[Boost-bugs] [Boost C++ Libraries] #8572: iosteams indirect_streambuf::init_put_area should seek if data has been read from the get buffer

Subject: [Boost-bugs] [Boost C++ Libraries] #8572: iosteams indirect_streambuf::init_put_area should seek if data has been read from the get buffer
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2013-05-14 15:54:33

#8572: iosteams indirect_streambuf::init_put_area should seek if data has been
read from the get buffer
-----------------------------------------------------+----------------------
 Reporter:  Alan Birtles <alan.birtles@…>            |       Owner:  turkanis 
     Type:  Bugs                                     |      Status:  new      
Milestone:  To Be Determined                         |   Component:  iostreams
  Version:  Boost 1.53.0                             |    Severity:  Problem  
 Keywords:                                           |  
-----------------------------------------------------+----------------------
 The following code with std::fstream prints 0x1801 but with
 boost::iostream prints 0x2000:
 {{{
   boost::iostreams::stream< boost::iostreams::file > ios(
 boost::iostreams::file( "test.dat", std::ios_base::binary |
 std::ios_base::in | std::ios_base::out | std::ios_base::trunc ), 0x800 );
   //std::fstream ios( "test.dat", std::ios_base::binary |
 std::ios_base::in | std::ios_base::out | std::ios_base::trunc );
   char buffer[ 0x2000 ];
   ios.write( buffer, 0x2000 );
   ios.seekg( -0x1000, std::ios_base::cur );
   ios.get();
   ios.write( buffer, 0x800 );
   std::cout << std::hex << ios.tellp() << std::endl;
   std::cout << std::hex << ios.tellg() << std::endl;
 }}}

 I believe the problem lies in indirect_streambuf::init_put_area. The
 current implementation is:

 {{{
     if (shared_buffer() && gptr() != 0)
         setg(0, 0, 0);
     if (output_buffered())
         setp(out().begin(), out().end());
     else
         setp(0, 0);
 }}}

 I think it should be:
 {{{
     if (shared_buffer() && gptr() != 0)
     {
         obj().seek(gptr()-egptr(), BOOST_IOS::cur, BOOST_IOS::in, next_);
         setg(0, 0, 0);
     }
     if (output_buffered())
         setp(out().begin(), out().end());
     else
         setp(0, 0);
 }}}

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/8572>
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