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8 | 'use strict'
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9 |
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14 |
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15 | var CACHE_CONTROL_NO_CACHE_REGEXP = /(?:^|,)\s*?no-cache\s*?(?:,|$)/
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21 |
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22 | module.exports = fresh
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23 |
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31 |
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32 |
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33 | function fresh (reqHeaders, resHeaders) {
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34 |
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35 | var modifiedSince = reqHeaders['if-modified-since']
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36 | var noneMatch = reqHeaders['if-none-match']
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37 |
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38 |
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39 | if (!modifiedSince && !noneMatch) {
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40 | return false
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41 | }
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42 |
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43 |
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44 |
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45 |
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46 | var cacheControl = reqHeaders['cache-control']
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47 | if (cacheControl && CACHE_CONTROL_NO_CACHE_REGEXP.test(cacheControl)) {
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48 | return false
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49 | }
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50 |
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51 |
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52 | if (noneMatch && noneMatch !== '*') {
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53 | var etag = resHeaders['etag']
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54 |
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55 | if (!etag) {
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56 | return false
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57 | }
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58 |
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59 | var etagStale = true
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60 | var matches = parseTokenList(noneMatch)
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61 | for (var i = 0; i < matches.length; i++) {
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62 | var match = matches[i]
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63 | if (match === etag || match === 'W/' + etag || 'W/' + match === etag) {
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64 | etagStale = false
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65 | break
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66 | }
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67 | }
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68 |
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69 | if (etagStale) {
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70 | return false
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71 | }
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72 | }
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73 |
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74 |
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75 | if (modifiedSince) {
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76 | var lastModified = resHeaders['last-modified']
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77 | var modifiedStale = !lastModified || !(parseHttpDate(lastModified) <= parseHttpDate(modifiedSince))
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78 |
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79 | if (modifiedStale) {
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80 | return false
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81 | }
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82 | }
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83 |
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84 | return true
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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 |
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93 |
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94 | function parseHttpDate (date) {
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95 | var timestamp = date && Date.parse(date)
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96 |
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97 |
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98 | return typeof timestamp === 'number'
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99 | ? timestamp
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100 | : NaN
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101 | }
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102 |
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103 |
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104 |
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105 |
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106 |
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107 |
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108 |
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109 |
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110 | function parseTokenList (str) {
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111 | var end = 0
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112 | var list = []
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113 | var start = 0
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114 |
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115 |
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116 | for (var i = 0, len = str.length; i < len; i++) {
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117 | switch (str.charCodeAt(i)) {
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118 | case 0x20:
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119 | if (start === end) {
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120 | start = end = i + 1
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121 | }
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122 | break
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123 | case 0x2c:
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124 | list.push(str.substring(start, end))
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125 | start = end = i + 1
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126 | break
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127 | default:
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128 | end = i + 1
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129 | break
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130 | }
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131 | }
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132 |
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133 |
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134 | list.push(str.substring(start, end))
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135 |
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136 | return list
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137 | }
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