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+bsdiff and bspatch are tools for building and applying patches to binary
+files. By using suffix sorting (specifically, 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 Xdelta, and 15% smaller
+than those produced by .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 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.