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Outputting to file in the most compressed form (c++)

  1. Sep 22, 2009 #1
    Hi, I'm just wondering, usually when I output to file in C++ I just do like:

    fout.open("output.txt",ios::eek:ut);
    fout.precision(13);
    fout << data1 << " " << data2 << " " << data3 << endl;

    or something to that effect. i.e. I use c++'s file streams. However, for my current application minimizing space is an absolute must. Therefore, are there other ways of outputting this same data (columns of 3 doubles) to a file that will create a smaller file? I've experimented with fprintf and such but it seems to create the same sized file. Any help is greatly appreciated.
     
  2. jcsd
  3. Sep 22, 2009 #2

    chroot

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    Use zlib, probably the most common compression library on the planet.

    If you want a C++ stream version of it, try gzstream

    - Warren
     
    Last edited: Sep 22, 2009
  4. Sep 22, 2009 #3
    I can't actually use any third party libraries because I have no control over the implementation, or the compiler.
     
  5. Sep 22, 2009 #4

    Hurkyl

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    Are those really problems?



    Anyways, if space really, really is a concern, then you shouldn't be writing anything in human readable text formats, because that is a huge waste of space. Use the C++ ostream::write or the fwrite functions to write raw bytes, e.g.

    Code (Text):

    double x;
    double y[3];
    fout.write(static_cast<const char*>(&x), sizeof(double));
    fout.write(static_cast<const char*>(y), sizeof(y));
     
    and read similarly. If the file needs to be transferable between different computers that lay things out differently in memory, then you need to do a little more work to write things out in a portable format.
     
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