Re: [Boost-users] asio::transfer_at_least strange behavior

Subject: Re: [Boost-users] asio::transfer_at_least strange behavior
From: Igor R (boost.lists_at_[hidden])
Date: 2009-02-12 16:22:58

>
> Yes, exactly. Code snippet may be uselese, but I'm using something like
> this:
> boost::asio::read(sock, buf, boost::asio::transfer_at_least(800),
> myhandler);
>
> and myhandler is never called (because no more data arrives).
>

So, probably 800 bytes do not arrive, or there's some other issue.

> This handler called after each read operation and bytes_transferred each
> time is 400, but minimum_ is 800.
>
>>
Look at the implementation of read():
(Note that bytes_transferred passed to the completion_condition is
accumulated each time)

template <typename SyncReadStream, typename MutableBufferSequence,
    typename CompletionCondition>
std::size_t read(SyncReadStream& s, const MutableBufferSequence& buffers,
    CompletionCondition completion_condition, boost::system::error_code& ec)
{
  ec = boost::system::error_code();
  boost::asio::detail::consuming_buffers<
    mutable_buffer, MutableBufferSequence> tmp(buffers);
  std::size_t total_transferred = 0;
  tmp.set_max_size(detail::adapt_completion_condition_result(
        completion_condition(ec, total_transferred)));
  while (tmp.begin() != tmp.end())
  {
    std::size_t bytes_transferred = s.read_some(tmp, ec);
    tmp.consume(bytes_transferred);
   * total_transferred += bytes_transferred;*
    tmp.set_max_size(detail::adapt_completion_condition_result(
          completion_condition(ec, total_transferred)));
  }
  return total_transferred;
}