121 lines
2.6 KiB
JavaScript
Executable File
121 lines
2.6 KiB
JavaScript
Executable File
module.exports = preferredEncodings;
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preferredEncodings.preferredEncodings = preferredEncodings;
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function parseAcceptEncoding(accept) {
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var acceptableEncodings;
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if (accept) {
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acceptableEncodings = accept.split(',').map(function(e) {
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return parseEncoding(e.trim());
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});
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} else {
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acceptableEncodings = [];
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}
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if (!acceptableEncodings.some(function(e) {
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return e && specify('identity', e);
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})) {
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/*
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* If identity doesn't explicitly appear in the accept-encoding header,
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* it's added to the list of acceptable encoding with the lowest q
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*
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*/
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var lowestQ = 1;
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for(var i = 0; i < acceptableEncodings.length; i++){
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var e = acceptableEncodings[i];
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if(e && e.q < lowestQ){
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lowestQ = e.q;
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}
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}
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acceptableEncodings.push({
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encoding: 'identity',
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q: lowestQ / 2,
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});
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}
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return acceptableEncodings.filter(function(e) {
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return e;
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});
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}
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function parseEncoding(s) {
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var match = s.match(/^\s*(\S+?)\s*(?:;(.*))?$/);
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if (!match) return null;
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var encoding = match[1];
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var q = 1;
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if (match[2]) {
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var params = match[2].split(';');
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for (var i = 0; i < params.length; i ++) {
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var p = params[i].trim().split('=');
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if (p[0] === 'q') {
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q = parseFloat(p[1]);
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break;
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}
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}
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}
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return {
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encoding: encoding,
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q: q
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};
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}
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function getEncodingPriority(encoding, accepted) {
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return (accepted.map(function(a) {
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return specify(encoding, a);
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}).filter(Boolean).sort(function (a, b) {
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if(a.s == b.s) {
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return a.q > b.q ? -1 : 1;
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} else {
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return a.s > b.s ? -1 : 1;
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}
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})[0] || {s: 0, q: 0});
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}
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function specify(encoding, spec) {
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var s = 0;
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if(spec.encoding === encoding){
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s |= 1;
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} else if (spec.encoding !== '*' ) {
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return null
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}
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return {
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s: s,
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q: spec.q,
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}
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};
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function preferredEncodings(accept, provided) {
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accept = parseAcceptEncoding(accept || '');
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if (provided) {
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return provided.map(function(type) {
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return [type, getEncodingPriority(type, accept)];
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}).filter(function(pair) {
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return pair[1].q > 0;
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}).sort(function(a, b) {
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var pa = a[1];
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var pb = b[1];
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if(pa.q == pb.q) {
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return pa.s < pb.s ? 1 : -1;
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} else {
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return pa.q < pb.q ? 1 : -1;
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}
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}).map(function(pair) {
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return pair[0];
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});
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} else {
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return accept.sort(function (a, b) {
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// revsort
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return a.q < b.q ? 1 : -1;
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}).filter(function(type){
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return type.q > 0;
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}).map(function(type) {
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return type.encoding;
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});
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}
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}
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