open-vcdiff: An Encoder and Decoder for RFC 3284

By Lincoln Smith, Software Engineering Team

Anyone interested in building a faster Web?

We are delighted to announce the initial release of open-vcdiff, an encoder and decoder for the draft-standard format described in RFC 3284: "The VCDIFF Generic Differencing and Compression Data Format."

The VCDIFF format can be used as part of an implementation of RFC 3229, "Delta encoding in HTTP", or to produce compact delta representations for revision control systems. Expressing each successive version of a file as a delta from the previous version can save disk space and network bandwidth.

open-vcdiff is an important building block for implementing Shared-Dictionary Compression over HTTP (also known as SDCH or "Sandwich".) The SDCH protocol was initially proposed at the Velocity 2008 Web Performance and Operations Conference last June, and is soon to be released for review. Its goal is to compress HTTP responses and so provide a faster browsing experience for low-bandwidth users. If this prospect interests you, SDCH has its own discussion group on Google Groups. VCDIFF was chosen as the compression format for SDCH because it is a published standard.

The open-vcdiff team welcomes discussion, comments, and code contributions. Please join the open-vcdiff discussion group to expand and enrich the community of open-vcdiff developers.