note description: "Summary description for {SERVER_ENCODING_NEGOTIATION}. Utility class to support Server Side Content Negotiation on encoding" date: "$Date$" revision: "$Revision$" description: "[ Reference : http://www.w3.org/Protocols/rfc2616/rfc2616-sec12.html#sec12.1 Server-driven Negotiation : If the selection of the best representation for a response is made by an algorithm located at the server, it is called server-driven negotiation. Selection is based on the available representations of the response (the dimensions over which it can vary; e.g. language, content-coding, etc.) and the contents of particular header fields in the request message or on other information pertaining to the request (such as the network address of the client). Server-driven negotiation is advantageous when the algorithm for selecting from among the available representations is difficult to describe to the user agent, or when the server desires to send its "best guess" to the client along with the first response (hoping to avoid the round-trip delay of a subsequent request if the "best guess" is good enough for the user). In order to improve the server's guess, the user agent MAY include request header fields (Accept, Accept-Language, Accept-Encoding, etc.) which describe its preferences for such a response. ]" EIS: "name=server driven negotiation", "src=http://www.w3.org/Protocols/rfc2616/rfc2616-sec12.html#sec12.", "protocol=uri" class SERVER_ENCODING_NEGOTIATION inherit REFACTORING_HELPER create make feature {NONE} -- Initialization make (a_encoding_dft: READABLE_STRING_8) do create accept_encoding_utilities set_default_encoding (a_encoding_dft) ensure default_encoding_set: default_encoding = a_encoding_dft end accept_encoding_utilities: HTTP_ANY_ACCEPT_HEADER_UTILITIES -- Encoding feature -- Access: Server Side Defaults Formats default_encoding: READABLE_STRING_8 -- Content-coding that is acceptable in the response. feature -- Change Element set_default_encoding (a_encoding: READABLE_STRING_8) -- Set `default_encoding' with `a_encoding' do default_encoding := a_encoding ensure default_encoding_set: a_encoding = default_encoding end feature -- Encoding Negotiation preference (a_server_encoding_supported: ITERABLE [READABLE_STRING_8]; a_header_value: detachable READABLE_STRING_8): HTTP_ACCEPT_ENCODING_VARIANTS -- `a_server_encoding_supported' represent a list of encoding supported by the server. -- `a_header_value' represent the Accept-Encoding header, ie, the client preferences. -- Return which Encoding to use in a response, if the server supports -- the requested Encoding, or empty in other case. note EIS: "name=encoding", "src=http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.3", "protocol=uri" local l_compression_match: READABLE_STRING_8 do create Result.make Result.set_supported_variants (a_server_encoding_supported) if a_header_value = Void or else a_header_value.is_empty then -- the request has no Accept-Encoding header, ie the header is empty, in this case do not compress representations Result.set_acceptable (True) Result.set_variant_value (default_encoding) else Result.set_vary_header_value -- select the best match, server support, client preferences l_compression_match := accept_encoding_utilities.best_match (a_server_encoding_supported, a_header_value) if l_compression_match.is_empty then -- The server does not support any of the compression types prefered by the client Result.set_acceptable (False) else -- Set the best match Result.set_variant_value (l_compression_match) Result.set_acceptable (True) end end end note copyright: "2011-2013, Javier Velilla, Jocelyn Fiat, Eiffel Software and others" license: "Eiffel Forum License v2 (see http://www.eiffel.com/licensing/forum.txt)" end