source: trip-planner-front/node_modules/webpack/lib/optimize/FlagIncludedChunksPlugin.js

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

"use strict";

/** @typedef {import("../Chunk")} Chunk */
/** @typedef {import("../Compiler")} Compiler */
/** @typedef {import("../Module")} Module */

class FlagIncludedChunksPlugin {
        /**
         * Apply the plugin
         * @param {Compiler} compiler the compiler instance
         * @returns {void}
         */
        apply(compiler) {
                compiler.hooks.compilation.tap("FlagIncludedChunksPlugin", compilation => {
                        compilation.hooks.optimizeChunkIds.tap(
                                "FlagIncludedChunksPlugin",
                                chunks => {
                                        const chunkGraph = compilation.chunkGraph;

                                        // prepare two bit integers for each module
                                        // 2^31 is the max number represented as SMI in v8
                                        // we want the bits distributed this way:
                                        // the bit 2^31 is pretty rar and only one module should get it
                                        // so it has a probability of 1 / modulesCount
                                        // the first bit (2^0) is the easiest and every module could get it
                                        // if it doesn't get a better bit
                                        // from bit 2^n to 2^(n+1) there is a probability of p
                                        // so 1 / modulesCount == p^31
                                        // <=> p = sqrt31(1 / modulesCount)
                                        // so we use a modulo of 1 / sqrt31(1 / modulesCount)
                                        /** @type {WeakMap<Module, number>} */
                                        const moduleBits = new WeakMap();
                                        const modulesCount = compilation.modules.size;

                                        // precalculate the modulo values for each bit
                                        const modulo = 1 / Math.pow(1 / modulesCount, 1 / 31);
                                        const modulos = Array.from(
                                                { length: 31 },
                                                (x, i) => Math.pow(modulo, i) | 0
                                        );

                                        // iterate all modules to generate bit values
                                        let i = 0;
                                        for (const module of compilation.modules) {
                                                let bit = 30;
                                                while (i % modulos[bit] !== 0) {
                                                        bit--;
                                                }
                                                moduleBits.set(module, 1 << bit);
                                                i++;
                                        }

                                        // iterate all chunks to generate bitmaps
                                        /** @type {WeakMap<Chunk, number>} */
                                        const chunkModulesHash = new WeakMap();
                                        for (const chunk of chunks) {
                                                let hash = 0;
                                                for (const module of chunkGraph.getChunkModulesIterable(chunk)) {
                                                        hash |= moduleBits.get(module);
                                                }
                                                chunkModulesHash.set(chunk, hash);
                                        }

                                        for (const chunkA of chunks) {
                                                const chunkAHash = chunkModulesHash.get(chunkA);
                                                const chunkAModulesCount =
                                                        chunkGraph.getNumberOfChunkModules(chunkA);
                                                if (chunkAModulesCount === 0) continue;
                                                let bestModule = undefined;
                                                for (const module of chunkGraph.getChunkModulesIterable(chunkA)) {
                                                        if (
                                                                bestModule === undefined ||
                                                                chunkGraph.getNumberOfModuleChunks(bestModule) >
                                                                        chunkGraph.getNumberOfModuleChunks(module)
                                                        )
                                                                bestModule = module;
                                                }
                                                loopB: for (const chunkB of chunkGraph.getModuleChunksIterable(
                                                        bestModule
                                                )) {
                                                        // as we iterate the same iterables twice
                                                        // skip if we find ourselves
                                                        if (chunkA === chunkB) continue;

                                                        const chunkBModulesCount =
                                                                chunkGraph.getNumberOfChunkModules(chunkB);

                                                        // ids for empty chunks are not included
                                                        if (chunkBModulesCount === 0) continue;

                                                        // instead of swapping A and B just bail
                                                        // as we loop twice the current A will be B and B then A
                                                        if (chunkAModulesCount > chunkBModulesCount) continue;

                                                        // is chunkA in chunkB?

                                                        // we do a cheap check for the hash value
                                                        const chunkBHash = chunkModulesHash.get(chunkB);
                                                        if ((chunkBHash & chunkAHash) !== chunkAHash) continue;

                                                        // compare all modules
                                                        for (const m of chunkGraph.getChunkModulesIterable(chunkA)) {
                                                                if (!chunkGraph.isModuleInChunk(m, chunkB)) continue loopB;
                                                        }
                                                        chunkB.ids.push(chunkA.id);
                                                }
                                        }
                                }
                        );
                });
        }
}
module.exports = FlagIncludedChunksPlugin;