On 2010-06-11 16:13:56 +0200, Philipp Kraus said:

On 2010-06-11 15:45:42 +0200, Roland Bock said:

Philipp Kraus wrote:

On 2010-06-11 13:06:46 +0200, Philipp Kraus said: 

On 2010-06-11 09:41:40 +0200, Roland Bock said: 

Kraus Philipp wrote: 

Hi, 

I have implemented this litte code to compress a file 

bio::filtering_streambuf< bio::input > l_deflate; 

switch (m_compress) { 

case gzip   : l_deflate.push( bio::gzip_compressor() );     break; 

case bzip2  : l_deflate.push( bio::bzip2_compressor() );    break; 

} 

l_deflate.push( bio::file_source(p_str, BOOST_IOS::binary) ); 

I need only the number of compressed bytes of l_deflate. I try to 

use l_deflate.size() but it returns only a fixed number. 

How I can read the number of compressed bytes? 

Thanks 

Phil 

The only method I know is to add a small filter which counts the Bytes. 

I have found this 

http://www.boost.org/doc/libs/1_43_0/boost/iostreams/filter/counter.hpp 

Can I use this class? I don't know how I can use the class (must I only 

create a new object and push it to my l_deflate) ? 

I have add this code: 

       bio::filtering_streambuf< bio::input > l_deflate; 

       switch (m_compress) { 

           case gzip   : l_deflate.push( bio::gzip_compressor() );     break; 

           case bzip2  : l_deflate.push( bio::bzip2_compressor() );    break; 

       } 

       // create counter structures 

       bio::counter l_counter; 

       l_deflate.push( boost::ref(l_counter) ); 

       l_deflate.push( bio::file_source(p_str1, BOOST_IOS::binary) ); 

but l_counter.characters() returns always zero. At next I have declared a filter_ostream and copy l_deflate to the ostream in which I pushed the l_counter. At this I run into a bus error. 

For testing I've copy the l_deflate to std::cout and I can see the compressed data. 

Thanks for help 

Hi,

I haven't actually used this filter myself, but here are some thoughts:

1. when you get the counter to work, it will probably count the uncompressed bytes. You should add it before the compressor, so that bytes travel from source to compressor to counter.

I swapped the lines

1. If l_counter.characters() is always zero, I'd suspect that the filter is copied, when it is pushed to the stream. I haven't found respective information in the documentation at once, so I would suggest to add some debug code to the filter class, to 
• see if the characters are actually finding their way through the filter
• make sure that the filter is not copied

Once you figure out what went wrong, maybe you could create a documentation ticket containing the relevant information.

I tested both examples

http://www.boost.org/doc/libs/1_43_0/libs/iostreams/doc/classes/counter.html#examples

but in both the character-methods returns alway zero.

In the second example there is also an error:

io::filtering_ostreams out; is wrong it sould be io::filtering_ostream out; without "s".

At this time it is a very bad situtation. 

I have found a solution:

    io::filtering_istream in;

    io::counter cnt;

    in.push(boost::ref(cnt));

    in.push(io::file_source("file.txt"));

    io::copy(in, std::cout);

    io::close(in); 

    std::cout << std::endl << std::endl << "Lines: " << cnt.lines() << " Chars: " << cnt.characters() << std::endl;

I must run the copy form the iostream, than I have the correct values in characters() and lines(). But I don't want to use the std::cout. I've found under http://www.boost.org/doc/libs/1_43_0/libs/iostreams/doc/classes/null.html a /dev/null device. At this time I don't know how to create a output stream that declares a null-sink or null-stream