opusdev/vector-similarity-api

1/*!2 * fresh3 * Copyright(c) 2012 TJ Holowaychuk4 * Copyright(c) 2016-2017 Douglas Christopher Wilson5 * MIT Licensed6 */7 8'use strict'9 10/**11 * RegExp to check for no-cache token in Cache-Control.12 * @private13 */14 15var CACHE_CONTROL_NO_CACHE_REGEXP = /(?:^|,)\s*?no-cache\s*?(?:,|$)/16 17/**18 * Module exports.19 * @public20 */21 22module.exports = fresh23 24/**25 * Check freshness of the response using request and response headers.26 *27 * @param {Object} reqHeaders28 * @param {Object} resHeaders29 * @return {Boolean}30 * @public31 */32 33function fresh (reqHeaders, resHeaders) {34  // fields35  var modifiedSince = reqHeaders['if-modified-since']36  var noneMatch = reqHeaders['if-none-match']37 38  // unconditional request39  if (!modifiedSince && !noneMatch) {40    return false41  }42 43  // Always return stale when Cache-Control: no-cache44  // to support end-to-end reload requests45  // https://tools.ietf.org/html/rfc2616#section-14.9.446  var cacheControl = reqHeaders['cache-control']47  if (cacheControl && CACHE_CONTROL_NO_CACHE_REGEXP.test(cacheControl)) {48    return false49  }50 51  // if-none-match52  if (noneMatch && noneMatch !== '*') {53    var etag = resHeaders['etag']54 55    if (!etag) {56      return false57    }58 59    var etagStale = true60    var matches = parseTokenList(noneMatch)61    for (var i = 0; i < matches.length; i++) {62      var match = matches[i]63      if (match === etag || match === 'W/' + etag || 'W/' + match === etag) {64        etagStale = false65        break66      }67    }68 69    if (etagStale) {70      return false71    }72  }73 74  // if-modified-since75  if (modifiedSince) {76    var lastModified = resHeaders['last-modified']77    var modifiedStale = !lastModified || !(parseHttpDate(lastModified) <= parseHttpDate(modifiedSince))78 79    if (modifiedStale) {80      return false81    }82  }83 84  return true85}86 87/**88 * Parse an HTTP Date into a number.89 *90 * @param {string} date91 * @private92 */93 94function parseHttpDate (date) {95  var timestamp = date && Date.parse(date)96 97  // istanbul ignore next: guard against date.js Date.parse patching98  return typeof timestamp === 'number'99    ? timestamp100    : NaN101}102 103/**104 * Parse a HTTP token list.105 *106 * @param {string} str107 * @private108 */109 110function parseTokenList (str) {111  var end = 0112  var list = []113  var start = 0114 115  // gather tokens116  for (var i = 0, len = str.length; i < len; i++) {117    switch (str.charCodeAt(i)) {118      case 0x20: /*   */119        if (start === end) {120          start = end = i + 1121        }122        break123      case 0x2c: /* , */124        list.push(str.substring(start, end))125        start = end = i + 1126        break127      default:128        end = i + 1129        break130    }131  }132 133  // final token134  list.push(str.substring(start, end))135 136  return list137}138