a compete demo of iostream filter chain

#include <sys/stat.h>
#include <fcntl.h>
#include <sstream>
#include <string>
#include <list>
#include <boost/iostreams/concepts.hpp>
#include <boost/filesystem.hpp>
#include <boost/iostreams/copy.hpp>
#include <boost/filesystem/exception.hpp>
#include <boost/filesystem/operations.hpp>
#include <boost/iostreams/device/file_descriptor.hpp>
#include <boost/iostreams/filtering_stream.hpp>
#include <boost/iostreams/filter/gzip.hpp>
#include <boost/iostreams/device/file.hpp>
#include <boost/iostreams/stream.hpp>
#include <time.h>
#include <unistd.h>
#include <stdio.h>
#include <iostream>

using namespace std;
namespace fs = boost::filesystem;
namespace io = boost::iostreams;

struct opipestream : io::stream< io::file_descriptor_sink >
{

  typedef io::stream< io::file_descriptor_sink > base ;

  explicit opipestream( const char* command )
	  :base( fileno( pipe = popen( command, "w" ) ) ) {}
  ~opipestream() { close() ; pclose( pipe ) ; }
  private : 
	FILE* pipe ;
};
class mydev : public io::sink {
public:
	std::streamsize write(const char* s, std::streamsize n) {
		cout<<s;
		(*opipe) << s;
	}
	mydev(const char* cmd){
		opipe = new opipestream(cmd);
	}
	~mydev(){
		delete opipe;
	}
private:
	opipestream *opipe;
};
int unpack(const char* src_file)
{
	fs::path out_dir = "/tmp/myunpack";
	if (fs::exists(out_dir)) {
		fs::remove_all(out_dir);
	}
	fs::create_directory(out_dir);
	string cmd = "/bin/tar xf - ";

	ifstream file(src_file, ios_base::in | ios_base::binary);
	io::filtering_streambuf<io::input> in;
	in.push(io::gzip_decompressor());
	in.push(file);

	//mydev out(cmd.c_str());
	FILE* tar = popen(cmd.c_str(),"w");
	io::file_descriptor_sink out(fileno(tar));
	io::copy(in,out);
	fclose(tar);
	return -1;

}

int main()
{
	return unpack("./cabal.tar.gz");

}

 

A complete demo of iostream