source: trip-planner-front/node_modules/compression/index.js@ fa375fe

Last change on this file since fa375fe was 6a3a178, checked in by Ema <ema_spirova@…>, 3 years ago

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1/*!
2 * compression
3 * Copyright(c) 2010 Sencha Inc.
4 * Copyright(c) 2011 TJ Holowaychuk
5 * Copyright(c) 2014 Jonathan Ong
6 * Copyright(c) 2014-2015 Douglas Christopher Wilson
7 * MIT Licensed
8 */
9
10'use strict'
11
12/**
13 * Module dependencies.
14 * @private
15 */
16
17var accepts = require('accepts')
18var Buffer = require('safe-buffer').Buffer
19var bytes = require('bytes')
20var compressible = require('compressible')
21var debug = require('debug')('compression')
22var onHeaders = require('on-headers')
23var vary = require('vary')
24var zlib = require('zlib')
25
26/**
27 * Module exports.
28 */
29
30module.exports = compression
31module.exports.filter = shouldCompress
32
33/**
34 * Module variables.
35 * @private
36 */
37
38var cacheControlNoTransformRegExp = /(?:^|,)\s*?no-transform\s*?(?:,|$)/
39
40/**
41 * Compress response data with gzip / deflate.
42 *
43 * @param {Object} [options]
44 * @return {Function} middleware
45 * @public
46 */
47
48function compression (options) {
49 var opts = options || {}
50
51 // options
52 var filter = opts.filter || shouldCompress
53 var threshold = bytes.parse(opts.threshold)
54
55 if (threshold == null) {
56 threshold = 1024
57 }
58
59 return function compression (req, res, next) {
60 var ended = false
61 var length
62 var listeners = []
63 var stream
64
65 var _end = res.end
66 var _on = res.on
67 var _write = res.write
68
69 // flush
70 res.flush = function flush () {
71 if (stream) {
72 stream.flush()
73 }
74 }
75
76 // proxy
77
78 res.write = function write (chunk, encoding) {
79 if (ended) {
80 return false
81 }
82
83 if (!this._header) {
84 this._implicitHeader()
85 }
86
87 return stream
88 ? stream.write(toBuffer(chunk, encoding))
89 : _write.call(this, chunk, encoding)
90 }
91
92 res.end = function end (chunk, encoding) {
93 if (ended) {
94 return false
95 }
96
97 if (!this._header) {
98 // estimate the length
99 if (!this.getHeader('Content-Length')) {
100 length = chunkLength(chunk, encoding)
101 }
102
103 this._implicitHeader()
104 }
105
106 if (!stream) {
107 return _end.call(this, chunk, encoding)
108 }
109
110 // mark ended
111 ended = true
112
113 // write Buffer for Node.js 0.8
114 return chunk
115 ? stream.end(toBuffer(chunk, encoding))
116 : stream.end()
117 }
118
119 res.on = function on (type, listener) {
120 if (!listeners || type !== 'drain') {
121 return _on.call(this, type, listener)
122 }
123
124 if (stream) {
125 return stream.on(type, listener)
126 }
127
128 // buffer listeners for future stream
129 listeners.push([type, listener])
130
131 return this
132 }
133
134 function nocompress (msg) {
135 debug('no compression: %s', msg)
136 addListeners(res, _on, listeners)
137 listeners = null
138 }
139
140 onHeaders(res, function onResponseHeaders () {
141 // determine if request is filtered
142 if (!filter(req, res)) {
143 nocompress('filtered')
144 return
145 }
146
147 // determine if the entity should be transformed
148 if (!shouldTransform(req, res)) {
149 nocompress('no transform')
150 return
151 }
152
153 // vary
154 vary(res, 'Accept-Encoding')
155
156 // content-length below threshold
157 if (Number(res.getHeader('Content-Length')) < threshold || length < threshold) {
158 nocompress('size below threshold')
159 return
160 }
161
162 var encoding = res.getHeader('Content-Encoding') || 'identity'
163
164 // already encoded
165 if (encoding !== 'identity') {
166 nocompress('already encoded')
167 return
168 }
169
170 // head
171 if (req.method === 'HEAD') {
172 nocompress('HEAD request')
173 return
174 }
175
176 // compression method
177 var accept = accepts(req)
178 var method = accept.encoding(['gzip', 'deflate', 'identity'])
179
180 // we really don't prefer deflate
181 if (method === 'deflate' && accept.encoding(['gzip'])) {
182 method = accept.encoding(['gzip', 'identity'])
183 }
184
185 // negotiation failed
186 if (!method || method === 'identity') {
187 nocompress('not acceptable')
188 return
189 }
190
191 // compression stream
192 debug('%s compression', method)
193 stream = method === 'gzip'
194 ? zlib.createGzip(opts)
195 : zlib.createDeflate(opts)
196
197 // add buffered listeners to stream
198 addListeners(stream, stream.on, listeners)
199
200 // header fields
201 res.setHeader('Content-Encoding', method)
202 res.removeHeader('Content-Length')
203
204 // compression
205 stream.on('data', function onStreamData (chunk) {
206 if (_write.call(res, chunk) === false) {
207 stream.pause()
208 }
209 })
210
211 stream.on('end', function onStreamEnd () {
212 _end.call(res)
213 })
214
215 _on.call(res, 'drain', function onResponseDrain () {
216 stream.resume()
217 })
218 })
219
220 next()
221 }
222}
223
224/**
225 * Add bufferred listeners to stream
226 * @private
227 */
228
229function addListeners (stream, on, listeners) {
230 for (var i = 0; i < listeners.length; i++) {
231 on.apply(stream, listeners[i])
232 }
233}
234
235/**
236 * Get the length of a given chunk
237 */
238
239function chunkLength (chunk, encoding) {
240 if (!chunk) {
241 return 0
242 }
243
244 return !Buffer.isBuffer(chunk)
245 ? Buffer.byteLength(chunk, encoding)
246 : chunk.length
247}
248
249/**
250 * Default filter function.
251 * @private
252 */
253
254function shouldCompress (req, res) {
255 var type = res.getHeader('Content-Type')
256
257 if (type === undefined || !compressible(type)) {
258 debug('%s not compressible', type)
259 return false
260 }
261
262 return true
263}
264
265/**
266 * Determine if the entity should be transformed.
267 * @private
268 */
269
270function shouldTransform (req, res) {
271 var cacheControl = res.getHeader('Cache-Control')
272
273 // Don't compress for Cache-Control: no-transform
274 // https://tools.ietf.org/html/rfc7234#section-5.2.2.4
275 return !cacheControl ||
276 !cacheControlNoTransformRegExp.test(cacheControl)
277}
278
279/**
280 * Coerce arguments to Buffer
281 * @private
282 */
283
284function toBuffer (chunk, encoding) {
285 return !Buffer.isBuffer(chunk)
286 ? Buffer.from(chunk, encoding)
287 : chunk
288}
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