Issue 7285 - Abstract caching logic

lib/elemHide.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-present eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
  */
 
 "use strict";
 
 /**
  * @fileOverview Element hiding implementation.
  */
 
 const {ElemHideExceptions} = require("./elemHideExceptions");
 const {filterNotifier} = require("./filterNotifier");
 const {normalizeHostname, suffixes} = require("./domain");
+const {Cache} = require("./caching");
 
 /**
  * The maximum number of selectors in a CSS rule. This is used by
  * <code>{@link createStyleSheet}</code> to split up a long list of selectors
  * into multiple rules.
  * @const {number}
  * @default
  */
 const selectorGroupSize = 1024;
 
 /**
- * The maximum number of entries to keep in
- * <code>{@link styleSheetCache}</code>.
- */
-const maxStyleSheetCacheEntries = 100;
-
-/**
  * Lookup table, active flag, by filter by domain.
  * (Only contains filters that aren't unconditionally matched for all domains.)
  * @type {Map.<string,Map.<Filter,boolean>>}
  */
 let filtersByDomain = new Map();
 
 /**
  * Lookup table, filter by selector. (Only used for selectors that are
  * unconditionally matched for all domains.)
  * @type {Map.<string,Filter>}
@@ skipping 21 matching lines @@
  * on selectors from all generic filters that are not in the
  * <code>{@link unconditionalSelectors}</code> list.
  * @type {?string}
  */
 let commonStyleSheet = null;
 
 /**
  * Cache of generated domain-specific style sheets. This contains entries for
  * only known domains. If a domain is unknown, it gets
  * <code>{@link commonStyleSheet}</code>.
- * @type {Map.<string,string>}
+ * @type {Cache.<string, string>}
  */
-let styleSheetCache = new Map();
+let styleSheetCache = new Cache(100);
 
 /**
  * Map to be used instead when a filter has a blank domains property.
  * @type {Map.<string,boolean>}
  * @const
  */
 let defaultDomains = new Map([["", true]]);
 
 /**
  * Set containing known element hiding filters
@@ skipping 127 matching lines @@
   return commonStyleSheet;
 }
 
 /**
  * Returns the domain-specific style sheet that applies on a given domain.
  * @param {string} domain
  * @returns {string}
  */
 function getDomainSpecificStyleSheet(domain)
 {
-  let styleSheet = styleSheetCache.get(domain);
+  let styleSheet = styleSheetCache.read(domain);
 
   if (typeof styleSheet == "undefined")
   {
     styleSheet = createStyleSheet(getConditionalSelectors(domain, false));
-
-    if (styleSheetCache.size >= maxStyleSheetCacheEntries)
-      styleSheetCache.clear();
-
-    styleSheetCache.set(domain, styleSheet);
+    styleSheetCache.save(domain, styleSheet);
   }
 
   return styleSheet;
 }
 
 ElemHideExceptions.on("added", ({domains, selector}) =>
 {
   styleSheetCache.clear();
   commonStyleSheet = null;
 
@@ skipping 248 matching lines @@
 {
   let styleSheet = "";
 
   for (let selectorGroup of splitSelectors(selectors))
     styleSheet += createRule(selectorGroup);
 
   return styleSheet;
 }
 
 exports.createStyleSheet = createStyleSheet;