VCDIFF
VCDIFF is a format and an algorithm for delta encoding, described in IETF's RFC 3284. The algorithm is based on Jon Bentley and Douglas McIlroy's paper "Data Compression Using Long Common Strings"[1] written in 1999. VCDIFF is used as one of the delta encoding algorithms in "Delta encoding in HTTP" (RFC 3229) and is employed in Google's Shared Dictionary Compression Over HTTP technology used in their Chrome browser.
Delta instructions
VCDIFF has 3 delta instructions. ADD, COPY, and RUN. ADD adds a new sequence, COPY copies from an old sequence, and RUN adds repeated data.
Implementations
Free software implementations include xdelta (version 3) and open-vcdiff.
- Google's Shared Dictionary Compression Over HTTP proposal uses this algorithm, and was included in the Google Chrome browser, up to version 58.[2]
- xdelta - A tool, which is an Open Source VCDIFF delta compression implementation
- open-vcdiff - Another Open Source VCDIFF delta compression implementation
- vczip as part of vcodex and ast-open packages (also part of UWIN)
- diffable - Java implementation, but some kind of original modification of VCDIFF
- jvcdiff - Full decoder/encoder Java implementation of VCDIFF
- vcdiff-java - another Java implementation of VCDIFF
- Miscellaneous Utility Library - C# implementation, decoding only
- CyanDelta - Updates CyanogenMod ROMs using Xdelta3 patches.
gollark: I was briefly very confused after seeing some messages at 01:10 or so after some from 01:50.
gollark: I'm mostly annoyed at having to change my watch, and the weirdness it causes for programs dealing with time.
gollark: They use one of those random number generators which always returns 4.
gollark: Moving all the walls around sounds annoying and tiring.
gollark: Something something status signalling, simple.
See also
References
- CiteSeerX — Data Compression Using Long Common Strings
- "Intent to Unship: SDCH". Retrieved 2017-08-08.
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