2 Copyright (c) 2011, Open Knowledge Foundation Ltd.
5 HTTP Content-Type Autonegotiation.
7 The functions in this package implement the behaviour specified in
8 http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html
10 Redistribution and use in source and binary forms, with or without
11 modification, are permitted provided that the following conditions are
14 Redistributions of source code must retain the above copyright
15 notice, this list of conditions and the following disclaimer.
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18 notice, this list of conditions and the following disclaimer in
19 the documentation and/or other materials provided with the
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23 names of its contributors may be used to endorse or promote
24 products derived from this software without specific prior written
27 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
28 "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
29 LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
30 A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
31 HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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49 // Structure to represent a clause in an HTTP Accept Header
53 Params map[string]string
56 // For internal use, so that we can use the sort interface
57 type accept_slice []Accept
59 func (accept accept_slice) Len() int {
60 slice := []Accept(accept)
64 func (accept accept_slice) Less(i, j int) bool {
65 slice := []Accept(accept)
66 ai, aj := slice[i], slice[j]
70 if ai.Type != "*" && aj.Type == "*" {
73 if ai.SubType != "*" && aj.SubType == "*" {
79 func (accept accept_slice) Swap(i, j int) {
80 slice := []Accept(accept)
81 slice[i], slice[j] = slice[j], slice[i]
84 // Parse an Accept Header string returning a sorted list
86 func ParseAccept(header string) (accept []Accept) {
87 parts := strings.Split(header, ",")
88 accept = make([]Accept, 0, len(parts))
89 for _, part := range parts {
90 part := strings.Trim(part, " ")
93 a.Params = make(map[string]string)
96 mrp := strings.Split(part, ";")
99 sp := strings.Split(media_range, "/")
100 a.Type = strings.Trim(sp[0], " ")
103 case len(sp) == 1 && a.Type == "*":
106 a.SubType = strings.Trim(sp[1], " ")
112 accept = append(accept, a)
116 for _, param := range mrp[1:] {
117 sp := strings.SplitN(param, "=", 2)
121 token := strings.Trim(sp[0], " ")
123 a.Q, _ = strconv.ParseFloat(sp[1], 32)
125 a.Params[token] = strings.Trim(sp[1], " ")
129 accept = append(accept, a)
132 slice := accept_slice(accept)
138 // Negotiate the most appropriate content_type given the accept header
139 // and a list of alternatives.
140 func Negotiate(header string, alternatives []string) (content_type string) {
141 asp := make([][]string, 0, len(alternatives))
142 for _, ctype := range alternatives {
143 asp = append(asp, strings.SplitN(ctype, "/", 2))
145 for _, clause := range ParseAccept(header) {
146 for i, ctsp := range asp {
147 if clause.Type == ctsp[0] && clause.SubType == ctsp[1] {
148 content_type = alternatives[i]
151 if clause.Type == ctsp[0] && clause.SubType == "*" {
152 content_type = alternatives[i]
155 if clause.Type == "*" && clause.SubType == "*" {
156 content_type = alternatives[i]