Issue 7285 - Abstract caching logic

lib/elemHide.js

Index: lib/elemHide.js
===================================================================
--- a/lib/elemHide.js
+++ b/lib/elemHide.js
@@ -19,33 +19,28 @@
 
 /**
  * @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
@@ -77,19 +72,19 @@
  * @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]]);
 
@@ -232,20 +227,16 @@
  */
 function getDomainSpecificStyleSheet(domain)
 {
   let styleSheet = styleSheetCache.get(domain);
 
   if (typeof styleSheet == "undefined")
   {
     styleSheet = createStyleSheet(getConditionalSelectors(domain, false));
-
-    if (styleSheetCache.size >= maxStyleSheetCacheEntries)
-      styleSheetCache.clear();
-
     styleSheetCache.set(domain, styleSheet);
   }
 
   return styleSheet;
 }
 
 ElemHideExceptions.on("added", ({domains, selector}) =>
 {