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23 lines
1.2 KiB
Text
23 lines
1.2 KiB
Text
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bsdiff and bspatch are tools for building and applying patches to binary
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files. By using suffix sorting (specifically, Larsson and Sadakane's qsufsort)
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and taking advantage of how executable files change, bsdiff routinely produces
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binary patches 50-80% smaller than those produced by Xdelta, and 15% smaller
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than those produced by .RTPatch (a $2750/seat commercial patch tool).
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These programs were originally named bdiff and bpatch, but the large number of
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other programs using those names lead to confusion; I'm not sure if the "bs"
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in refers to "binary software" (because bsdiff produces exceptionally small
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patches for executable files) or "bytewise subtraction" (which is the key to
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how well it performs). Feel free to offer other suggestions.
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bsdiff is quite memory-hungry. It requires max(17*n,9*n+m)+O(1) bytes of
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memory, where n is the size of the old file and m is the size of the new
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file. bspatch requires n+m+O(1) bytes.
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bsdiff runs in O((n+m) log n) time; on a 200MHz Pentium Pro, building a binary
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patch for a 4MB file takes about 90 seconds. bspatch runs in O(n+m) time; on
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the same machine, applying that patch takes about two seconds.
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Providing that off_t is defined properly, bsdiff and bspatch support files of
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up to 2^61-1 = 2Ei-1 bytes.
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