file compression to handle intermediary output in c++ - c++

Question

I want to compress a intermediate output of my program ( in C++) and then decompress it.

Answer 1

You can use Boost IOStreams to compress your data, for example something along these lines to compress/decompresses into/from a file (example adapted from Boost docs):
#include <fstream>
#include <iostream>
#include <boost/iostreams/filtering_stream.hpp>
#include <boost/iostreams/filtering_streambuf.hpp>
#include <boost/iostreams/copy.hpp>
#include <boost/iostreams/filter/gzip.hpp>
namespace bo = boost::iostreams;
int main()
{
{
std::ofstream ofile("hello.gz", std::ios_base::out | std::ios_base::binary);
bo::filtering_ostream out;
out.push(bo::gzip_compressor());
out.push(ofile);
out << "This is a gz file\n";
}
{
std::ifstream ifile("hello.gz", std::ios_base::in | std::ios_base::binary);
bo::filtering_streambuf<bo::input> in;
in.push(bo::gzip_decompressor());
in.push(ifile);
boost::iostreams::copy(in, std::cout);
}
}
You can also have a look at Boost Serialization - which can make saving your data much easier. It is possible to combine the two approaches (example). IOStreams support bzip compression as well.
EDIT: To address your last comment - you can compress an existing file... but it would be better to write it as compressed to begin with. If you really want, you could tweak the following code:
std::ifstream ifile("file", std::ios_base::in | std::ios_base::binary);
std::ofstream ofile("file.gz", std::ios_base::out | std::ios_base::binary);
bo::filtering_streambuf<bo::output> out;
out.push(bo::gzip_compressor());
out.push(ofile);
bo::copy(ifile, out);