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Parse::SVNDiff - Subversion binary diff format parser


This document describes version 0.05 of Parse::SVNDiff, released January 3, 2006.


    use Parse::SVNDiff;
    $diff = Parse::SVNDiff->new;
    $raw_svndiff = $diff->dump;
    $target_text = $diff->apply($source_text);

    $diff->apply_fh($source_fh, $target_fh);


This module implements a parser and a dumper for Subversion's svndiff binary diff format. The API is still subject to change in the next few versions.

Lazy Diffs

If you pass the lazy option to the constructor;

  $diff = Parse::SVNDiff->new( lazy => 1 );

Then the module does not actually parse the diff until you either dump it or apply it to something.

Note that Lazy Diffs are so lazy that they also forget their contents after a apply or dump so can't be applied twice. This is under the assumption that if you're doing it lazy, you're probably only going to want to do one of those.

You can also make individual data windows lazy load parts of themselves; it remains to be seen whether this will see a new performance improvement or degradation. The option is;

  $diff = Parse::SVNDiff->new( lazy => 1,
                               lazy_windows => 1,

Currently you can't use lazy_windows unless the input stream to ->parse() is seekable.

Bitches at the SVN Diff binary format

Each window specifies a "source" offset that is from the beginning of the file, not a relative position from its last position. It would be much better if that was the case, as well as it not being allowed to be negative. That way, the "source" data stream would be able to be a stream and not a seekable file.

This means two things;

  • The "source" filehandle in apply_fh() must permit seeking

  • Very large window sizes are not currently treated in a lazy fashion; each window is processed in a chunk. This limitation is just a matter of getting more tuits to handle large chunk sizes properly, however.


Audrey Tang <>

Sam Vilain <>


Copyright 2004, 2005, 2006 by Audrey Tang, Sam Vilain.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.