std::size_t write(SyncWriteStream& s,
    asio::basic_streambuf<Allocator>& b,
    CompletionCondition completion_condition, asio::error_code& ec)
{
  std::size_t bytes_transferred = write(s, b.data(), completion_condition, ec);
  b.consume(bytes_transferred);
  return bytes_transferred;
}

std::size_t write_at(SyncRandomAccessWriteDevice& d,
    boost::uint64_t offset, asio::basic_streambuf<Allocator>& b,
    CompletionCondition completion_condition, asio::error_code& ec)
{
  std::size_t bytes_transferred = write_at(
      d, offset, b.data(), completion_condition, ec);
  b.consume(bytes_transferred);
  return bytes_transferred;
}

std::size_t read_until(SyncReadStream& s,
    asio::basic_streambuf<Allocator>& b, const boost::regex& expr,
    asio::error_code& ec)
{
  std::size_t search_position = 0;
  for (;;)
  {
    // Determine the range of the data to be searched.
    typedef typename asio::basic_streambuf<
      Allocator>::const_buffers_type const_buffers_type;
    typedef asio::buffers_iterator<const_buffers_type> iterator;
    const_buffers_type buffers = b.data();
    iterator begin = iterator::begin(buffers);
    iterator start_pos = begin + search_position;
    iterator end = iterator::end(buffers);

    // Look for a match.
    boost::match_results<iterator,
      typename std::vector<boost::sub_match<iterator> >::allocator_type>
        match_results;
    if (regex_search(start_pos, end, match_results, expr,
          boost::match_default | boost::match_partial))
    {
      if (match_results[0].matched)
      {
        // Full match. We're done.
        ec = asio::error_code();
        return match_results[0].second - begin;
      }
      else
      {
        // Partial match. Next search needs to start from beginning of match.
        search_position = match_results[0].first - begin;
      }
    }
    else
    {
      // No match. Next search can start with the new data.
      search_position = end - begin;
    }

    // Check if buffer is full.
    if (b.size() == b.max_size())
    {
      ec = error::not_found;
      return 0;
    }

    // Need more data.
    std::size_t bytes_to_read = read_size_helper(b, 65536);
    b.commit(s.read_some(b.prepare(bytes_to_read), ec));
    if (ec)
      return 0;
  }
}

inline void async_write_at(AsyncRandomAccessWriteDevice& d,
    boost::uint64_t offset, asio::basic_streambuf<Allocator>& b,
    CompletionCondition completion_condition, WriteHandler handler)
{
  async_write_at(d, offset, b.data(), completion_condition,
      detail::write_at_streambuf_op<
        AsyncRandomAccessWriteDevice, Allocator, WriteHandler>(b, handler));
}

inline void async_write(AsyncWriteStream& s,
    asio::basic_streambuf<Allocator>& b,
    CompletionCondition completion_condition, WriteHandler handler)
{
  async_write(s, b.data(), completion_condition,
      detail::write_streambuf_handler<
        AsyncWriteStream, Allocator, WriteHandler>(b, handler));
}

std::size_t read(SyncReadStream& s,
    asio::basic_streambuf<Allocator>& b,
    CompletionCondition completion_condition, asio::error_code& ec)
{
  ec = asio::error_code();
  std::size_t total_transferred = 0;
  std::size_t max_size = detail::adapt_completion_condition_result(
        completion_condition(ec, total_transferred));
  std::size_t bytes_available = read_size_helper(b, max_size);
  while (bytes_available > 0)
  {
    std::size_t bytes_transferred = s.read_some(b.prepare(bytes_available), ec);
    b.commit(bytes_transferred);
    total_transferred += bytes_transferred;
    max_size = detail::adapt_completion_condition_result(
          completion_condition(ec, total_transferred));
    bytes_available = read_size_helper(b, max_size);
  }
  return total_transferred;
}

std::size_t read_at(SyncRandomAccessReadDevice& d,
    boost::uint64_t offset, asio::basic_streambuf<Allocator>& b,
    CompletionCondition completion_condition, asio::error_code& ec)
{
  ec = asio::error_code();
  std::size_t total_transferred = 0;
  std::size_t max_size = detail::adapt_completion_condition_result(
        completion_condition(ec, total_transferred));
  std::size_t bytes_available = read_size_helper(b, max_size);
  while (bytes_available > 0)
  {
    std::size_t bytes_transferred = d.read_some_at(
        offset + total_transferred, b.prepare(bytes_available), ec);
    b.commit(bytes_transferred);
    total_transferred += bytes_transferred;
    max_size = detail::adapt_completion_condition_result(
          completion_condition(ec, total_transferred));
    bytes_available = read_size_helper(b, max_size);
  }
  return total_transferred;
}

inline void async_write_at(AsyncRandomAccessWriteDevice& d,
    boost::uint64_t offset, asio::basic_streambuf<Allocator>& b,
    WriteHandler handler)
{
  // If you get an error on the following line it means that your handler does
  // not meet the documented type requirements for a WriteHandler.
  ASIO_WRITE_HANDLER_CHECK(WriteHandler, handler) type_check;

  async_write_at(d, offset, b.data(), transfer_all(),
      detail::write_at_streambuf_op<
        AsyncRandomAccessWriteDevice, Allocator, WriteHandler>(b, handler));
}