Issue 7052 - Use string-based matching for literal patterns

lib/filterClasses.js

Index: lib/filterClasses.js
===================================================================
--- a/lib/filterClasses.js
+++ b/lib/filterClasses.js
@@ -21,22 +21,42 @@
  * @fileOverview Definition of Filter class and its subclasses.
  */
 
 const {filterNotifier} = require("./filterNotifier");
 const {extend} = require("./coreUtils");
 const {filterToRegExp} = require("./common");
 
 /**
+ * Regular expression used to match the <code>||</code> prefix in an otherwise
+ * literal pattern.
+ * @type {RegExp}
+ */
+let tripleAnchorRegExp = new RegExp(filterToRegExp("|||"));
+
+/**
  * All known unique domain sources mapped to their parsed values.
  * @type {Map.<string,Map.<string,boolean>>}
  */
 let knownDomainMaps = new Map();
 
 /**
+ * Checks whether the given pattern is a string of literal characters with no
+ * wildcards or any other special characters. If the pattern is prefixed with a
+ * <code>||</code> but otherwise contains no special characters, it is still
+ * considered to be a literal pattern.
+ * @param {string} pattern
+ * @returns {boolean}
+ */
+function isLiteralPattern(pattern)
+{
+  return !/[*^|]/.test(pattern.replace(/^\|{2}/, ""));
+}
+
+/**
  * Abstract base class for filters
  *
  * @param {string} text   string representation of the filter
  * @constructor
  */
 function Filter(text)
 {
   this.text = text;
@@ -688,16 +708,19 @@
     // The filter is a regular expression - convert it immediately to
     // catch syntax errors
     let regexp = new RegExp(regexpSource.substr(1, regexpSource.length - 2),
                             this.matchCase ? "" : "i");
     Object.defineProperty(this, "regexp", {value: regexp});
   }
   else
   {
+    if (!this.matchCase && isLiteralPattern(regexpSource))

[Manish Jethani, 2018/10/17 09:05:04]

Lowercase the pattern once here if it is literal and case-insensitive.

+      regexpSource = regexpSource.toLowerCase();
+
     // No need to convert this filter to regular expression yet, do it on demand
     this.pattern = regexpSource;
   }
 }
 exports.RegExpFilter = RegExpFilter;
 
 RegExpFilter.prototype = extend(ActiveFilter, {
   /**
@@ -719,20 +742,27 @@
    */
   pattern: null,
   /**
    * Regular expression to be used when testing against this filter
    * @type {RegExp}
    */
   get regexp()
   {
-    let source = filterToRegExp(this.pattern, this.rewrite != null);
-    let regexp = new RegExp(source, this.matchCase ? "" : "i");
-    Object.defineProperty(this, "regexp", {value: regexp});
-    return regexp;
+    let value = null;
+
+    let {pattern, rewrite} = this;
+    if (rewrite != null || !isLiteralPattern(pattern))
+    {
+      value = new RegExp(filterToRegExp(pattern, rewrite != null),
+                         this.matchCase ? "" : "i");
+    }
+
+    Object.defineProperty(this, "regexp", {value});
+    return value;
   },
   /**
    * Content types the filter applies to, combination of values from
    * RegExpFilter.typeMap
    * @type {number}
    */
   contentType: 0x7FFFFFFF,
   /**
@@ -783,17 +813,49 @@
    * @param {string} [sitekey] public key provided by the document
    * @return {boolean} true in case of a match
    */
   matches(location, typeMask, docDomain, thirdParty, sitekey)
   {
     return (this.contentType & typeMask) != 0 &&
            (this.thirdParty == null || this.thirdParty == thirdParty) &&
            this.isActiveOnDomain(docDomain, sitekey) &&
-           this.regexp.test(location);
+           this.matchesLocation(location);
+  },
+
+  /**
+   * Checks whether the given URL matches this filter's pattern.
+   * @param {string} location The URL to check.
+   * @returns {boolean} <code>true</code> if the URL matches.
+   */
+  matchesLocation(location)
+  {
+    let {regexp} = this;
+
+    if (regexp)
+      return regexp.test(location);
+
+    if (!this.matchCase)
+      location = location.toLowerCase();
+
+    let {pattern} = this;
+
+    if (pattern[0] == "|" && pattern[1] == "|")
+    {
+      let index = location.indexOf(pattern.substring(2));
+
+      // The "||" prefix requires that the text that follows does not start
+      // with a forward slash. Normally this is part of the generated regular
+      // expression, but since we're faking it here with string-based matching
+      // we need to do the check ourselves.
+      return index != -1 && location[index] != "/" &&

[Manish Jethani, 2018/10/17 09:05:04]

If the index is not -1 then it's highly unlikely that it'll fail the other two
tests; this is why it makes sense to get the index first.

+             tripleAnchorRegExp.test(location.substring(0, index));
+    }
+
+    return location.includes(pattern);
   }
 });
 
 /**
  * Yields the filter itself (required to optimize {@link Matcher}).
  * @yields {RegExpFilter}
  */
 RegExpFilter.prototype[Symbol.iterator] = function*()