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FlagIncludedChunksPlugin.js
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Thu, Feb 13, 18:54

FlagIncludedChunksPlugin.js
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/*
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;

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