Re: [Boost-users] count compressed bytes

Subject: Re: [Boost-users] count compressed bytes
From: Philipp Kraus (philipp.kraus_at_[hidden])
Date: 2010-06-11 09:25:54

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