Re: [Boost-bugs] [Boost C++ Libraries] #3627: boost::asio::async_read() cannot be used with null_buffers()

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #3627: boost::asio::async_read() cannot be used with null_buffers()
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2010-01-12 14:16:28

#3627: boost::asio::async_read() cannot be used with null_buffers()
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 Reporter:  Dmitry Goncharov <dgoncharov@…>                     |       Owner:  chris_kohlhoff
     Type:  Bugs                                                |      Status:  new           
Milestone:  Boost 1.41.0                                        |   Component:  asio          
  Version:  Boost 1.40.0                                        |    Severity:  Regression    
 Keywords:  asio async_read null_buffers                        |  
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Changes (by jkp@…):

  * severity:  Problem => Regression

Comment:

 I can also confirm that this is the case on OS X.  The question I have is
 whether the change is intended?  The new documentation seems to imply it
 is:

 {{{
 If the total size of all buffers in the sequence mb is 0, the asynchronous
 read operation shall complete immediately and pass 0 as the argument to
 the handler that specifies the number of bytes read.
 }}}

 Also, the changelist for 1.40.0 says the following:

 {{{
 Changed the buffered*_stream<> templates to treat 0-byte reads and writes
 as no-ops, to comply with the documented type requirements for
 SyncReadStream, AsyncReadStream, SyncWriteStream and AsyncWriteStream.
 }}}

 It's unclear what the intendended behaviour is from these two snippets.
 Certainly pre 1.40.0 you could call async_read with null_buffers and get a
 callback when some new data had arrived.  This is extremely useful
 functionality, esp for code that has layered other streams on-top of the
 asio ones.  Right now I have no way to check for data (async) without
 reading it off the socket.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/3627#comment:1>
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