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Binary diff/patch utility
bsdiff and bspatch are tools for building and applying patches to
binary files. By using suffix sorting (specifically, [1]Larsson and
Sadakane's qsufsort) and taking advantage of how executable files
change, bsdiff routinely produces binary patches 50-80% smaller than
those produced by [2]Xdelta, and 15% smaller than those produced by
[3].RTPatch (a $2750/seat commercial patch tool).
These programs were originally named bdiff and bpatch, but the large
number of other programs using those names lead to confusion; I'm not
sure if the "bs" in refers to "binary software" (because bsdiff
produces exceptionally small patches for executable files) or "bytewise
subtraction" (which is the key to how well it performs). Feel free to
offer other suggestions.
bsdiff and bspatch use bzip2; by default they assume it is in /usr/bin.
bsdiff is quite memory-hungry. It requires max(17*n,9*n+m)+O(1) bytes
of memory, where n is the size of the old file and m is the size of the
new file. bspatch requires n+m+O(1) bytes.
bsdiff runs in O((n+m) log n) time; on a 200MHz Pentium Pro, building a
binary patch for a 4MB file takes about 90 seconds. bspatch runs in
O(n+m) time; on the same machine, applying that patch takes about two
seconds.
Providing that off_t is defined properly, bsdiff and bspatch support
files of up to 2^61-1 = 2Ei-1 bytes.
Version 4.3 is available [4]here with MD5 hash
e6d812394f0e0ecc8d5df255aa1db22a. Version 4.2 is available in the
FreeBSD, NetBSD, and OpenBSD ports trees as misc/bsdiff, in Darwinports
as devel/bsdiff, and in gentoo as dev-util/bsdiff. It has also been
made into a [5]Python extension module, and there is a [6]Windows port
available.
The algorithm used by BSDiff 4 is described in my (unpublished) paper
[7]Naive differences of executable code; please cite this in papers as
Colin Percival, Naive differences of executable code,
http://www.daemonology.net/bsdiff/, 2003.
A far more sophisticated algorithm, which typically provides roughly
20% smaller patches, is described in my [8]doctoral thesis.
References
1. http://www.cs.lth.se/Research/Algorithms/Papers/jesper5.ps
2. http://sourceforge.net/projects/xdelta/
3. http://www.pocketsoft.com/products.html
4. http://www.daemonology.net/bsdiff/bsdiff-4.3.tar.gz
5. http://starship.python.net/crew/atuining/cx_bsdiff/index.html
6. http://sites.inka.de/tesla/f_others.html#bsdiff
7. http://www.daemonology.net/papers/bsdiff.pdf
8. http://www.daemonology.net/papers/thesis.pdf
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