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