note description: "Summary description for {SERVER_CHARSET_NEGOTIATION}. Utility class to support Server Side Content Negotiation on charset " 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_CHARSET_NEGOTIATION inherit REFACTORING_HELPER create make feature {NONE} -- Initialization make (a_charset_dft: READABLE_STRING_8) do create accept_charset_utilities set_default_charset (a_charset_dft) ensure default_charset_set: default_charset = a_charset_dft end accept_charset_utilities: HTTP_ANY_ACCEPT_HEADER_UTILITIES -- Charset feature -- Access: Server Side Defaults Formats default_charset: READABLE_STRING_8 -- Character set that is acceptable for the response. feature -- Change Element set_default_charset (a_charset: READABLE_STRING_8) -- Set `default_charset' with `a_charset' do default_charset := a_charset ensure default_charset_set: a_charset = default_charset end feature -- Charset Negotiation preference (a_server_charset_supported: ITERABLE [READABLE_STRING_8]; a_header: detachable READABLE_STRING_8): HTTP_ACCEPT_CHARSET_VARIANTS -- `a_server_charset_supported' represent a list of character sets supported by the server. -- `a_header' represents the Accept-Charset header, ie, the client preferences. -- Return which Charset to use in a response, if the server supports -- the requested Charset, or empty in other case. note EIS: "name=charset", "src=http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.2", "protocol=uri" local l_charset_match: READABLE_STRING_8 do create Result.make Result.set_supported_variants (a_server_charset_supported) if a_header = Void or else a_header.is_empty then -- the request has no Accept-Charset header, ie the header is empty, in this case use default charset encoding Result.set_acceptable (True) Result.set_variant_value (default_charset) else Result.set_vary_header_value -- select the best match, server support, client preferences l_charset_match := accept_charset_utilities.best_match (a_server_charset_supported, a_header) if l_charset_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_charset_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