# librsync 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`. librsync is for building other programs that transfer files as efficiently as rsync. You can use librsync to make backup tools, 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. ## Copyright librsync is Copyright 1999-2014 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/>. ## Contact librsync's home is - https://github.com/librsync/librsync/ - http://librsync.sourcefrog.net/ 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. ## Requirements 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/ * automake, libtool, and autoconf ## Compiling If you're building from a git tree you must first create the autoconf files: $ ./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 ## Note for Windows 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. ## Library Versions 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. ## Platforms librsync should be widely portable. Patches to fix portability bugs are welcome. ## Documentation Documentation for the rdiff command-line tool: - http://librsync.sourcefrog.net/doc/rdiff.html - http://librsync.sourcefrog.net/doc/rdiff.pdf and for the library: - http://librsync.sourcefrog.net/doc/librsync.html - http://librsync.sourcefrog.net/doc/librsync.pdf These are all produced from the source tree. ## Debugging 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. ## Testing You can run the tests with `make check`. Tests are automatically run at https://travis-ci.org/librsync/librsync.