What is sdelta3?

sdelta3 is a program similar to the programs "patch" and "diff".
While "patch" is only for text files in directories
sdelta3 accepts two files of any type.
Then, it creates a delta or patch file.
The delta describes the fewest amount of changes 
required to transform the first file into the second file.


    Why sdelta3?

sdelta3 has one primary purpose.
System administrators can download the miniscule 
compressed sdelta3 patch files to update previously 
downloaded source tarballs to current versions.
Compressed sdelta3 patches are often 10% the size 
of full new source tarball.
Therefore, downloading, uncompressing, and applying
sdelta3 patches are faster than downloading and
uncompressing a full source tarballs.
 

    How does sdelta3 work?

sdelta3 attempts to find long matching sequences 
of bytes that the two files share in common.
It outputs references to the bytes that both files have in common.
Finally, it outputs the byte sequences in the the second 
file has which can not be matched in the first file.


    How well does sdelta3 perform?

sdelta3's overall efficiency on creating compressible
patches of source tarballs is unmatched.
However sdelta3's nearest competitor is bdelta.
http://deltup.sunsite.dk/
 
bdelta and sdelta3 use different aproaches for the task.
sdelta3 is honed to the characteristics of textual files,
such as source tarballs.
bdelta uses a more generic whittling down algorithim
that is insensitive to the characteristics of file type.

In terms of speed sdelta3 tends to be faster than bdelta
on small files, however on 100M+ files bdelta tends to
be faster than sdelta3.
Both bdelta and sdelta3 are incredibly 
efficient and fast delta generators.

I speculate that bdelta may be better than
sdelta3 on non textual or binary data.
However no comparisons between bdelta and
sdelta3 on non source tarballs were done.

Both bdelta and sdelta3 outperform xdelta, bsdiff
and any other delta generator I could find.


    Thank who?

sdelta3 inherits from Kyle Sallee's sdelta which is an 
original project that was not forked from any other project.
sdelta3 was inspired in part by John Whitney's bdelta.
bdelta produced better patches than sdelta, but required longer.
sdelta was inspired by Joshua MacDonald's xdelta program.
However bdelta is far more like xdelta than sdelta or sdelta3.