Use boost::iostreams::pipe

Following code implements the same function as "tar cf - workspace |gzip -9 -c >1.tar.gz"

performance is also good.

#include <boost/iostreams/device/file.hpp>
#include <iostream>
#include <string>
#include <boost/iostreams/pipeline.hpp>
#include <boost/iostreams/filtering_stream.hpp>
#include <boost/iostreams/filter/gzip.hpp>

using namespace std;

namespace io = boost::iostreams;

int main(int argc, char** argv)
{
	using namespace io::gzip;

	if (argc<2) {
		cout<<"Usage: "<<argv[0]<<" <dir>"<<endl;
		return -1;
	}
	//io::file_descriptor_source src(fileno(pf));
	io::filtering_ostream out;
	io::gzip_params gp(9);
	out.push(io::gzip_compressor(gp));
	out.push(io::file_sink("1.tar.gz"));

	string cmd = "tar cf - ";
	cmd += argv[1];
	FILE* pf = popen(cmd.c_str(),"r");
	if (pf != NULL) {
		char buf[8192];
		size_t r;
		//fflush(pf);
		while(!feof(pf)&&!ferror(pf)&&
			(r=fread(buf, 1, sizeof(buf)-1, pf))>0) {
			//cout << "read :"<<r<<endl;
			out.write(buf, r);
		}
		if (ferror(pf))
		{
			perror("\nerror:");
			pclose(pf);
			return -1;
		}
		
		pclose(pf);
	}
	return 0;
}

 $ time mytargz workspace/

real    0m0.704s
user    0m0.668s
sys    0m0.036s

$ time (tar cf - workspace |gzip -9 -c >1.tar.gz )

real    0m0.744s
user    0m0.728s
sys    0m0.020s

 

Another method is to use io::copy(in,out,bufsize), which just short the coding, looks no performance benifit.

const io::file_descriptor_source src(fileno(pf));
io::stream<io::file_descriptor_source > is(src);
io::copy(is, out, 8192);