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9 | 'use strict';
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15 |
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16 | module.exports = preferredEncodings;
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17 | module.exports.preferredEncodings = preferredEncodings;
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18 |
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19 |
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20 |
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21 |
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22 |
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23 |
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24 | var simpleEncodingRegExp = /^\s*([^\s;]+)\s*(?:;(.*))?$/;
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25 |
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26 |
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27 |
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28 |
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29 |
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30 |
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31 | function parseAcceptEncoding(accept) {
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32 | var accepts = accept.split(',');
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33 | var hasIdentity = false;
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34 | var minQuality = 1;
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35 |
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36 | for (var i = 0, j = 0; i < accepts.length; i++) {
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37 | var encoding = parseEncoding(accepts[i].trim(), i);
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38 |
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39 | if (encoding) {
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40 | accepts[j++] = encoding;
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41 | hasIdentity = hasIdentity || specify('identity', encoding);
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42 | minQuality = Math.min(minQuality, encoding.q || 1);
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43 | }
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44 | }
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45 |
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46 | if (!hasIdentity) {
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47 | |
48 |
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49 |
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50 |
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51 | accepts[j++] = {
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52 | encoding: 'identity',
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53 | q: minQuality,
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54 | i: i
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55 | };
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56 | }
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57 |
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58 |
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59 | accepts.length = j;
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60 |
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61 | return accepts;
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62 | }
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63 |
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64 |
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65 |
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66 |
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67 |
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68 |
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69 | function parseEncoding(str, i) {
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70 | var match = simpleEncodingRegExp.exec(str);
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71 | if (!match) return null;
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72 |
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73 | var encoding = match[1];
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74 | var q = 1;
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75 | if (match[2]) {
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76 | var params = match[2].split(';');
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77 | for (var j = 0; j < params.length; j++) {
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78 | var p = params[j].trim().split('=');
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79 | if (p[0] === 'q') {
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80 | q = parseFloat(p[1]);
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81 | break;
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82 | }
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83 | }
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84 | }
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85 |
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86 | return {
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87 | encoding: encoding,
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88 | q: q,
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89 | i: i
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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 |
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95 |
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96 |
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97 |
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98 | function getEncodingPriority(encoding, accepted, index) {
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99 | var priority = {o: -1, q: 0, s: 0};
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100 |
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101 | for (var i = 0; i < accepted.length; i++) {
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102 | var spec = specify(encoding, accepted[i], index);
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103 |
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104 | if (spec && (priority.s - spec.s || priority.q - spec.q || priority.o - spec.o) < 0) {
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105 | priority = spec;
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106 | }
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107 | }
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108 |
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109 | return priority;
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110 | }
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111 |
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112 |
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113 |
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114 |
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115 |
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116 |
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117 | function specify(encoding, spec, index) {
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118 | var s = 0;
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119 | if(spec.encoding.toLowerCase() === encoding.toLowerCase()){
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120 | s |= 1;
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121 | } else if (spec.encoding !== '*' ) {
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122 | return null
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123 | }
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124 |
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125 | return {
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126 | i: index,
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127 | o: spec.i,
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128 | q: spec.q,
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129 | s: s
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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 |
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135 |
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136 |
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137 |
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138 | function preferredEncodings(accept, provided) {
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139 | var accepts = parseAcceptEncoding(accept || '');
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140 |
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141 | if (!provided) {
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142 |
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143 | return accepts
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144 | .filter(isQuality)
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145 | .sort(compareSpecs)
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146 | .map(getFullEncoding);
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147 | }
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148 |
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149 | var priorities = provided.map(function getPriority(type, index) {
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150 | return getEncodingPriority(type, accepts, index);
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151 | });
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152 |
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153 |
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154 | return priorities.filter(isQuality).sort(compareSpecs).map(function getEncoding(priority) {
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155 | return provided[priorities.indexOf(priority)];
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156 | });
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157 | }
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158 |
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159 |
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160 |
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161 |
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162 |
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163 |
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164 | function compareSpecs(a, b) {
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165 | return (b.q - a.q) || (b.s - a.s) || (a.o - b.o) || (a.i - b.i) || 0;
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166 | }
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167 |
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168 |
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169 |
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170 |
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171 |
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172 |
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173 | function getFullEncoding(spec) {
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174 | return spec.encoding;
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175 | }
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176 |
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177 |
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178 |
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179 |
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180 |
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181 |
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182 | function isQuality(spec) {
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183 | return spec.q > 0;
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184 | }
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