warning::
+ *
+ *   Deprecated.  :rfc:`7540` priorities are deprecated by
+ *   :rfc:`9113`.  Consider migrating to :rfc:`9218` extensible
+ *   prioritization scheme.  In the future release after the end of
+ *   2024, this function will always return 0 without doing anything.
+ *
  * Creates idle stream with the given |stream_id|, and priority
  * |pri_spec|.
  *
@@ -3715,10 +4258,6 @@ nghttp2_session_create_idle_stream(nghttp2_session *session, int32_t stream_id,
 /**
  * @function
  *
- * Performs post-process of HTTP Upgrade request.  This function can
- * be called from both client and server, but the behavior is very
- * different in each other.
- *
  * .. warning::
  *
  *   This function is deprecated in favor of
@@ -3730,6 +4269,10 @@ nghttp2_session_create_idle_stream(nghttp2_session *session, int32_t stream_id,
  *   HEAD is used in request, the length of response body must be 0
  *   regardless of value included in content-length header field.
  *
+ * Performs post-process of HTTP Upgrade request.  This function can
+ * be called from both client and server, but the behavior is very
+ * different in each other.
+ *
  * If called from client side, the |settings_payload| must be the
  * value sent in ``HTTP2-Settings`` header field and must be decoded
  * by base64url decoder.  The |settings_payloadlen| is the length of
@@ -3809,9 +4352,14 @@ NGHTTP2_EXTERN int nghttp2_session_upgrade2(nghttp2_session *session,
                                             int head_request,
                                             void *stream_user_data);
 
+#ifndef NGHTTP2_NO_SSIZE_T
 /**
  * @function
  *
+ * .. warning::
+ *
+ *   Deprecated.  Use `nghttp2_pack_settings_payload2()` instead.
+ *
  * Serializes the SETTINGS values |iv| in the |buf|.  The size of the
  * |buf| is specified by |buflen|.  The number of entries in the |iv|
  * array is given by |niv|.  The required space in |buf| for the |niv|
@@ -3833,6 +4381,32 @@ NGHTTP2_EXTERN int nghttp2_session_upgrade2(nghttp2_session *session,
 NGHTTP2_EXTERN ssize_t nghttp2_pack_settings_payload(
     uint8_t *buf, size_t buflen, const nghttp2_settings_entry *iv, size_t niv);
 
+#endif /* NGHTTP2_NO_SSIZE_T */
+
+/**
+ * @function
+ *
+ * Serializes the SETTINGS values |iv| in the |buf|.  The size of the
+ * |buf| is specified by |buflen|.  The number of entries in the |iv|
+ * array is given by |niv|.  The required space in |buf| for the |niv|
+ * entries is ``6*niv`` bytes and if the given buffer is too small, an
+ * error is returned.  This function is used mainly for creating a
+ * SETTINGS payload to be sent with the ``HTTP2-Settings`` header
+ * field in an HTTP Upgrade request.  The data written in |buf| is NOT
+ * base64url encoded and the application is responsible for encoding.
+ *
+ * This function returns the number of bytes written in |buf|, or one
+ * of the following negative error codes:
+ *
+ * :enum:`nghttp2_error.NGHTTP2_ERR_INVALID_ARGUMENT`
+ *     The |iv| contains duplicate settings ID or invalid value.
+ *
+ * :enum:`nghttp2_error.NGHTTP2_ERR_INSUFF_BUFSIZE`
+ *     The provided |buflen| size is too small to hold the output.
+ */
+NGHTTP2_EXTERN nghttp2_ssize nghttp2_pack_settings_payload2(
+    uint8_t *buf, size_t buflen, const nghttp2_settings_entry *iv, size_t niv);
+
 /**
  * @function
  *
@@ -3854,6 +4428,12 @@ NGHTTP2_EXTERN const char *nghttp2_http2_strerror(uint32_t error_code);
 /**
  * @function
  *
+ * .. warning::
+ *
+ *   Deprecated.  :rfc:`7540` priorities are deprecated by
+ *   :rfc:`9113`.  Consider migrating to :rfc:`9218` extensible
+ *   prioritization scheme.
+ *
  * Initializes |pri_spec| with the |stream_id| of the stream to depend
  * on with |weight| and its exclusive flag.  If |exclusive| is
  * nonzero, exclusive flag is set.
@@ -3868,6 +4448,12 @@ NGHTTP2_EXTERN void nghttp2_priority_spec_init(nghttp2_priority_spec *pri_spec,
 /**
  * @function
  *
+ * .. warning::
+ *
+ *   Deprecated.  :rfc:`7540` priorities are deprecated by
+ *   :rfc:`9113`.  Consider migrating to :rfc:`9218` extensible
+ *   prioritization scheme.
+ *
  * Initializes |pri_spec| with the default values.  The default values
  * are: stream_id = 0, weight = :macro:`NGHTTP2_DEFAULT_WEIGHT` and
  * exclusive = 0.
@@ -3878,18 +4464,29 @@ nghttp2_priority_spec_default_init(nghttp2_priority_spec *pri_spec);
 /**
  * @function
  *
+ * .. warning::
+ *
+ *   Deprecated.  :rfc:`7540` priorities are deprecated by
+ *   :rfc:`9113`.  Consider migrating to :rfc:`9218` extensible
+ *   prioritization scheme.
+ *
  * Returns nonzero if the |pri_spec| is filled with default values.
  */
 NGHTTP2_EXTERN int
 nghttp2_priority_spec_check_default(const nghttp2_priority_spec *pri_spec);
 
+#ifndef NGHTTP2_NO_SSIZE_T
 /**
  * @function
  *
+ * .. warning::
+ *
+ *   Deprecated.  Use `nghttp2_submit_request2()` instead.
+ *
  * Submits HEADERS frame and optionally one or more DATA frames.
  *
- * The |pri_spec| is priority specification of this request.  ``NULL``
- * means the default priority (see
+ * The |pri_spec| is a deprecated priority specification of this
+ * request.  ``NULL`` means the default priority (see
  * `nghttp2_priority_spec_default_init()`).  To specify the priority,
  * use `nghttp2_priority_spec_init()`.  If |pri_spec| is not ``NULL``,
  * this function will copy its data members.
@@ -3970,9 +4567,105 @@ NGHTTP2_EXTERN int32_t nghttp2_submit_request(
     const nghttp2_nv *nva, size_t nvlen, const nghttp2_data_provider *data_prd,
     void *stream_user_data);
 
+#endif /* NGHTTP2_NO_SSIZE_T */
+
 /**
  * @function
  *
+ * Submits HEADERS frame and optionally one or more DATA frames.
+ *
+ * The |pri_spec| is a deprecated priority specification of this
+ * request.  ``NULL`` means the default priority (see
+ * `nghttp2_priority_spec_default_init()`).  To specify the priority,
+ * use `nghttp2_priority_spec_init()`.  If |pri_spec| is not ``NULL``,
+ * this function will copy its data members.  In the future release
+ * after the end of 2024, this function will ignore |pri_spec| and
+ * behave as if ``NULL`` is given.
+ *
+ * The ``pri_spec->weight`` must be in [:macro:`NGHTTP2_MIN_WEIGHT`,
+ * :macro:`NGHTTP2_MAX_WEIGHT`], inclusive.  If ``pri_spec->weight``
+ * is strictly less than :macro:`NGHTTP2_MIN_WEIGHT`, it becomes
+ * :macro:`NGHTTP2_MIN_WEIGHT`.  If it is strictly greater than
+ * :macro:`NGHTTP2_MAX_WEIGHT`, it becomes
+ * :macro:`NGHTTP2_MAX_WEIGHT`.
+ *
+ * If
+ * :enum:`nghttp2_settings_id.NGHTTP2_SETTINGS_NO_RFC7540_PRIORITIES`
+ * of value of 1 is received by a remote endpoint, |pri_spec| is
+ * ignored, and treated as if ``NULL`` is specified.
+ *
+ * The |nva| is an array of name/value pair :type:`nghttp2_nv` with
+ * |nvlen| elements.  The application is responsible to include
+ * required pseudo-header fields (header field whose name starts with
+ * ":") in |nva| and must place pseudo-headers before regular header
+ * fields.
+ *
+ * This function creates copies of all name/value pairs in |nva|.  It
+ * also lower-cases all names in |nva|.  The order of elements in
+ * |nva| is preserved.  For header fields with
+ * :enum:`nghttp2_nv_flag.NGHTTP2_NV_FLAG_NO_COPY_NAME` and
+ * :enum:`nghttp2_nv_flag.NGHTTP2_NV_FLAG_NO_COPY_VALUE` are set,
+ * header field name and value are not copied respectively.  With
+ * :enum:`nghttp2_nv_flag.NGHTTP2_NV_FLAG_NO_COPY_NAME`, application
+ * is responsible to pass header field name in lowercase.  The
+ * application should maintain the references to them until
+ * :type:`nghttp2_on_frame_send_callback` or
+ * :type:`nghttp2_on_frame_not_send_callback` is called.
+ *
+ * HTTP/2 specification has requirement about header fields in the
+ * request HEADERS.  See the specification for more details.
+ *
+ * If |data_prd| is not ``NULL``, it provides data which will be sent
+ * in subsequent DATA frames.  In this case, a method that allows
+ * request message bodies
+ * (https://tools.ietf.org/html/rfc7231#section-4) must be specified
+ * with ``:method`` key in |nva| (e.g. ``POST``).  This function does
+ * not take ownership of the |data_prd|.  The function copies the
+ * members of the |data_prd|.  If |data_prd| is ``NULL``, HEADERS have
+ * END_STREAM set.  The |stream_user_data| is data associated to the
+ * stream opened by this request and can be an arbitrary pointer,
+ * which can be retrieved later by
+ * `nghttp2_session_get_stream_user_data()`.
+ *
+ * This function returns assigned stream ID if it succeeds, or one of
+ * the following negative error codes:
+ *
+ * :enum:`nghttp2_error.NGHTTP2_ERR_NOMEM`
+ *     Out of memory.
+ * :enum:`nghttp2_error.NGHTTP2_ERR_STREAM_ID_NOT_AVAILABLE`
+ *     No stream ID is available because maximum stream ID was
+ *     reached.
+ * :enum:`nghttp2_error.NGHTTP2_ERR_INVALID_ARGUMENT`
+ *     Trying to depend on itself (new stream ID equals
+ *     ``pri_spec->stream_id``).
+ * :enum:`nghttp2_error.NGHTTP2_ERR_PROTO`
+ *     The |session| is server session.
+ *
+ * .. warning::
+ *
+ *   This function returns assigned stream ID if it succeeds.  But
+ *   that stream is not created yet.  The application must not submit
+ *   frame to that stream ID before
+ *   :type:`nghttp2_before_frame_send_callback` is called for this
+ *   frame.  This means `nghttp2_session_get_stream_user_data()` does
+ *   not work before the callback.  But
+ *   `nghttp2_session_set_stream_user_data()` handles this situation
+ *   specially, and it can set data to a stream during this period.
+ *
+ */
+NGHTTP2_EXTERN int32_t nghttp2_submit_request2(
+    nghttp2_session *session, const nghttp2_priority_spec *pri_spec,
+    const nghttp2_nv *nva, size_t nvlen, const nghttp2_data_provider2 *data_prd,
+    void *stream_user_data);
+
+#ifndef NGHTTP2_NO_SSIZE_T
+/**
+ * @function
+ *
+ * .. warning::
+ *
+ *   Deprecated.  Use `nghttp2_submit_response2()` instead.
+ *
  * Submits response HEADERS frame and optionally one or more DATA
  * frames against the stream |stream_id|.
  *
@@ -4039,6 +4732,77 @@ nghttp2_submit_response(nghttp2_session *session, int32_t stream_id,
                         const nghttp2_nv *nva, size_t nvlen,
                         const nghttp2_data_provider *data_prd);
 
+#endif /* NGHTTP2_NO_SSIZE_T */
+
+/**
+ * @function
+ *
+ * Submits response HEADERS frame and optionally one or more DATA
+ * frames against the stream |stream_id|.
+ *
+ * The |nva| is an array of name/value pair :type:`nghttp2_nv` with
+ * |nvlen| elements.  The application is responsible to include
+ * required pseudo-header fields (header field whose name starts with
+ * ":") in |nva| and must place pseudo-headers before regular header
+ * fields.
+ *
+ * This function creates copies of all name/value pairs in |nva|.  It
+ * also lower-cases all names in |nva|.  The order of elements in
+ * |nva| is preserved.  For header fields with
+ * :enum:`nghttp2_nv_flag.NGHTTP2_NV_FLAG_NO_COPY_NAME` and
+ * :enum:`nghttp2_nv_flag.NGHTTP2_NV_FLAG_NO_COPY_VALUE` are set,
+ * header field name and value are not copied respectively.  With
+ * :enum:`nghttp2_nv_flag.NGHTTP2_NV_FLAG_NO_COPY_NAME`, application
+ * is responsible to pass header field name in lowercase.  The
+ * application should maintain the references to them until
+ * :type:`nghttp2_on_frame_send_callback` or
+ * :type:`nghttp2_on_frame_not_send_callback` is called.
+ *
+ * HTTP/2 specification has requirement about header fields in the
+ * response HEADERS.  See the specification for more details.
+ *
+ * If |data_prd| is not ``NULL``, it provides data which will be sent
+ * in subsequent DATA frames.  This function does not take ownership
+ * of the |data_prd|.  The function copies the members of the
+ * |data_prd|.  If |data_prd| is ``NULL``, HEADERS will have
+ * END_STREAM flag set.
+ *
+ * This method can be used as normal HTTP response and push response.
+ * When pushing a resource using this function, the |session| must be
+ * configured using `nghttp2_session_server_new()` or its variants and
+ * the target stream denoted by the |stream_id| must be reserved using
+ * `nghttp2_submit_push_promise()`.
+ *
+ * To send non-final response headers (e.g., HTTP status 101), don't
+ * use this function because this function half-closes the outbound
+ * stream.  Instead, use `nghttp2_submit_headers()` for this purpose.
+ *
+ * This function returns 0 if it succeeds, or one of the following
+ * negative error codes:
+ *
+ * :enum:`nghttp2_error.NGHTTP2_ERR_NOMEM`
+ *     Out of memory.
+ * :enum:`nghttp2_error.NGHTTP2_ERR_INVALID_ARGUMENT`
+ *     The |stream_id| is 0.
+ * :enum:`nghttp2_error.NGHTTP2_ERR_DATA_EXIST`
+ *     DATA or HEADERS has been already submitted and not fully
+ *     processed yet.  Normally, this does not happen, but when
+ *     application wrongly calls `nghttp2_submit_response2()` twice,
+ *     this may happen.
+ * :enum:`nghttp2_error.NGHTTP2_ERR_PROTO`
+ *     The |session| is client session.
+ *
+ * .. warning::
+ *
+ *   Calling this function twice for the same stream ID may lead to
+ *   program crash.  It is generally considered to a programming error
+ *   to commit response twice.
+ */
+NGHTTP2_EXTERN int
+nghttp2_submit_response2(nghttp2_session *session, int32_t stream_id,
+                         const nghttp2_nv *nva, size_t nvlen,
+                         const nghttp2_data_provider2 *data_prd);
+
 /**
  * @function
  *
@@ -4064,22 +4828,23 @@ nghttp2_submit_response(nghttp2_session *session, int32_t stream_id,
  * DATA without END_STREAM flat set.  The library does not enforce
  * this requirement, and applications should do this for themselves.
  * If `nghttp2_submit_trailer()` is called before any response HEADERS
- * submission (usually by `nghttp2_submit_response()`), the content of
- * |nva| will be sent as response headers, which will result in error.
+ * submission (usually by `nghttp2_submit_response2()`), the content
+ * of |nva| will be sent as response headers, which will result in
+ * error.
  *
  * This function has the same effect with `nghttp2_submit_headers()`,
  * with flags = :enum:`nghttp2_flag.NGHTTP2_FLAG_END_STREAM` and both
  * pri_spec and stream_user_data to NULL.
  *
- * To submit trailer fields after `nghttp2_submit_response()` is
+ * To submit trailer fields after `nghttp2_submit_response2()` is
  * called, the application has to specify
- * :type:`nghttp2_data_provider` to `nghttp2_submit_response()`.
- * Inside of :type:`nghttp2_data_source_read_callback`, when setting
+ * :type:`nghttp2_data_provider2` to `nghttp2_submit_response2()`.
+ * Inside of :type:`nghttp2_data_source_read_callback2`, when setting
  * :enum:`nghttp2_data_flag.NGHTTP2_DATA_FLAG_EOF`, also set
  * :enum:`nghttp2_data_flag.NGHTTP2_DATA_FLAG_NO_END_STREAM`.  After
  * that, the application can send trailer fields using
  * `nghttp2_submit_trailer()`.  `nghttp2_submit_trailer()` can be used
- * inside :type:`nghttp2_data_source_read_callback`.
+ * inside :type:`nghttp2_data_source_read_callback2`.
  *
  * This function returns 0 if it succeeds and |stream_id| is -1.
  * Otherwise, this function returns 0 if it succeeds, or one of the
@@ -4114,11 +4879,13 @@ NGHTTP2_EXTERN int nghttp2_submit_trailer(nghttp2_session *session,
  * assigned stream ID will be returned.  Otherwise, specify stream ID
  * in |stream_id|.
  *
- * The |pri_spec| is priority specification of this request.  ``NULL``
- * means the default priority (see
+ * The |pri_spec| is a deprecated priority specification of this
+ * request.  ``NULL`` means the default priority (see
  * `nghttp2_priority_spec_default_init()`).  To specify the priority,
  * use `nghttp2_priority_spec_init()`.  If |pri_spec| is not ``NULL``,
- * this function will copy its data members.
+ * this function will copy its data members.  In the future release
+ * after the end of 2024, this function will ignore |pri_spec| and
+ * behave as if ``NULL`` is given.
  *
  * The ``pri_spec->weight`` must be in [:macro:`NGHTTP2_MIN_WEIGHT`,
  * :macro:`NGHTTP2_MAX_WEIGHT`], inclusive.  If ``pri_spec->weight``
@@ -4156,8 +4923,8 @@ NGHTTP2_EXTERN int nghttp2_submit_trailer(nghttp2_session *session,
  *
  * This function is low-level in a sense that the application code can
  * specify flags directly.  For usual HTTP request,
- * `nghttp2_submit_request()` is useful.  Likewise, for HTTP response,
- * prefer `nghttp2_submit_response()`.
+ * `nghttp2_submit_request2()` is useful.  Likewise, for HTTP
+ * response, prefer `nghttp2_submit_response2()`.
  *
  * This function returns newly assigned stream ID if it succeeds and
  * |stream_id| is -1.  Otherwise, this function returns 0 if it
@@ -4192,9 +4959,14 @@ NGHTTP2_EXTERN int32_t nghttp2_submit_headers(
     const nghttp2_priority_spec *pri_spec, const nghttp2_nv *nva, size_t nvlen,
     void *stream_user_data);
 
+#ifndef NGHTTP2_NO_SSIZE_T
 /**
  * @function
  *
+ * .. warning::
+ *
+ *   Deprecated.  Use `nghttp2_submit_data2()` instead.
+ *
  * Submits one or more DATA frames to the stream |stream_id|.  The
  * data to be sent are provided by |data_prd|.  If |flags| contains
  * :enum:`nghttp2_flag.NGHTTP2_FLAG_END_STREAM`, the last DATA frame
@@ -4237,19 +5009,73 @@ NGHTTP2_EXTERN int nghttp2_submit_data(nghttp2_session *session, uint8_t flags,
                                        int32_t stream_id,
                                        const nghttp2_data_provider *data_prd);
 
+#endif /* NGHTTP2_NO_SSIZE_T */
+
 /**
  * @function
  *
+ * Submits one or more DATA frames to the stream |stream_id|.  The
+ * data to be sent are provided by |data_prd|.  If |flags| contains
+ * :enum:`nghttp2_flag.NGHTTP2_FLAG_END_STREAM`, the last DATA frame
+ * has END_STREAM flag set.
+ *
+ * This function does not take ownership of the |data_prd|.  The
+ * function copies the members of the |data_prd|.
+ *
+ * This function returns 0 if it succeeds, or one of the following
+ * negative error codes:
+ *
+ * :enum:`nghttp2_error.NGHTTP2_ERR_NOMEM`
+ *     Out of memory.
+ * :enum:`nghttp2_error.NGHTTP2_ERR_DATA_EXIST`
+ *     DATA or HEADERS has been already submitted and not fully
+ *     processed yet.
+ * :enum:`nghttp2_error.NGHTTP2_ERR_INVALID_ARGUMENT`
+ *     The |stream_id| is 0.
+ * :enum:`nghttp2_error.NGHTTP2_ERR_STREAM_CLOSED`
+ *     The stream was already closed; or the |stream_id| is invalid.
+ *
+ * .. note::
+ *
+ *   Currently, only one DATA or HEADERS is allowed for a stream at a
+ *   time.  Submitting these frames more than once before first DATA
+ *   or HEADERS is finished results in
+ *   :enum:`nghttp2_error.NGHTTP2_ERR_DATA_EXIST` error code.  The
+ *   earliest callback which tells that previous frame is done is
+ *   :type:`nghttp2_on_frame_send_callback`.  In side that callback,
+ *   new data can be submitted using `nghttp2_submit_data2()`.  Of
+ *   course, all data except for last one must not have
+ *   :enum:`nghttp2_flag.NGHTTP2_FLAG_END_STREAM` flag set in |flags|.
+ *   This sounds a bit complicated, and we recommend to use
+ *   `nghttp2_submit_request2()` and `nghttp2_submit_response2()` to
+ *   avoid this cascading issue.  The experience shows that for HTTP
+ *   use, these two functions are enough to implement both client and
+ *   server.
+ */
+NGHTTP2_EXTERN int nghttp2_submit_data2(nghttp2_session *session, uint8_t flags,
+                                        int32_t stream_id,
+                                        const nghttp2_data_provider2 *data_prd);
+
+/**
+ * @function
+ *
+ * .. warning::
+ *
+ *   Deprecated.  :rfc:`7540` priorities are deprecated by
+ *   :rfc:`9113`.  Consider migrating to :rfc:`9218` extensible
+ *   prioritization scheme.  In the future release after the end of
+ *   2024, this function will always return 0 without doing anything.
+ *
  * Submits PRIORITY frame to change the priority of stream |stream_id|
  * to the priority specification |pri_spec|.
  *
  * The |flags| is currently ignored and should be
  * :enum:`nghttp2_flag.NGHTTP2_FLAG_NONE`.
  *
- * The |pri_spec| is priority specification of this request.  ``NULL``
- * is not allowed for this function. To specify the priority, use
- * `nghttp2_priority_spec_init()`.  This function will copy its data
- * members.
+ * The |pri_spec| is a deprecated priority specification of this
+ * request.  ``NULL`` is not allowed for this function. To specify the
+ * priority, use `nghttp2_priority_spec_init()`.  This function will
+ * copy its data members.
  *
  * The ``pri_spec->weight`` must be in [:macro:`NGHTTP2_MIN_WEIGHT`,
  * :macro:`NGHTTP2_MAX_WEIGHT`], inclusive.  If ``pri_spec->weight``
@@ -4429,7 +5255,7 @@ NGHTTP2_EXTERN int nghttp2_submit_settings(nghttp2_session *session,
  * The client side is not allowed to use this function.
  *
  * To submit response headers and data, use
- * `nghttp2_submit_response()`.
+ * `nghttp2_submit_response2()`.
  *
  * This function returns assigned promised stream ID if it succeeds,
  * or one of the following negative error codes:
@@ -4568,10 +5394,11 @@ nghttp2_session_get_last_proc_stream_id(nghttp2_session *session);
  * reasons are: session is server; stream ID has been spent; GOAWAY
  * has been sent or received.
  *
- * The application can call `nghttp2_submit_request()` without
- * consulting this function.  In that case, `nghttp2_submit_request()`
- * may return error.  Or, request is failed to sent, and
- * :type:`nghttp2_on_stream_close_callback` is called.
+ * The application can call `nghttp2_submit_request2()` without
+ * consulting this function.  In that case,
+ * `nghttp2_submit_request2()` may return error.  Or, request is
+ * failed to sent, and :type:`nghttp2_on_stream_close_callback` is
+ * called.
  */
 NGHTTP2_EXTERN int
 nghttp2_session_check_request_allowed(nghttp2_session *session);
@@ -4673,11 +5500,11 @@ nghttp2_session_set_local_window_size(nghttp2_session *session, uint8_t flags,
  * Application can pass arbitrary frame flags and stream ID in |flags|
  * and |stream_id| respectively.  The |payload| is opaque pointer, and
  * it can be accessible though ``frame->ext.payload`` in
- * :type:`nghttp2_pack_extension_callback`.  The library will not own
+ * :type:`nghttp2_pack_extension_callback2`.  The library will not own
  * passed |payload| pointer.
  *
- * The application must set :type:`nghttp2_pack_extension_callback`
- * using `nghttp2_session_callbacks_set_pack_extension_callback()`.
+ * The application must set :type:`nghttp2_pack_extension_callback2`
+ * using `nghttp2_session_callbacks_set_pack_extension_callback2()`.
  *
  * The application should retain the memory pointed by |payload| until
  * the transmission of extension frame is done (which is indicated by
@@ -4685,7 +5512,7 @@ nghttp2_session_set_local_window_size(nghttp2_session *session, uint8_t flags,
  * (which is indicated by :type:`nghttp2_on_frame_not_send_callback`).
  * If application does not touch this memory region after packing it
  * into a wire format, application can free it inside
- * :type:`nghttp2_pack_extension_callback`.
+ * :type:`nghttp2_pack_extension_callback2`.
  *
  * The standard HTTP/2 frame cannot be sent with this function, so
  * |type| must be strictly grater than 0x9.  Otherwise, this function
@@ -4696,7 +5523,7 @@ nghttp2_session_set_local_window_size(nghttp2_session *session, uint8_t flags,
  * negative error codes:
  *
  * :enum:`nghttp2_error.NGHTTP2_ERR_INVALID_STATE`
- *     If :type:`nghttp2_pack_extension_callback` is not set.
+ *     If :type:`nghttp2_pack_extension_callback2` is not set.
  * :enum:`nghttp2_error.NGHTTP2_ERR_INVALID_ARGUMENT`
  *     If  |type| specifies  standard  HTTP/2 frame  type.  The  frame
  *     types  in the  rage [0x0,  0x9], both  inclusive, are  standard
@@ -5317,9 +6144,14 @@ NGHTTP2_EXTERN int
 nghttp2_hd_deflate_change_table_size(nghttp2_hd_deflater *deflater,
                                      size_t settings_max_dynamic_table_size);
 
+#ifndef NGHTTP2_NO_SSIZE_T
 /**
  * @function
  *
+ * .. warning::
+ *
+ *   Deprecated.  Use `nghttp2_hd_deflate_hd2()` instead.
+ *
  * Deflates the |nva|, which has the |nvlen| name/value pairs, into
  * the |buf| of length |buflen|.
  *
@@ -5349,9 +6181,47 @@ NGHTTP2_EXTERN ssize_t nghttp2_hd_deflate_hd(nghttp2_hd_deflater *deflater,
                                              const nghttp2_nv *nva,
                                              size_t nvlen);
 
+#endif /* NGHTTP2_NO_SSIZE_T */
+
+/**
+ * @function
+ *
+ * Deflates the |nva|, which has the |nvlen| name/value pairs, into
+ * the |buf| of length |buflen|.
+ *
+ * If |buf| is not large enough to store the deflated header block,
+ * this function fails with
+ * :enum:`nghttp2_error.NGHTTP2_ERR_INSUFF_BUFSIZE`.  The caller
+ * should use `nghttp2_hd_deflate_bound()` to know the upper bound of
+ * buffer size required to deflate given header name/value pairs.
+ *
+ * Once this function fails, subsequent call of this function always
+ * returns :enum:`nghttp2_error.NGHTTP2_ERR_HEADER_COMP`.
+ *
+ * After this function returns, it is safe to delete the |nva|.
+ *
+ * This function returns the number of bytes written to |buf| if it
+ * succeeds, or one of the following negative error codes:
+ *
+ * :enum:`nghttp2_error.NGHTTP2_ERR_NOMEM`
+ *     Out of memory.
+ * :enum:`nghttp2_error.NGHTTP2_ERR_HEADER_COMP`
+ *     Deflation process has failed.
+ * :enum:`nghttp2_error.NGHTTP2_ERR_INSUFF_BUFSIZE`
+ *     The provided |buflen| size is too small to hold the output.
+ */
+NGHTTP2_EXTERN nghttp2_ssize
+nghttp2_hd_deflate_hd2(nghttp2_hd_deflater *deflater, uint8_t *buf,
+                       size_t buflen, const nghttp2_nv *nva, size_t nvlen);
+
+#ifndef NGHTTP2_NO_SSIZE_T
 /**
  * @function
  *
+ * .. warning::
+ *
+ *   Deprecated.  Use `nghttp2_hd_deflate_hd_vec2()` instead.
+ *
  * Deflates the |nva|, which has the |nvlen| name/value pairs, into
  * the |veclen| size of buf vector |vec|.  The each size of buffer
  * must be set in len field of :type:`nghttp2_vec`.  If and only if
@@ -5383,6 +6253,40 @@ NGHTTP2_EXTERN ssize_t nghttp2_hd_deflate_hd_vec(nghttp2_hd_deflater *deflater,
                                                  const nghttp2_nv *nva,
                                                  size_t nvlen);
 
+#endif /* NGHTTP2_NO_SSIZE_T */
+
+/**
+ * @function
+ *
+ * Deflates the |nva|, which has the |nvlen| name/value pairs, into
+ * the |veclen| size of buf vector |vec|.  The each size of buffer
+ * must be set in len field of :type:`nghttp2_vec`.  If and only if
+ * one chunk is filled up completely, next chunk will be used.  If
+ * |vec| is not large enough to store the deflated header block, this
+ * function fails with
+ * :enum:`nghttp2_error.NGHTTP2_ERR_INSUFF_BUFSIZE`.  The caller
+ * should use `nghttp2_hd_deflate_bound()` to know the upper bound of
+ * buffer size required to deflate given header name/value pairs.
+ *
+ * Once this function fails, subsequent call of this function always
+ * returns :enum:`nghttp2_error.NGHTTP2_ERR_HEADER_COMP`.
+ *
+ * After this function returns, it is safe to delete the |nva|.
+ *
+ * This function returns the number of bytes written to |vec| if it
+ * succeeds, or one of the following negative error codes:
+ *
+ * :enum:`nghttp2_error.NGHTTP2_ERR_NOMEM`
+ *     Out of memory.
+ * :enum:`nghttp2_error.NGHTTP2_ERR_HEADER_COMP`
+ *     Deflation process has failed.
+ * :enum:`nghttp2_error.NGHTTP2_ERR_INSUFF_BUFSIZE`
+ *     The provided |buflen| size is too small to hold the output.
+ */
+NGHTTP2_EXTERN nghttp2_ssize nghttp2_hd_deflate_hd_vec2(
+    nghttp2_hd_deflater *deflater, const nghttp2_vec *vec, size_t veclen,
+    const nghttp2_nv *nva, size_t nvlen);
+
 /**
  * @function
  *
@@ -5496,7 +6400,7 @@ NGHTTP2_EXTERN void nghttp2_hd_inflate_del(nghttp2_hd_inflater *inflater);
  * This function must not be called while header block is being
  * inflated.  In other words, this function must be called after
  * initialization of |inflater|, but before calling
- * `nghttp2_hd_inflate_hd2()`, or after
+ * `nghttp2_hd_inflate_hd3()`, or after
  * `nghttp2_hd_inflate_end_headers()`.  Otherwise,
  * `NGHTTP2_ERR_INVALID_STATE` was returned.
  *
@@ -5534,6 +6438,7 @@ typedef enum {
   NGHTTP2_HD_INFLATE_EMIT = 0x02
 } nghttp2_hd_inflate_flag;
 
+#ifndef NGHTTP2_NO_SSIZE_T
 /**
  * @function
  *
@@ -5621,9 +6526,16 @@ NGHTTP2_EXTERN ssize_t nghttp2_hd_inflate_hd(nghttp2_hd_inflater *inflater,
                                              int *inflate_flags, uint8_t *in,
                                              size_t inlen, int in_final);
 
+#endif /* NGHTTP2_NO_SSIZE_T */
+
+#ifndef NGHTTP2_NO_SSIZE_T
 /**
  * @function
  *
+ * .. warning::
+ *
+ *   Deprecated.  Use `nghttp2_hd_inflate_hd3()` instead.
+ *
  * Inflates name/value block stored in |in| with length |inlen|.  This
  * function performs decompression.  For each successful emission of
  * header name/value pair,
@@ -5710,6 +6622,95 @@ NGHTTP2_EXTERN ssize_t nghttp2_hd_inflate_hd2(nghttp2_hd_inflater *inflater,
                                               const uint8_t *in, size_t inlen,
                                               int in_final);
 
+#endif /* NGHTTP2_NO_SSIZE_T */
+
+/**
+ * @function
+ *
+ * Inflates name/value block stored in |in| with length |inlen|.  This
+ * function performs decompression.  For each successful emission of
+ * header name/value pair,
+ * :enum:`nghttp2_hd_inflate_flag.NGHTTP2_HD_INFLATE_EMIT` is set in
+ * |*inflate_flags| and name/value pair is assigned to the |nv_out|
+ * and the function returns.  The caller must not free the members of
+ * |nv_out|.
+ *
+ * The |nv_out| may include pointers to the memory region in the |in|.
+ * The caller must retain the |in| while the |nv_out| is used.
+ *
+ * The application should call this function repeatedly until the
+ * ``(*inflate_flags) & NGHTTP2_HD_INFLATE_FINAL`` is nonzero and
+ * return value is non-negative.  If that happens, all given input
+ * data (|inlen| bytes) are processed successfully.  Then the
+ * application must call `nghttp2_hd_inflate_end_headers()` to prepare
+ * for the next header block input.
+ *
+ * In other words, if |in_final| is nonzero, and this function returns
+ * |inlen|, you can assert that
+ * :enum:`nghttp2_hd_inflate_final.NGHTTP2_HD_INFLATE_FINAL` is set in
+ * |*inflate_flags|.
+ *
+ * The caller can feed complete compressed header block.  It also can
+ * feed it in several chunks.  The caller must set |in_final| to
+ * nonzero if the given input is the last block of the compressed
+ * header.
+ *
+ * This function returns the number of bytes processed if it succeeds,
+ * or one of the following negative error codes:
+ *
+ * :enum:`nghttp2_error.NGHTTP2_ERR_NOMEM`
+ *     Out of memory.
+ * :enum:`nghttp2_error.NGHTTP2_ERR_HEADER_COMP`
+ *     Inflation process has failed.
+ * :enum:`nghttp2_error.NGHTTP2_ERR_BUFFER_ERROR`
+ *     The header field name or value is too large.
+ *
+ * Example follows::
+ *
+ *     int inflate_header_block(nghttp2_hd_inflater *hd_inflater,
+ *                              uint8_t *in, size_t inlen, int final)
+ *     {
+ *         nghttp2_ssize rv;
+ *
+ *         for(;;) {
+ *             nghttp2_nv nv;
+ *             int inflate_flags = 0;
+ *
+ *             rv = nghttp2_hd_inflate_hd3(hd_inflater, &nv, &inflate_flags,
+ *                                         in, inlen, final);
+ *
+ *             if(rv < 0) {
+ *                 fprintf(stderr, "inflate failed with error code %td", rv);
+ *                 return -1;
+ *             }
+ *
+ *             in += rv;
+ *             inlen -= rv;
+ *
+ *             if(inflate_flags & NGHTTP2_HD_INFLATE_EMIT) {
+ *                 fwrite(nv.name, nv.namelen, 1, stderr);
+ *                 fprintf(stderr, ": ");
+ *                 fwrite(nv.value, nv.valuelen, 1, stderr);
+ *                 fprintf(stderr, "\n");
+ *             }
+ *             if(inflate_flags & NGHTTP2_HD_INFLATE_FINAL) {
+ *                 nghttp2_hd_inflate_end_headers(hd_inflater);
+ *                 break;
+ *             }
+ *             if((inflate_flags & NGHTTP2_HD_INFLATE_EMIT) == 0 &&
+ *                inlen == 0) {
+ *                break;
+ *             }
+ *         }
+ *
+ *         return 0;
+ *     }
+ *
+ */
+NGHTTP2_EXTERN nghttp2_ssize nghttp2_hd_inflate_hd3(
+    nghttp2_hd_inflater *inflater, nghttp2_nv *nv_out, int *inflate_flags,
+    const uint8_t *in, size_t inlen, int in_final);
+
 /**
  * @function
  *
@@ -5783,8 +6784,8 @@ typedef struct nghttp2_stream nghttp2_stream;
  * `nghttp2_session_get_root_stream()`) if 0 is given in |stream_id|.
  *
  * Unless |stream_id| == 0, the returned pointer is valid until next
- * call of `nghttp2_session_send()`, `nghttp2_session_mem_send()`,
- * `nghttp2_session_recv()`, and `nghttp2_session_mem_recv()`.
+ * call of `nghttp2_session_send()`, `nghttp2_session_mem_send2()`,
+ * `nghttp2_session_recv()`, and `nghttp2_session_mem_recv2()`.
  */
 NGHTTP2_EXTERN nghttp2_stream *
 nghttp2_session_find_stream(nghttp2_session *session, int32_t stream_id);
@@ -5838,6 +6839,12 @@ nghttp2_stream_get_state(nghttp2_stream *stream);
 /**
  * @function
  *
+ * .. warning::
+ *
+ *   Deprecated.  :rfc:`7540` priorities are deprecated by
+ *   :rfc:`9113`.  Consider migrating to :rfc:`9218` extensible
+ *   prioritization scheme.
+ *
  * Returns root of dependency tree, which is imaginary stream with
  * stream ID 0.  The returned pointer is valid until |session| is
  * freed by `nghttp2_session_del()`.
@@ -5848,6 +6855,13 @@ nghttp2_session_get_root_stream(nghttp2_session *session);
 /**
  * @function
  *
+ * .. warning::
+ *
+ *   Deprecated.  :rfc:`7540` priorities are deprecated by
+ *   :rfc:`9113`.  Consider migrating to :rfc:`9218` extensible
+ *   prioritization scheme.  In the future release after the end of
+ *   2024, this function will always return NULL.
+ *
  * Returns the parent stream of |stream| in dependency tree.  Returns
  * NULL if there is no such stream.
  */
@@ -5859,6 +6873,13 @@ NGHTTP2_EXTERN int32_t nghttp2_stream_get_stream_id(nghttp2_stream *stream);
 /**
  * @function
  *
+ * .. warning::
+ *
+ *   Deprecated.  :rfc:`7540` priorities are deprecated by
+ *   :rfc:`9113`.  Consider migrating to :rfc:`9218` extensible
+ *   prioritization scheme.  In the future release after the end of
+ *   2024, this function will always return NULL.
+ *
  * Returns the next sibling stream of |stream| in dependency tree.
  * Returns NULL if there is no such stream.
  */
@@ -5868,6 +6889,13 @@ nghttp2_stream_get_next_sibling(nghttp2_stream *stream);
 /**
  * @function
  *
+ * .. warning::
+ *
+ *   Deprecated.  :rfc:`7540` priorities are deprecated by
+ *   :rfc:`9113`.  Consider migrating to :rfc:`9218` extensible
+ *   prioritization scheme.  In the future release after the end of
+ *   2024, this function will always return NULL.
+ *
  * Returns the previous sibling stream of |stream| in dependency tree.
  * Returns NULL if there is no such stream.
  */
@@ -5877,6 +6905,13 @@ nghttp2_stream_get_previous_sibling(nghttp2_stream *stream);
 /**
  * @function
  *
+ * .. warning::
+ *
+ *   Deprecated.  :rfc:`7540` priorities are deprecated by
+ *   :rfc:`9113`.  Consider migrating to :rfc:`9218` extensible
+ *   prioritization scheme.  In the future release after the end of
+ *   2024, this function will always return NULL.
+ *
  * Returns the first child stream of |stream| in dependency tree.
  * Returns NULL if there is no such stream.
  */
@@ -5886,6 +6921,14 @@ nghttp2_stream_get_first_child(nghttp2_stream *stream);
 /**
  * @function
  *
+ * .. warning::
+ *
+ *   Deprecated.  :rfc:`7540` priorities are deprecated by
+ *   :rfc:`9113`.  Consider migrating to :rfc:`9218` extensible
+ *   prioritization scheme.  In the future release after the end of
+ *   2024, this function will always return
+ *   :macro:`NGHTTP2_DEFAULT_WEIGHT`.
+ *
  * Returns dependency weight to the parent stream of |stream|.
  */
 NGHTTP2_EXTERN int32_t nghttp2_stream_get_weight(nghttp2_stream *stream);
@@ -5893,6 +6936,13 @@ NGHTTP2_EXTERN int32_t nghttp2_stream_get_weight(nghttp2_stream *stream);
 /**
  * @function
  *
+ * .. warning::
+ *
+ *   Deprecated.  :rfc:`7540` priorities are deprecated by
+ *   :rfc:`9113`.  Consider migrating to :rfc:`9218` extensible
+ *   prioritization scheme.  In the future release after the end of
+ *   2024, this function will always return 0.
+ *
  * Returns the sum of the weight for |stream|'s children.
  */
 NGHTTP2_EXTERN int32_t
diff --git a/lib/nghttp2_buf.c b/lib/nghttp2_buf.c
index a328447..101035f 100644
--- a/lib/nghttp2_buf.c
+++ b/lib/nghttp2_buf.c
@@ -430,7 +430,7 @@ int nghttp2_bufs_orb_hold(nghttp2_bufs *bufs, uint8_t b) {
   return 0;
 }
 
-ssize_t nghttp2_bufs_remove(nghttp2_bufs *bufs, uint8_t **out) {
+nghttp2_ssize nghttp2_bufs_remove(nghttp2_bufs *bufs, uint8_t **out) {
   size_t len;
   nghttp2_buf_chain *chain;
   nghttp2_buf *buf;
@@ -462,7 +462,7 @@ ssize_t nghttp2_bufs_remove(nghttp2_bufs *bufs, uint8_t **out) {
 
   *out = res;
 
-  return (ssize_t)len;
+  return (nghttp2_ssize)len;
 }
 
 size_t nghttp2_bufs_remove_copy(nghttp2_bufs *bufs, uint8_t *out) {
diff --git a/lib/nghttp2_buf.h b/lib/nghttp2_buf.h
index 45f62f1..95ff370 100644
--- a/lib/nghttp2_buf.h
+++ b/lib/nghttp2_buf.h
@@ -349,7 +349,7 @@ int nghttp2_bufs_orb_hold(nghttp2_bufs *bufs, uint8_t b);
  * NGHTTP2_ERR_NOMEM
  *     Out of memory
  */
-ssize_t nghttp2_bufs_remove(nghttp2_bufs *bufs, uint8_t **out);
+nghttp2_ssize nghttp2_bufs_remove(nghttp2_bufs *bufs, uint8_t **out);
 
 /*
  * Copies all data stored in |bufs| to |out|.  This function assumes
diff --git a/lib/nghttp2_callbacks.c b/lib/nghttp2_callbacks.c
index 3c38214..1776f7d 100644
--- a/lib/nghttp2_callbacks.c
+++ b/lib/nghttp2_callbacks.c
@@ -45,11 +45,21 @@ void nghttp2_session_callbacks_set_send_callback(
   cbs->send_callback = send_callback;
 }
 
+void nghttp2_session_callbacks_set_send_callback2(
+    nghttp2_session_callbacks *cbs, nghttp2_send_callback2 send_callback) {
+  cbs->send_callback2 = send_callback;
+}
+
 void nghttp2_session_callbacks_set_recv_callback(
     nghttp2_session_callbacks *cbs, nghttp2_recv_callback recv_callback) {
   cbs->recv_callback = recv_callback;
 }
 
+void nghttp2_session_callbacks_set_recv_callback2(
+    nghttp2_session_callbacks *cbs, nghttp2_recv_callback2 recv_callback) {
+  cbs->recv_callback2 = recv_callback;
+}
+
 void nghttp2_session_callbacks_set_on_frame_recv_callback(
     nghttp2_session_callbacks *cbs,
     nghttp2_on_frame_recv_callback on_frame_recv_callback) {
@@ -128,12 +138,24 @@ void nghttp2_session_callbacks_set_select_padding_callback(
   cbs->select_padding_callback = select_padding_callback;
 }
 
+void nghttp2_session_callbacks_set_select_padding_callback2(
+    nghttp2_session_callbacks *cbs,
+    nghttp2_select_padding_callback2 select_padding_callback) {
+  cbs->select_padding_callback2 = select_padding_callback;
+}
+
 void nghttp2_session_callbacks_set_data_source_read_length_callback(
     nghttp2_session_callbacks *cbs,
     nghttp2_data_source_read_length_callback data_source_read_length_callback) {
   cbs->read_length_callback = data_source_read_length_callback;
 }
 
+void nghttp2_session_callbacks_set_data_source_read_length_callback2(
+    nghttp2_session_callbacks *cbs, nghttp2_data_source_read_length_callback2
+                                        data_source_read_length_callback) {
+  cbs->read_length_callback2 = data_source_read_length_callback;
+}
+
 void nghttp2_session_callbacks_set_on_begin_frame_callback(
     nghttp2_session_callbacks *cbs,
     nghttp2_on_begin_frame_callback on_begin_frame_callback) {
@@ -152,6 +174,12 @@ void nghttp2_session_callbacks_set_pack_extension_callback(
   cbs->pack_extension_callback = pack_extension_callback;
 }
 
+void nghttp2_session_callbacks_set_pack_extension_callback2(
+    nghttp2_session_callbacks *cbs,
+    nghttp2_pack_extension_callback2 pack_extension_callback) {
+  cbs->pack_extension_callback2 = pack_extension_callback;
+}
+
 void nghttp2_session_callbacks_set_unpack_extension_callback(
     nghttp2_session_callbacks *cbs,
     nghttp2_unpack_extension_callback unpack_extension_callback) {
diff --git a/lib/nghttp2_callbacks.h b/lib/nghttp2_callbacks.h
index 61e51fa..a611f48 100644
--- a/lib/nghttp2_callbacks.h
+++ b/lib/nghttp2_callbacks.h
@@ -36,19 +36,33 @@
  */
 struct nghttp2_session_callbacks {
   /**
+   * Deprecated.  Use send_callback2 instead.  Callback function
+   * invoked when the session wants to send data to the remote peer.
+   * This callback is not necessary if the application uses solely
+   * `nghttp2_session_mem_send()` to serialize data to transmit.
+   */
+  nghttp2_send_callback send_callback;
+  /**
    * Callback function invoked when the session wants to send data to
    * the remote peer.  This callback is not necessary if the
-   * application uses solely `nghttp2_session_mem_send()` to serialize
-   * data to transmit.
+   * application uses solely `nghttp2_session_mem_send2()` to
+   * serialize data to transmit.
    */
-  nghttp2_send_callback send_callback;
+  nghttp2_send_callback2 send_callback2;
+  /**
+   * Deprecated.  Use recv_callback2 instead.  Callback function
+   * invoked when the session wants to receive data from the remote
+   * peer.  This callback is not necessary if the application uses
+   * solely `nghttp2_session_mem_recv()` to process received data.
+   */
+  nghttp2_recv_callback recv_callback;
   /**
    * Callback function invoked when the session wants to receive data
    * from the remote peer.  This callback is not necessary if the
-   * application uses solely `nghttp2_session_mem_recv()` to process
+   * application uses solely `nghttp2_session_mem_recv2()` to process
    * received data.
    */
-  nghttp2_recv_callback recv_callback;
+  nghttp2_recv_callback2 recv_callback2;
   /**
    * Callback function invoked by `nghttp2_session_recv()` when a
    * frame is received.
@@ -100,22 +114,39 @@ struct nghttp2_session_callbacks {
   nghttp2_on_invalid_header_callback on_invalid_header_callback;
   nghttp2_on_invalid_header_callback2 on_invalid_header_callback2;
   /**
+   * Deprecated.  Use select_padding_callback2 instead.  Callback
+   * function invoked when the library asks application how many
+   * padding bytes are required for the transmission of the given
+   * frame.
+   */
+  nghttp2_select_padding_callback select_padding_callback;
+  /**
    * Callback function invoked when the library asks application how
    * many padding bytes are required for the transmission of the given
    * frame.
    */
-  nghttp2_select_padding_callback select_padding_callback;
+  nghttp2_select_padding_callback2 select_padding_callback2;
   /**
-   * The callback function used to determine the length allowed in
+   * Deprecated.  Use read_length_callback2 instead.  The callback
+   * function used to determine the length allowed in
    * `nghttp2_data_source_read_callback()`
    */
   nghttp2_data_source_read_length_callback read_length_callback;
   /**
+   * The callback function used to determine the length allowed in
+   * `nghttp2_data_source_read_callback2()`
+   */
+  nghttp2_data_source_read_length_callback2 read_length_callback2;
+  /**
    * Sets callback function invoked when a frame header is received.
    */
   nghttp2_on_begin_frame_callback on_begin_frame_callback;
   nghttp2_send_data_callback send_data_callback;
+  /**
+   * Deprecated.  Use pack_extension_callback2 instead.
+   */
   nghttp2_pack_extension_callback pack_extension_callback;
+  nghttp2_pack_extension_callback2 pack_extension_callback2;
   nghttp2_unpack_extension_callback unpack_extension_callback;
   nghttp2_on_extension_chunk_recv_callback on_extension_chunk_recv_callback;
   nghttp2_error_callback error_callback;
diff --git a/lib/nghttp2_hd.c b/lib/nghttp2_hd.c
index 8a2bda6..1b0c713 100644
--- a/lib/nghttp2_hd.c
+++ b/lib/nghttp2_hd.c
@@ -850,9 +850,10 @@ static size_t encode_length(uint8_t *buf, size_t n, size_t prefix) {
  * in the next call will be stored in |*shift_ptr|) and returns number
  * of bytes processed, or returns -1, indicating decoding error.
  */
-static ssize_t decode_length(uint32_t *res, size_t *shift_ptr, int *fin,
-                             uint32_t initial, size_t shift, const uint8_t *in,
-                             const uint8_t *last, size_t prefix) {
+static nghttp2_ssize decode_length(uint32_t *res, size_t *shift_ptr, int *fin,
+                                   uint32_t initial, size_t shift,
+                                   const uint8_t *in, const uint8_t *last,
+                                   size_t prefix) {
   uint32_t k = (uint8_t)((1 << prefix) - 1);
   uint32_t n = initial;
   const uint8_t *start = in;
@@ -871,7 +872,7 @@ static ssize_t decode_length(uint32_t *res, size_t *shift_ptr, int *fin,
 
     if (++in == last) {
       *res = n;
-      return (ssize_t)(in - start);
+      return (nghttp2_ssize)(in - start);
     }
   }
 
@@ -906,12 +907,12 @@ static ssize_t decode_length(uint32_t *res, size_t *shift_ptr, int *fin,
 
   if (in == last) {
     *res = n;
-    return (ssize_t)(in - start);
+    return (nghttp2_ssize)(in - start);
   }
 
   *res = n;
   *fin = 1;
-  return (ssize_t)(in + 1 - start);
+  return (nghttp2_ssize)(in + 1 - start);
 }
 
 static int emit_table_size(nghttp2_bufs *bufs, size_t table_size) {
@@ -1164,7 +1165,7 @@ static int add_hd_table_incremental(nghttp2_hd_context *context,
 }
 
 typedef struct {
-  ssize_t index;
+  nghttp2_ssize index;
   /* Nonzero if both name and value are matched. */
   int name_value_match;
 } search_result;
@@ -1213,8 +1214,8 @@ static search_result search_hd_table(nghttp2_hd_context *context,
     return res;
   }
 
-  res.index =
-      (ssize_t)(context->next_seq - 1 - ent->seq + NGHTTP2_STATIC_TABLE_LENGTH);
+  res.index = (nghttp2_ssize)(context->next_seq - 1 - ent->seq +
+                              NGHTTP2_STATIC_TABLE_LENGTH);
   res.name_value_match = exact_match;
 
   return res;
@@ -1343,7 +1344,7 @@ static int deflate_nv(nghttp2_hd_deflater *deflater, nghttp2_bufs *bufs,
                       const nghttp2_nv *nv) {
   int rv;
   search_result res;
-  ssize_t idx;
+  nghttp2_ssize idx;
   int indexing_mode;
   int32_t token;
   nghttp2_mem *mem;
@@ -1379,7 +1380,7 @@ static int deflate_nv(nghttp2_hd_deflater *deflater, nghttp2_bufs *bufs,
 
   if (res.name_value_match) {
 
-    DEBUGF("deflatehd: name/value match index=%zd\n", idx);
+    DEBUGF("deflatehd: name/value match index=%td\n", idx);
 
     rv = emit_indexed_block(bufs, (size_t)idx);
     if (rv != 0) {
@@ -1390,7 +1391,7 @@ static int deflate_nv(nghttp2_hd_deflater *deflater, nghttp2_bufs *bufs,
   }
 
   if (res.index != -1) {
-    DEBUGF("deflatehd: name match index=%zd\n", res.index);
+    DEBUGF("deflatehd: name match index=%td\n", res.index);
   }
 
   if (indexing_mode == NGHTTP2_HD_WITH_INDEXING) {
@@ -1491,6 +1492,12 @@ fail:
 ssize_t nghttp2_hd_deflate_hd(nghttp2_hd_deflater *deflater, uint8_t *buf,
                               size_t buflen, const nghttp2_nv *nv,
                               size_t nvlen) {
+  return (ssize_t)nghttp2_hd_deflate_hd2(deflater, buf, buflen, nv, nvlen);
+}
+
+nghttp2_ssize nghttp2_hd_deflate_hd2(nghttp2_hd_deflater *deflater,
+                                     uint8_t *buf, size_t buflen,
+                                     const nghttp2_nv *nv, size_t nvlen) {
   nghttp2_bufs bufs;
   int rv;
   nghttp2_mem *mem;
@@ -1517,12 +1524,18 @@ ssize_t nghttp2_hd_deflate_hd(nghttp2_hd_deflater *deflater, uint8_t *buf,
     return rv;
   }
 
-  return (ssize_t)buflen;
+  return (nghttp2_ssize)buflen;
 }
 
 ssize_t nghttp2_hd_deflate_hd_vec(nghttp2_hd_deflater *deflater,
                                   const nghttp2_vec *vec, size_t veclen,
                                   const nghttp2_nv *nv, size_t nvlen) {
+  return (ssize_t)nghttp2_hd_deflate_hd_vec2(deflater, vec, veclen, nv, nvlen);
+}
+
+nghttp2_ssize nghttp2_hd_deflate_hd_vec2(nghttp2_hd_deflater *deflater,
+                                         const nghttp2_vec *vec, size_t veclen,
+                                         const nghttp2_nv *nv, size_t nvlen) {
   nghttp2_bufs bufs;
   int rv;
   nghttp2_mem *mem;
@@ -1550,7 +1563,7 @@ ssize_t nghttp2_hd_deflate_hd_vec(nghttp2_hd_deflater *deflater,
     return rv;
   }
 
-  return (ssize_t)buflen;
+  return (nghttp2_ssize)buflen;
 }
 
 size_t nghttp2_hd_deflate_bound(nghttp2_hd_deflater *deflater,
@@ -1643,10 +1656,11 @@ static void hd_inflate_set_huffman_encoded(nghttp2_hd_inflater *inflater,
  * NGHTTP2_ERR_HEADER_COMP
  *   Integer decoding failed
  */
-static ssize_t hd_inflate_read_len(nghttp2_hd_inflater *inflater, int *rfin,
-                                   const uint8_t *in, const uint8_t *last,
-                                   size_t prefix, size_t maxlen) {
-  ssize_t rv;
+static nghttp2_ssize hd_inflate_read_len(nghttp2_hd_inflater *inflater,
+                                         int *rfin, const uint8_t *in,
+                                         const uint8_t *last, size_t prefix,
+                                         size_t maxlen) {
+  nghttp2_ssize rv;
   uint32_t out;
 
   *rfin = 0;
@@ -1684,10 +1698,10 @@ static ssize_t hd_inflate_read_len(nghttp2_hd_inflater *inflater, int *rfin,
  * NGHTTP2_ERR_HEADER_COMP
  *   Huffman decoding failed
  */
-static ssize_t hd_inflate_read_huff(nghttp2_hd_inflater *inflater,
-                                    nghttp2_buf *buf, const uint8_t *in,
-                                    const uint8_t *last) {
-  ssize_t readlen;
+static nghttp2_ssize hd_inflate_read_huff(nghttp2_hd_inflater *inflater,
+                                          nghttp2_buf *buf, const uint8_t *in,
+                                          const uint8_t *last) {
+  nghttp2_ssize readlen;
   int fin = 0;
   if ((size_t)(last - in) >= inflater->left) {
     last = in + inflater->left;
@@ -1721,14 +1735,15 @@ static ssize_t hd_inflate_read_huff(nghttp2_hd_inflater *inflater,
  * NGHTTP2_ERR_HEADER_COMP
  *   Header decompression failed
  */
-static ssize_t hd_inflate_read(nghttp2_hd_inflater *inflater, nghttp2_buf *buf,
-                               const uint8_t *in, const uint8_t *last) {
+static nghttp2_ssize hd_inflate_read(nghttp2_hd_inflater *inflater,
+                                     nghttp2_buf *buf, const uint8_t *in,
+                                     const uint8_t *last) {
   size_t len = nghttp2_min((size_t)(last - in), inflater->left);
 
   buf->last = nghttp2_cpymem(buf->last, in, len);
 
   inflater->left -= len;
-  return (ssize_t)len;
+  return (nghttp2_ssize)len;
 }
 
 /*
@@ -1843,7 +1858,15 @@ ssize_t nghttp2_hd_inflate_hd(nghttp2_hd_inflater *inflater, nghttp2_nv *nv_out,
 ssize_t nghttp2_hd_inflate_hd2(nghttp2_hd_inflater *inflater,
                                nghttp2_nv *nv_out, int *inflate_flags,
                                const uint8_t *in, size_t inlen, int in_final) {
-  ssize_t rv;
+  return (nghttp2_ssize)nghttp2_hd_inflate_hd3(inflater, nv_out, inflate_flags,
+                                               in, inlen, in_final);
+}
+
+nghttp2_ssize nghttp2_hd_inflate_hd3(nghttp2_hd_inflater *inflater,
+                                     nghttp2_nv *nv_out, int *inflate_flags,
+                                     const uint8_t *in, size_t inlen,
+                                     int in_final) {
+  nghttp2_ssize rv;
   nghttp2_hd_nv hd_nv;
 
   rv = nghttp2_hd_inflate_hd_nv(inflater, &hd_nv, inflate_flags, in, inlen,
@@ -1866,11 +1889,11 @@ ssize_t nghttp2_hd_inflate_hd2(nghttp2_hd_inflater *inflater,
   return rv;
 }
 
-ssize_t nghttp2_hd_inflate_hd_nv(nghttp2_hd_inflater *inflater,
-                                 nghttp2_hd_nv *nv_out, int *inflate_flags,
-                                 const uint8_t *in, size_t inlen,
-                                 int in_final) {
-  ssize_t rv = 0;
+nghttp2_ssize nghttp2_hd_inflate_hd_nv(nghttp2_hd_inflater *inflater,
+                                       nghttp2_hd_nv *nv_out,
+                                       int *inflate_flags, const uint8_t *in,
+                                       size_t inlen, int in_final) {
+  nghttp2_ssize rv = 0;
   const uint8_t *first = in;
   const uint8_t *last = in + inlen;
   int rfin = 0;
@@ -1992,7 +2015,7 @@ ssize_t nghttp2_hd_inflate_hd_nv(nghttp2_hd_inflater *inflater,
 
         inflater->state = NGHTTP2_HD_STATE_OPCODE;
         *inflate_flags |= NGHTTP2_HD_INFLATE_EMIT;
-        return (ssize_t)(in - first);
+        return (nghttp2_ssize)(in - first);
       } else {
         inflater->index = inflater->left;
         --inflater->index;
@@ -2050,7 +2073,7 @@ ssize_t nghttp2_hd_inflate_hd_nv(nghttp2_hd_inflater *inflater,
 
       in += rv;
 
-      DEBUGF("inflatehd: %zd bytes read\n", rv);
+      DEBUGF("inflatehd: %td bytes read\n", rv);
 
       if (inflater->left) {
         DEBUGF("inflatehd: still %zu bytes to go\n", inflater->left);
@@ -2072,7 +2095,7 @@ ssize_t nghttp2_hd_inflate_hd_nv(nghttp2_hd_inflater *inflater,
 
       in += rv;
 
-      DEBUGF("inflatehd: %zd bytes read\n", rv);
+      DEBUGF("inflatehd: %td bytes read\n", rv);
       if (inflater->left) {
         DEBUGF("inflatehd: still %zu bytes to go\n", inflater->left);
 
@@ -2138,7 +2161,7 @@ ssize_t nghttp2_hd_inflate_hd_nv(nghttp2_hd_inflater *inflater,
 
       in += rv;
 
-      DEBUGF("inflatehd: %zd bytes read\n", rv);
+      DEBUGF("inflatehd: %td bytes read\n", rv);
 
       if (inflater->left) {
         DEBUGF("inflatehd: still %zu bytes to go\n", inflater->left);
@@ -2162,18 +2185,18 @@ ssize_t nghttp2_hd_inflate_hd_nv(nghttp2_hd_inflater *inflater,
       inflater->state = NGHTTP2_HD_STATE_OPCODE;
       *inflate_flags |= NGHTTP2_HD_INFLATE_EMIT;
 
-      return (ssize_t)(in - first);
+      return (nghttp2_ssize)(in - first);
     case NGHTTP2_HD_STATE_READ_VALUE:
       rv = hd_inflate_read(inflater, &inflater->valuebuf, in, last);
       if (rv < 0) {
-        DEBUGF("inflatehd: value read failure %zd: %s\n", rv,
+        DEBUGF("inflatehd: value read failure %td: %s\n", rv,
                nghttp2_strerror((int)rv));
         goto fail;
       }
 
       in += rv;
 
-      DEBUGF("inflatehd: %zd bytes read\n", rv);
+      DEBUGF("inflatehd: %td bytes read\n", rv);
 
       if (inflater->left) {
         DEBUGF("inflatehd: still %zu bytes to go\n", inflater->left);
@@ -2196,7 +2219,7 @@ ssize_t nghttp2_hd_inflate_hd_nv(nghttp2_hd_inflater *inflater,
       inflater->state = NGHTTP2_HD_STATE_OPCODE;
       *inflate_flags |= NGHTTP2_HD_INFLATE_EMIT;
 
-      return (ssize_t)(in - first);
+      return (nghttp2_ssize)(in - first);
     }
   }
 
@@ -2216,7 +2239,7 @@ ssize_t nghttp2_hd_inflate_hd_nv(nghttp2_hd_inflater *inflater,
     }
     *inflate_flags |= NGHTTP2_HD_INFLATE_FINAL;
   }
-  return (ssize_t)(in - first);
+  return (nghttp2_ssize)(in - first);
 
 almost_ok:
   if (in_final) {
@@ -2226,10 +2249,10 @@ almost_ok:
 
     goto fail;
   }
-  return (ssize_t)(in - first);
+  return (nghttp2_ssize)(in - first);
 
 fail:
-  DEBUGF("inflatehd: error return %zd\n", rv);
+  DEBUGF("inflatehd: error return %td\n", rv);
 
   inflater->ctx.bad = 1;
   return rv;
@@ -2297,9 +2320,10 @@ int nghttp2_hd_emit_table_size(nghttp2_bufs *bufs, size_t table_size) {
   return emit_table_size(bufs, table_size);
 }
 
-ssize_t nghttp2_hd_decode_length(uint32_t *res, size_t *shift_ptr, int *fin,
-                                 uint32_t initial, size_t shift, uint8_t *in,
-                                 uint8_t *last, size_t prefix) {
+nghttp2_ssize nghttp2_hd_decode_length(uint32_t *res, size_t *shift_ptr,
+                                       int *fin, uint32_t initial, size_t shift,
+                                       uint8_t *in, uint8_t *last,
+                                       size_t prefix) {
   return decode_length(res, shift_ptr, fin, initial, shift, in, last, prefix);
 }
 
diff --git a/lib/nghttp2_hd.h b/lib/nghttp2_hd.h
index 6de0052..38a31a8 100644
--- a/lib/nghttp2_hd.h
+++ b/lib/nghttp2_hd.h
@@ -357,9 +357,10 @@ void nghttp2_hd_inflate_free(nghttp2_hd_inflater *inflater);
  * that return values and semantics are the same as
  * nghttp2_hd_inflate_hd().
  */
-ssize_t nghttp2_hd_inflate_hd_nv(nghttp2_hd_inflater *inflater,
-                                 nghttp2_hd_nv *nv_out, int *inflate_flags,
-                                 const uint8_t *in, size_t inlen, int in_final);
+nghttp2_ssize nghttp2_hd_inflate_hd_nv(nghttp2_hd_inflater *inflater,
+                                       nghttp2_hd_nv *nv_out,
+                                       int *inflate_flags, const uint8_t *in,
+                                       size_t inlen, int in_final);
 
 /* For unittesting purpose */
 int nghttp2_hd_emit_indname_block(nghttp2_bufs *bufs, size_t index,
@@ -376,9 +377,10 @@ int nghttp2_hd_emit_table_size(nghttp2_bufs *bufs, size_t table_size);
 nghttp2_hd_nv nghttp2_hd_table_get(nghttp2_hd_context *context, size_t index);
 
 /* For unittesting purpose */
-ssize_t nghttp2_hd_decode_length(uint32_t *res, size_t *shift_ptr, int *fin,
-                                 uint32_t initial, size_t shift, uint8_t *in,
-                                 uint8_t *last, size_t prefix);
+nghttp2_ssize nghttp2_hd_decode_length(uint32_t *res, size_t *shift_ptr,
+                                       int *fin, uint32_t initial, size_t shift,
+                                       uint8_t *in, uint8_t *last,
+                                       size_t prefix);
 
 /* Huffman encoding/decoding functions */
 
@@ -427,9 +429,9 @@ void nghttp2_hd_huff_decode_context_init(nghttp2_hd_huff_decode_context *ctx);
  * NGHTTP2_ERR_HEADER_COMP
  *     Decoding process has failed.
  */
-ssize_t nghttp2_hd_huff_decode(nghttp2_hd_huff_decode_context *ctx,
-                               nghttp2_buf *buf, const uint8_t *src,
-                               size_t srclen, int fin);
+nghttp2_ssize nghttp2_hd_huff_decode(nghttp2_hd_huff_decode_context *ctx,
+                                     nghttp2_buf *buf, const uint8_t *src,
+                                     size_t srclen, int fin);
 
 /*
  * nghttp2_hd_huff_decode_failure_state returns nonzero if |ctx|
diff --git a/lib/nghttp2_hd_huffman.c b/lib/nghttp2_hd_huffman.c
index ac90f49..959053f 100644
--- a/lib/nghttp2_hd_huffman.c
+++ b/lib/nghttp2_hd_huffman.c
@@ -107,9 +107,9 @@ void nghttp2_hd_huff_decode_context_init(nghttp2_hd_huff_decode_context *ctx) {
   ctx->fstate = NGHTTP2_HUFF_ACCEPTED;
 }
 
-ssize_t nghttp2_hd_huff_decode(nghttp2_hd_huff_decode_context *ctx,
-                               nghttp2_buf *buf, const uint8_t *src,
-                               size_t srclen, int final) {
+nghttp2_ssize nghttp2_hd_huff_decode(nghttp2_hd_huff_decode_context *ctx,
+                                     nghttp2_buf *buf, const uint8_t *src,
+                                     size_t srclen, int final) {
   const uint8_t *end = src + srclen;
   nghttp2_huff_decode node = {ctx->fstate, 0};
   const nghttp2_huff_decode *t = &node;
@@ -136,7 +136,7 @@ ssize_t nghttp2_hd_huff_decode(nghttp2_hd_huff_decode_context *ctx,
     return NGHTTP2_ERR_HEADER_COMP;
   }
 
-  return (ssize_t)srclen;
+  return (nghttp2_ssize)srclen;
 }
 
 int nghttp2_hd_huff_decode_failure_state(nghttp2_hd_huff_decode_context *ctx) {
diff --git a/lib/nghttp2_outbound_item.c b/lib/nghttp2_outbound_item.c
index 2a3041d..a9e9f76 100644
--- a/lib/nghttp2_outbound_item.c
+++ b/lib/nghttp2_outbound_item.c
@@ -27,6 +27,32 @@
 #include <assert.h>
 #include <string.h>
 
+nghttp2_data_provider_wrap *
+nghttp2_data_provider_wrap_v1(nghttp2_data_provider_wrap *dpw,
+                              const nghttp2_data_provider *data_prd) {
+  if (!data_prd) {
+    return NULL;
+  }
+
+  dpw->version = NGHTTP2_DATA_PROVIDER_V1;
+  dpw->data_prd.v1 = *data_prd;
+
+  return dpw;
+}
+
+nghttp2_data_provider_wrap *
+nghttp2_data_provider_wrap_v2(nghttp2_data_provider_wrap *dpw,
+                              const nghttp2_data_provider2 *data_prd) {
+  if (!data_prd) {
+    return NULL;
+  }
+
+  dpw->version = NGHTTP2_DATA_PROVIDER_V2;
+  dpw->data_prd.v2 = *data_prd;
+
+  return dpw;
+}
+
 void nghttp2_outbound_item_init(nghttp2_outbound_item *item) {
   item->cycle = 0;
   item->qnext = NULL;
diff --git a/lib/nghttp2_outbound_item.h b/lib/nghttp2_outbound_item.h
index bd4611b..4e91750 100644
--- a/lib/nghttp2_outbound_item.h
+++ b/lib/nghttp2_outbound_item.h
@@ -33,9 +33,32 @@
 #include "nghttp2_frame.h"
 #include "nghttp2_mem.h"
 
+#define NGHTTP2_DATA_PROVIDER_V1 1
+#define NGHTTP2_DATA_PROVIDER_V2 2
+
+typedef struct nghttp2_data_provider_wrap {
+  int version;
+  union {
+    struct {
+      nghttp2_data_source source;
+      void *read_callback;
+    };
+    nghttp2_data_provider v1;
+    nghttp2_data_provider2 v2;
+  } data_prd;
+} nghttp2_data_provider_wrap;
+
+nghttp2_data_provider_wrap *
+nghttp2_data_provider_wrap_v1(nghttp2_data_provider_wrap *dpw,
+                              const nghttp2_data_provider *data_prd);
+
+nghttp2_data_provider_wrap *
+nghttp2_data_provider_wrap_v2(nghttp2_data_provider_wrap *dpw,
+                              const nghttp2_data_provider2 *data_prd);
+
 /* struct used for HEADERS and PUSH_PROMISE frame */
 typedef struct {
-  nghttp2_data_provider data_prd;
+  nghttp2_data_provider_wrap dpw;
   void *stream_user_data;
   /* error code when request HEADERS is canceled by RST_STREAM while
      it is in queue. */
@@ -50,7 +73,7 @@ typedef struct {
   /**
    * The data to be sent for this DATA frame.
    */
-  nghttp2_data_provider data_prd;
+  nghttp2_data_provider_wrap dpw;
   /**
    * The flags of DATA frame.  We use separate flags here and
    * nghttp2_data frame.  The latter contains flags actually sent to
diff --git a/lib/nghttp2_session.c b/lib/nghttp2_session.c
index ce21caf..226cdd5 100644
--- a/lib/nghttp2_session.c
+++ b/lib/nghttp2_session.c
@@ -39,6 +39,7 @@
 #include "nghttp2_extpri.h"
 #include "nghttp2_time.h"
 #include "nghttp2_debug.h"
+#include "nghttp2_submit.h"
 
 /*
  * Returns non-zero if the number of outgoing opened streams is larger
@@ -2103,10 +2104,9 @@ static int session_predicate_priority_update_send(nghttp2_session *session,
 
 /* Take into account settings max frame size and both connection-level
    flow control here */
-static ssize_t
-nghttp2_session_enforce_flow_control_limits(nghttp2_session *session,
-                                            nghttp2_stream *stream,
-                                            ssize_t requested_window_size) {
+static nghttp2_ssize nghttp2_session_enforce_flow_control_limits(
+    nghttp2_session *session, nghttp2_stream *stream,
+    nghttp2_ssize requested_window_size) {
   DEBUGF("send: remote windowsize connection=%d, remote maxframsize=%u, "
          "stream(id %d)=%d\n",
          session->remote_window_size, session->remote_settings.max_frame_size,
@@ -2126,12 +2126,12 @@ nghttp2_session_enforce_flow_control_limits(nghttp2_session *session,
  */
 static size_t nghttp2_session_next_data_read(nghttp2_session *session,
                                              nghttp2_stream *stream) {
-  ssize_t window_size;
+  nghttp2_ssize window_size;
 
   window_size = nghttp2_session_enforce_flow_control_limits(
       session, stream, NGHTTP2_DATA_PAYLOADLEN);
 
-  DEBUGF("send: available window=%zd\n", window_size);
+  DEBUGF("send: available window=%td\n", window_size);
 
   return window_size > 0 ? (size_t)window_size : 0;
 }
@@ -2186,29 +2186,33 @@ static int nghttp2_session_predicate_data_send(nghttp2_session *session,
   return NGHTTP2_ERR_INVALID_STREAM_STATE;
 }
 
-static ssize_t session_call_select_padding(nghttp2_session *session,
-                                           const nghttp2_frame *frame,
-                                           size_t max_payloadlen) {
-  ssize_t rv;
+static nghttp2_ssize session_call_select_padding(nghttp2_session *session,
+                                                 const nghttp2_frame *frame,
+                                                 size_t max_payloadlen) {
+  nghttp2_ssize rv;
+  size_t max_paddedlen;
 
-  if (frame->hd.length >= max_payloadlen) {
-    return (ssize_t)frame->hd.length;
+  if (frame->hd.length >= max_payloadlen ||
+      (!session->callbacks.select_padding_callback2 &&
+       !session->callbacks.select_padding_callback)) {
+    return (nghttp2_ssize)frame->hd.length;
   }
 
-  if (session->callbacks.select_padding_callback) {
-    size_t max_paddedlen;
-
-    max_paddedlen =
-        nghttp2_min(frame->hd.length + NGHTTP2_MAX_PADLEN, max_payloadlen);
+  max_paddedlen =
+      nghttp2_min(frame->hd.length + NGHTTP2_MAX_PADLEN, max_payloadlen);
 
-    rv = session->callbacks.select_padding_callback(
+  if (session->callbacks.select_padding_callback2) {
+    rv = session->callbacks.select_padding_callback2(
         session, frame, max_paddedlen, session->user_data);
-    if (rv < (ssize_t)frame->hd.length || rv > (ssize_t)max_paddedlen) {
-      return NGHTTP2_ERR_CALLBACK_FAILURE;
-    }
-    return rv;
+  } else {
+    rv = (nghttp2_ssize)session->callbacks.select_padding_callback(
+        session, frame, max_paddedlen, session->user_data);
+  }
+  if (rv < (nghttp2_ssize)frame->hd.length ||
+      rv > (nghttp2_ssize)max_paddedlen) {
+    return NGHTTP2_ERR_CALLBACK_FAILURE;
   }
-  return (ssize_t)frame->hd.length;
+  return rv;
 }
 
 /* Add padding to HEADERS or PUSH_PROMISE. We use
@@ -2216,7 +2220,7 @@ static ssize_t session_call_select_padding(nghttp2_session *session,
    frame->push_promise has also padlen in the same position. */
 static int session_headers_add_pad(nghttp2_session *session,
                                    nghttp2_frame *frame) {
-  ssize_t padded_payloadlen;
+  nghttp2_ssize padded_payloadlen;
   nghttp2_active_outbound_item *aob;
   nghttp2_bufs *framebufs;
   size_t padlen;
@@ -2237,7 +2241,7 @@ static int session_headers_add_pad(nghttp2_session *session,
 
   padlen = (size_t)padded_payloadlen - frame->hd.length;
 
-  DEBUGF("send: padding selected: payloadlen=%zd, padlen=%zu\n",
+  DEBUGF("send: padding selected: payloadlen=%td, padlen=%zu\n",
          padded_payloadlen, padlen);
 
   nghttp2_frame_add_pad(framebufs, &frame->hd, padlen, 0);
@@ -2257,18 +2261,24 @@ static size_t session_estimate_headers_payload(nghttp2_session *session,
 
 static int session_pack_extension(nghttp2_session *session, nghttp2_bufs *bufs,
                                   nghttp2_frame *frame) {
-  ssize_t rv;
+  nghttp2_ssize rv;
   nghttp2_buf *buf;
   size_t buflen;
   size_t framelen;
 
-  assert(session->callbacks.pack_extension_callback);
+  assert(session->callbacks.pack_extension_callback2 ||
+         session->callbacks.pack_extension_callback);
 
   buf = &bufs->head->buf;
   buflen = nghttp2_min(nghttp2_buf_avail(buf), NGHTTP2_MAX_PAYLOADLEN);
 
-  rv = session->callbacks.pack_extension_callback(session, buf->last, buflen,
-                                                  frame, session->user_data);
+  if (session->callbacks.pack_extension_callback2) {
+    rv = session->callbacks.pack_extension_callback2(session, buf->last, buflen,
+                                                     frame, session->user_data);
+  } else {
+    rv = (nghttp2_ssize)session->callbacks.pack_extension_callback(
+        session, buf->last, buflen, frame, session->user_data);
+  }
   if (rv == NGHTTP2_ERR_CANCEL) {
     return (int)rv;
   }
@@ -2451,7 +2461,7 @@ static int session_prep_frame(nghttp2_session *session,
       return rv;
     }
 
-    DEBUGF("send: before padding, HEADERS serialized in %zd bytes\n",
+    DEBUGF("send: before padding, HEADERS serialized in %zu bytes\n",
            nghttp2_bufs_len(&session->aob.framebufs));
 
     rv = session_headers_add_pad(session, frame);
@@ -2460,7 +2470,7 @@ static int session_prep_frame(nghttp2_session *session,
       return rv;
     }
 
-    DEBUGF("send: HEADERS finally serialized in %zd bytes\n",
+    DEBUGF("send: HEADERS finally serialized in %zu bytes\n",
            nghttp2_bufs_len(&session->aob.framebufs));
 
     if (frame->headers.cat == NGHTTP2_HCAT_REQUEST) {
@@ -2877,7 +2887,7 @@ static int session_after_frame_sent1(nghttp2_session *session) {
 
       /* Call on_frame_send_callback after
          nghttp2_stream_detach_item(), so that application can issue
-         nghttp2_submit_data() in the callback. */
+         nghttp2_submit_data2() in the callback. */
       if (session->callbacks.on_frame_send_callback) {
         rv = session_call_on_frame_send(session, frame);
         if (nghttp2_is_fatal(rv)) {
@@ -2949,15 +2959,17 @@ static int session_after_frame_sent1(nghttp2_session *session) {
       }
       /* We assume aux_data is a pointer to nghttp2_headers_aux_data */
       aux_data = &item->aux_data.headers;
-      if (aux_data->data_prd.read_callback) {
-        /* nghttp2_submit_data() makes a copy of aux_data->data_prd */
-        rv = nghttp2_submit_data(session, NGHTTP2_FLAG_END_STREAM,
-                                 frame->hd.stream_id, &aux_data->data_prd);
+      if (aux_data->dpw.data_prd.read_callback) {
+        /* nghttp2_submit_data_shared() makes a copy of
+           aux_data->dpw */
+        rv = nghttp2_submit_data_shared(session, NGHTTP2_FLAG_END_STREAM,
+                                        frame->hd.stream_id, &aux_data->dpw);
         if (nghttp2_is_fatal(rv)) {
           return rv;
         }
-        /* TODO nghttp2_submit_data() may fail if stream has already
-           DATA frame item.  We might have to handle it here. */
+        /* TODO nghttp2_submit_data_shared() may fail if stream has
+           already DATA frame item.  We might have to handle it
+           here. */
       }
       return 0;
     }
@@ -2978,14 +2990,15 @@ static int session_after_frame_sent1(nghttp2_session *session) {
       }
       /* We assume aux_data is a pointer to nghttp2_headers_aux_data */
       aux_data = &item->aux_data.headers;
-      if (aux_data->data_prd.read_callback) {
-        rv = nghttp2_submit_data(session, NGHTTP2_FLAG_END_STREAM,
-                                 frame->hd.stream_id, &aux_data->data_prd);
+      if (aux_data->dpw.data_prd.read_callback) {
+        rv = nghttp2_submit_data_shared(session, NGHTTP2_FLAG_END_STREAM,
+                                        frame->hd.stream_id, &aux_data->dpw);
         if (nghttp2_is_fatal(rv)) {
           return rv;
         }
-        /* TODO nghttp2_submit_data() may fail if stream has already
-           DATA frame item.  We might have to handle it here. */
+        /* TODO nghttp2_submit_data_shared() may fail if stream has
+           already DATA frame item.  We might have to handle it
+           here. */
       }
       return 0;
     default:
@@ -3144,7 +3157,7 @@ static void session_after_frame_sent2(nghttp2_session *session) {
   aux_data = &item->aux_data.data;
 
   /* On EOF, we have already detached data.  Please note that
-     application may issue nghttp2_submit_data() in
+     application may issue nghttp2_submit_data2() in
      on_frame_send_callback (call from session_after_frame_sent1),
      which attach data to stream.  We don't want to detach it. */
   if (aux_data->eof) {
@@ -3191,7 +3204,7 @@ static int session_call_send_data(nghttp2_session *session,
   aux_data = &item->aux_data.data;
 
   rv = session->callbacks.send_data_callback(session, frame, buf->pos, length,
-                                             &aux_data->data_prd.source,
+                                             &aux_data->dpw.data_prd.source,
                                              session->user_data);
 
   switch (rv) {
@@ -3205,9 +3218,9 @@ static int session_call_send_data(nghttp2_session *session,
   }
 }
 
-static ssize_t nghttp2_session_mem_send_internal(nghttp2_session *session,
-                                                 const uint8_t **data_ptr,
-                                                 int fast_cb) {
+static nghttp2_ssize nghttp2_session_mem_send_internal(nghttp2_session *session,
+                                                       const uint8_t **data_ptr,
+                                                       int fast_cb) {
   int rv;
   nghttp2_active_outbound_item *aob;
   nghttp2_bufs *framebufs;
@@ -3385,7 +3398,7 @@ static ssize_t nghttp2_session_mem_send_internal(nghttp2_session *session,
         }
       }
 
-      DEBUGF("send: start transmitting frame type=%u, length=%zd\n",
+      DEBUGF("send: start transmitting frame type=%u, length=%td\n",
              framebufs->cur->buf.pos[3],
              framebufs->cur->buf.last - framebufs->cur->buf.pos);
 
@@ -3425,7 +3438,7 @@ static ssize_t nghttp2_session_mem_send_internal(nghttp2_session *session,
          everything, we will adjust it. */
       buf->pos += datalen;
 
-      return (ssize_t)datalen;
+      return (nghttp2_ssize)datalen;
     }
     case NGHTTP2_OB_SEND_NO_COPY: {
       nghttp2_stream *stream;
@@ -3502,7 +3515,7 @@ static ssize_t nghttp2_session_mem_send_internal(nghttp2_session *session,
 
       buf->pos += datalen;
 
-      return (ssize_t)datalen;
+      return (nghttp2_ssize)datalen;
     }
     }
   }
@@ -3510,8 +3523,13 @@ static ssize_t nghttp2_session_mem_send_internal(nghttp2_session *session,
 
 ssize_t nghttp2_session_mem_send(nghttp2_session *session,
                                  const uint8_t **data_ptr) {
+  return (ssize_t)nghttp2_session_mem_send2(session, data_ptr);
+}
+
+nghttp2_ssize nghttp2_session_mem_send2(nghttp2_session *session,
+                                        const uint8_t **data_ptr) {
   int rv;
-  ssize_t len;
+  nghttp2_ssize len;
 
   *data_ptr = NULL;
 
@@ -3528,7 +3546,7 @@ ssize_t nghttp2_session_mem_send(nghttp2_session *session,
     rv = session_after_frame_sent1(session);
     if (rv < 0) {
       assert(nghttp2_is_fatal(rv));
-      return (ssize_t)rv;
+      return (nghttp2_ssize)rv;
     }
   }
 
@@ -3537,8 +3555,8 @@ ssize_t nghttp2_session_mem_send(nghttp2_session *session,
 
 int nghttp2_session_send(nghttp2_session *session) {
   const uint8_t *data = NULL;
-  ssize_t datalen;
-  ssize_t sentlen;
+  nghttp2_ssize datalen;
+  nghttp2_ssize sentlen;
   nghttp2_bufs *framebufs;
 
   framebufs = &session->aob.framebufs;
@@ -3548,8 +3566,13 @@ int nghttp2_session_send(nghttp2_session *session) {
     if (datalen <= 0) {
       return (int)datalen;
     }
-    sentlen = session->callbacks.send_callback(session, data, (size_t)datalen,
-                                               0, session->user_data);
+    if (session->callbacks.send_callback2) {
+      sentlen = session->callbacks.send_callback2(
+          session, data, (size_t)datalen, 0, session->user_data);
+    } else {
+      sentlen = (nghttp2_ssize)session->callbacks.send_callback(
+          session, data, (size_t)datalen, 0, session->user_data);
+    }
     if (sentlen < 0) {
       if (sentlen == NGHTTP2_ERR_WOULDBLOCK) {
         /* Transmission canceled. Rewind the offset */
@@ -3564,11 +3587,17 @@ int nghttp2_session_send(nghttp2_session *session) {
   }
 }
 
-static ssize_t session_recv(nghttp2_session *session, uint8_t *buf,
-                            size_t len) {
-  ssize_t rv;
-  rv = session->callbacks.recv_callback(session, buf, len, 0,
-                                        session->user_data);
+static nghttp2_ssize session_recv(nghttp2_session *session, uint8_t *buf,
+                                  size_t len) {
+  nghttp2_ssize rv;
+
+  if (session->callbacks.recv_callback2) {
+    rv = session->callbacks.recv_callback2(session, buf, len, 0,
+                                           session->user_data);
+  } else {
+    rv = (nghttp2_ssize)session->callbacks.recv_callback(session, buf, len, 0,
+                                                         session->user_data);
+  }
   if (rv > 0) {
     if ((size_t)rv > len) {
       return NGHTTP2_ERR_CALLBACK_FAILURE;
@@ -3870,7 +3899,7 @@ static int session_inflate_handle_invalid_connection(nghttp2_session *session,
 static int inflate_header_block(nghttp2_session *session, nghttp2_frame *frame,
                                 size_t *readlen_ptr, uint8_t *in, size_t inlen,
                                 int final, int call_header_cb) {
-  ssize_t proclen;
+  nghttp2_ssize proclen;
   int rv;
   int inflate_flags;
   nghttp2_hd_nv nv;
@@ -3923,7 +3952,7 @@ static int inflate_header_block(nghttp2_session *session, nghttp2_frame *frame,
     inlen -= (size_t)proclen;
     *readlen_ptr += (size_t)proclen;
 
-    DEBUGF("recv: proclen=%zd\n", proclen);
+    DEBUGF("recv: proclen=%td\n", proclen);
 
     if (call_header_cb && (inflate_flags & NGHTTP2_HD_INFLATE_EMIT)) {
       rv = 0;
@@ -5763,7 +5792,7 @@ static int inbound_frame_handle_pad(nghttp2_inbound_frame *iframe,
  * Computes number of padding based on flags. This function returns
  * the calculated length if it succeeds, or -1.
  */
-static ssize_t inbound_frame_compute_pad(nghttp2_inbound_frame *iframe) {
+static nghttp2_ssize inbound_frame_compute_pad(nghttp2_inbound_frame *iframe) {
   size_t padlen;
 
   /* 1 for Pad Length field */
@@ -5778,7 +5807,7 @@ static ssize_t inbound_frame_compute_pad(nghttp2_inbound_frame *iframe) {
 
   iframe->padlen = padlen;
 
-  return (ssize_t)padlen;
+  return (nghttp2_ssize)padlen;
 }
 
 /*
@@ -5787,9 +5816,9 @@ static ssize_t inbound_frame_compute_pad(nghttp2_inbound_frame *iframe) {
  * |payloadleft| does not include |readlen|. If padding was started
  * strictly before this data chunk, this function returns -1.
  */
-static ssize_t inbound_frame_effective_readlen(nghttp2_inbound_frame *iframe,
-                                               size_t payloadleft,
-                                               size_t readlen) {
+static nghttp2_ssize
+inbound_frame_effective_readlen(nghttp2_inbound_frame *iframe,
+                                size_t payloadleft, size_t readlen) {
   size_t trail_padlen =
       nghttp2_frame_trail_padlen(&iframe->frame, iframe->padlen);
 
@@ -5799,19 +5828,24 @@ static ssize_t inbound_frame_effective_readlen(nghttp2_inbound_frame *iframe,
     if (readlen < padlen) {
       return -1;
     }
-    return (ssize_t)(readlen - padlen);
+    return (nghttp2_ssize)(readlen - padlen);
   }
-  return (ssize_t)(readlen);
+  return (nghttp2_ssize)(readlen);
 }
 
 static const uint8_t static_in[] = {0};
 
 ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
                                  size_t inlen) {
+  return (ssize_t)nghttp2_session_mem_recv2(session, in, inlen);
+}
+
+nghttp2_ssize nghttp2_session_mem_recv2(nghttp2_session *session,
+                                        const uint8_t *in, size_t inlen) {
   const uint8_t *first, *last;
   nghttp2_inbound_frame *iframe = &session->iframe;
   size_t readlen;
-  ssize_t padlen;
+  nghttp2_ssize padlen;
   int rv;
   int busy = 0;
   nghttp2_frame_hd cont_hd;
@@ -5841,7 +5875,7 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
   }
 
   if (!nghttp2_session_want_read(session)) {
-    return (ssize_t)inlen;
+    return (nghttp2_ssize)inlen;
   }
 
   for (;;) {
@@ -5871,7 +5905,7 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
       in += readlen;
 
       if (nghttp2_buf_mark_avail(&iframe->sbuf)) {
-        return (ssize_t)(in - first);
+        return (nghttp2_ssize)(in - first);
       }
 
       if (iframe->sbuf.pos[3] != NGHTTP2_SETTINGS ||
@@ -5893,7 +5927,7 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
           return rv;
         }
 
-        return (ssize_t)inlen;
+        return (nghttp2_ssize)inlen;
       }
 
       iframe->state = NGHTTP2_IB_READ_HEAD;
@@ -5908,7 +5942,7 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
       in += readlen;
 
       if (nghttp2_buf_mark_avail(&iframe->sbuf)) {
-        return (ssize_t)(in - first);
+        return (nghttp2_ssize)(in - first);
       }
 
       nghttp2_frame_unpack_frame_hd(&iframe->frame.hd, iframe->sbuf.pos);
@@ -5929,7 +5963,7 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
           return rv;
         }
 
-        return (ssize_t)inlen;
+        return (nghttp2_ssize)inlen;
       }
 
       switch (iframe->frame.hd.type) {
@@ -5944,7 +5978,7 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
 
         rv = session_on_data_received_fail_fast(session);
         if (iframe->state == NGHTTP2_IB_IGN_ALL) {
-          return (ssize_t)inlen;
+          return (nghttp2_ssize)inlen;
         }
         if (rv == NGHTTP2_ERR_IGN_PAYLOAD) {
           DEBUGF("recv: DATA not allowed stream_id=%d\n",
@@ -5966,7 +6000,7 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
           if (nghttp2_is_fatal(rv)) {
             return rv;
           }
-          return (ssize_t)inlen;
+          return (nghttp2_ssize)inlen;
         }
 
         if (rv == 1) {
@@ -5993,7 +6027,7 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
           if (nghttp2_is_fatal(rv)) {
             return rv;
           }
-          return (ssize_t)inlen;
+          return (nghttp2_ssize)inlen;
         }
 
         if (rv == 1) {
@@ -6036,7 +6070,7 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
         busy = 1;
 
         if (iframe->state == NGHTTP2_IB_IGN_ALL) {
-          return (ssize_t)inlen;
+          return (nghttp2_ssize)inlen;
         }
 
         if (rv == NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE) {
@@ -6137,7 +6171,7 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
             if (nghttp2_is_fatal(rv)) {
               return rv;
             }
-            return (ssize_t)inlen;
+            return (nghttp2_ssize)inlen;
           }
 
           iframe->iv = nghttp2_mem_malloc(mem, sizeof(nghttp2_settings_entry) *
@@ -6175,7 +6209,7 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
           if (nghttp2_is_fatal(rv)) {
             return rv;
           }
-          return (ssize_t)inlen;
+          return (nghttp2_ssize)inlen;
         }
 
         if (rv == 1) {
@@ -6235,7 +6269,7 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
           return rv;
         }
 
-        return (ssize_t)inlen;
+        return (nghttp2_ssize)inlen;
       default:
         DEBUGF("recv: extension frame\n");
 
@@ -6346,7 +6380,7 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
               if (nghttp2_is_fatal(rv)) {
                 return rv;
               }
-              return (ssize_t)inlen;
+              return (nghttp2_ssize)inlen;
             }
 
             if (iframe->payloadleft < 4) {
@@ -6404,11 +6438,11 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
       in += readlen;
       iframe->payloadleft -= readlen;
 
-      DEBUGF("recv: readlen=%zu, payloadleft=%zu, left=%zd\n", readlen,
+      DEBUGF("recv: readlen=%zu, payloadleft=%zu, left=%zu\n", readlen,
              iframe->payloadleft, nghttp2_buf_mark_avail(&iframe->sbuf));
 
       if (nghttp2_buf_mark_avail(&iframe->sbuf)) {
-        return (ssize_t)(in - first);
+        return (nghttp2_ssize)(in - first);
       }
 
       switch (iframe->frame.hd.type) {
@@ -6424,7 +6458,7 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
             if (nghttp2_is_fatal(rv)) {
               return rv;
             }
-            return (ssize_t)inlen;
+            return (nghttp2_ssize)inlen;
           }
           iframe->frame.headers.padlen = (size_t)padlen;
 
@@ -6451,7 +6485,7 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
         busy = 1;
 
         if (iframe->state == NGHTTP2_IB_IGN_ALL) {
-          return (ssize_t)inlen;
+          return (nghttp2_ssize)inlen;
         }
 
         if (rv == NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE) {
@@ -6481,7 +6515,7 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
           }
 
           if (iframe->state == NGHTTP2_IB_IGN_ALL) {
-            return (ssize_t)inlen;
+            return (nghttp2_ssize)inlen;
           }
         }
 
@@ -6495,7 +6529,7 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
         }
 
         if (iframe->state == NGHTTP2_IB_IGN_ALL) {
-          return (ssize_t)inlen;
+          return (nghttp2_ssize)inlen;
         }
 
         session_inbound_frame_reset(session);
@@ -6513,7 +6547,7 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
             if (nghttp2_is_fatal(rv)) {
               return rv;
             }
-            return (ssize_t)inlen;
+            return (nghttp2_ssize)inlen;
           }
 
           iframe->frame.push_promise.padlen = (size_t)padlen;
@@ -6539,7 +6573,7 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
         busy = 1;
 
         if (iframe->state == NGHTTP2_IB_IGN_ALL) {
-          return (ssize_t)inlen;
+          return (nghttp2_ssize)inlen;
         }
 
         if (rv == NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE) {
@@ -6568,7 +6602,7 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
         }
 
         if (iframe->state == NGHTTP2_IB_IGN_ALL) {
-          return (ssize_t)inlen;
+          return (nghttp2_ssize)inlen;
         }
 
         session_inbound_frame_reset(session);
@@ -6603,7 +6637,7 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
         }
 
         if (iframe->state == NGHTTP2_IB_IGN_ALL) {
-          return (ssize_t)inlen;
+          return (nghttp2_ssize)inlen;
         }
 
         session_inbound_frame_reset(session);
@@ -6661,7 +6695,7 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
       break;
     case NGHTTP2_IB_READ_HEADER_BLOCK:
     case NGHTTP2_IB_IGN_HEADER_BLOCK: {
-      ssize_t data_readlen;
+      nghttp2_ssize data_readlen;
       size_t trail_padlen;
       int final;
 #ifdef DEBUGBUILD
@@ -6705,14 +6739,14 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
         }
 
         if (iframe->state == NGHTTP2_IB_IGN_ALL) {
-          return (ssize_t)inlen;
+          return (nghttp2_ssize)inlen;
         }
 
         if (rv == NGHTTP2_ERR_PAUSE) {
           in += hd_proclen;
           iframe->payloadleft -= hd_proclen;
 
-          return (ssize_t)(in - first);
+          return (nghttp2_ssize)(in - first);
         }
 
         if (rv == NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE) {
@@ -6819,7 +6853,7 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
 
       assert(iframe->state == NGHTTP2_IB_IGN_ALL);
 
-      return (ssize_t)inlen;
+      return (nghttp2_ssize)inlen;
     case NGHTTP2_IB_READ_SETTINGS:
       DEBUGF("recv: [IB_READ_SETTINGS]\n");
 
@@ -6849,7 +6883,7 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
       }
 
       if (iframe->state == NGHTTP2_IB_IGN_ALL) {
-        return (ssize_t)inlen;
+        return (nghttp2_ssize)inlen;
       }
 
       session_inbound_frame_reset(session);
@@ -6883,7 +6917,7 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
       }
 
       if (iframe->state == NGHTTP2_IB_IGN_ALL) {
-        return (ssize_t)inlen;
+        return (nghttp2_ssize)inlen;
       }
 
       session_inbound_frame_reset(session);
@@ -6903,7 +6937,7 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
       in += readlen;
 
       if (nghttp2_buf_mark_avail(&iframe->sbuf)) {
-        return (ssize_t)(in - first);
+        return (nghttp2_ssize)(in - first);
       }
 
       nghttp2_frame_unpack_frame_hd(&cont_hd, iframe->sbuf.pos);
@@ -6925,7 +6959,7 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
           return rv;
         }
 
-        return (ssize_t)inlen;
+        return (nghttp2_ssize)inlen;
       }
 
       /* CONTINUATION won't bear NGHTTP2_PADDED flag */
@@ -6961,7 +6995,7 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
              iframe->payloadleft, nghttp2_buf_mark_avail(&iframe->sbuf));
 
       if (nghttp2_buf_mark_avail(&iframe->sbuf)) {
-        return (ssize_t)(in - first);
+        return (nghttp2_ssize)(in - first);
       }
 
       /* Pad Length field is subject to flow control */
@@ -6971,7 +7005,7 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
       }
 
       if (iframe->state == NGHTTP2_IB_IGN_ALL) {
-        return (ssize_t)inlen;
+        return (nghttp2_ssize)inlen;
       }
 
       /* Pad Length field is consumed immediately */
@@ -6983,7 +7017,7 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
       }
 
       if (iframe->state == NGHTTP2_IB_IGN_ALL) {
-        return (ssize_t)inlen;
+        return (nghttp2_ssize)inlen;
       }
 
       stream = nghttp2_session_get_stream(session, iframe->frame.hd.stream_id);
@@ -7006,7 +7040,7 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
         if (nghttp2_is_fatal(rv)) {
           return rv;
         }
-        return (ssize_t)inlen;
+        return (nghttp2_ssize)inlen;
       }
 
       iframe->frame.data.padlen = (size_t)padlen;
@@ -7033,7 +7067,7 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
              iframe->payloadleft);
 
       if (readlen > 0) {
-        ssize_t data_readlen;
+        nghttp2_ssize data_readlen;
 
         rv = nghttp2_session_update_recv_connection_window_size(session,
                                                                 readlen);
@@ -7042,7 +7076,7 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
         }
 
         if (iframe->state == NGHTTP2_IB_IGN_ALL) {
-          return (ssize_t)inlen;
+          return (nghttp2_ssize)inlen;
         }
 
         rv = nghttp2_session_update_recv_stream_window_size(
@@ -7061,7 +7095,7 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
           data_readlen = 0;
         }
 
-        padlen = (ssize_t)readlen - data_readlen;
+        padlen = (nghttp2_ssize)readlen - data_readlen;
 
         if (padlen > 0) {
           /* Padding is considered as "consumed" immediately */
@@ -7073,11 +7107,11 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
           }
 
           if (iframe->state == NGHTTP2_IB_IGN_ALL) {
-            return (ssize_t)inlen;
+            return (nghttp2_ssize)inlen;
           }
         }
 
-        DEBUGF("recv: data_readlen=%zd\n", data_readlen);
+        DEBUGF("recv: data_readlen=%td\n", data_readlen);
 
         if (data_readlen > 0) {
           if (session_enforce_http_messaging(session)) {
@@ -7092,7 +7126,7 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
                 }
 
                 if (iframe->state == NGHTTP2_IB_IGN_DATA) {
-                  return (ssize_t)inlen;
+                  return (nghttp2_ssize)inlen;
                 }
               }
 
@@ -7111,7 +7145,7 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
                 session, iframe->frame.hd.flags, iframe->frame.hd.stream_id,
                 in - readlen, (size_t)data_readlen, session->user_data);
             if (rv == NGHTTP2_ERR_PAUSE) {
-              return (ssize_t)(in - first);
+              return (nghttp2_ssize)(in - first);
             }
 
             if (nghttp2_is_fatal(rv)) {
@@ -7153,7 +7187,7 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
         }
 
         if (iframe->state == NGHTTP2_IB_IGN_ALL) {
-          return (ssize_t)inlen;
+          return (nghttp2_ssize)inlen;
         }
 
         if (session->opt_flags & NGHTTP2_OPTMASK_NO_AUTO_WINDOW_UPDATE) {
@@ -7166,7 +7200,7 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
           }
 
           if (iframe->state == NGHTTP2_IB_IGN_ALL) {
-            return (ssize_t)inlen;
+            return (nghttp2_ssize)inlen;
           }
         }
       }
@@ -7179,7 +7213,7 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
 
       break;
     case NGHTTP2_IB_IGN_ALL:
-      return (ssize_t)inlen;
+      return (nghttp2_ssize)inlen;
     case NGHTTP2_IB_READ_EXTENSION_PAYLOAD:
       DEBUGF("recv: [IB_READ_EXTENSION_PAYLOAD]\n");
 
@@ -7274,7 +7308,7 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
       }
 
       if (iframe->state == NGHTTP2_IB_IGN_ALL) {
-        return (ssize_t)inlen;
+        return (nghttp2_ssize)inlen;
       }
 
       session_inbound_frame_reset(session);
@@ -7291,16 +7325,17 @@ ssize_t nghttp2_session_mem_recv(nghttp2_session *session, const uint8_t *in,
 
   assert(in == last);
 
-  return (ssize_t)(in - first);
+  return (nghttp2_ssize)(in - first);
 }
 
 int nghttp2_session_recv(nghttp2_session *session) {
   uint8_t buf[NGHTTP2_INBOUND_BUFFER_LENGTH];
   while (1) {
-    ssize_t readlen;
+    nghttp2_ssize readlen;
     readlen = session_recv(session, buf, sizeof(buf));
     if (readlen > 0) {
-      ssize_t proclen = nghttp2_session_mem_recv(session, buf, (size_t)readlen);
+      nghttp2_ssize proclen =
+          nghttp2_session_mem_recv2(session, buf, (size_t)readlen);
       if (proclen < 0) {
         return (int)proclen;
       }
@@ -7642,8 +7677,8 @@ int nghttp2_session_pack_data(nghttp2_session *session, nghttp2_bufs *bufs,
                               nghttp2_stream *stream) {
   int rv;
   uint32_t data_flags;
-  ssize_t payloadlen;
-  ssize_t padded_payloadlen;
+  nghttp2_ssize payloadlen;
+  nghttp2_ssize padded_payloadlen;
   nghttp2_buf *buf;
   size_t max_payloadlen;
 
@@ -7651,19 +7686,26 @@ int nghttp2_session_pack_data(nghttp2_session *session, nghttp2_bufs *bufs,
 
   buf = &bufs->cur->buf;
 
-  if (session->callbacks.read_length_callback) {
-
-    payloadlen = session->callbacks.read_length_callback(
-        session, frame->hd.type, stream->stream_id, session->remote_window_size,
-        stream->remote_window_size, session->remote_settings.max_frame_size,
-        session->user_data);
+  if (session->callbacks.read_length_callback2 ||
+      session->callbacks.read_length_callback) {
+    if (session->callbacks.read_length_callback2) {
+      payloadlen = session->callbacks.read_length_callback2(
+          session, frame->hd.type, stream->stream_id,
+          session->remote_window_size, stream->remote_window_size,
+          session->remote_settings.max_frame_size, session->user_data);
+    } else {
+      payloadlen = (nghttp2_ssize)session->callbacks.read_length_callback(
+          session, frame->hd.type, stream->stream_id,
+          session->remote_window_size, stream->remote_window_size,
+          session->remote_settings.max_frame_size, session->user_data);
+    }
 
-    DEBUGF("send: read_length_callback=%zd\n", payloadlen);
+    DEBUGF("send: read_length_callback=%td\n", payloadlen);
 
     payloadlen = nghttp2_session_enforce_flow_control_limits(session, stream,
                                                              payloadlen);
 
-    DEBUGF("send: read_length_callback after flow control=%zd\n", payloadlen);
+    DEBUGF("send: read_length_callback after flow control=%td\n", payloadlen);
 
     if (payloadlen <= 0) {
       return NGHTTP2_ERR_CALLBACK_FAILURE;
@@ -7679,9 +7721,9 @@ int nghttp2_session_pack_data(nghttp2_session *session, nghttp2_bufs *bufs,
         DEBUGF("send: realloc buffer failed rv=%d", rv);
         /* If reallocation failed, old buffers are still in tact.  So
            use safe limit. */
-        payloadlen = (ssize_t)datamax;
+        payloadlen = (nghttp2_ssize)datamax;
 
-        DEBUGF("send: use safe limit payloadlen=%zd", payloadlen);
+        DEBUGF("send: use safe limit payloadlen=%td", payloadlen);
       } else {
         assert(&session->aob.framebufs == bufs);
 
@@ -7695,9 +7737,23 @@ int nghttp2_session_pack_data(nghttp2_session *session, nghttp2_bufs *bufs,
   assert(nghttp2_buf_avail(buf) >= datamax);
 
   data_flags = NGHTTP2_DATA_FLAG_NONE;
-  payloadlen = aux_data->data_prd.read_callback(
-      session, frame->hd.stream_id, buf->pos, datamax, &data_flags,
-      &aux_data->data_prd.source, session->user_data);
+  switch (aux_data->dpw.version) {
+  case NGHTTP2_DATA_PROVIDER_V1:
+    payloadlen = (nghttp2_ssize)aux_data->dpw.data_prd.v1.read_callback(
+        session, frame->hd.stream_id, buf->pos, datamax, &data_flags,
+        &aux_data->dpw.data_prd.source, session->user_data);
+
+    break;
+  case NGHTTP2_DATA_PROVIDER_V2:
+    payloadlen = aux_data->dpw.data_prd.v2.read_callback(
+        session, frame->hd.stream_id, buf->pos, datamax, &data_flags,
+        &aux_data->dpw.data_prd.source, session->user_data);
+
+    break;
+  default:
+    assert(0);
+    abort();
+  }
 
   if (payloadlen == NGHTTP2_ERR_DEFERRED ||
       payloadlen == NGHTTP2_ERR_TEMPORAL_CALLBACK_FAILURE ||
@@ -8275,7 +8331,7 @@ int nghttp2_session_change_stream_priority(
   /* We don't intentionally call nghttp2_session_adjust_idle_stream()
      so that idle stream created by this function, and existing ones
      are kept for application.  We will adjust number of idle stream
-     in nghttp2_session_mem_send or nghttp2_session_mem_recv is
+     in nghttp2_session_mem_send2 or nghttp2_session_mem_recv2 is
      called. */
   return 0;
 }
@@ -8313,7 +8369,7 @@ int nghttp2_session_create_idle_stream(nghttp2_session *session,
   /* We don't intentionally call nghttp2_session_adjust_idle_stream()
      so that idle stream created by this function, and existing ones
      are kept for application.  We will adjust number of idle stream
-     in nghttp2_session_mem_send or nghttp2_session_mem_recv is
+     in nghttp2_session_mem_send2 or nghttp2_session_mem_recv2 is
      called. */
   return 0;
 }
diff --git a/lib/nghttp2_submit.c b/lib/nghttp2_submit.c
index f5554eb..f947969 100644
--- a/lib/nghttp2_submit.c
+++ b/lib/nghttp2_submit.c
@@ -68,7 +68,7 @@ static int32_t submit_headers_shared(nghttp2_session *session, uint8_t flags,
                                      int32_t stream_id,
                                      const nghttp2_priority_spec *pri_spec,
                                      nghttp2_nv *nva_copy, size_t nvlen,
-                                     const nghttp2_data_provider *data_prd,
+                                     const nghttp2_data_provider_wrap *dpw,
                                      void *stream_user_data) {
   int rv;
   uint8_t flags_copy;
@@ -87,8 +87,8 @@ static int32_t submit_headers_shared(nghttp2_session *session, uint8_t flags,
 
   nghttp2_outbound_item_init(item);
 
-  if (data_prd != NULL && data_prd->read_callback != NULL) {
-    item->aux_data.headers.data_prd = *data_prd;
+  if (dpw != NULL && dpw->data_prd.read_callback != NULL) {
+    item->aux_data.headers.dpw = *dpw;
   }
 
   item->aux_data.headers.stream_user_data = stream_user_data;
@@ -143,7 +143,7 @@ static int32_t submit_headers_shared_nva(nghttp2_session *session,
                                          uint8_t flags, int32_t stream_id,
                                          const nghttp2_priority_spec *pri_spec,
                                          const nghttp2_nv *nva, size_t nvlen,
-                                         const nghttp2_data_provider *data_prd,
+                                         const nghttp2_data_provider_wrap *dpw,
                                          void *stream_user_data) {
   int rv;
   nghttp2_nv *nva_copy;
@@ -165,7 +165,7 @@ static int32_t submit_headers_shared_nva(nghttp2_session *session,
   }
 
   return submit_headers_shared(session, flags, stream_id, &copy_pri_spec,
-                               nva_copy, nvlen, data_prd, stream_user_data);
+                               nva_copy, nvlen, dpw, stream_user_data);
 }
 
 int nghttp2_submit_trailer(nghttp2_session *session, int32_t stream_id,
@@ -740,9 +740,9 @@ fail_item_malloc:
 }
 
 static uint8_t set_request_flags(const nghttp2_priority_spec *pri_spec,
-                                 const nghttp2_data_provider *data_prd) {
+                                 const nghttp2_data_provider_wrap *dpw) {
   uint8_t flags = NGHTTP2_FLAG_NONE;
-  if (data_prd == NULL || data_prd->read_callback == NULL) {
+  if (dpw == NULL || dpw->data_prd.read_callback == NULL) {
     flags |= NGHTTP2_FLAG_END_STREAM;
   }
 
@@ -753,11 +753,11 @@ static uint8_t set_request_flags(const nghttp2_priority_spec *pri_spec,
   return flags;
 }
 
-int32_t nghttp2_submit_request(nghttp2_session *session,
-                               const nghttp2_priority_spec *pri_spec,
-                               const nghttp2_nv *nva, size_t nvlen,
-                               const nghttp2_data_provider *data_prd,
-                               void *stream_user_data) {
+static int32_t submit_request_shared(nghttp2_session *session,
+                                     const nghttp2_priority_spec *pri_spec,
+                                     const nghttp2_nv *nva, size_t nvlen,
+                                     const nghttp2_data_provider_wrap *dpw,
+                                     void *stream_user_data) {
   uint8_t flags;
   int rv;
 
@@ -775,23 +775,47 @@ int32_t nghttp2_submit_request(nghttp2_session *session,
     pri_spec = NULL;
   }
 
-  flags = set_request_flags(pri_spec, data_prd);
+  flags = set_request_flags(pri_spec, dpw);
 
   return submit_headers_shared_nva(session, flags, -1, pri_spec, nva, nvlen,
-                                   data_prd, stream_user_data);
+                                   dpw, stream_user_data);
+}
+
+int32_t nghttp2_submit_request(nghttp2_session *session,
+                               const nghttp2_priority_spec *pri_spec,
+                               const nghttp2_nv *nva, size_t nvlen,
+                               const nghttp2_data_provider *data_prd,
+                               void *stream_user_data) {
+  nghttp2_data_provider_wrap dpw;
+
+  return submit_request_shared(session, pri_spec, nva, nvlen,
+                               nghttp2_data_provider_wrap_v1(&dpw, data_prd),
+                               stream_user_data);
+}
+
+int32_t nghttp2_submit_request2(nghttp2_session *session,
+                                const nghttp2_priority_spec *pri_spec,
+                                const nghttp2_nv *nva, size_t nvlen,
+                                const nghttp2_data_provider2 *data_prd,
+                                void *stream_user_data) {
+  nghttp2_data_provider_wrap dpw;
+
+  return submit_request_shared(session, pri_spec, nva, nvlen,
+                               nghttp2_data_provider_wrap_v2(&dpw, data_prd),
+                               stream_user_data);
 }
 
-static uint8_t set_response_flags(const nghttp2_data_provider *data_prd) {
+static uint8_t set_response_flags(const nghttp2_data_provider_wrap *dpw) {
   uint8_t flags = NGHTTP2_FLAG_NONE;
-  if (data_prd == NULL || data_prd->read_callback == NULL) {
+  if (dpw == NULL || dpw->data_prd.read_callback == NULL) {
     flags |= NGHTTP2_FLAG_END_STREAM;
   }
   return flags;
 }
 
-int nghttp2_submit_response(nghttp2_session *session, int32_t stream_id,
-                            const nghttp2_nv *nva, size_t nvlen,
-                            const nghttp2_data_provider *data_prd) {
+static int submit_response_shared(nghttp2_session *session, int32_t stream_id,
+                                  const nghttp2_nv *nva, size_t nvlen,
+                                  const nghttp2_data_provider_wrap *dpw) {
   uint8_t flags;
 
   if (stream_id <= 0) {
@@ -802,14 +826,32 @@ int nghttp2_submit_response(nghttp2_session *session, int32_t stream_id,
     return NGHTTP2_ERR_PROTO;
   }
 
-  flags = set_response_flags(data_prd);
+  flags = set_response_flags(dpw);
   return submit_headers_shared_nva(session, flags, stream_id, NULL, nva, nvlen,
-                                   data_prd, NULL);
+                                   dpw, NULL);
 }
 
-int nghttp2_submit_data(nghttp2_session *session, uint8_t flags,
-                        int32_t stream_id,
-                        const nghttp2_data_provider *data_prd) {
+int nghttp2_submit_response(nghttp2_session *session, int32_t stream_id,
+                            const nghttp2_nv *nva, size_t nvlen,
+                            const nghttp2_data_provider *data_prd) {
+  nghttp2_data_provider_wrap dpw;
+
+  return submit_response_shared(session, stream_id, nva, nvlen,
+                                nghttp2_data_provider_wrap_v1(&dpw, data_prd));
+}
+
+int nghttp2_submit_response2(nghttp2_session *session, int32_t stream_id,
+                             const nghttp2_nv *nva, size_t nvlen,
+                             const nghttp2_data_provider2 *data_prd) {
+  nghttp2_data_provider_wrap dpw;
+
+  return submit_response_shared(session, stream_id, nva, nvlen,
+                                nghttp2_data_provider_wrap_v2(&dpw, data_prd));
+}
+
+int nghttp2_submit_data_shared(nghttp2_session *session, uint8_t flags,
+                               int32_t stream_id,
+                               const nghttp2_data_provider_wrap *dpw) {
   int rv;
   nghttp2_outbound_item *item;
   nghttp2_frame *frame;
@@ -832,7 +874,7 @@ int nghttp2_submit_data(nghttp2_session *session, uint8_t flags,
 
   frame = &item->frame;
   aux_data = &item->aux_data.data;
-  aux_data->data_prd = *data_prd;
+  aux_data->dpw = *dpw;
   aux_data->eof = 0;
   aux_data->flags = nflags;
 
@@ -848,9 +890,37 @@ int nghttp2_submit_data(nghttp2_session *session, uint8_t flags,
   return 0;
 }
 
+int nghttp2_submit_data(nghttp2_session *session, uint8_t flags,
+                        int32_t stream_id,
+                        const nghttp2_data_provider *data_prd) {
+  nghttp2_data_provider_wrap dpw;
+
+  assert(data_prd);
+
+  return nghttp2_submit_data_shared(
+      session, flags, stream_id, nghttp2_data_provider_wrap_v1(&dpw, data_prd));
+}
+
+int nghttp2_submit_data2(nghttp2_session *session, uint8_t flags,
+                         int32_t stream_id,
+                         const nghttp2_data_provider2 *data_prd) {
+  nghttp2_data_provider_wrap dpw;
+
+  assert(data_prd);
+
+  return nghttp2_submit_data_shared(
+      session, flags, stream_id, nghttp2_data_provider_wrap_v2(&dpw, data_prd));
+}
+
 ssize_t nghttp2_pack_settings_payload(uint8_t *buf, size_t buflen,
                                       const nghttp2_settings_entry *iv,
                                       size_t niv) {
+  return (ssize_t)nghttp2_pack_settings_payload2(buf, buflen, iv, niv);
+}
+
+nghttp2_ssize nghttp2_pack_settings_payload2(uint8_t *buf, size_t buflen,
+                                             const nghttp2_settings_entry *iv,
+                                             size_t niv) {
   if (!nghttp2_iv_check(iv, niv)) {
     return NGHTTP2_ERR_INVALID_ARGUMENT;
   }
@@ -859,7 +929,7 @@ ssize_t nghttp2_pack_settings_payload(uint8_t *buf, size_t buflen,
     return NGHTTP2_ERR_INSUFF_BUFSIZE;
   }
 
-  return (ssize_t)nghttp2_frame_pack_settings_payload(buf, iv, niv);
+  return (nghttp2_ssize)nghttp2_frame_pack_settings_payload(buf, iv, niv);
 }
 
 int nghttp2_submit_extension(nghttp2_session *session, uint8_t type,
@@ -875,7 +945,8 @@ int nghttp2_submit_extension(nghttp2_session *session, uint8_t type,
     return NGHTTP2_ERR_INVALID_ARGUMENT;
   }
 
-  if (!session->callbacks.pack_extension_callback) {
+  if (!session->callbacks.pack_extension_callback2 &&
+      !session->callbacks.pack_extension_callback) {
     return NGHTTP2_ERR_INVALID_STATE;
   }
 
diff --git a/lib/nghttp2_submit.h b/lib/nghttp2_submit.h
index 74d702f..96781d2 100644
--- a/lib/nghttp2_submit.h
+++ b/lib/nghttp2_submit.h
@@ -31,4 +31,10 @@
 
 #include <nghttp2/nghttp2.h>
 
+typedef struct nghttp2_data_provider_wrap nghttp2_data_provider_wrap;
+
+int nghttp2_submit_data_shared(nghttp2_session *session, uint8_t flags,
+                               int32_t stream_id,
+                               const nghttp2_data_provider_wrap *dpw);
+
 #endif /* NGHTTP2_SUBMIT_H */