Boost C++ Libraries: Ticket #2449: tellg() not working for filtering_istream

attachment set

rbock@… — Fri, 31 Oct 2008 09:57:07 GMT

attachment → IoStreams.cpp

A short sample showing that filtering_istream::tellg() does not work (and corrupts the stream).

status changed

Jonathan Turkanis — Fri, 31 Oct 2008 18:11:32 GMT

status new → assigned

Steven Watanabe — Wed, 16 Jun 2010 14:35:38 GMT

The underlying device has to support seeking, for tellg to work.

Steven Watanabe — Wed, 16 Jun 2010 16:06:27 GMT

After poking through the source for a while, I'm beginning to think that this behavior is by design. You can make the example work using

boost::iostreams::filtering_stream<boost::iostreams::input_seekable>

rbock@… — Wed, 16 Jun 2010 16:17:28 GMT

Replying to steven_watanabe:

After poking through the source for a while, I'm beginning to think that this behavior is by design. You can make the example work using
boost::iostreams::filtering_stream<boost::iostreams::input_seekable>

Hmm. In that case, wouldn't it be better to throw an exception with some meaningful text instead of just returning -1 and invalidating the stream (good() == false)?

Steven Watanabe — Wed, 16 Jun 2010 16:41:44 GMT

I get an exception with msvc-10 and the trunk. If you don't get an exception, it's probably because std::istream is swallowing it.

status changed; resolution set

Steven Watanabe — Thu, 17 Jun 2010 01:41:54 GMT

status assigned → closed
resolution → wontfix

anonymous — Mon, 20 Jan 2014 23:49:40 GMT

Replying to steven_watanabe: Hi, I tried using boost::iostreams::filtering_stream<boost::iostreams::input_seekable>, but, I am not able to push gzip_decompressor object into this filter (push(boost::iostreams::gzip_decompressor())). Can you please let me know if there is workaround for this.

thanks, Edwin.

Tue, 21 Jan 2014 17:31:37 GMT

Hi, Were you able to use boost::iostreams::filtering_stream<boost::iostreams::input_seekable> and push boost::iostreams::gzip_decompressor() into the filter. I am not able to.. please let me know how you got around this.

thanks, Edwin.