1 | var EventEmitter = require('events').EventEmitter
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2 |
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3 | module.exports = Channel
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4 |
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5 | function Channel(options) {
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6 | options = options || {}
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7 |
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8 | EventEmitter.call(this, options)
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9 |
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10 | this.concurrency = options.concurrency || Infinity
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11 |
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12 | this.closed = !(options.closed === false || options.open)
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13 | this.discard = options.discard
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14 |
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15 | this.fns = []
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16 | this.results = []
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17 |
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18 | this.fnIndex = 0
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19 | this.resultIndex = 0
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20 | this.pending = 0
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21 | this.errors = 0
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22 |
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23 | this.reading = true
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24 | }
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25 |
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26 | Object.defineProperty(Channel.prototype, 'pushable', {
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27 | get: function () {
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28 | return this.reading && this.pending < this.concurrency
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29 | }
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30 | })
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31 |
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32 |
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33 | Object.defineProperty(Channel.prototype, 'queue', {
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34 | get: function () {
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35 | var queue = this.results.length + this.fns.length
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36 | if (this.discard) queue += this.pending
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37 | return queue
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38 | }
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39 | })
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40 |
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41 |
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42 | Object.defineProperty(Channel.prototype, 'readable', {
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43 | get: function () {
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44 | return this.queue || !this.closed
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45 | }
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46 | })
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47 |
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48 | Channel.prototype.open = function () {
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49 | this.closed = false
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50 | this.emit('open')
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51 | return this
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52 | }
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53 |
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54 | Channel.prototype.close = function () {
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55 | this.closed = true
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56 | this.emit('close')
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57 | return this
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58 | }
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59 |
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60 |
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61 |
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62 |
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63 | Channel.prototype.pushed = function (done) {
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64 | if (this.closed) return done(null, false)
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65 | if (this.queue) return done(null, true)
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66 |
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67 | var self = this
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68 | this.on('close', close)
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69 | this.on('push', push)
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70 |
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71 | function close() {
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72 | cleanup()
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73 | done(null, false)
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74 | }
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75 |
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76 | function push() {
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77 | cleanup()
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78 | done(null, true)
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79 | }
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80 |
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81 | function cleanup() {
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82 | self.removeListener('close', close)
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83 | self.removeListener('push', push)
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84 | }
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85 | }
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86 |
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87 |
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88 |
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89 |
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90 |
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91 |
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92 | Channel.prototype.push = function (fn) {
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93 | if (fn == null) return this.close()
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94 |
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95 | if (typeof fn !== 'function')
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96 | throw new TypeError('you may only push functions')
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97 |
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98 | this.fns.push(fn)
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99 | if (!this.discard) this.results.length++
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100 | this._call()
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101 | this.emit('push')
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102 | return this
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103 | }
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104 |
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105 | Channel.prototype._call = function () {
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106 | if (!this.pushable) return
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107 | if (!this.fns.length) return
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108 |
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109 | var fn = this.fns.shift()
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110 | var index = this.fnIndex++
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111 | this.pending++
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112 |
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113 | var self = this
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114 | fn(function (err, res) {
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115 | self.pending--
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116 | if (err) {
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117 | self.reading = false
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118 | self.errors++
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119 | if (self.discard) {
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120 | self.results.push(err)
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121 | } else {
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122 | self.results[index - self.resultIndex] = err
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123 | }
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124 | } else if (!self.discard) {
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125 | self.results[index - self.resultIndex] = arguments.length > 2
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126 | ? [].slice.call(arguments, 1)
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127 | : res
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128 | }
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129 |
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130 | self.emit(String(index))
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131 | self.emit('callback')
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132 | self._call()
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133 | })
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134 | }
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135 |
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136 | Channel.prototype._read = function (done) {
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137 | var results = this.results
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138 |
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139 | if (!this.reading && !this.errors) this.reading = true
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140 |
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141 | if (!this.discard) {
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142 | if (results.length && 0 in results) {
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143 | var res = results.shift()
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144 | this.resultIndex++
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145 | if (res instanceof Error) {
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146 | this.errors--
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147 | done(res)
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148 | } else {
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149 | done(null, res)
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150 | }
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151 | return
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152 | }
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153 | } else if (results.length) {
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154 |
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155 | this.errors--
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156 | done(results.shift())
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157 | return
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158 | }
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159 |
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160 |
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161 | this._next(done)
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162 | }
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163 |
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164 | Channel.prototype._next = function (done) {
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165 | var event = this.discard
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166 | ? 'callback'
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167 | : String(this.resultIndex)
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168 |
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169 | var self = this
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170 | this.once(event, onevent)
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171 | if (!this.closed && !this.queue) this.once('close', onclose)
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172 |
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173 | function onevent() {
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174 | cleanup()
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175 | if (!this.discard) {
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176 | var res = this.results.shift()
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177 | this.resultIndex++
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178 | if (res instanceof Error) {
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179 | this.errors--
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180 | done(res)
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181 | } else {
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182 | done(null, res)
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183 | }
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184 | } else if (this.results.length) {
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185 |
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186 | this.errors--
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187 | done(this.results.shift())
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188 | } else {
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189 | done()
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190 | }
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191 | }
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192 |
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193 | function onclose() {
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194 | cleanup()
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195 | done()
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196 | }
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197 |
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198 | function cleanup() {
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199 | self.removeListener(event, onevent)
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200 | self.removeListener('close', onclose)
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201 | }
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202 | }
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203 |
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204 | Channel.prototype._flush = function* () {
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205 | if (this.discard) {
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206 | while (this.readable) yield this
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207 | return
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208 | }
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209 |
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210 | var results = []
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211 | while (this.readable) results.push(yield this)
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212 | return results
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213 | } |
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