The librsync library implements network delta-compression of streams and
files. The algorithm is similar to that used in the rsync(1) and xdelta(2)
programs, but specialized for transfer of arbitrary-length octet streams.
Unlike most diff programs, librsync does not require access to both of the
files on the same machine, but rather only a short ``signature'' of the
old file and the complete contents of the new file.

WWW: https://github.com/librsync/librsync