resend of content-encoding / gzip design

I tried to send this last night, but it got filtered because it's
written in html.

Here's a text translation:

                    Gzip Content-Encoding in Squid Design

Version Choice

The goal will be to get these changes into Squid3 HEAD.

Content-Encoding

New HttpHdrContCode module, that parses related HTTP headers, and
arranges
for encoding or decoding appropriately. To be called from
clientProcessRequest, cacheHit, and processReplyHeader.

New HttpContentCoder abstract type, with functions:

     encodeStart(): called from HttpHdrContCode
     encodeEnd(): called from comm_close handler
     encodeChunk(): called from storeClientCopy handler

     decodeStart(): called from HttpStateData::processReplyHeader
     decodeEnd(): called from comm_close handler
     decodeChunk(): called from comm_read handler

     doSaveEncoded()

New per-coded-object ContentCoderState, to handle coding state. It will
include fields:

     HttpContentCoder *coder
     off_t codedOffset

The HttpStateData class will have a usually nulled reference to a
ContentEncoder. It will only be non-null for objects which are being
encoded
or decoded.

Other changes needed:
*Add new content_coding field to HttpReply.
*New httpHeaderGetContentEncoding(HttpReply *) function in
HttpHeader.cc.

Gzip

A new GzipContentCoder module, which will be an instance of
HttpContentCoder.

Data encoding will be handled by the gzip.org zlib library. The gzip
card
drivers are expected to include a binary-compatible zlib library.

Functions:

     gzEncodeStart: call inflateInit2(), write header
     gzEncodeEnd: write trailer
     gzEncodeChunk: call inflate()

     gzDecodeStart: call deflateInit2(), read and verify header
     gzDecodeEnd: verify trailer
     gzDecodeChunk: call deflate()

     gzDoSaveEncoded(): true

Test Strategy

Must pass the test suite.

Must add appropriate tests, including sending gzipped content to oneself

successfully.

Will also test against Apache mod_gzip implementation, and maybe even
gunzip.
Received on Thu Feb 26 2004 - 14:18:46 MST