buffer.cpp

Go to the documentation of this file.

// Copyright (c) 2018, The Monero Project
// 
// All rights reserved.
// 
// Redistribution and use in source and binary forms, with or without modification, are
// permitted provided that the following conditions are met:
// 
// 1. Redistributions of source code must retain the above copyright notice, this list of
//    conditions and the following disclaimer.
// 
// 2. Redistributions in binary form must reproduce the above copyright notice, this list
//    of conditions and the following disclaimer in the documentation and/or other
//    materials provided with the distribution.
// 
// 3. Neither the name of the copyright holder nor the names of its contributors may be
//    used to endorse or promote products derived from this software without specific
//    prior written permission.
// 
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
#include <string.h>
#include "net/buffer.h"
#include <limits>
#undef ELECTRONEUM_DEFAULT_LOG_CATEGORY
#define ELECTRONEUM_DEFAULT_LOG_CATEGORY "net.buffer"
 
namespace epee
{
namespace net_utils
{
 
void buffer::append(const void *data, size_t sz)
{
  const size_t capacity = storage.capacity();
  const size_t avail = capacity - storage.size();
 
  CHECK_AND_ASSERT_THROW_MES(storage.size() < std::numeric_limits<size_t>::max() - sz, "Too much data to append");
 
  // decide when to move
  if (sz > avail)
  {
    // we have to reallocate or move
    const bool move = size() + sz <= capacity;
    if (move)
    {
      const size_t bytes = storage.size() - offset;
      NET_BUFFER_LOG("appending " << sz << " from " << size() << " by moving " << bytes << " from offset " << offset << " first (forced)");
      memmove(storage.data(), storage.data() + offset, bytes);
      storage.resize(bytes);
      offset = 0;
    }
    else
    {
      NET_BUFFER_LOG("appending " << sz << " from " << size() << " by reallocating");
      std::vector<uint8_t> new_storage;
      size_t reserve = (((size() + sz) * 3 / 2) + 4095) & ~4095;
      new_storage.reserve(reserve);
      new_storage.resize(size());
      if (size() > 0)
        memcpy(new_storage.data(), storage.data() + offset, storage.size() - offset);
      offset = 0;
      std::swap(storage, new_storage);
    }
  }
  else
  {
    // we have space already
    if (size() <= 4096 && offset > 4096 * 16 && offset >= capacity / 2)
    {
      // we have little to move, and we're far enough into the buffer that it's probably a win to move anyway
      const size_t pos = storage.size() - offset;
      NET_BUFFER_LOG("appending " << sz << " from " << size() << " by moving " << pos << " from offset " << offset << " first (unforced)");
      memmove(storage.data(), storage.data() + offset, storage.size() - offset);
      storage.resize(pos);
      offset = 0;
    }
    else
    {
      NET_BUFFER_LOG("appending " << sz << " from " << size() << " by writing to existing capacity");
    }
  }
 
  // add the new data
  storage.insert(storage.end(), (const uint8_t*)data, (const uint8_t*)data + sz);
 
  NET_BUFFER_LOG("storage now " << offset << "/" << storage.size() << "/" << storage.capacity());
}
 
}
}