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Subject: Re: [boost] [asio] buffered_read_stream issue, with async_read()
From: Michael Caisse (boost_at_[hidden])
Date: 2009-06-04 16:04:10

brad higgins wrote:
> 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
> _______________________________________________
> Unsubscribe & other changes:

Brad -

Perhaps you can consider changing your completion routine for the header
read. If the header indicates that the body is 0 bytes then there
is no need to read a body. Simply read the next header.

I have a similar setup for some of servers.

Best Regards -

Michael Caisse
Object Modeling Designs

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