librsync is a library for calculating and applying network deltas, with an
interface designed to ease integration into diverse network applications.

librsync encapsulates the core algorithms of the rsync protocol, which help
with efficient calculation of the differences between two files. The rsync
algorithm is different from most differencing algorithms because it does
not require the presence of the two files to calculate the delta. Instead,
it requires a set of checksums of each block of one file, which together
form a signature for that file. Blocks at any position in the other file
which have the same checksum are likely to be identical, and whatever
remains is the difference.

This algorithm transfers the differences between two files without needing
both files on the same system.

librsync is for building other programs that transfer files as efficiently
as rsync. You can use librsync in a program you write to do backups,
distribute binary patches to programs, or sync directories to a server or
between peers.

This tree also produces the rdiff command that exposes the key operations
of librsync: generating file signatures, generating the delta from a
signature to a new file, and applying the delta to regenerate the new file
given the old file.

librsync was originally written for the rproxy experiment in
delta-compression for HTTP. librsync is used by: Dropbox, rdiff-backup,
Duplicity, and others. (If you would like to be listed here, let me know.)

• Egor Ignatov
• Michael Shigorin
• Ivan Melnikov
• Dmitry V. Levin
• Igor Vlasenko
• Vitaly Lipatov

• librsync
• librsync-debuginfo
• librsync-devel
• librsync-doc