librsync implements the rolling-checksum algorithm of remote file synchronization that was popularized by the rsync utility.
This algorithm transfers the differences between 2 files without needing both files on the same system.
librsync does not implement the rsync wire protocol. If you want to talk to
an rsync server to transfer files you'll need to shell out to rsync.
You cannot make use of librsync to talk to an rsync server.
librsync also does not include any network functions for talking to SSH or any other server. To access a remote filesystem, you need to provide your own code or make use of some other virtual filesystem layer.
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-line tool 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 is Copyright 1999-2015 Martin Pool and others.
librsync is distributed under the GNU LGPL v2.1 (see COPYING), which basically means that you can dynamically link librsync into non-GPL programs, but you must redistribute the librsync source, with any modifications you have made.
librsync contains the BLAKE2 hash algorithm, written by Samuel Neves and released under the CC0 public domain dedication, http://creativecommons.org/publicdomain/zero/1.0/.
librsync's home is
There are two mailing lists:
- https://groups.google.com/forum/#!forum/librsync-announce
- https://groups.google.com/forum/#!forum/librsync
There are some questions and answers about librsync on stackoverflow.com tagged
librsync. That is a good place to start if you have questions.
To build librsync you will need:
-
A C compiler and appropriate headers and libraries
-
Make
-
popt command line parsing library
Available from http://rpm5.org/files/popt/
A cut-down version of popt1.5 is included and will be used automatically if there is no popt library on your build host.
-
automake, libtool, and autoconf
$ ./autogen.sh
To build and test librsync then do
$ ./configure
$ make all check
You can also do what's called a VPATH build, where the build products are
kept separate from the source tree:
$ mkdir _build # for example
$ cd _build
$ ../configure && make check
After building you can install rdiff and librsync for system-wide use. The
destination is controlled by --prefix and related options to ./configure.
$ sudo make install
With cygwin you can build using gcc as under a normal unix system. It is also possible to compile under cygwin using MSVC++. You must have environment variables needed by MSCV set using the Vcvars32.bat script. With these variables set, you just do;
$ ./configure.msc
$ make all check
The PCbuild directory contains a project and pre-generated config files for use with the MSVC++ IDE. This should be enought to compile rdiff.exe without requiring cygwin.
librsync uses the GNU libtool library versioning system, so the filename does not correspond to the librsync release. To show the library release and version, use the librsyncinfo tool. See libversions.txt for more information.
librsync should be widely portable. Patches to fix portability bugs are welcome.
Documentation for the rdiff command-line tool:
and for the library:
These are all produced from the source tree.
If you are using GNU libc, you might like to use
MALLOC_CHECK_=2 ./rdiff
to detect some allocation bugs.
librsync has annotations for the SPLINT static checking tool.
You can run the tests with make check.
Tests are automatically run at https://travis-ci.org/librsync/librsync.