webpack/lib/util/createHash.js

Packs ECMAScript/CommonJs/AMD modules for the browser. Allows you to split your codebase into multiple bundles, which can be loaded on demand. Supports loaders to preprocess files, i.e. json, jsx, es7, css, less, ... and your custom stuff.

/*
	MIT License http://www.opensource.org/licenses/mit-license.php
	Author Tobias Koppers @sokra
*/

"use strict";

const Hash = require("./Hash");

const BULK_SIZE = 2000;

// We are using an object instead of a Map as this will stay static during the runtime
// so access to it can be optimized by v8
/** @type {{[key: string]: Map<string, string>}} */
const digestCaches = {};

/** @typedef {function(): Hash} HashFactory */

class BulkUpdateDecorator extends Hash {
	/**
	 * @param {Hash | HashFactory} hashOrFactory function to create a hash
	 * @param {string=} hashKey key for caching
	 */
	constructor(hashOrFactory, hashKey) {
		super();
		this.hashKey = hashKey;
		if (typeof hashOrFactory === "function") {
			this.hashFactory = hashOrFactory;
			this.hash = undefined;
		} else {
			this.hashFactory = undefined;
			this.hash = hashOrFactory;
		}
		this.buffer = "";
	}

	/**
	 * Update hash {@link https://nodejs.org/api/crypto.html#crypto_hash_update_data_inputencoding}
	 * @param {string|Buffer} data data
	 * @param {string=} inputEncoding data encoding
	 * @returns {this} updated hash
	 */
	update(data, inputEncoding) {
		if (
			inputEncoding !== undefined ||
			typeof data !== "string" ||
			data.length > BULK_SIZE
		) {
			if (this.hash === undefined)
				this.hash = /** @type {HashFactory} */ (this.hashFactory)();
			if (this.buffer.length > 0) {
				this.hash.update(this.buffer);
				this.buffer = "";
			}
			this.hash.update(data, inputEncoding);
		} else {
			this.buffer += data;
			if (this.buffer.length > BULK_SIZE) {
				if (this.hash === undefined)
					this.hash = /** @type {HashFactory} */ (this.hashFactory)();
				this.hash.update(this.buffer);
				this.buffer = "";
			}
		}
		return this;
	}

	/**
	 * Calculates the digest {@link https://nodejs.org/api/crypto.html#crypto_hash_digest_encoding}
	 * @param {string=} encoding encoding of the return value
	 * @returns {string|Buffer} digest
	 */
	digest(encoding) {
		let digestCache;
		const buffer = this.buffer;
		if (this.hash === undefined) {
			// short data for hash, we can use caching
			const cacheKey = `${this.hashKey}-${encoding}`;
			digestCache = digestCaches[cacheKey];
			if (digestCache === undefined) {
				digestCache = digestCaches[cacheKey] = new Map();
			}
			const cacheEntry = digestCache.get(buffer);
			if (cacheEntry !== undefined) return cacheEntry;
			this.hash = /** @type {HashFactory} */ (this.hashFactory)();
		}
		if (buffer.length > 0) {
			this.hash.update(buffer);
		}
		const digestResult = this.hash.digest(encoding);
		const result =
			typeof digestResult === "string" ? digestResult : digestResult.toString();
		if (digestCache !== undefined) {
			digestCache.set(buffer, result);
		}
		return result;
	}
}

/* istanbul ignore next */
class DebugHash extends Hash {
	constructor() {
		super();
		this.string = "";
	}

	/**
	 * Update hash {@link https://nodejs.org/api/crypto.html#crypto_hash_update_data_inputencoding}
	 * @param {string|Buffer} data data
	 * @param {string=} inputEncoding data encoding
	 * @returns {this} updated hash
	 */
	update(data, inputEncoding) {
		if (typeof data !== "string") data = data.toString("utf-8");
		const prefix = Buffer.from("@webpack-debug-digest@").toString("hex");
		if (data.startsWith(prefix)) {
			data = Buffer.from(data.slice(prefix.length), "hex").toString();
		}
		this.string += `[${data}](${
			/** @type {string} */ (new Error().stack).split("\n", 3)[2]
		})\n`;
		return this;
	}

	/**
	 * Calculates the digest {@link https://nodejs.org/api/crypto.html#crypto_hash_digest_encoding}
	 * @param {string=} encoding encoding of the return value
	 * @returns {string|Buffer} digest
	 */
	digest(encoding) {
		return Buffer.from("@webpack-debug-digest@" + this.string).toString("hex");
	}
}

/** @type {typeof import("crypto") | undefined} */
let crypto = undefined;
/** @type {typeof import("./hash/xxhash64") | undefined} */
let createXXHash64 = undefined;
/** @type {typeof import("./hash/md4") | undefined} */
let createMd4 = undefined;
/** @type {typeof import("./hash/BatchedHash") | undefined} */
let BatchedHash = undefined;

/**
 * Creates a hash by name or function
 * @param {string | typeof Hash} algorithm the algorithm name or a constructor creating a hash
 * @returns {Hash} the hash
 */
module.exports = algorithm => {
	if (typeof algorithm === "function") {
		return new BulkUpdateDecorator(() => new algorithm());
	}
	switch (algorithm) {
		// TODO add non-cryptographic algorithm here
		case "debug":
			return new DebugHash();
		case "xxhash64":
			if (createXXHash64 === undefined) {
				createXXHash64 = require("./hash/xxhash64");
				if (BatchedHash === undefined) {
					BatchedHash = require("./hash/BatchedHash");
				}
			}
			return new /** @type {typeof import("./hash/BatchedHash")} */ (
				BatchedHash
			)(createXXHash64());
		case "md4":
			if (createMd4 === undefined) {
				createMd4 = require("./hash/md4");
				if (BatchedHash === undefined) {
					BatchedHash = require("./hash/BatchedHash");
				}
			}
			return new /** @type {typeof import("./hash/BatchedHash")} */ (
				BatchedHash
			)(createMd4());
		case "native-md4":
			if (crypto === undefined) crypto = require("crypto");
			return new BulkUpdateDecorator(
				() => /** @type {typeof import("crypto")} */ (crypto).createHash("md4"),
				"md4"
			);
		default:
			if (crypto === undefined) crypto = require("crypto");
			return new BulkUpdateDecorator(
				() =>
					/** @type {typeof import("crypto")} */ (crypto).createHash(algorithm),
				algorithm
			);
	}
};