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
|
/**
* negotiator
* Copyright(c) 2012 Isaac Z. Schlueter
* Copyright(c) 2014 Federico Romero
* Copyright(c) 2014-2015 Douglas Christopher Wilson
* MIT Licensed
*/
'use strict';
/**
* Module exports.
* @public
*/
module.exports = preferredEncodings;
module.exports.preferredEncodings = preferredEncodings;
/**
* Module variables.
* @private
*/
var simpleEncodingRegExp = /^\s*([^\s;]+)\s*(?:;(.*))?$/;
/**
* Parse the Accept-Encoding header.
* @private
*/
function parseAcceptEncoding(accept) {
var accepts = accept.split(',');
var hasIdentity = false;
var minQuality = 1;
for (var i = 0, j = 0; i < accepts.length; i++) {
var encoding = parseEncoding(accepts[i].trim(), i);
if (encoding) {
accepts[j++] = encoding;
hasIdentity = hasIdentity || specify('identity', encoding);
minQuality = Math.min(minQuality, encoding.q || 1);
}
}
if (!hasIdentity) {
/*
* If identity doesn't explicitly appear in the accept-encoding header,
* it's added to the list of acceptable encoding with the lowest q
*/
accepts[j++] = {
encoding: 'identity',
q: minQuality,
i: i
};
}
// trim accepts
accepts.length = j;
return accepts;
}
/**
* Parse an encoding from the Accept-Encoding header.
* @private
*/
function parseEncoding(str, i) {
var match = simpleEncodingRegExp.exec(str);
if (!match) return null;
var encoding = match[1];
var q = 1;
if (match[2]) {
var params = match[2].split(';');
for (var i = 0; i < params.length; i ++) {
var p = params[i].trim().split('=');
if (p[0] === 'q') {
q = parseFloat(p[1]);
break;
}
}
}
return {
encoding: encoding,
q: q,
i: i
};
}
/**
* Get the priority of an encoding.
* @private
*/
function getEncodingPriority(encoding, accepted, index) {
var priority = {o: -1, q: 0, s: 0};
for (var i = 0; i < accepted.length; i++) {
var spec = specify(encoding, accepted[i], index);
if (spec && (priority.s - spec.s || priority.q - spec.q || priority.o - spec.o) < 0) {
priority = spec;
}
}
return priority;
}
/**
* Get the specificity of the encoding.
* @private
*/
function specify(encoding, spec, index) {
var s = 0;
if(spec.encoding.toLowerCase() === encoding.toLowerCase()){
s |= 1;
} else if (spec.encoding !== '*' ) {
return null
}
return {
i: index,
o: spec.i,
q: spec.q,
s: s
}
};
/**
* Get the preferred encodings from an Accept-Encoding header.
* @public
*/
function preferredEncodings(accept, provided) {
var accepts = parseAcceptEncoding(accept || '');
if (!provided) {
// sorted list of all encodings
return accepts
.filter(isQuality)
.sort(compareSpecs)
.map(getFullEncoding);
}
var priorities = provided.map(function getPriority(type, index) {
return getEncodingPriority(type, accepts, index);
});
// sorted list of accepted encodings
return priorities.filter(isQuality).sort(compareSpecs).map(function getEncoding(priority) {
return provided[priorities.indexOf(priority)];
});
}
/**
* Compare two specs.
* @private
*/
function compareSpecs(a, b) {
return (b.q - a.q) || (b.s - a.s) || (a.o - b.o) || (a.i - b.i) || 0;
}
/**
* Get full encoding string.
* @private
*/
function getFullEncoding(spec) {
return spec.encoding;
}
/**
* Check if a spec has any quality.
* @private
*/
function isQuality(spec) {
return spec.q > 0;
}
|
