138 lines
2.7 KiB
JavaScript
138 lines
2.7 KiB
JavaScript
/*!
|
|
* 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;
|
|
}
|