/*
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MIT License http://www.opensource.org/licenses/mit-license.php
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Author Tobias Koppers @sokra
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*/
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"use strict";
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class FlagIncludedChunksPlugin {
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apply(compiler) {
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compiler.hooks.compilation.tap("FlagIncludedChunksPlugin", compilation => {
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compilation.hooks.optimizeChunkIds.tap(
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"FlagIncludedChunksPlugin",
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chunks => {
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// prepare two bit integers for each module
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// 2^31 is the max number represented as SMI in v8
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// we want the bits distributed this way:
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// the bit 2^31 is pretty rar and only one module should get it
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// so it has a probability of 1 / modulesCount
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// the first bit (2^0) is the easiest and every module could get it
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// if it doesn't get a better bit
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// from bit 2^n to 2^(n+1) there is a probability of p
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// so 1 / modulesCount == p^31
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// <=> p = sqrt31(1 / modulesCount)
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// so we use a modulo of 1 / sqrt31(1 / modulesCount)
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const moduleBits = new WeakMap();
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const modulesCount = compilation.modules.length;
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// precalculate the modulo values for each bit
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const modulo = 1 / Math.pow(1 / modulesCount, 1 / 31);
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const modulos = Array.from(
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{ length: 31 },
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(x, i) => Math.pow(modulo, i) | 0
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);
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// iterate all modules to generate bit values
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let i = 0;
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for (const module of compilation.modules) {
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let bit = 30;
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while (i % modulos[bit] !== 0) {
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bit--;
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}
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moduleBits.set(module, 1 << bit);
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i++;
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}
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// interate all chunks to generate bitmaps
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const chunkModulesHash = new WeakMap();
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for (const chunk of chunks) {
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let hash = 0;
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for (const module of chunk.modulesIterable) {
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hash |= moduleBits.get(module);
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}
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chunkModulesHash.set(chunk, hash);
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}
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for (const chunkA of chunks) {
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const chunkAHash = chunkModulesHash.get(chunkA);
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const chunkAModulesCount = chunkA.getNumberOfModules();
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if (chunkAModulesCount === 0) continue;
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let bestModule = undefined;
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for (const module of chunkA.modulesIterable) {
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if (
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bestModule === undefined ||
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bestModule.getNumberOfChunks() > module.getNumberOfChunks()
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)
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bestModule = module;
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}
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loopB: for (const chunkB of bestModule.chunksIterable) {
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// as we iterate the same iterables twice
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// skip if we find ourselves
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if (chunkA === chunkB) continue;
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const chunkBModulesCount = chunkB.getNumberOfModules();
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// ids for empty chunks are not included
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if (chunkBModulesCount === 0) continue;
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// instead of swapping A and B just bail
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// as we loop twice the current A will be B and B then A
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if (chunkAModulesCount > chunkBModulesCount) continue;
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// is chunkA in chunkB?
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// we do a cheap check for the hash value
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const chunkBHash = chunkModulesHash.get(chunkB);
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if ((chunkBHash & chunkAHash) !== chunkAHash) continue;
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// compare all modules
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for (const m of chunkA.modulesIterable) {
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if (!chunkB.containsModule(m)) continue loopB;
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}
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chunkB.ids.push(chunkA.id);
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}
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}
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}
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);
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});
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}
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}
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module.exports = FlagIncludedChunksPlugin;
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