Adding upstream version 18.2.2.upstream/18.2.2

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

1 files changed, 2358 insertions, 0 deletions

diff --git a/src/common/buffer.cc b/src/common/buffer.cc
new file mode 100644
index 000000000..b363b9957
--- /dev/null
+++ b/src/common/buffer.cc
@@ -0,0 +1,2358 @@
+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
+// vim: ts=8 sw=2 smarttab
+/*
+ * Ceph - scalable distributed file system
+ *
+ * Copyright (C) 2004-2006 Sage Weil <sage@newdream.net>
+ *
+ * This is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License version 2.1, as published by the Free Software
+ * Foundation.  See file COPYING.
+ *
+ */
+
+#include <atomic>
+#include <cstring>
+#include <errno.h>
+#include <limits.h>
+
+#include <sys/uio.h>
+
+#include "include/ceph_assert.h"
+#include "include/types.h"
+#include "include/buffer_raw.h"
+#include "include/compat.h"
+#include "include/mempool.h"
+#include "armor.h"
+#include "common/environment.h"
+#include "common/errno.h"
+#include "common/error_code.h"
+#include "common/safe_io.h"
+#include "common/strtol.h"
+#include "common/likely.h"
+#include "common/valgrind.h"
+#include "common/deleter.h"
+#include "common/error_code.h"
+#include "include/intarith.h"
+#include "include/spinlock.h"
+#include "include/scope_guard.h"
+
+using std::cerr;
+using std::make_pair;
+using std::pair;
+using std::string;
+
+using namespace ceph;
+
+#define CEPH_BUFFER_ALLOC_UNIT  4096u
+#define CEPH_BUFFER_APPEND_SIZE (CEPH_BUFFER_ALLOC_UNIT - sizeof(raw_combined))
+
+// 256K is the maximum "small" object size in tcmalloc above which allocations come from
+// the central heap.  For now let's keep this below that threshold.
+#define CEPH_BUFFER_ALLOC_UNIT_MAX std::size_t { 256*1024 }
+
+#ifdef BUFFER_DEBUG
+static ceph::spinlock debug_lock;
+# define bdout { std::lock_guard<ceph::spinlock> lg(debug_lock); std::cout
+# define bendl std::endl; }
+#else
+# define bdout if (0) { std::cout
+# define bendl std::endl; }
+#endif
+
+  static ceph::atomic<unsigned> buffer_cached_crc { 0 };
+  static ceph::atomic<unsigned> buffer_cached_crc_adjusted { 0 };
+  static ceph::atomic<unsigned> buffer_missed_crc { 0 };
+
+  static bool buffer_track_crc = get_env_bool("CEPH_BUFFER_TRACK");
+
+  void buffer::track_cached_crc(bool b) {
+    buffer_track_crc = b;
+  }
+  int buffer::get_cached_crc() {
+    return buffer_cached_crc;
+  }
+  int buffer::get_cached_crc_adjusted() {
+    return buffer_cached_crc_adjusted;
+  }
+
+  int buffer::get_missed_crc() {
+    return buffer_missed_crc;
+  }
+
+  /*
+   * raw_combined is always placed within a single allocation along
+   * with the data buffer.  the data goes at the beginning, and
+   * raw_combined at the end.
+   */
+  class buffer::raw_combined : public buffer::raw {
+  public:
+    raw_combined(char *dataptr, unsigned l, int mempool)
+      : raw(dataptr, l, mempool) {
+    }
+
+    static ceph::unique_leakable_ptr<buffer::raw>
+    create(unsigned len,
+	   unsigned align,
+	   int mempool = mempool::mempool_buffer_anon)
+    {
+      // posix_memalign() requires a multiple of sizeof(void *)
+      align = std::max<unsigned>(align, sizeof(void *));
+      size_t rawlen = round_up_to(sizeof(buffer::raw_combined),
+				  alignof(buffer::raw_combined));
+      size_t datalen = round_up_to(len, alignof(buffer::raw_combined));
+
+#ifdef DARWIN
+      char *ptr = (char *) valloc(rawlen + datalen);
+#else
+      char *ptr = 0;
+      int r = ::posix_memalign((void**)(void*)&ptr, align, rawlen + datalen);
+      if (r)
+	throw bad_alloc();
+#endif /* DARWIN */
+      if (!ptr)
+	throw bad_alloc();
+
+      // actual data first, since it has presumably larger alignment restriction
+      // then put the raw_combined at the end
+      return ceph::unique_leakable_ptr<buffer::raw>(
+	new (ptr + datalen) raw_combined(ptr, len, mempool));
+    }
+
+    static void operator delete(void *ptr) {
+      raw_combined *raw = (raw_combined *)ptr;
+      aligned_free((void *)raw->data);
+    }
+  };
+
+  class buffer::raw_malloc : public buffer::raw {
+  public:
+    MEMPOOL_CLASS_HELPERS();
+
+    explicit raw_malloc(unsigned l) : raw(l) {
+      if (len) {
+	data = (char *)malloc(len);
+        if (!data)
+          throw bad_alloc();
+      } else {
+	data = 0;
+      }
+      bdout << "raw_malloc " << this << " alloc " << (void *)data << " " << l << bendl;
+    }
+    raw_malloc(unsigned l, char *b) : raw(b, l) {
+      bdout << "raw_malloc " << this << " alloc " << (void *)data << " " << l << bendl;
+    }
+    ~raw_malloc() override {
+      free(data);
+      bdout << "raw_malloc " << this << " free " << (void *)data << " " << bendl;
+    }
+  };
+
+#ifndef __CYGWIN__
+  class buffer::raw_posix_aligned : public buffer::raw {
+  public:
+    MEMPOOL_CLASS_HELPERS();
+
+    raw_posix_aligned(unsigned l, unsigned align) : raw(l) {
+      // posix_memalign() requires a multiple of sizeof(void *)
+      align = std::max<unsigned>(align, sizeof(void *));
+#ifdef DARWIN
+      data = (char *) valloc(len);
+#else
+      int r = ::posix_memalign((void**)(void*)&data, align, len);
+      if (r)
+	throw bad_alloc();
+#endif /* DARWIN */
+      if (!data)
+	throw bad_alloc();
+      bdout << "raw_posix_aligned " << this << " alloc " << (void *)data
+	    << " l=" << l << ", align=" << align << bendl;
+    }
+    ~raw_posix_aligned() override {
+      aligned_free(data);
+      bdout << "raw_posix_aligned " << this << " free " << (void *)data << bendl;
+    }
+  };
+#endif
+
+#ifdef __CYGWIN__
+  class buffer::raw_hack_aligned : public buffer::raw {
+    char *realdata;
+  public:
+    raw_hack_aligned(unsigned l, unsigned align) : raw(l) {
+      realdata = new char[len+align-1];
+      unsigned off = ((uintptr_t)realdata) & (align-1);
+      if (off)
+	data = realdata + align - off;
+      else
+	data = realdata;
+      //cout << "hack aligned " << (unsigned)data
+      //<< " in raw " << (unsigned)realdata
+      //<< " off " << off << std::endl;
+      ceph_assert(((uintptr_t)data & (align-1)) == 0);
+    }
+    ~raw_hack_aligned() {
+      delete[] realdata;
+    }
+  };
+#endif
+
+  /*
+   * primitive buffer types
+   */
+  class buffer::raw_claimed_char : public buffer::raw {
+  public:
+    MEMPOOL_CLASS_HELPERS();
+
+    explicit raw_claimed_char(unsigned l, char *b) : raw(b, l) {
+      bdout << "raw_claimed_char " << this << " alloc " << (void *)data
+	    << " " << l << bendl;
+    }
+    ~raw_claimed_char() override {
+      bdout << "raw_claimed_char " << this << " free " << (void *)data
+	    << bendl;
+    }
+  };
+
+  class buffer::raw_static : public buffer::raw {
+  public:
+    MEMPOOL_CLASS_HELPERS();
+
+    raw_static(const char *d, unsigned l) : raw((char*)d, l) { }
+    ~raw_static() override {}
+  };
+
+  class buffer::raw_claim_buffer : public buffer::raw {
+    deleter del;
+   public:
+    raw_claim_buffer(const char *b, unsigned l, deleter d)
+        : raw((char*)b, l), del(std::move(d)) { }
+    ~raw_claim_buffer() override {}
+  };
+
+  ceph::unique_leakable_ptr<buffer::raw> buffer::copy(const char *c, unsigned len) {
+    auto r = buffer::create_aligned(len, sizeof(size_t));
+    memcpy(r->get_data(), c, len);
+    return r;
+  }
+
+  ceph::unique_leakable_ptr<buffer::raw> buffer::create(unsigned len) {
+    return buffer::create_aligned(len, sizeof(size_t));
+  }
+  ceph::unique_leakable_ptr<buffer::raw> buffer::create(unsigned len, char c) {
+    auto ret = buffer::create_aligned(len, sizeof(size_t));
+    memset(ret->get_data(), c, len);
+    return ret;
+  }
+  ceph::unique_leakable_ptr<buffer::raw>
+  buffer::create_in_mempool(unsigned len, int mempool) {
+    return buffer::create_aligned_in_mempool(len, sizeof(size_t), mempool);
+  }
+  ceph::unique_leakable_ptr<buffer::raw>
+  buffer::claim_char(unsigned len, char *buf) {
+    return ceph::unique_leakable_ptr<buffer::raw>(
+      new raw_claimed_char(len, buf));
+  }
+  ceph::unique_leakable_ptr<buffer::raw> buffer::create_malloc(unsigned len) {
+    return ceph::unique_leakable_ptr<buffer::raw>(new raw_malloc(len));
+  }
+  ceph::unique_leakable_ptr<buffer::raw>
+  buffer::claim_malloc(unsigned len, char *buf) {
+    return ceph::unique_leakable_ptr<buffer::raw>(new raw_malloc(len, buf));
+  }
+  ceph::unique_leakable_ptr<buffer::raw>
+  buffer::create_static(unsigned len, char *buf) {
+    return ceph::unique_leakable_ptr<buffer::raw>(new raw_static(buf, len));
+  }
+  ceph::unique_leakable_ptr<buffer::raw>
+  buffer::claim_buffer(unsigned len, char *buf, deleter del) {
+    return ceph::unique_leakable_ptr<buffer::raw>(
+      new raw_claim_buffer(buf, len, std::move(del)));
+  }
+
+  ceph::unique_leakable_ptr<buffer::raw> buffer::create_aligned_in_mempool(
+    unsigned len, unsigned align, int mempool)
+  {
+    // If alignment is a page multiple, use a separate buffer::raw to
+    // avoid fragmenting the heap.
+    //
+    // Somewhat unexpectedly, I see consistently better performance
+    // from raw_combined than from raw even when the allocation size is
+    // a page multiple (but alignment is not).
+    //
+    // I also see better performance from a separate buffer::raw once the
+    // size passes 8KB.
+    if ((align & ~CEPH_PAGE_MASK) == 0 ||
+	len >= CEPH_PAGE_SIZE * 2) {
+#ifndef __CYGWIN__
+      return ceph::unique_leakable_ptr<buffer::raw>(new raw_posix_aligned(len, align));
+#else
+      return ceph::unique_leakable_ptr<buffer::raw>(new raw_hack_aligned(len, align));
+#endif
+    }
+    return raw_combined::create(len, align, mempool);
+  }
+  ceph::unique_leakable_ptr<buffer::raw> buffer::create_aligned(
+    unsigned len, unsigned align) {
+    return create_aligned_in_mempool(len, align,
+				     mempool::mempool_buffer_anon);
+  }
+
+  ceph::unique_leakable_ptr<buffer::raw> buffer::create_page_aligned(unsigned len) {
+    return create_aligned(len, CEPH_PAGE_SIZE);
+  }
+  ceph::unique_leakable_ptr<buffer::raw> buffer::create_small_page_aligned(unsigned len) {
+    if (len < CEPH_PAGE_SIZE) {
+      return create_aligned(len, CEPH_BUFFER_ALLOC_UNIT);
+    } else {
+      return create_aligned(len, CEPH_PAGE_SIZE);
+    }
+  }
+
+  buffer::ptr::ptr(ceph::unique_leakable_ptr<raw> r)
+    : _raw(r.release()),
+      _off(0),
+      _len(_raw->get_len())
+  {
+    _raw->nref.store(1, std::memory_order_release);
+    bdout << "ptr " << this << " get " << _raw << bendl;
+  }
+  buffer::ptr::ptr(unsigned l) : _off(0), _len(l)
+  {
+    _raw = buffer::create(l).release();
+    _raw->nref.store(1, std::memory_order_release);
+    bdout << "ptr " << this << " get " << _raw << bendl;
+  }
+  buffer::ptr::ptr(const char *d, unsigned l) : _off(0), _len(l)    // ditto.
+  {
+    _raw = buffer::copy(d, l).release();
+    _raw->nref.store(1, std::memory_order_release);
+    bdout << "ptr " << this << " get " << _raw << bendl;
+  }
+  buffer::ptr::ptr(const ptr& p) : _raw(p._raw), _off(p._off), _len(p._len)
+  {
+    if (_raw) {
+      _raw->nref++;
+      bdout << "ptr " << this << " get " << _raw << bendl;
+    }
+  }
+  buffer::ptr::ptr(ptr&& p) noexcept : _raw(p._raw), _off(p._off), _len(p._len)
+  {
+    p._raw = nullptr;
+    p._off = p._len = 0;
+  }
+  buffer::ptr::ptr(const ptr& p, unsigned o, unsigned l)
+    : _raw(p._raw), _off(p._off + o), _len(l)
+  {
+    ceph_assert(o+l <= p._len);
+    ceph_assert(_raw);
+    _raw->nref++;
+    bdout << "ptr " << this << " get " << _raw << bendl;
+  }
+  buffer::ptr::ptr(const ptr& p, ceph::unique_leakable_ptr<raw> r)
+    : _raw(r.release()),
+      _off(p._off),
+      _len(p._len)
+  {
+    _raw->nref.store(1, std::memory_order_release);
+    bdout << "ptr " << this << " get " << _raw << bendl;
+  }
+  buffer::ptr& buffer::ptr::operator= (const ptr& p)
+  {
+    if (p._raw) {
+      p._raw->nref++;
+      bdout << "ptr " << this << " get " << _raw << bendl;
+    }
+    buffer::raw *raw = p._raw; 
+    release();
+    if (raw) {
+      _raw = raw;
+      _off = p._off;
+      _len = p._len;
+    } else {
+      _off = _len = 0;
+    }
+    return *this;
+  }
+  buffer::ptr& buffer::ptr::operator= (ptr&& p) noexcept
+  {
+    release();
+    buffer::raw *raw = p._raw;
+    if (raw) {
+      _raw = raw;
+      _off = p._off;
+      _len = p._len;
+      p._raw = nullptr;
+      p._off = p._len = 0;
+    } else {
+      _off = _len = 0;
+    }
+    return *this;
+  }
+
+  void buffer::ptr::swap(ptr& other) noexcept
+  {
+    raw *r = _raw;
+    unsigned o = _off;
+    unsigned l = _len;
+    _raw = other._raw;
+    _off = other._off;
+    _len = other._len;
+    other._raw = r;
+    other._off = o;
+    other._len = l;
+  }
+
+  void buffer::ptr::release()
+  {
+    // BE CAREFUL: this is called also for hypercombined ptr_node. After
+    // freeing underlying raw, `*this` can become inaccessible as well!
+    //
+    // cache the pointer to avoid unncecessary reloads and repeated
+    // checks.
+    if (auto* const cached_raw = std::exchange(_raw, nullptr);
+	cached_raw) {
+      bdout << "ptr " << this << " release " << cached_raw << bendl;
+      // optimize the common case where a particular `buffer::raw` has
+      // only a single reference. Altogether with initializing `nref` of
+      // freshly fabricated one with `1` through the std::atomic's ctor
+      // (which doesn't impose a memory barrier on the strongly-ordered
+      // x86), this allows to avoid all atomical operations in such case.
+      const bool last_one = \
+        (1 == cached_raw->nref.load(std::memory_order_acquire));
+      if (likely(last_one) || --cached_raw->nref == 0) {
+	bdout << "deleting raw " << static_cast<void*>(cached_raw)
+	      << " len " << cached_raw->get_len() << bendl;
+	ANNOTATE_HAPPENS_AFTER(&cached_raw->nref);
+	ANNOTATE_HAPPENS_BEFORE_FORGET_ALL(&cached_raw->nref);
+	delete cached_raw;  // dealloc old (if any)
+      } else {
+	ANNOTATE_HAPPENS_BEFORE(&cached_raw->nref);
+      }
+    }
+  }
+
+  int buffer::ptr::get_mempool() const {
+    if (_raw) {
+      return _raw->mempool;
+    }
+    return mempool::mempool_buffer_anon;
+  }
+
+  void buffer::ptr::reassign_to_mempool(int pool) {
+    if (_raw) {
+      _raw->reassign_to_mempool(pool);
+    }
+  }
+  void buffer::ptr::try_assign_to_mempool(int pool) {
+    if (_raw) {
+      _raw->try_assign_to_mempool(pool);
+    }
+  }
+
+  const char *buffer::ptr::c_str() const {
+    ceph_assert(_raw);
+    return _raw->get_data() + _off;
+  }
+  char *buffer::ptr::c_str() {
+    ceph_assert(_raw);
+    return _raw->get_data() + _off;
+  }
+  const char *buffer::ptr::end_c_str() const {
+    ceph_assert(_raw);
+    return _raw->get_data() + _off + _len;
+  }
+  char *buffer::ptr::end_c_str() {
+    ceph_assert(_raw);
+    return _raw->get_data() + _off + _len;
+  }
+
+  unsigned buffer::ptr::unused_tail_length() const
+  {
+    return _raw ? _raw->get_len() - (_off + _len) : 0;
+  }
+  const char& buffer::ptr::operator[](unsigned n) const
+  {
+    ceph_assert(_raw);
+    ceph_assert(n < _len);
+    return _raw->get_data()[_off + n];
+  }
+  char& buffer::ptr::operator[](unsigned n)
+  {
+    ceph_assert(_raw);
+    ceph_assert(n < _len);
+    return _raw->get_data()[_off + n];
+  }
+
+  const char *buffer::ptr::raw_c_str() const { ceph_assert(_raw); return _raw->get_data(); }
+  unsigned buffer::ptr::raw_length() const { ceph_assert(_raw); return _raw->get_len(); }
+  int buffer::ptr::raw_nref() const { ceph_assert(_raw); return _raw->nref; }
+
+  void buffer::ptr::copy_out(unsigned o, unsigned l, char *dest) const {
+    ceph_assert(_raw);
+    if (o+l > _len)
+        throw end_of_buffer();
+    char* src =  _raw->get_data() + _off + o;
+    maybe_inline_memcpy(dest, src, l, 8);
+  }
+
+  unsigned buffer::ptr::wasted() const
+  {
+    return _raw->get_len() - _len;
+  }
+
+  int buffer::ptr::cmp(const ptr& o) const
+  {
+    int l = _len < o._len ? _len : o._len;
+    if (l) {
+      int r = memcmp(c_str(), o.c_str(), l);
+      if (r)
+	return r;
+    }
+    if (_len < o._len)
+      return -1;
+    if (_len > o._len)
+      return 1;
+    return 0;
+  }
+
+  bool buffer::ptr::is_zero() const
+  {
+    return mem_is_zero(c_str(), _len);
+  }
+
+  unsigned buffer::ptr::append(char c)
+  {
+    ceph_assert(_raw);
+    ceph_assert(1 <= unused_tail_length());
+    char* ptr = _raw->get_data() + _off + _len;
+    *ptr = c;
+    _len++;
+    return _len + _off;
+  }
+
+  unsigned buffer::ptr::append(const char *p, unsigned l)
+  {
+    ceph_assert(_raw);
+    ceph_assert(l <= unused_tail_length());
+    char* c = _raw->get_data() + _off + _len;
+    maybe_inline_memcpy(c, p, l, 32);
+    _len += l;
+    return _len + _off;
+  }
+
+  unsigned buffer::ptr::append_zeros(unsigned l)
+  {
+    ceph_assert(_raw);
+    ceph_assert(l <= unused_tail_length());
+    char* c = _raw->get_data() + _off + _len;
+    // FIPS zeroization audit 20191115: this memset is not security related.
+    memset(c, 0, l);
+    _len += l;
+    return _len + _off;
+  }
+
+  void buffer::ptr::copy_in(unsigned o, unsigned l, const char *src, bool crc_reset)
+  {
+    ceph_assert(_raw);
+    ceph_assert(o <= _len);
+    ceph_assert(o+l <= _len);
+    char* dest = _raw->get_data() + _off + o;
+    if (crc_reset)
+        _raw->invalidate_crc();
+    maybe_inline_memcpy(dest, src, l, 64);
+  }
+
+  void buffer::ptr::zero(bool crc_reset)
+  {
+    if (crc_reset)
+        _raw->invalidate_crc();
+    // FIPS zeroization audit 20191115: this memset is not security related.
+    memset(c_str(), 0, _len);
+  }
+
+  void buffer::ptr::zero(unsigned o, unsigned l, bool crc_reset)
+  {
+    ceph_assert(o+l <= _len);
+    if (crc_reset)
+        _raw->invalidate_crc();
+    // FIPS zeroization audit 20191115: this memset is not security related.
+    memset(c_str()+o, 0, l);
+  }
+
+  template<bool B>
+  buffer::ptr::iterator_impl<B>& buffer::ptr::iterator_impl<B>::operator +=(size_t len) {
+    pos += len;
+    if (pos > end_ptr)
+      throw end_of_buffer();
+    return *this;
+  }
+
+  template buffer::ptr::iterator_impl<false>&
+  buffer::ptr::iterator_impl<false>::operator +=(size_t len);
+  template buffer::ptr::iterator_impl<true>&
+  buffer::ptr::iterator_impl<true>::operator +=(size_t len);
+
+  // -- buffer::list::iterator --
+  /*
+  buffer::list::iterator operator=(const buffer::list::iterator& other)
+  {
+    if (this != &other) {
+      bl = other.bl;
+      ls = other.ls;
+      off = other.off;
+      p = other.p;
+      p_off = other.p_off;
+    }
+    return *this;
+    }*/
+
+  template<bool is_const>
+  buffer::list::iterator_impl<is_const>::iterator_impl(bl_t *l, unsigned o)
+    : bl(l), ls(&bl->_buffers), p(ls->begin()), off(0), p_off(0)
+  {
+    *this += o;
+  }
+
+  template<bool is_const>
+  buffer::list::iterator_impl<is_const>::iterator_impl(const buffer::list::iterator& i)
+    : iterator_impl<is_const>(i.bl, i.off, i.p, i.p_off) {}
+
+  template<bool is_const>
+  auto buffer::list::iterator_impl<is_const>::operator +=(unsigned o)
+    -> iterator_impl&
+  {
+    //cout << this << " advance " << o << " from " << off
+    //     << " (p_off " << p_off << " in " << p->length() << ")"
+    //     << std::endl;
+
+    p_off +=o;
+    while (p != ls->end()) {
+      if (p_off >= p->length()) {
+        // skip this buffer
+        p_off -= p->length();
+        p++;
+      } else {
+        // somewhere in this buffer!
+        break;
+      }
+    }
+    if (p == ls->end() && p_off) {
+      throw end_of_buffer();
+    }
+    off += o;
+    return *this;
+  }
+
+  template<bool is_const>
+  void buffer::list::iterator_impl<is_const>::seek(unsigned o)
+  {
+    p = ls->begin();
+    off = p_off = 0;
+    *this += o;
+  }
+
+  template<bool is_const>
+  char buffer::list::iterator_impl<is_const>::operator*() const
+  {
+    if (p == ls->end())
+      throw end_of_buffer();
+    return (*p)[p_off];
+  }
+
+  template<bool is_const>
+  buffer::list::iterator_impl<is_const>&
+  buffer::list::iterator_impl<is_const>::operator++()
+  {
+    if (p == ls->end())
+      throw end_of_buffer();
+    *this += 1;
+    return *this;
+  }
+
+  template<bool is_const>
+  buffer::ptr buffer::list::iterator_impl<is_const>::get_current_ptr() const
+  {
+    if (p == ls->end())
+      throw end_of_buffer();
+    return ptr(*p, p_off, p->length() - p_off);
+  }
+
+  template<bool is_const>
+  bool buffer::list::iterator_impl<is_const>::is_pointing_same_raw(
+    const ptr& other) const
+  {
+    if (p == ls->end())
+      throw end_of_buffer();
+    return p->_raw == other._raw;
+  }
+
+  // copy data out.
+  // note that these all _append_ to dest!
+  template<bool is_const>
+  void buffer::list::iterator_impl<is_const>::copy(unsigned len, char *dest)
+  {
+    if (p == ls->end()) seek(off);
+    while (len > 0) {
+      if (p == ls->end())
+	throw end_of_buffer();
+
+      unsigned howmuch = p->length() - p_off;
+      if (len < howmuch) howmuch = len;
+      p->copy_out(p_off, howmuch, dest);
+      dest += howmuch;
+
+      len -= howmuch;
+      *this += howmuch;
+    }
+  }
+
+  template<bool is_const>
+  void buffer::list::iterator_impl<is_const>::copy(unsigned len, ptr &dest)
+  {
+    copy_deep(len, dest);
+  }
+
+  template<bool is_const>
+  void buffer::list::iterator_impl<is_const>::copy_deep(unsigned len, ptr &dest)
+  {
+    if (!len) {
+      return;
+    }
+    if (p == ls->end())
+      throw end_of_buffer();
+    dest = create(len);
+    copy(len, dest.c_str());
+  }
+  template<bool is_const>
+  void buffer::list::iterator_impl<is_const>::copy_shallow(unsigned len,
+							   ptr &dest)
+  {
+    if (!len) {
+      return;
+    }
+    if (p == ls->end())
+      throw end_of_buffer();
+    unsigned howmuch = p->length() - p_off;
+    if (howmuch < len) {
+      dest = create(len);
+      copy(len, dest.c_str());
+    } else {
+      dest = ptr(*p, p_off, len);
+      *this += len;
+    }
+  }
+
+  template<bool is_const>
+  void buffer::list::iterator_impl<is_const>::copy(unsigned len, list &dest)
+  {
+    if (p == ls->end())
+      seek(off);
+    while (len > 0) {
+      if (p == ls->end())
+	throw end_of_buffer();
+
+      unsigned howmuch = p->length() - p_off;
+      if (len < howmuch)
+	howmuch = len;
+      dest.append(*p, p_off, howmuch);
+
+      len -= howmuch;
+      *this += howmuch;
+    }
+  }
+
+  template<bool is_const>
+  void buffer::list::iterator_impl<is_const>::copy(unsigned len, std::string &dest)
+  {
+    if (p == ls->end())
+      seek(off);
+    while (len > 0) {
+      if (p == ls->end())
+	throw end_of_buffer();
+
+      unsigned howmuch = p->length() - p_off;
+      const char *c_str = p->c_str();
+      if (len < howmuch)
+	howmuch = len;
+      dest.append(c_str + p_off, howmuch);
+
+      len -= howmuch;
+      *this += howmuch;
+    }
+  }
+
+  template<bool is_const>
+  void buffer::list::iterator_impl<is_const>::copy_all(list &dest)
+  {
+    if (p == ls->end())
+      seek(off);
+    while (1) {
+      if (p == ls->end())
+	return;
+
+      unsigned howmuch = p->length() - p_off;
+      const char *c_str = p->c_str();
+      dest.append(c_str + p_off, howmuch);
+
+      *this += howmuch;
+    }
+  }
+
+  template<bool is_const>
+  size_t buffer::list::iterator_impl<is_const>::get_ptr_and_advance(
+    size_t want, const char **data)
+  {
+    if (p == ls->end()) {
+      seek(off);
+      if (p == ls->end()) {
+	return 0;
+      }
+    }
+    *data = p->c_str() + p_off;
+    size_t l = std::min<size_t>(p->length() - p_off, want);
+    p_off += l;
+    if (p_off == p->length()) {
+      ++p;
+      p_off = 0;
+    }
+    off += l;
+    return l;
+  }
+
+  template<bool is_const>
+  uint32_t buffer::list::iterator_impl<is_const>::crc32c(
+    size_t length, uint32_t crc)
+  {
+    length = std::min<size_t>(length, get_remaining());
+    while (length > 0) {
+      const char *p;
+      size_t l = get_ptr_and_advance(length, &p);
+      crc = ceph_crc32c(crc, (unsigned char*)p, l);
+      length -= l;
+    }
+    return crc;
+  }
+
+  // explicitly instantiate only the iterator types we need, so we can hide the
+  // details in this compilation unit without introducing unnecessary link time
+  // dependencies.
+  template class buffer::list::iterator_impl<true>;
+  template class buffer::list::iterator_impl<false>;
+
+  buffer::list::iterator::iterator(bl_t *l, unsigned o)
+    : iterator_impl(l, o)
+  {}
+
+  buffer::list::iterator::iterator(bl_t *l, unsigned o, list_iter_t ip, unsigned po)
+    : iterator_impl(l, o, ip, po)
+  {}
+
+  // copy data in
+  void buffer::list::iterator::copy_in(unsigned len, const char *src, bool crc_reset)
+  {
+    // copy
+    if (p == ls->end())
+      seek(off);
+    while (len > 0) {
+      if (p == ls->end())
+	throw end_of_buffer();
+      
+      unsigned howmuch = p->length() - p_off;
+      if (len < howmuch)
+	howmuch = len;
+      p->copy_in(p_off, howmuch, src, crc_reset);
+	
+      src += howmuch;
+      len -= howmuch;
+      *this += howmuch;
+    }
+  }
+  
+  void buffer::list::iterator::copy_in(unsigned len, const list& otherl)
+  {
+    if (p == ls->end())
+      seek(off);
+    unsigned left = len;
+    for (const auto& node : otherl._buffers) {
+      unsigned l = node.length();
+      if (left < l)
+	l = left;
+      copy_in(l, node.c_str());
+      left -= l;
+      if (left == 0)
+	break;
+    }
+  }
+
+  // -- buffer::list --
+
+  void buffer::list::swap(list& other) noexcept
+  {
+    std::swap(_len, other._len);
+    std::swap(_num, other._num);
+    std::swap(_carriage, other._carriage);
+    _buffers.swap(other._buffers);
+  }
+
+  bool buffer::list::contents_equal(const ceph::buffer::list& other) const
+  {
+    if (length() != other.length())
+      return false;
+
+    // buffer-wise comparison
+    if (true) {
+      auto a = std::cbegin(_buffers);
+      auto b = std::cbegin(other._buffers);
+      unsigned aoff = 0, boff = 0;
+      while (a != std::cend(_buffers)) {
+	unsigned len = a->length() - aoff;
+	if (len > b->length() - boff)
+	  len = b->length() - boff;
+	if (memcmp(a->c_str() + aoff, b->c_str() + boff, len) != 0)
+	  return false;
+	aoff += len;
+	if (aoff == a->length()) {
+	  aoff = 0;
+	  ++a;
+	}
+	boff += len;
+	if (boff == b->length()) {
+	  boff = 0;
+	  ++b;
+	}
+      }
+      return true;
+    }
+
+    // byte-wise comparison
+    if (false) {
+      bufferlist::const_iterator me = begin();
+      bufferlist::const_iterator him = other.begin();
+      while (!me.end()) {
+	if (*me != *him)
+	  return false;
+	++me;
+	++him;
+      }
+      return true;
+    }
+  }
+
+  bool buffer::list::contents_equal(const void* const other,
+                                    size_t length) const
+  {
+    if (this->length() != length) {
+      return false;
+    }
+
+    const auto* other_buf = reinterpret_cast<const char*>(other);
+    for (const auto& bp : buffers()) {
+      assert(bp.length() <= length);
+      if (std::memcmp(bp.c_str(), other_buf, bp.length()) != 0) {
+        return false;
+      } else {
+        length -= bp.length();
+        other_buf += bp.length();
+      }
+    }
+
+    return true;
+  }
+
+  bool buffer::list::is_provided_buffer(const char* const dst) const
+  {
+    if (_buffers.empty()) {
+      return false;
+    }
+    return (is_contiguous() && (_buffers.front().c_str() == dst));
+  }
+
+  bool buffer::list::is_aligned(const unsigned align) const
+  {
+    for (const auto& node : _buffers) {
+      if (!node.is_aligned(align)) {
+	return false;
+      }
+    }
+    return true;
+  }
+
+  bool buffer::list::is_n_align_sized(const unsigned align) const
+  {
+    for (const auto& node : _buffers) {
+      if (!node.is_n_align_sized(align)) {
+	return false;
+      }
+    }
+    return true;
+  }
+
+  bool buffer::list::is_aligned_size_and_memory(
+    const unsigned align_size,
+    const unsigned align_memory) const
+  {
+    for (const auto& node : _buffers) {
+      if (!node.is_aligned(align_memory) || !node.is_n_align_sized(align_size)) {
+	return false;
+      }
+    }
+    return true;
+  }
+
+  bool buffer::list::is_zero() const {
+    for (const auto& node : _buffers) {
+      if (!node.is_zero()) {
+	return false;
+      }
+    }
+    return true;
+  }
+
+  void buffer::list::zero()
+  {
+    for (auto& node : _buffers) {
+      node.zero();
+    }
+  }
+
+  void buffer::list::zero(const unsigned o, const unsigned l)
+  {
+    ceph_assert(o+l <= _len);
+    unsigned p = 0;
+    for (auto& node : _buffers) {
+      if (p + node.length() > o) {
+        if (p >= o && p+node.length() <= o+l) {
+          // 'o'------------- l -----------|
+          //      'p'-- node.length() --|
+	  node.zero();
+        } else if (p >= o) {
+          // 'o'------------- l -----------|
+          //    'p'------- node.length() -------|
+	  node.zero(0, o+l-p);
+        } else if (p + node.length() <= o+l) {
+          //     'o'------------- l -----------|
+          // 'p'------- node.length() -------|
+	  node.zero(o-p, node.length()-(o-p));
+        } else {
+          //       'o'----------- l -----------|
+          // 'p'---------- node.length() ----------|
+          node.zero(o-p, l);
+        }
+      }
+      p += node.length();
+      if (o+l <= p) {
+	break;  // done
+      }
+    }
+  }
+
+  bool buffer::list::is_contiguous() const
+  {
+    return _num <= 1;
+  }
+
+  bool buffer::list::is_n_page_sized() const
+  {
+    return is_n_align_sized(CEPH_PAGE_SIZE);
+  }
+
+  bool buffer::list::is_page_aligned() const
+  {
+    return is_aligned(CEPH_PAGE_SIZE);
+  }
+
+  int buffer::list::get_mempool() const
+  {
+    if (_buffers.empty()) {
+      return mempool::mempool_buffer_anon;
+    }
+    return _buffers.back().get_mempool();
+  }
+
+  void buffer::list::reassign_to_mempool(int pool)
+  {
+    for (auto& p : _buffers) {
+      p._raw->reassign_to_mempool(pool);
+    }
+  }
+
+  void buffer::list::try_assign_to_mempool(int pool)
+  {
+    for (auto& p : _buffers) {
+      p._raw->try_assign_to_mempool(pool);
+    }
+  }
+
+  uint64_t buffer::list::get_wasted_space() const
+  {
+    if (_num == 1)
+      return _buffers.back().wasted();
+
+    std::vector<const raw*> raw_vec;
+    raw_vec.reserve(_num);
+    for (const auto& p : _buffers)
+      raw_vec.push_back(p._raw);
+    std::sort(raw_vec.begin(), raw_vec.end());
+
+    uint64_t total = 0;
+    const raw *last = nullptr;
+    for (const auto r : raw_vec) {
+      if (r == last)
+	continue;
+      last = r;
+      total += r->get_len();
+    }
+    // If multiple buffers are sharing the same raw buffer and they overlap
+    // with each other, the wasted space will be underestimated.
+    if (total <= length())
+      return 0;
+    return total - length();
+  }
+
+  void buffer::list::rebuild()
+  {
+    if (_len == 0) {
+      _carriage = &always_empty_bptr;
+      _buffers.clear_and_dispose();
+      _num = 0;
+      return;
+    }
+    if ((_len & ~CEPH_PAGE_MASK) == 0)
+      rebuild(ptr_node::create(buffer::create_page_aligned(_len)));
+    else
+      rebuild(ptr_node::create(buffer::create(_len)));
+  }
+
+  void buffer::list::rebuild(
+    std::unique_ptr<buffer::ptr_node, buffer::ptr_node::disposer> nb)
+  {
+    unsigned pos = 0;
+    int mempool = _buffers.front().get_mempool();
+    nb->reassign_to_mempool(mempool);
+    for (auto& node : _buffers) {
+      nb->copy_in(pos, node.length(), node.c_str(), false);
+      pos += node.length();
+    }
+    _buffers.clear_and_dispose();
+    if (likely(nb->length())) {
+      _carriage = nb.get();
+      _buffers.push_back(*nb.release());
+      _num = 1;
+    } else {
+      _carriage = &always_empty_bptr;
+      _num = 0;
+    }
+    invalidate_crc();
+  }
+
+  bool buffer::list::rebuild_aligned(unsigned align)
+  {
+    return rebuild_aligned_size_and_memory(align, align);
+  }
+  
+  bool buffer::list::rebuild_aligned_size_and_memory(unsigned align_size,
+						    unsigned align_memory,
+						    unsigned max_buffers)
+  {
+    bool had_to_rebuild = false;
+
+    if (max_buffers && _num > max_buffers && _len > (max_buffers * align_size)) {
+      align_size = round_up_to(round_up_to(_len, max_buffers) / max_buffers, align_size);
+    }
+    auto p = std::begin(_buffers);
+    auto p_prev = _buffers.before_begin();
+    while (p != std::end(_buffers)) {
+      // keep anything that's already align and sized aligned
+      if (p->is_aligned(align_memory) && p->is_n_align_sized(align_size)) {
+        /*cout << " segment " << (void*)p->c_str()
+  	     << " offset " << ((unsigned long)p->c_str() & (align - 1))
+  	     << " length " << p->length()
+  	     << " " << (p->length() & (align - 1)) << " ok" << std::endl;
+        */
+        p_prev = p++;
+        continue;
+      }
+      
+      // consolidate unaligned items, until we get something that is sized+aligned
+      list unaligned;
+      unsigned offset = 0;
+      do {
+        /*cout << " segment " << (void*)p->c_str()
+               << " offset " << ((unsigned long)p->c_str() & (align - 1))
+               << " length " << p->length() << " " << (p->length() & (align - 1))
+               << " overall offset " << offset << " " << (offset & (align - 1))
+  	     << " not ok" << std::endl;
+        */
+        offset += p->length();
+        // no need to reallocate, relinking is enough thankfully to bi::list.
+        auto p_after = _buffers.erase_after(p_prev);
+        _num -= 1;
+        unaligned._buffers.push_back(*p);
+        unaligned._len += p->length();
+        unaligned._num += 1;
+        p = p_after;
+      } while (p != std::end(_buffers) &&
+  	     (!p->is_aligned(align_memory) ||
+  	      !p->is_n_align_sized(align_size) ||
+  	      (offset % align_size)));
+      if (!(unaligned.is_contiguous() && unaligned._buffers.front().is_aligned(align_memory))) {
+        unaligned.rebuild(
+          ptr_node::create(
+            buffer::create_aligned(unaligned._len, align_memory)));
+        had_to_rebuild = true;
+      }
+      if (unaligned.get_num_buffers()) {
+        _buffers.insert_after(p_prev, *ptr_node::create(unaligned._buffers.front()).release());
+        _num += 1;
+      } else {
+        // a bufferlist containing only 0-length bptrs is rebuilt as empty
+      }
+      ++p_prev;
+    }
+    return had_to_rebuild;
+  }
+  
+  bool buffer::list::rebuild_page_aligned()
+  {
+   return  rebuild_aligned(CEPH_PAGE_SIZE);
+  }
+
+  void buffer::list::reserve(size_t prealloc)
+  {
+    if (get_append_buffer_unused_tail_length() < prealloc) {
+      auto ptr = ptr_node::create(buffer::create_small_page_aligned(prealloc));
+      ptr->set_length(0);   // unused, so far.
+      _carriage = ptr.get();
+      _buffers.push_back(*ptr.release());
+      _num += 1;
+    }
+  }
+
+  void buffer::list::claim_append(list& bl)
+  {
+    // check overflow
+    assert(_len + bl._len >= _len);
+    // steal the other guy's buffers
+    _len += bl._len;
+    _num += bl._num;
+    _buffers.splice_back(bl._buffers);
+    bl.clear();
+  }
+
+  void buffer::list::append(char c)
+  {
+    // put what we can into the existing append_buffer.
+    unsigned gap = get_append_buffer_unused_tail_length();
+    if (!gap) {
+      // make a new buffer!
+      auto buf = ptr_node::create(
+	raw_combined::create(CEPH_BUFFER_APPEND_SIZE, 0, get_mempool()));
+      buf->set_length(0);   // unused, so far.
+      _carriage = buf.get();
+      _buffers.push_back(*buf.release());
+      _num += 1;
+    } else if (unlikely(_carriage != &_buffers.back())) {
+      auto bptr = ptr_node::create(*_carriage, _carriage->length(), 0);
+      _carriage = bptr.get();
+      _buffers.push_back(*bptr.release());
+      _num += 1;
+    }
+    _carriage->append(c);
+    _len++;
+  }
+
+  buffer::ptr_node buffer::list::always_empty_bptr;
+
+  buffer::ptr_node& buffer::list::refill_append_space(const unsigned len)
+  {
+    // make a new buffer.  fill out a complete page, factoring in the
+    // raw_combined overhead.
+    size_t need = round_up_to(len, sizeof(size_t)) + sizeof(raw_combined);
+    size_t alen = round_up_to(need, CEPH_BUFFER_ALLOC_UNIT);
+    if (_carriage == &_buffers.back()) {
+      size_t nlen = round_up_to(_carriage->raw_length(), CEPH_BUFFER_ALLOC_UNIT) * 2;
+      nlen = std::min(nlen, CEPH_BUFFER_ALLOC_UNIT_MAX);
+      alen = std::max(alen, nlen);
+    }
+    alen -= sizeof(raw_combined);
+
+    auto new_back = \
+      ptr_node::create(raw_combined::create(alen, 0, get_mempool()));
+    new_back->set_length(0);   // unused, so far.
+    _carriage = new_back.get();
+    _buffers.push_back(*new_back.release());
+    _num += 1;
+    return _buffers.back();
+  }
+
+  void buffer::list::append(const char *data, unsigned len)
+  {
+    _len += len;
+
+    const unsigned free_in_last = get_append_buffer_unused_tail_length();
+    const unsigned first_round = std::min(len, free_in_last);
+    if (first_round) {
+      // _buffers and carriage can desynchronize when 1) a new ptr
+      // we don't own has been added into the _buffers 2) _buffers
+      // has been emptied as as a result of std::move or stolen by
+      // claim_append.
+      if (unlikely(_carriage != &_buffers.back())) {
+        auto bptr = ptr_node::create(*_carriage, _carriage->length(), 0);
+	_carriage = bptr.get();
+	_buffers.push_back(*bptr.release());
+        _num += 1;
+      }
+      _carriage->append(data, first_round);
+    }
+
+    const unsigned second_round = len - first_round;
+    if (second_round) {
+      auto& new_back = refill_append_space(second_round);
+      new_back.append(data + first_round, second_round);
+    }
+  }
+
+  buffer::list::reserve_t buffer::list::obtain_contiguous_space(
+    const unsigned len)
+  {
+    // note: if len < the normal append_buffer size it *might*
+    // be better to allocate a normal-sized append_buffer and
+    // use part of it.  however, that optimizes for the case of
+    // old-style types including new-style types.  and in most
+    // such cases, this won't be the very first thing encoded to
+    // the list, so append_buffer will already be allocated.
+    // OTOH if everything is new-style, we *should* allocate
+    // only what we need and conserve memory.
+    if (unlikely(get_append_buffer_unused_tail_length() < len)) {
+      auto new_back = \
+	buffer::ptr_node::create(buffer::create(len)).release();
+      new_back->set_length(0);   // unused, so far.
+      _buffers.push_back(*new_back);
+      _num += 1;
+      _carriage = new_back;
+      return { new_back->c_str(), &new_back->_len, &_len };
+    } else {
+      ceph_assert(!_buffers.empty());
+      if (unlikely(_carriage != &_buffers.back())) {
+        auto bptr = ptr_node::create(*_carriage, _carriage->length(), 0);
+	_carriage = bptr.get();
+	_buffers.push_back(*bptr.release());
+        _num += 1;
+      }
+      return { _carriage->end_c_str(), &_carriage->_len, &_len };
+    }
+  }
+
+  void buffer::list::append(const ptr& bp)
+  {
+      push_back(bp);
+  }
+
+  void buffer::list::append(ptr&& bp)
+  {
+      push_back(std::move(bp));
+  }
+
+  void buffer::list::append(const ptr& bp, unsigned off, unsigned len)
+  {
+    ceph_assert(len+off <= bp.length());
+    if (!_buffers.empty()) {
+      ptr &l = _buffers.back();
+      if (l._raw == bp._raw && l.end() == bp.start() + off) {
+	// yay contiguous with tail bp!
+	l.set_length(l.length()+len);
+	_len += len;
+	return;
+      }
+    }
+    // add new item to list
+    _buffers.push_back(*ptr_node::create(bp, off, len).release());
+    _len += len;
+    _num += 1;
+  }
+
+  void buffer::list::append(const list& bl)
+  {
+    _len += bl._len;
+    _num += bl._num;
+    for (const auto& node : bl._buffers) {
+      _buffers.push_back(*ptr_node::create(node).release());
+    }
+  }
+
+  void buffer::list::append(std::istream& in)
+  {
+    while (!in.eof()) {
+      std::string s;
+      getline(in, s);
+      append(s.c_str(), s.length());
+      if (s.length())
+	append("\n", 1);
+    }
+  }
+
+  buffer::list::contiguous_filler buffer::list::append_hole(const unsigned len)
+  {
+    _len += len;
+
+    if (unlikely(get_append_buffer_unused_tail_length() < len)) {
+      // make a new append_buffer.  fill out a complete page, factoring in
+      // the raw_combined overhead.
+      auto& new_back = refill_append_space(len);
+      new_back.set_length(len);
+      return { new_back.c_str() };
+    } else if (unlikely(_carriage != &_buffers.back())) {
+      auto bptr = ptr_node::create(*_carriage, _carriage->length(), 0);
+      _carriage = bptr.get();
+      _buffers.push_back(*bptr.release());
+      _num += 1;
+    }
+    _carriage->set_length(_carriage->length() + len);
+    return { _carriage->end_c_str() - len };
+  }
+
+  void buffer::list::prepend_zero(unsigned len)
+  {
+    auto bp = ptr_node::create(len);
+    bp->zero(false);
+    _len += len;
+    _num += 1;
+    _buffers.push_front(*bp.release());
+  }
+  
+  void buffer::list::append_zero(unsigned len)
+  {
+    _len += len;
+
+    const unsigned free_in_last = get_append_buffer_unused_tail_length();
+    const unsigned first_round = std::min(len, free_in_last);
+    if (first_round) {
+      if (unlikely(_carriage != &_buffers.back())) {
+        auto bptr = ptr_node::create(*_carriage, _carriage->length(), 0);
+	_carriage = bptr.get();
+	_buffers.push_back(*bptr.release());
+        _num += 1;
+      }
+      _carriage->append_zeros(first_round);
+    }
+
+    const unsigned second_round = len - first_round;
+    if (second_round) {
+      auto& new_back = refill_append_space(second_round);
+      new_back.set_length(second_round);
+      new_back.zero(false);
+    }
+  }
+
+  
+  /*
+   * get a char
+   */
+  const char& buffer::list::operator[](unsigned n) const
+  {
+    if (n >= _len)
+      throw end_of_buffer();
+    
+    for (const auto& node : _buffers) {
+      if (n >= node.length()) {
+	n -= node.length();
+	continue;
+      }
+      return node[n];
+    }
+    ceph_abort();
+  }
+
+  /*
+   * return a contiguous ptr to whole bufferlist contents.
+   */
+  char *buffer::list::c_str()
+  {
+    if (const auto len = length(); len == 0) {
+      return nullptr;                         // no non-empty buffers
+    } else if (len != _buffers.front().length()) {
+      rebuild();
+    } else {
+      // there are two *main* scenarios that hit this branch:
+      //   1. bufferlist with single, non-empty buffer;
+      //   2. bufferlist with single, non-empty buffer followed by
+      //      empty buffer. splice() tries to not waste our appendable
+      //      space; to carry it an empty bptr is added at the end.
+      // we account for these and don't rebuild unnecessarily
+    }
+    return _buffers.front().c_str();
+  }
+
+  string buffer::list::to_str() const {
+    string s;
+    s.reserve(length());
+    for (const auto& node : _buffers) {
+      if (node.length()) {
+	s.append(node.c_str(), node.length());
+      }
+    }
+    return s;
+  }
+
+  void buffer::list::substr_of(const list& other, unsigned off, unsigned len)
+  {
+    if (off + len > other.length())
+      throw end_of_buffer();
+
+    clear();
+
+    // skip off
+    auto curbuf = std::cbegin(other._buffers);
+    while (off > 0 && off >= curbuf->length()) {
+      // skip this buffer
+      //cout << "skipping over " << *curbuf << std::endl;
+      off -= (*curbuf).length();
+      ++curbuf;
+    }
+    ceph_assert(len == 0 || curbuf != std::cend(other._buffers));
+    
+    while (len > 0) {
+      // partial?
+      if (off + len < curbuf->length()) {
+	//cout << "copying partial of " << *curbuf << std::endl;
+	_buffers.push_back(*ptr_node::create(*curbuf, off, len).release());
+	_len += len;
+        _num += 1;
+	break;
+      }
+      
+      // through end
+      //cout << "copying end (all?) of " << *curbuf << std::endl;
+      unsigned howmuch = curbuf->length() - off;
+      _buffers.push_back(*ptr_node::create(*curbuf, off, howmuch).release());
+      _len += howmuch;
+      _num += 1;
+      len -= howmuch;
+      off = 0;
+      ++curbuf;
+    }
+  }
+
+  // funky modifer
+  void buffer::list::splice(unsigned off, unsigned len, list *claim_by /*, bufferlist& replace_with */)
+  {    // fixme?
+    if (len == 0)
+      return;
+
+    if (off >= length())
+      throw end_of_buffer();
+
+    ceph_assert(len > 0);
+    //cout << "splice off " << off << " len " << len << " ... mylen = " << length() << std::endl;
+      
+    // skip off
+    auto curbuf = std::begin(_buffers);
+    auto curbuf_prev = _buffers.before_begin();
+    while (off > 0) {
+      ceph_assert(curbuf != std::end(_buffers));
+      if (off >= (*curbuf).length()) {
+	// skip this buffer
+	//cout << "off = " << off << " skipping over " << *curbuf << std::endl;
+	off -= (*curbuf).length();
+	curbuf_prev = curbuf++;
+      } else {
+	// somewhere in this buffer!
+	//cout << "off = " << off << " somewhere in " << *curbuf << std::endl;
+	break;
+      }
+    }
+    
+    if (off) {
+      // add a reference to the front bit, insert it before curbuf (which
+      // we'll lose).
+      //cout << "keeping front " << off << " of " << *curbuf << std::endl;
+      _buffers.insert_after(curbuf_prev,
+			    *ptr_node::create(*curbuf, 0, off).release());
+      _len += off;
+      _num += 1;
+      ++curbuf_prev;
+    }
+    
+    while (len > 0) {
+      // partial or the last (appendable) one?
+      if (const auto to_drop = off + len; to_drop < curbuf->length()) {
+	//cout << "keeping end of " << *curbuf << ", losing first " << off+len << std::endl;
+	if (claim_by) 
+	  claim_by->append(*curbuf, off, len);
+	curbuf->set_offset(to_drop + curbuf->offset());    // ignore beginning big
+	curbuf->set_length(curbuf->length() - to_drop);
+	_len -= to_drop;
+	//cout << " now " << *curbuf << std::endl;
+	break;
+      }
+
+      // hose though the end
+      unsigned howmuch = curbuf->length() - off;
+      //cout << "discarding " << howmuch << " of " << *curbuf << std::endl;
+      if (claim_by) 
+	claim_by->append(*curbuf, off, howmuch);
+      _len -= curbuf->length();
+      if (curbuf == _carriage) {
+        // no need to reallocate, shrinking and relinking is enough.
+        curbuf = _buffers.erase_after(curbuf_prev);
+	_carriage->set_offset(_carriage->offset() + _carriage->length());
+	_carriage->set_length(0);
+	_buffers.push_back(*_carriage);
+      } else {
+	curbuf = _buffers.erase_after_and_dispose(curbuf_prev);
+	_num -= 1;
+      }
+      len -= howmuch;
+      off = 0;
+    }
+
+    // splice in *replace (implement me later?)
+  }
+
+  void buffer::list::write(int off, int len, std::ostream& out) const
+  {
+    list s;
+    s.substr_of(*this, off, len);
+    for (const auto& node : s._buffers) {
+      if (node.length()) {
+	out.write(node.c_str(), node.length());
+      }
+    }
+  }
+  
+void buffer::list::encode_base64(buffer::list& o)
+{
+  bufferptr bp(length() * 4 / 3 + 3);
+  int l = ceph_armor(bp.c_str(), bp.c_str() + bp.length(), c_str(), c_str() + length());
+  bp.set_length(l);
+  o.push_back(std::move(bp));
+}
+
+void buffer::list::decode_base64(buffer::list& e)
+{
+  bufferptr bp(4 + ((e.length() * 3) / 4));
+  int l = ceph_unarmor(bp.c_str(), bp.c_str() + bp.length(), e.c_str(), e.c_str() + e.length());
+  if (l < 0) {
+    std::ostringstream oss;
+    oss << "decode_base64: decoding failed:\n";
+    hexdump(oss);
+    throw buffer::malformed_input(oss.str().c_str());
+  }
+  ceph_assert(l <= (int)bp.length());
+  bp.set_length(l);
+  push_back(std::move(bp));
+}
+
+ssize_t buffer::list::pread_file(const char *fn, uint64_t off, uint64_t len, std::string *error)
+{
+  int fd = TEMP_FAILURE_RETRY(::open(fn, O_RDONLY|O_CLOEXEC|O_BINARY));
+  if (fd < 0) {
+    int err = errno;
+    std::ostringstream oss;
+    oss << "can't open " << fn << ": " << cpp_strerror(err);
+    *error = oss.str();
+    return -err;
+  }
+
+  struct stat st;
+  // FIPS zeroization audit 20191115: this memset is not security related.
+  memset(&st, 0, sizeof(st));
+  if (::fstat(fd, &st) < 0) {
+    int err = errno;
+    std::ostringstream oss;
+    oss << "bufferlist::read_file(" << fn << "): stat error: "
+        << cpp_strerror(err);
+    *error = oss.str();
+    VOID_TEMP_FAILURE_RETRY(::close(fd));
+    return -err;
+  }
+
+  if (off > (uint64_t)st.st_size) {
+    std::ostringstream oss;
+    oss << "bufferlist::read_file(" << fn << "): read error: size < offset";
+    *error = oss.str();
+    VOID_TEMP_FAILURE_RETRY(::close(fd));
+    return 0;
+  }
+
+  if (len > st.st_size - off) {
+    len = st.st_size - off;
+  }
+  ssize_t ret = lseek64(fd, off, SEEK_SET);
+  if (ret != (ssize_t)off) {
+    return -errno;
+  }
+
+  ret = read_fd(fd, len);
+  if (ret < 0) {
+    std::ostringstream oss;
+    oss << "bufferlist::read_file(" << fn << "): read error:"
+	<< cpp_strerror(ret);
+    *error = oss.str();
+    VOID_TEMP_FAILURE_RETRY(::close(fd));
+    return ret;
+  } else if (ret != (ssize_t)len) {
+    // Premature EOF.
+    // Perhaps the file changed between stat() and read()?
+    std::ostringstream oss;
+    oss << "bufferlist::read_file(" << fn << "): warning: got premature EOF.";
+    *error = oss.str();
+    // not actually an error, but weird
+  }
+  VOID_TEMP_FAILURE_RETRY(::close(fd));
+  return 0;
+}
+
+int buffer::list::read_file(const char *fn, std::string *error)
+{
+  int fd = TEMP_FAILURE_RETRY(::open(fn, O_RDONLY|O_CLOEXEC|O_BINARY));
+  if (fd < 0) {
+    int err = errno;
+    std::ostringstream oss;
+    oss << "can't open " << fn << ": " << cpp_strerror(err);
+    *error = oss.str();
+    return -err;
+  }
+
+  struct stat st;
+  // FIPS zeroization audit 20191115: this memset is not security related.
+  memset(&st, 0, sizeof(st));
+  if (::fstat(fd, &st) < 0) {
+    int err = errno;
+    std::ostringstream oss;
+    oss << "bufferlist::read_file(" << fn << "): stat error: "
+        << cpp_strerror(err);
+    *error = oss.str();
+    VOID_TEMP_FAILURE_RETRY(::close(fd));
+    return -err;
+  }
+
+  ssize_t ret = read_fd(fd, st.st_size);
+  if (ret < 0) {
+    std::ostringstream oss;
+    oss << "bufferlist::read_file(" << fn << "): read error:"
+	<< cpp_strerror(ret);
+    *error = oss.str();
+    VOID_TEMP_FAILURE_RETRY(::close(fd));
+    return ret;
+  }
+  else if (ret != st.st_size) {
+    // Premature EOF.
+    // Perhaps the file changed between stat() and read()?
+    std::ostringstream oss;
+    oss << "bufferlist::read_file(" << fn << "): warning: got premature EOF.";
+    *error = oss.str();
+    // not actually an error, but weird
+  }
+  VOID_TEMP_FAILURE_RETRY(::close(fd));
+  return 0;
+}
+
+ssize_t buffer::list::read_fd(int fd, size_t len)
+{
+  auto bp = ptr_node::create(buffer::create(len));
+  ssize_t ret = safe_read(fd, (void*)bp->c_str(), len);
+  if (ret >= 0) {
+    bp->set_length(ret);
+    push_back(std::move(bp));
+  }
+  return ret;
+}
+
+ssize_t buffer::list::recv_fd(int fd, size_t len)
+{
+  auto bp = ptr_node::create(buffer::create(len));
+  ssize_t ret = safe_recv(fd, (void*)bp->c_str(), len);
+  if (ret >= 0) {
+    bp->set_length(ret);
+    push_back(std::move(bp));
+  }
+  return ret;
+}
+
+int buffer::list::write_file(const char *fn, int mode)
+{
+  int fd = TEMP_FAILURE_RETRY(::open(fn, O_WRONLY|O_CREAT|O_TRUNC|O_CLOEXEC|O_BINARY, mode));
+  if (fd < 0) {
+    int err = errno;
+    cerr << "bufferlist::write_file(" << fn << "): failed to open file: "
+	 << cpp_strerror(err) << std::endl;
+    return -err;
+  }
+  int ret = write_fd(fd);
+  if (ret) {
+    cerr << "bufferlist::write_fd(" << fn << "): write_fd error: "
+	 << cpp_strerror(ret) << std::endl;
+    VOID_TEMP_FAILURE_RETRY(::close(fd));
+    return ret;
+  }
+  if (TEMP_FAILURE_RETRY(::close(fd))) {
+    int err = errno;
+    cerr << "bufferlist::write_file(" << fn << "): close error: "
+	 << cpp_strerror(err) << std::endl;
+    return -err;
+  }
+  return 0;
+}
+
+static int do_writev(int fd, struct iovec *vec, uint64_t offset, unsigned veclen, unsigned bytes)
+{
+  while (bytes > 0) {
+    ssize_t r = 0;
+#ifdef HAVE_PWRITEV
+    r = ::pwritev(fd, vec, veclen, offset);
+#else
+    r = ::lseek64(fd, offset, SEEK_SET);
+    if (r != offset) {
+      return -errno;
+    }
+    r = ::writev(fd, vec, veclen);
+#endif
+    if (r < 0) {
+      if (errno == EINTR)
+        continue;
+      return -errno;
+    }
+
+    bytes -= r;
+    offset += r;
+    if (bytes == 0) break;
+
+    while (r > 0) {
+      if (vec[0].iov_len <= (size_t)r) {
+        // drain this whole item
+        r -= vec[0].iov_len;
+        ++vec;
+        --veclen;
+      } else {
+        vec[0].iov_base = (char *)vec[0].iov_base + r;
+        vec[0].iov_len -= r;
+        break;
+      }
+    }
+  }
+  return 0;
+}
+
+#ifndef _WIN32
+int buffer::list::write_fd(int fd) const
+{
+  // use writev!
+  iovec iov[IOV_MAX];
+  int iovlen = 0;
+  ssize_t bytes = 0;
+
+  auto p = std::cbegin(_buffers);
+  while (p != std::cend(_buffers)) {
+    if (p->length() > 0) {
+      iov[iovlen].iov_base = (void *)p->c_str();
+      iov[iovlen].iov_len = p->length();
+      bytes += p->length();
+      iovlen++;
+    }
+    ++p;
+
+    if (iovlen == IOV_MAX ||
+	p == _buffers.end()) {
+      iovec *start = iov;
+      int num = iovlen;
+      ssize_t wrote;
+    retry:
+      wrote = ::writev(fd, start, num);
+      if (wrote < 0) {
+	int err = errno;
+	if (err == EINTR)
+	  goto retry;
+	return -err;
+      }
+      if (wrote < bytes) {
+	// partial write, recover!
+	while ((size_t)wrote >= start[0].iov_len) {
+	  wrote -= start[0].iov_len;
+	  bytes -= start[0].iov_len;
+	  start++;
+	  num--;
+	}
+	if (wrote > 0) {
+	  start[0].iov_len -= wrote;
+	  start[0].iov_base = (char *)start[0].iov_base + wrote;
+	  bytes -= wrote;
+	}
+	goto retry;
+      }
+      iovlen = 0;
+      bytes = 0;
+    }
+  }
+  return 0;
+}
+
+int buffer::list::send_fd(int fd) const {
+  return buffer::list::write_fd(fd);
+}
+
+int buffer::list::write_fd(int fd, uint64_t offset) const
+{
+  iovec iov[IOV_MAX];
+
+  auto p = std::cbegin(_buffers);
+  uint64_t left_pbrs = get_num_buffers();
+  while (left_pbrs) {
+    ssize_t bytes = 0;
+    unsigned iovlen = 0;
+    uint64_t size = std::min<uint64_t>(left_pbrs, IOV_MAX);
+    left_pbrs -= size;
+    while (size > 0) {
+      iov[iovlen].iov_base = (void *)p->c_str();
+      iov[iovlen].iov_len = p->length();
+      iovlen++;
+      bytes += p->length();
+      ++p;
+      size--;
+    }
+
+    int r = do_writev(fd, iov, offset, iovlen, bytes);
+    if (r < 0)
+      return r;
+    offset += bytes;
+  }
+  return 0;
+}
+#else
+int buffer::list::write_fd(int fd) const
+{
+  // There's no writev on Windows. WriteFileGather may be an option,
+  // but it has strict requirements in terms of buffer size and alignment.
+  auto p = std::cbegin(_buffers);
+  uint64_t left_pbrs = get_num_buffers();
+  while (left_pbrs) {
+    int written = 0;
+    while (written < p->length()) {
+      int r = ::write(fd, p->c_str(), p->length() - written);
+      if (r < 0)
+        return -errno;
+
+      written += r;
+    }
+
+    left_pbrs--;
+    p++;
+  }
+
+  return 0;
+}
+
+int buffer::list::send_fd(int fd) const
+{
+  // There's no writev on Windows. WriteFileGather may be an option,
+  // but it has strict requirements in terms of buffer size and alignment.
+  auto p = std::cbegin(_buffers);
+  uint64_t left_pbrs = get_num_buffers();
+  while (left_pbrs) {
+    int written = 0;
+    while (written < p->length()) {
+      int r = ::send(fd, p->c_str(), p->length() - written, 0);
+      if (r < 0)
+        return -ceph_sock_errno();
+
+      written += r;
+    }
+
+    left_pbrs--;
+    p++;
+  }
+
+  return 0;
+}
+
+int buffer::list::write_fd(int fd, uint64_t offset) const
+{
+  int r = ::lseek64(fd, offset, SEEK_SET);
+  if (r != offset)
+    return -errno;
+
+  return write_fd(fd);
+}
+#endif
+
+buffer::list::iov_vec_t buffer::list::prepare_iovs() const
+{
+  size_t index = 0;
+  uint64_t off = 0;
+  iov_vec_t iovs{_num / IOV_MAX + 1};
+  auto it = iovs.begin();
+  for (auto& bp : _buffers) {
+    if (index == 0) {
+      it->offset = off;
+      it->length = 0;
+      size_t nr_iov_created = std::distance(iovs.begin(), it);
+      it->iov.resize(
+	std::min(_num - IOV_MAX * nr_iov_created, (size_t)IOV_MAX));
+    }
+    it->iov[index].iov_base = (void*)bp.c_str();
+    it->iov[index].iov_len = bp.length();
+    off += bp.length();
+    it->length += bp.length();
+    if (++index == IOV_MAX) {
+      // continue with a new vector<iov> if we have more buf
+      ++it;
+      index = 0;
+    }
+  }
+  return iovs;
+}
+
+__u32 buffer::list::crc32c(__u32 crc) const
+{
+  int cache_misses = 0;
+  int cache_hits = 0;
+  int cache_adjusts = 0;
+
+  for (const auto& node : _buffers) {
+    if (node.length()) {
+      raw* const r = node._raw;
+      pair<size_t, size_t> ofs(node.offset(), node.offset() + node.length());
+      pair<uint32_t, uint32_t> ccrc;
+      if (r->get_crc(ofs, &ccrc)) {
+	if (ccrc.first == crc) {
+	  // got it already
+	  crc = ccrc.second;
+	  cache_hits++;
+	} else {
+	  /* If we have cached crc32c(buf, v) for initial value v,
+	   * we can convert this to a different initial value v' by:
+	   * crc32c(buf, v') = crc32c(buf, v) ^ adjustment
+	   * where adjustment = crc32c(0*len(buf), v ^ v')
+	   *
+	   * http://crcutil.googlecode.com/files/crc-doc.1.0.pdf
+	   * note, u for our crc32c implementation is 0
+	   */
+	  crc = ccrc.second ^ ceph_crc32c(ccrc.first ^ crc, NULL, node.length());
+	  cache_adjusts++;
+	}
+      } else {
+	cache_misses++;
+	uint32_t base = crc;
+	crc = ceph_crc32c(crc, (unsigned char*)node.c_str(), node.length());
+	r->set_crc(ofs, make_pair(base, crc));
+      }
+    }
+  }
+
+  if (buffer_track_crc) {
+    if (cache_adjusts)
+      buffer_cached_crc_adjusted += cache_adjusts;
+    if (cache_hits)
+      buffer_cached_crc += cache_hits;
+    if (cache_misses)
+      buffer_missed_crc += cache_misses;
+  }
+
+  return crc;
+}
+
+void buffer::list::invalidate_crc()
+{
+  for (const auto& node : _buffers) {
+    if (node._raw) {
+      node._raw->invalidate_crc();
+    }
+  }
+}
+
+/**
+ * Binary write all contents to a C++ stream
+ */
+void buffer::list::write_stream(std::ostream &out) const
+{
+  for (const auto& node : _buffers) {
+    if (node.length() > 0) {
+      out.write(node.c_str(), node.length());
+    }
+  }
+}
+
+
+void buffer::list::hexdump(std::ostream &out, bool trailing_newline) const
+{
+  if (!length())
+    return;
+
+  std::ios_base::fmtflags original_flags = out.flags();
+
+  // do our best to match the output of hexdump -C, for better
+  // diff'ing!
+
+  out.setf(std::ios::right);
+  out.fill('0');
+
+  unsigned per = 16;
+  char last_row_char = '\0';
+  bool was_same = false, did_star = false;
+  for (unsigned o=0; o<length(); o += per) {
+    if (o == 0) {
+      last_row_char = (*this)[o];
+    }
+
+    if (o + per < length()) {
+      bool row_is_same = true;
+      for (unsigned i=0; i<per && o+i<length(); i++) {
+        char current_char = (*this)[o+i];
+        if (current_char != last_row_char) {
+          if (i == 0) {
+            last_row_char = current_char;
+            was_same = false;
+            did_star = false;
+          } else {
+	    row_is_same = false;
+          }
+	}
+      }
+      if (row_is_same) {
+	if (was_same) {
+	  if (!did_star) {
+	    out << "\n*";
+	    did_star = true;
+	  }
+	  continue;
+	}
+	was_same = true;
+      } else {
+	was_same = false;
+	did_star = false;
+      }
+    }
+    if (o)
+      out << "\n";
+    out << std::hex << std::setw(8) << o << " ";
+
+    unsigned i;
+    for (i=0; i<per && o+i<length(); i++) {
+      if (i == 8)
+	out << ' ';
+      out << " " << std::setw(2) << ((unsigned)(*this)[o+i] & 0xff);
+    }
+    for (; i<per; i++) {
+      if (i == 8)
+	out << ' ';
+      out << "   ";
+    }
+    
+    out << "  |";
+    for (i=0; i<per && o+i<length(); i++) {
+      char c = (*this)[o+i];
+      if (isupper(c) || islower(c) || isdigit(c) || c == ' ' || ispunct(c))
+	out << c;
+      else
+	out << '.';
+    }
+    out << '|' << std::dec;
+  }
+  if (trailing_newline) {
+    out << "\n" << std::hex << std::setw(8) << length();
+    out << "\n";
+  }
+
+  out.flags(original_flags);
+}
+
+
+buffer::list buffer::list::static_from_mem(char* c, size_t l) {
+  list bl;
+  bl.push_back(ptr_node::create(create_static(l, c)));
+  return bl;
+}
+
+buffer::list buffer::list::static_from_cstring(char* c) {
+  return static_from_mem(c, std::strlen(c));
+}
+
+buffer::list buffer::list::static_from_string(string& s) {
+  // C++14 just has string::data return a char* from a non-const
+  // string.
+  return static_from_mem(const_cast<char*>(s.data()), s.length());
+  // But the way buffer::list mostly doesn't work in a sane way with
+  // const makes me generally sad.
+}
+
+// buffer::raw is not a standard layout type.
+#define BUF_OFFSETOF(type, field)					\
+  (reinterpret_cast<std::uintptr_t>(&(((type*)1024)->field)) - 1024u)
+
+bool buffer::ptr_node::dispose_if_hypercombined(
+  buffer::ptr_node* const delete_this)
+{
+  // in case _raw is nullptr
+  const std::uintptr_t bptr =
+    (reinterpret_cast<std::uintptr_t>(delete_this->_raw) +
+     BUF_OFFSETOF(buffer::raw, bptr_storage));
+  const bool is_hypercombined =
+    reinterpret_cast<std::uintptr_t>(delete_this) == bptr;
+  if (is_hypercombined) {
+    ceph_assert_always("hypercombining is currently disabled" == nullptr);
+    delete_this->~ptr_node();
+    return true;
+  } else {
+    return false;
+  }
+}
+
+std::unique_ptr<buffer::ptr_node, buffer::ptr_node::disposer>
+buffer::ptr_node::create_hypercombined(ceph::unique_leakable_ptr<buffer::raw> r)
+{
+  // FIXME: we don't currently hypercombine buffers due to crashes
+  // observed in the rados suite. After fixing we'll use placement
+  // new to create ptr_node on buffer::raw::bptr_storage.
+  return std::unique_ptr<buffer::ptr_node, buffer::ptr_node::disposer>(
+    new ptr_node(std::move(r)));
+}
+
+buffer::ptr_node* buffer::ptr_node::cloner::operator()(
+  const buffer::ptr_node& clone_this)
+{
+  return new ptr_node(clone_this);
+}
+
+std::ostream& buffer::operator<<(std::ostream& out, const buffer::raw &r) {
+  return out << "buffer::raw("
+             << (void*)r.get_data() << " len " << r.get_len()
+             << " nref " << r.nref.load() << ")";
+}
+
+std::ostream& buffer::operator<<(std::ostream& out, const buffer::ptr& bp) {
+  if (bp.have_raw())
+    out << "buffer::ptr(" << bp.offset() << "~" << bp.length()
+	<< " " << (void*)bp.c_str()
+	<< " in raw " << (void*)bp.raw_c_str()
+	<< " len " << bp.raw_length()
+	<< " nref " << bp.raw_nref() << ")";
+  else
+    out << "buffer:ptr(" << bp.offset() << "~" << bp.length() << " no raw)";
+  return out;
+}
+
+std::ostream& buffer::operator<<(std::ostream& out, const buffer::list& bl) {
+  out << "buffer::list(len=" << bl.length() << ",\n";
+
+  for (const auto& node : bl.buffers()) {
+    out << "\t" << node;
+    if (&node != &bl.buffers().back()) {
+      out << ",\n";
+    }
+  }
+  out << "\n)";
+  return out;
+}
+
+MEMPOOL_DEFINE_OBJECT_FACTORY(buffer::raw_malloc, buffer_raw_malloc,
+			      buffer_meta);
+MEMPOOL_DEFINE_OBJECT_FACTORY(buffer::raw_posix_aligned,
+			      buffer_raw_posix_aligned, buffer_meta);
+MEMPOOL_DEFINE_OBJECT_FACTORY(buffer::raw_claimed_char, buffer_raw_claimed_char,
+			      buffer_meta);
+MEMPOOL_DEFINE_OBJECT_FACTORY(buffer::raw_static, buffer_raw_static,
+			      buffer_meta);
+
+
+void ceph::buffer::list::page_aligned_appender::_refill(size_t len) {
+  const unsigned alloc =
+    std::max(min_alloc,
+	     shift_round_up(static_cast<unsigned>(len),
+			    static_cast<unsigned>(CEPH_PAGE_SHIFT)));
+  auto new_back = \
+    ptr_node::create(buffer::create_page_aligned(alloc));
+  new_back->set_length(0);   // unused, so far.
+  bl.push_back(std::move(new_back));
+}
+
+namespace ceph::buffer {
+inline namespace v15_2_0 {
+
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wnon-virtual-dtor"
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wnon-virtual-dtor"
+class buffer_error_category : public ceph::converting_category {
+public:
+  buffer_error_category(){}
+  const char* name() const noexcept override;
+  const char* message(int ev, char*, std::size_t) const noexcept override;
+  std::string message(int ev) const override;
+  boost::system::error_condition default_error_condition(int ev) const noexcept
+    override;
+  using ceph::converting_category::equivalent;
+  bool equivalent(int ev, const boost::system::error_condition& c) const
+    noexcept override;
+  int from_code(int ev) const noexcept override;
+};
+#pragma GCC diagnostic pop
+#pragma clang diagnostic pop
+
+const char* buffer_error_category::name() const noexcept {
+  return "buffer";
+}
+
+const char*
+buffer_error_category::message(int ev, char*, std::size_t) const noexcept {
+  using ceph::buffer::errc;
+  if (ev == 0)
+    return "No error";
+
+  switch (static_cast<errc>(ev)) {
+  case errc::bad_alloc:
+    return "Bad allocation";
+
+  case errc::end_of_buffer:
+    return "End of buffer";
+
+  case errc::malformed_input:
+    return "Malformed input";
+  }
+
+  return "Unknown error";
+}
+
+std::string buffer_error_category::message(int ev) const {
+  return message(ev, nullptr, 0);
+}
+
+boost::system::error_condition
+buffer_error_category::default_error_condition(int ev)const noexcept {
+  using ceph::buffer::errc;
+  switch (static_cast<errc>(ev)) {
+  case errc::bad_alloc:
+    return boost::system::errc::not_enough_memory;
+  case errc::end_of_buffer:
+  case errc::malformed_input:
+    return boost::system::errc::io_error;
+  }
+  return { ev, *this };
+}
+
+bool buffer_error_category::equivalent(int ev, const boost::system::error_condition& c) const noexcept {
+  return default_error_condition(ev) == c;
+}
+
+int buffer_error_category::from_code(int ev) const noexcept {
+  using ceph::buffer::errc;
+  switch (static_cast<errc>(ev)) {
+  case errc::bad_alloc:
+    return -ENOMEM;
+
+  case errc::end_of_buffer:
+    return -EIO;
+
+  case errc::malformed_input:
+    return -EIO;
+  }
+  return -EDOM;
+}
+
+const boost::system::error_category& buffer_category() noexcept {
+  static const buffer_error_category c;
+  return c;
+}
+}
+}