Re: [Boost-users] concat files for compression

Subject: Re: [Boost-users] concat files for compression
From: Kraus Philipp (philipp.kraus_at_[hidden])
Date: 2010-06-15 11:41:03

Am 13.06.2010 um 15:41 schrieb Roland Bock:

> Philipp Kraus wrote:
>> On 2010-06-11 09:34:27 +0200, Roland Bock said:
>>
>>> Kraus Philipp wrote:
>>>> Hi,
>>>>
>>>> on my previous posting I have another questing:
>>>>
>>>> I create my compression stream with
>>>>
>>>> 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;
>>>> }
>>>>
>>>> For a single file I push it to zip with:
>>>>
>>>> l_deflate.push( bio::file_source(p_str1, BOOST_IOS::binary) );
>>>>
>>>> I need a concatination for two files like:
>>>> l_deflate.push( bio::file_source(p_str1, BOOST_IOS::binary) );
>>>> l_deflate.push( bio::file_source(p_str2, BOOST_IOS::binary) );
>>>>
>>>> for unix shell I do this with:
>>>>
>>>> cat file1.txt > tozip.txt
>>>> cat file2.txt >> tozip.txt
>>>>
>>>> How I can push a concatinated file to the deflate stream buffer?
>>>>
>>>> Thanks
>>>>
>>>> Phil
>>>
>>> Hi,
>>>
>>> I see two options:
>>>
>>> a) You write a new multi_file_source class which can any number of  
>>> input
>>> files.
>>>
>>> b) Instead of working with a source, you could work with a sink at  
>>> the
>>> other end of the pipeline. Then just copy the content of the two  
>>> files
>>> into the stream.
>>
>> Hi,
>>
>> I think I would like to use the second idea, but how I can do this?
>>
>> Thx
>>
>> Phil
> Hi,
>
> currently, all your examples are using filtering input streams with  
> a source. For concatination and compression I would use a filtering  
> output stream and a sink (for instance a file sink).
>
> Then you open an ifstream for the first file and copy its content  
> into the filtering output stream.
> Then you open an ifstream for the second file and copy its content  
> into the filtering output stream.

Thanks that was a very big hint.

My code is now:

bio::basic_null_sink<char> l_out;
bio::counter l_counter;
bio::filtering_streambuf< bio::output > l_deflate;

l_deflate.push( bio::gzip_compressor() );
l_deflate.push( boost::ref(l_counter) );
l_deflate.push( l_out );

std::ifstream l_file( p_str1.c_str(), std::ifstream::in |  
std::ifstream::binary );
bio::copy( l_file, l_deflate );
l_file.close();

l_file.open( p_str2.c_str(), std::ifstream::in |  
std::ifstream::binary );
  ===> bio::copy( l_file, l_deflate ); <==== error
l_file.close();

It works perfectly, except the second copy. On this line I get a  
"segmentation fault" (sorry I can't use the debugger, because the code  
runs on another system).

Thanks a lot

Phil