[boost] [asio] buffered_read_stream issue, with async_read()

Subject: [boost] [asio] buffered_read_stream issue, with async_read()
From: brad higgins (bhiggins_at_[hidden])
Date: 2009-06-04 15:31:46

Hi,
   I am using boost asio in a project.  My program has  a TCP protocol  
which reads a fixed size message header, followed by a variable-sized  
message body.  It is possible to have a message with a 0-byte body,  
and it is possible that no messages are received for some time.

   I have an issue when attempting to async_read() a 0-byte body with  
the buffered_read_stream, detailed here:

(1) My program reads a fixed-sized header
(2) After this succeeds, my program issues an async read for 0 bytes,  
for the message body
(3) buffered_read_stream sees that storage_ is empty, so it calls  
async_fill(), to fill it
(4) no more messages arrive for some time, so there is no data  
available to fill
(5) BUG -> My program's 0-byte read timer expires, rather than the  
read() succeeding and calling my handler immediately

   If I use the boost::asio::tcp::socket instead of the  
buffered_read_stream, the 0-byte read occurs immediately, and does not  
time out.  I believe the read() with the buffered_read_stream is  
getting 'blocked' in async_fill(), rather than succeeding immediately.

   Do you think the buffered_read_stream should have special cases for  
0 byte reads to cover this case, or do you think client code should  
avoid issuing 0 byte reads?

Thanks,
Brad