54 lines
2.4 KiB
Plaintext
54 lines
2.4 KiB
Plaintext
|
|
Content Encoding Support for libcurl
|
|
|
|
* About content encodings:
|
|
|
|
HTTP/1.1 [RFC 2616] specifies that a client may request that a server encode
|
|
its response. This is usually used to compress a response using one of a set
|
|
of commonly available compression techniques. These schemes are `deflate'
|
|
(the zlib algorithm), `gzip' and `compress' [sec 3.5, RFC 2616]. A client
|
|
requests that the sever perform an encoding by including an Accept-Encoding
|
|
header in the request document. The value of the header should be one of the
|
|
recognized tokens `deflate', ... (there's a way to register new
|
|
schemes/tokens, see sec 3.5 of the spec). A server MAY honor the client's
|
|
encoding request. When a response is encoded, the server includes a
|
|
Content-Encoding header in the response. The value of the Content-Encoding
|
|
header indicates which scheme was used to encode the data.
|
|
|
|
A client may tell a server that it can understand several different encoding
|
|
schemes. In this case the server may choose any one of those and use it to
|
|
encode the response (indicating which one using the Content-Encoding header).
|
|
It's also possible for a client to attach priorities to different schemes so
|
|
that the server knows which it prefers. See sec 14.3 of RFC 2616 for more
|
|
information on the Accept-Encoding header.
|
|
|
|
* Current support for content encoding:
|
|
|
|
I added support for the 'deflate' content encoding to both libcurl and curl.
|
|
Both regular and chunked transfers should work although I've tested only the
|
|
former. The library zlib is required for this feature. Places where I
|
|
modified the source code are commented and typically include my initials and
|
|
the date (e.g., 08/29/02 jhrg).
|
|
|
|
* The libcurl interface:
|
|
|
|
To cause libcurl to request a content encoding use:
|
|
|
|
curl_easy_setopt(curl, CURLOPT_ENCODING, <string>)
|
|
|
|
where <string> is the intended value of the Accept-Encoding header.
|
|
|
|
Currently, libcurl only understands how to process responses that use the
|
|
`deflate' Content-Encoding, so the only value for CURLOPT_ENCODING that will
|
|
work (besides "identity," which does nothing) is "deflate." If a response is
|
|
encoded using either the `gzip' or `compress' methods, libcurl will return an
|
|
error indicating that the response could not be decoded. If <string> is null
|
|
or empty no Accept-Encoding header is generated.
|
|
|
|
* The curl interface:
|
|
|
|
Use the --compressed option with curl to cause it to ask servers to compress
|
|
responses using deflate.
|
|
|
|
James Gallagher <jgallagher@gso.uri.edu>
|