tellg() not working for filtering_istream

[rbock@…]

Hi,

tellg() member function is not working for boost::iostreams::filtering_istream (see attached example).

This means that filtering_istream cannot be treated like an std::istream without having strange effects. In my eyes this is practically a showstopper for using filtering_istream.

Regards,

Roland

[rbock@…]

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

[Steven Watanabe]

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

[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>

[rbock@…]

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]

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.

[anonymous]

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.

[Edwin Ramayya <redwinbosco@…>]

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.