118 lines
3.6 KiB
JavaScript
118 lines
3.6 KiB
JavaScript
/*
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MIT License http://www.opensource.org/licenses/mit-license.php
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Author Mark Knichel @mknichel
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*/
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"use strict";
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let dualStringBufferCaching = true;
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/**
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* @returns {boolean} Whether the optimization to cache copies of both the
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* string and buffer version of source content is enabled. This is enabled by
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* default to improve performance but can consume more memory since values are
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* stored twice.
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*/
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function isDualStringBufferCachingEnabled() {
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return dualStringBufferCaching;
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}
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/**
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* Enables an optimization to save both string and buffer in memory to avoid
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* repeat conversions between the two formats when they are requested. This
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* is enabled by default. This option can improve performance but can consume
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* additional memory since values are stored twice.
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* @returns {void}
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*/
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function enableDualStringBufferCaching() {
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dualStringBufferCaching = true;
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}
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/**
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* Disables the optimization to save both string and buffer in memory. This
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* may increase performance but should reduce memory usage in the Webpack
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* compiler.
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* @returns {void}
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*/
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function disableDualStringBufferCaching() {
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dualStringBufferCaching = false;
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}
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const interningStringMap = new Map();
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let enableStringInterningRefCount = 0;
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/**
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* @returns {boolean} value
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*/
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function isStringInterningEnabled() {
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return enableStringInterningRefCount > 0;
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}
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/**
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* Starts a memory optimization to avoid repeat copies of the same string in
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* memory by caching a single reference to the string. This can reduce memory
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* usage if the same string is repeated many times in the compiler, such as
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* when Webpack layers are used with the same files.
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*
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* {@link exitStringInterningRange} should be called when string interning is
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* no longer necessary to free up the memory used by the interned strings. If
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* {@link enterStringInterningRange} has been called multiple times, then
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* this method may not immediately free all the memory until
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* {@link exitStringInterningRange} has been called to end all string
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* interning ranges.
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* @returns {void}
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*/
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function enterStringInterningRange() {
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enableStringInterningRefCount++;
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}
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/**
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* Stops the current string interning range. Once all string interning ranges
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* have been exited, this method will free all the memory used by the interned
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* strings. This method should be called once for each time that
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* {@link enterStringInterningRange} was called.
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* @returns {void}
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*/
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function exitStringInterningRange() {
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if (--enableStringInterningRefCount <= 0) {
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interningStringMap.clear();
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enableStringInterningRefCount = 0;
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}
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}
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/**
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* Saves the string in a map to ensure that only one copy of the string exists
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* in memory at a given time. This is controlled by {@link enableStringInterning}
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* and {@link disableStringInterning}. Callers are expect to manage the memory
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* of the interned strings by calling {@link disableStringInterning} after the
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* compiler no longer needs to save the interned memory.
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* @param {string} str A string to be interned.
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* @returns {string} The original string or a reference to an existing string of the same value if it has already been interned.
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*/
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function internString(str) {
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if (
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!isStringInterningEnabled() ||
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!str ||
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str.length < 128 ||
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typeof str !== "string"
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) {
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return str;
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}
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let internedString = interningStringMap.get(str);
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if (internedString === undefined) {
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internedString = str;
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interningStringMap.set(str, internedString);
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}
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return internedString;
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}
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module.exports = {
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disableDualStringBufferCaching,
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enableDualStringBufferCaching,
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internString,
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isDualStringBufferCachingEnabled,
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enterStringInterningRange,
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exitStringInterningRange,
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};
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