import quincy beta 17.1.0

[ceph.git] / ceph / src / common / buffer.cc

// -*- 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 {
    size_t alignment;
  public:
    raw_combined(char *dataptr, unsigned l, unsigned align,
                 int mempool)
      : raw(dataptr, l, mempool),
        alignment(align) {
    }
    raw* clone_empty() override {
      return create(len, alignment).release();
    }

    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, align, 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;
    }
    raw* clone_empty() override {
      return new raw_malloc(len);
    }
  };

#ifndef __CYGWIN__
  class buffer::raw_posix_aligned : public buffer::raw {
    unsigned align;
  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;
    }
    raw* clone_empty() override {
      return new raw_posix_aligned(len, align);
    }
  };
#endif

#ifdef __CYGWIN__
  class buffer::raw_hack_aligned : public buffer::raw {
    unsigned align;
    char *realdata;
  public:
    raw_hack_aligned(unsigned l, unsigned _align) : raw(l) {
      align = _align;
      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;
    }
    raw* clone_empty() {
      return new raw_hack_aligned(len, align);
    }
  };
#endif

  /*
   * primitive buffer types
   */
  class buffer::raw_char : public buffer::raw {
  public:
    MEMPOOL_CLASS_HELPERS();

    explicit raw_char(unsigned l) : raw(l) {
      if (len)
        data = new char[len];
      else
        data = 0;
      bdout << "raw_char " << this << " alloc " << (void *)data << " " << l << bendl;
    }
    raw_char(unsigned l, char *b) : raw(b, l) {
      bdout << "raw_char " << this << " alloc " << (void *)data << " " << l << bendl;
    }
    ~raw_char() override {
      delete[] data;
      bdout << "raw_char " << this << " free " << (void *)data << bendl;
    }
    raw* clone_empty() override {
      return new raw_char(len);
    }
  };

  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;
    }
    raw* clone_empty() override {
      return new raw_char(len);
    }
  };

  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 {}
    raw* clone_empty() override {
      return new buffer::raw_char(len);
    }
  };

  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 {}
    raw* clone_empty() override {
      return new buffer::raw_char(len);
    }
  };

  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;
  }

  ceph::unique_leakable_ptr<buffer::raw> buffer::ptr::clone()
  {
    return _raw->clone();
  }

  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)
  {
    // 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_char, buffer_raw_char, 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;
}
}
}