webpack/lib/util/source.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";

/** @typedef {import("webpack-sources").Source} Source */
/** @typedef {import("./Hash")} Hash */

/** @type {WeakMap<Source, WeakMap<Source, boolean>>} */
const equalityCache = new WeakMap();

/**
 * Checks whether source equal true, when both sources are equal.
 * @param {Source} a a source
 * @param {Source} b another source
 * @returns {boolean} true, when both sources are equal
 */
const _isSourceEqual = (a, b) => {
	// prefer .buffer(), it's called anyway during emit
	/** @type {Buffer | string} */
	let aSource = typeof a.buffer === "function" ? a.buffer() : a.source();
	/** @type {Buffer | string} */
	let bSource = typeof b.buffer === "function" ? b.buffer() : b.source();
	if (aSource === bSource) return true;
	if (typeof aSource === "string" && typeof bSource === "string") return false;
	if (!Buffer.isBuffer(aSource)) aSource = Buffer.from(aSource, "utf8");
	if (!Buffer.isBuffer(bSource)) bSource = Buffer.from(bSource, "utf8");
	return aSource.equals(bSource);
};

/**
 * Checks whether this object is source equal.
 * @param {Source} a a source
 * @param {Source} b another source
 * @returns {boolean} true, when both sources are equal
 */
const isSourceEqual = (a, b) => {
	if (a === b) return true;
	const cache1 = equalityCache.get(a);
	if (cache1 !== undefined) {
		const result = cache1.get(b);
		if (result !== undefined) return result;
	}
	const result = _isSourceEqual(a, b);
	if (cache1 !== undefined) {
		cache1.set(b, result);
	} else {
		const map = new WeakMap();
		map.set(b, result);
		equalityCache.set(a, map);
	}
	const cache2 = equalityCache.get(b);
	if (cache2 !== undefined) {
		cache2.set(a, result);
	} else {
		const map = new WeakMap();
		map.set(a, result);
		equalityCache.set(b, map);
	}
	return result;
};

// TODO remove in webpack 6, this is protection against authors who directly use `webpack-sources` outdated version
/**
 * Feeds the Source's content into a Hash without forcing a single
 * concatenated Buffer. Uses webpack-sources >= 3.4.0 `buffers()` when
 * available so `ConcatSource` can stream its children directly.
 * @param {Hash} hash hash to update
 * @param {Source} source source whose bytes are appended
 * @returns {void}
 */
const updateHashFromSource = (hash, source) => {
	// TODO webpack 6: drop the `buffers` check, require webpack-sources >= 3.4
	// and call `source.buffers()` unconditionally.
	if (typeof source.buffers === "function") {
		for (const buf of source.buffers()) hash.update(buf);
	} else {
		hash.update(source.buffer());
	}
};

module.exports.isSourceEqual = isSourceEqual;
module.exports.updateHashFromSource = updateHashFromSource;