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