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81 lines
2.1 KiB
81 lines
2.1 KiB
/* |
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MIT License http://www.opensource.org/licenses/mit-license.php |
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Author Tobias Koppers @sokra |
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*/ |
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"use strict"; |
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const createHash = require("../util/createHash"); |
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/** @typedef {import("../util/Hash")} Hash */ |
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/** @typedef {typeof import("../util/Hash")} HashConstructor */ |
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/** |
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* @typedef {Object} HashableObject |
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* @property {function(Hash): void} updateHash |
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*/ |
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class LazyHashedEtag { |
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/** |
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* @param {HashableObject} obj object with updateHash method |
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* @param {string | HashConstructor} hashFunction the hash function to use |
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*/ |
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constructor(obj, hashFunction = "md4") { |
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this._obj = obj; |
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this._hash = undefined; |
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this._hashFunction = hashFunction; |
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} |
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/** |
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* @returns {string} hash of object |
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*/ |
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toString() { |
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if (this._hash === undefined) { |
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const hash = createHash(this._hashFunction); |
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this._obj.updateHash(hash); |
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this._hash = /** @type {string} */ (hash.digest("base64")); |
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} |
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return this._hash; |
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} |
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} |
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/** @type {Map<string | HashConstructor, WeakMap<HashableObject, LazyHashedEtag>>} */ |
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const mapStrings = new Map(); |
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/** @type {WeakMap<HashConstructor, WeakMap<HashableObject, LazyHashedEtag>>} */ |
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const mapObjects = new WeakMap(); |
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/** |
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* @param {HashableObject} obj object with updateHash method |
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* @param {string | HashConstructor} hashFunction the hash function to use |
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* @returns {LazyHashedEtag} etag |
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*/ |
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const getter = (obj, hashFunction = "md4") => { |
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let innerMap; |
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if (typeof hashFunction === "string") { |
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innerMap = mapStrings.get(hashFunction); |
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if (innerMap === undefined) { |
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const newHash = new LazyHashedEtag(obj, hashFunction); |
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innerMap = new WeakMap(); |
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innerMap.set(obj, newHash); |
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mapStrings.set(hashFunction, innerMap); |
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return newHash; |
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} |
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} else { |
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innerMap = mapObjects.get(hashFunction); |
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if (innerMap === undefined) { |
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const newHash = new LazyHashedEtag(obj, hashFunction); |
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innerMap = new WeakMap(); |
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innerMap.set(obj, newHash); |
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mapObjects.set(hashFunction, innerMap); |
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return newHash; |
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} |
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} |
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const hash = innerMap.get(obj); |
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if (hash !== undefined) return hash; |
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const newHash = new LazyHashedEtag(obj, hashFunction); |
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innerMap.set(obj, newHash); |
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return newHash; |
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}; |
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module.exports = getter;
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