1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
|
/*
HTTP Content-Type Autonegotiation.
The functions in this package implement the behaviour specified in
http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html
Copyright (c) 2011, Open Knowledge Foundation Ltd.
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:
Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in
the documentation and/or other materials provided with the
distribution.
Neither the name of the Open Knowledge Foundation Ltd. nor the
names of its contributors may be used to endorse or promote
products derived from this software without specific prior written
permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package goautoneg
import (
"sort"
"strconv"
"strings"
)
// Structure to represent a clause in an HTTP Accept Header
type Accept struct {
Type, SubType string
Q float64
Params map[string]string
}
// acceptSlice is defined to implement sort interface.
type acceptSlice []Accept
func (slice acceptSlice) Len() int {
return len(slice)
}
func (slice acceptSlice) Less(i, j int) bool {
ai, aj := slice[i], slice[j]
if ai.Q > aj.Q {
return true
}
if ai.Type != "*" && aj.Type == "*" {
return true
}
if ai.SubType != "*" && aj.SubType == "*" {
return true
}
return false
}
func (slice acceptSlice) Swap(i, j int) {
slice[i], slice[j] = slice[j], slice[i]
}
func stringTrimSpaceCutset(r rune) bool {
return r == ' '
}
func nextSplitElement(s, sep string) (item string, remaining string) {
if index := strings.Index(s, sep); index != -1 {
return s[:index], s[index+1:]
}
return s, ""
}
// Parse an Accept Header string returning a sorted list
// of clauses
func ParseAccept(header string) acceptSlice {
partsCount := 0
remaining := header
for len(remaining) > 0 {
partsCount++
_, remaining = nextSplitElement(remaining, ",")
}
accept := make(acceptSlice, 0, partsCount)
remaining = header
var part string
for len(remaining) > 0 {
part, remaining = nextSplitElement(remaining, ",")
part = strings.TrimFunc(part, stringTrimSpaceCutset)
a := Accept{
Q: 1.0,
}
sp, remainingPart := nextSplitElement(part, ";")
sp0, spRemaining := nextSplitElement(sp, "/")
a.Type = strings.TrimFunc(sp0, stringTrimSpaceCutset)
switch {
case len(spRemaining) == 0:
if a.Type == "*" {
a.SubType = "*"
} else {
continue
}
default:
var sp1 string
sp1, spRemaining = nextSplitElement(spRemaining, "/")
if len(spRemaining) > 0 {
continue
}
a.SubType = strings.TrimFunc(sp1, stringTrimSpaceCutset)
}
if len(remainingPart) == 0 {
accept = append(accept, a)
continue
}
a.Params = make(map[string]string)
for len(remainingPart) > 0 {
sp, remainingPart = nextSplitElement(remainingPart, ";")
sp0, spRemaining = nextSplitElement(sp, "=")
if len(spRemaining) == 0 {
continue
}
var sp1 string
sp1, spRemaining = nextSplitElement(spRemaining, "=")
if len(spRemaining) != 0 {
continue
}
token := strings.TrimFunc(sp0, stringTrimSpaceCutset)
if token == "q" {
a.Q, _ = strconv.ParseFloat(sp1, 32)
} else {
a.Params[token] = strings.TrimFunc(sp1, stringTrimSpaceCutset)
}
}
accept = append(accept, a)
}
sort.Sort(accept)
return accept
}
// Negotiate the most appropriate content_type given the accept header
// and a list of alternatives.
func Negotiate(header string, alternatives []string) (content_type string) {
asp := make([][]string, 0, len(alternatives))
for _, ctype := range alternatives {
asp = append(asp, strings.SplitN(ctype, "/", 2))
}
for _, clause := range ParseAccept(header) {
for i, ctsp := range asp {
if clause.Type == ctsp[0] && clause.SubType == ctsp[1] {
content_type = alternatives[i]
return
}
if clause.Type == ctsp[0] && clause.SubType == "*" {
content_type = alternatives[i]
return
}
if clause.Type == "*" && clause.SubType == "*" {
content_type = alternatives[i]
return
}
}
}
return
}
|
