AK-21/Graphite-Industrial-Intelligence

1/*!2 * etag3 * Copyright(c) 2014-2016 Douglas Christopher Wilson4 * MIT Licensed5 */6 7'use strict'8 9/**10 * Module exports.11 * @public12 */13 14module.exports = etag15 16/**17 * Module dependencies.18 * @private19 */20 21var crypto = require('crypto')22var Stats = require('fs').Stats23 24/**25 * Module variables.26 * @private27 */28 29var toString = Object.prototype.toString30 31/**32 * Generate an entity tag.33 *34 * @param {Buffer|string} entity35 * @return {string}36 * @private37 */38 39function entitytag (entity) {40  if (entity.length === 0) {41    // fast-path empty42    return '"0-2jmj7l5rSw0yVb/vlWAYkK/YBwk"'43  }44 45  // compute hash of entity46  var hash = crypto47    .createHash('sha1')48    .update(entity, 'utf8')49    .digest('base64')50    .substring(0, 27)51 52  // compute length of entity53  var len = typeof entity === 'string'54    ? Buffer.byteLength(entity, 'utf8')55    : entity.length56 57  return '"' + len.toString(16) + '-' + hash + '"'58}59 60/**61 * Create a simple ETag.62 *63 * @param {string|Buffer|Stats} entity64 * @param {object} [options]65 * @param {boolean} [options.weak]66 * @return {String}67 * @public68 */69 70function etag (entity, options) {71  if (entity == null) {72    throw new TypeError('argument entity is required')73  }74 75  // support fs.Stats object76  var isStats = isstats(entity)77  var weak = options && typeof options.weak === 'boolean'78    ? options.weak79    : isStats80 81  // validate argument82  if (!isStats && typeof entity !== 'string' && !Buffer.isBuffer(entity)) {83    throw new TypeError('argument entity must be string, Buffer, or fs.Stats')84  }85 86  // generate entity tag87  var tag = isStats88    ? stattag(entity)89    : entitytag(entity)90 91  return weak92    ? 'W/' + tag93    : tag94}95 96/**97 * Determine if object is a Stats object.98 *99 * @param {object} obj100 * @return {boolean}101 * @api private102 */103 104function isstats (obj) {105  // genuine fs.Stats106  if (typeof Stats === 'function' && obj instanceof Stats) {107    return true108  }109 110  // quack quack111  return obj && typeof obj === 'object' &&112    'ctime' in obj && toString.call(obj.ctime) === '[object Date]' &&113    'mtime' in obj && toString.call(obj.mtime) === '[object Date]' &&114    'ino' in obj && typeof obj.ino === 'number' &&115    'size' in obj && typeof obj.size === 'number'116}117 118/**119 * Generate a tag for a stat.120 *121 * @param {object} stat122 * @return {string}123 * @private124 */125 126function stattag (stat) {127  var mtime = stat.mtime.getTime().toString(16)128  var size = stat.size.toString(16)129 130  return '"' + size + '-' + mtime + '"'131}132