boost :: iostreams :::: copy似乎过慢

Question

I am using boost::iostreams::::copy in it's common role of as part compressing a stream in memory. However, it seems excessively slow when copying a rather large compressed stream: ~30 MB may take ~2 minutes.

Here is my code:

std::stringstream compress(std::stringstream& data)
{
    namespace bio = boost::iostreams;

    std::stringstream comp;
    bio::filtering_streambuf<bio::input> out;
    out.push(bio::gzip_compressor(bio::gzip_params(bio::gzip::best_compression)));
    out.push(data);
    bio::copy(out, comp);

    return comp;
}

The culprit is the line:

bio::copy(out, comp);

The data is in bytes and contains NULs if that matters but I need to use std::stringstream .

Does anyone see an issue with my code or have suggestions on what may improve my code? Perhaps it just takes that long though it seems excessive.

Answer 1

In a stunning- no, jaw-dropping- turn of events, it seems bio::gzip::best_compression is the real culprit.

When I changed it to bio::gzip::best_speed , I got these (rough) results:

bio::gzip::best_compression: output size 6589968 bytes     elapsed time: 105881 ms
bio::gzip::best_speed: output size: 6589596 bytes     elapsed time: 6065 ms

So it seems in my case (without regard to exactly why- probably the nature of the data) the answer is to change compression level.

Note: That's with VC++ 2017 in debug.