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.
The canonical use of librsync is in the rproxy(8)
reference implementation of the rsync proposed extension to
HTTP. It may be useful to other programs which wish to do
delta-compression in HTTP, or within their own protocol. There are
HTTP-specific utility functions within librsync, but they need
not be used.
A number of tools such as rdiff(1) provide command-line and
scriptable access to rsync functions.
The rsync protocol is still evolving. There may be bugs in the
implementation. The interface may change in the future, but it is
becoming more stable.
Many routines will panic in case of error rather than returning an
error code to the caller. Patches to fix this are welcome, but at the
current state of development aborting seems as useful as trusting to
possibly-incomplete checking in the client.