| /*! |
| * fresh |
| * Copyright(c) 2012 TJ Holowaychuk |
| * Copyright(c) 2016-2017 Douglas Christopher Wilson |
| * MIT Licensed |
| */ |
| |
| 'use strict' |
| |
| /** |
| * RegExp to check for no-cache token in Cache-Control. |
| * @private |
| */ |
| |
| var CACHE_CONTROL_NO_CACHE_REGEXP = /(?:^|,)\s*?no-cache\s*?(?:,|$)/ |
| |
| /** |
| * Module exports. |
| * @public |
| */ |
| |
| module.exports = fresh |
| |
| /** |
| * Check freshness of the response using request and response headers. |
| * |
| * @param {Object} reqHeaders |
| * @param {Object} resHeaders |
| * @return {Boolean} |
| * @public |
| */ |
| |
| function fresh (reqHeaders, resHeaders) { |
| // fields |
| var modifiedSince = reqHeaders['if-modified-since'] |
| var noneMatch = reqHeaders['if-none-match'] |
| |
| // unconditional request |
| if (!modifiedSince && !noneMatch) { |
| return false |
| } |
| |
| // Always return stale when Cache-Control: no-cache |
| // to support end-to-end reload requests |
| // https://tools.ietf.org/html/rfc2616#section-14.9.4 |
| var cacheControl = reqHeaders['cache-control'] |
| if (cacheControl && CACHE_CONTROL_NO_CACHE_REGEXP.test(cacheControl)) { |
| return false |
| } |
| |
| // if-none-match |
| if (noneMatch && noneMatch !== '*') { |
| var etag = resHeaders['etag'] |
| |
| if (!etag) { |
| return false |
| } |
| |
| var etagStale = true |
| var matches = parseTokenList(noneMatch) |
| for (var i = 0; i < matches.length; i++) { |
| var match = matches[i] |
| if (match === etag || match === 'W/' + etag || 'W/' + match === etag) { |
| etagStale = false |
| break |
| } |
| } |
| |
| if (etagStale) { |
| return false |
| } |
| } |
| |
| // if-modified-since |
| if (modifiedSince) { |
| var lastModified = resHeaders['last-modified'] |
| var modifiedStale = !lastModified || !(parseHttpDate(lastModified) <= parseHttpDate(modifiedSince)) |
| |
| if (modifiedStale) { |
| return false |
| } |
| } |
| |
| return true |
| } |
| |
| /** |
| * Parse an HTTP Date into a number. |
| * |
| * @param {string} date |
| * @private |
| */ |
| |
| function parseHttpDate (date) { |
| var timestamp = date && Date.parse(date) |
| |
| // istanbul ignore next: guard against date.js Date.parse patching |
| return typeof timestamp === 'number' |
| ? timestamp |
| : NaN |
| } |
| |
| /** |
| * Parse a HTTP token list. |
| * |
| * @param {string} str |
| * @private |
| */ |
| |
| function parseTokenList (str) { |
| var end = 0 |
| var list = [] |
| var start = 0 |
| |
| // gather tokens |
| for (var i = 0, len = str.length; i < len; i++) { |
| switch (str.charCodeAt(i)) { |
| case 0x20: /* */ |
| if (start === end) { |
| start = end = i + 1 |
| } |
| break |
| case 0x2c: /* , */ |
| list.push(str.substring(start, end)) |
| start = end = i + 1 |
| break |
| default: |
| end = i + 1 |
| break |
| } |
| } |
| |
| // final token |
| list.push(str.substring(start, end)) |
| |
| return list |
| } |