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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.

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

"use strict";

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

/** @typedef {import("webpack-sources").Source} Source */
/** @typedef {import("../Cache").Etag} Etag */
/** @typedef {import("../Compiler")} Compiler */
/** @typedef {import("../Module")} Module */

class MemoryWithGcCachePlugin {
	/**
	 * @param {object} options Options
	 * @param {number} options.maxGenerations max generations
	 */
	constructor({ maxGenerations }) {
		this._maxGenerations = maxGenerations;
	}
	/**
	 * Apply the plugin
	 * @param {Compiler} compiler the compiler instance
	 * @returns {void}
	 */
	apply(compiler) {
		const maxGenerations = this._maxGenerations;
		/** @type {Map} */
		const cache = new Map();
		/** @type {Map} */
		const oldCache = new Map();
		let generation = 0;
		let cachePosition = 0;
		const logger = compiler.getInfrastructureLogger("MemoryWithGcCachePlugin");
		compiler.hooks.afterDone.tap("MemoryWithGcCachePlugin", () => {
			generation++;
			let clearedEntries = 0;
			let lastClearedIdentifier;
			// Avoid coverage problems due indirect changes
			/* istanbul ignore next */
			for (const [identifier, entry] of oldCache) {
				if (entry.until > generation) break;

				oldCache.delete(identifier);
				if (cache.get(identifier) === undefined) {
					cache.delete(identifier);
					clearedEntries++;
					lastClearedIdentifier = identifier;
				}
			}
			if (clearedEntries > 0 || oldCache.size > 0) {
				logger.log(
					`${cache.size - oldCache.size} active entries, ${
						oldCache.size
					} recently unused cached entries${
						clearedEntries > 0
							? `, ${clearedEntries} old unused cache entries removed e. g. ${lastClearedIdentifier}`
							: ""
					}`
				);
			}
			let i = (cache.size / maxGenerations) | 0;
			let j = cachePosition >= cache.size ? 0 : cachePosition;
			cachePosition = j + i;
			for (const [identifier, entry] of cache) {
				if (j !== 0) {
					j--;
					continue;
				}
				if (entry !== undefined) {
					// We don't delete the cache entry, but set it to undefined instead
					// This reserves the location in the data table and avoids rehashing
					// when constantly adding and removing entries.
					// It will be deleted when removed from oldCache.
					cache.set(identifier, undefined);
					oldCache.delete(identifier);
					oldCache.set(identifier, {
						entry,
						until: generation + maxGenerations
					});
					if (i-- === 0) break;
				}
			}
		});
		compiler.cache.hooks.store.tap(
			{ name: "MemoryWithGcCachePlugin", stage: Cache.STAGE_MEMORY },
			(identifier, etag, data) => {
				cache.set(identifier, { etag, data });
			}
		);
		compiler.cache.hooks.get.tap(
			{ name: "MemoryWithGcCachePlugin", stage: Cache.STAGE_MEMORY },
			(identifier, etag, gotHandlers) => {
				const cacheEntry = cache.get(identifier);
				if (cacheEntry === null) {
					return null;
				} else if (cacheEntry !== undefined) {
					return cacheEntry.etag === etag ? cacheEntry.data : null;
				}
				const oldCacheEntry = oldCache.get(identifier);
				if (oldCacheEntry !== undefined) {
					const cacheEntry = oldCacheEntry.entry;
					if (cacheEntry === null) {
						oldCache.delete(identifier);
						cache.set(identifier, cacheEntry);
						return null;
					} else {
						if (cacheEntry.etag !== etag) return null;
						oldCache.delete(identifier);
						cache.set(identifier, cacheEntry);
						return cacheEntry.data;
					}
				}
				gotHandlers.push((result, callback) => {
					if (result === undefined) {
						cache.set(identifier, null);
					} else {
						cache.set(identifier, { etag, data: result });
					}
					return callback();
				});
			}
		);
		compiler.cache.hooks.shutdown.tap(
			{ name: "MemoryWithGcCachePlugin", stage: Cache.STAGE_MEMORY },
			() => {
				cache.clear();
				oldCache.clear();
			}
		);
	}
}
module.exports = MemoryWithGcCachePlugin;