pysync 1.2 ---------- A Python implementation of the rsync algorithm. This is a demonstration implementation of the rsync algorithm in Python. It is not fast and is not optimised. The primary aim is to provide a simple example implementation of the algorithm for reference, so code clarity is more important than performance. Ideas have been liberaly taken from libhsync, xdelta and rsync. Release 1.2 introduced the new zlib-like API, allowing for incremental calculation of deltas and applying patches. The comments at the top of pysync.py explains it all; # Low level API signature calculation sig=calcsig(oldfile) # Low level API rsync style incremental delta calc from sig and newdata delta=rdeltaobj(sig) # or for xdelta style incremental delta calc from oldfile and newdata # delta=xdeltaobj(oldfile) incdelta=delta.calcdelta(newdata) : incdelta=delta.flush() # Low level API applying incremental delta to oldfile to get newdata patch=patchobj(oldfile) newdata=patch.calcpatch(incdelta) : The rdeltaobj.flush() method supports R_SYNC_FLUSH and R_FINISH flush modes that behave the same as their zlib equivalents. Next on the TODO list is incremental signature calculation, and further cleanups. Eventualy I plan to create a md4sum module and move the rolling checksum stuff into C code. The performance has been marginaly hurt by this new API. Interestingly, the python profiler shows that most of the time is wasted performing string-copies when taking slices from input buffers, not actualy doing the rsync. This suggests that significant performance increases might be achievable by re- arranging things a bit, rather than moving python code into C. I have also added a pysync-test.py script for thorough formal testing of pysync. It generates/reuses random test files that make pysync really work hard, verifying that it behaves as it should. Incidentaly, release 1.2 also fixed a rather embarassing bug introduced in release 0.9's adler32.py that corrupted the rolling checksums, resulting in heaps of missed matches. This bug caused seriously bad performance and very large deltas. URL: http://freshmeat.net/projects/pysync/ Download: ftp://minkirri.apana.org.au/pub/python/pysync/pysync-1.2.tar.bz2 License: LGPL Categories: Encryption/Encoding Donovan Baarda (abo@minkirri.apana.org.au) http://sourceforge.net/users/abo/ -- ABO: finger abo@minkirri.apana.org.au for more information.