Issue 7250 - Optimize third-party request check

lib/domain.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";
 
 const publicSuffixes = require("../data/publicSuffixList.json");
 
+/**
+ * Map of public suffixes to their offsets.
+ * @type {Map.<string,number>}
+ */
 let publicSuffixMap = buildPublicSuffixMap();

[Manish Jethani, 2019/01/31 10:14:15]

Maps are faster for dynamic lookups (where the property name is not known) and
also safer in such cases.

 
+/**
+ * Builds a map of public suffixes to their offsets.
+ * @returns {Map.<string,number>}
+ */
 function buildPublicSuffixMap()
 {
   let map = new Map();
 
   for (let key in publicSuffixes)
     map.set(key, publicSuffixes[key]);
 
   return map;
 }
 
+/**
+ * Yields all suffixes for a domain. For example, given the domain
+ * <code>www.example.com</code>, this function yields
+ * <code>www.example.com</code>, <code>example.com</code>, and
+ * <code>com</code>, in that order.
+ *
+ * @param {string} domain The domain.
+ * @yields {string} The next suffix for the domain.
+ */
 function* suffixes(domain)

[Manish Jethani, 2019/01/31 10:14:15]

We will reuse this function in other places (e.g. isActiveOnDomain).

 {
   while (domain != "")
   {
     yield domain;
 
     let dotIndex = domain.indexOf(".");
     domain = dotIndex == -1 ? "" : domain.substr(dotIndex + 1);
   }
 }
 
@@ skipping 13 matching lines @@
   // just check whether there are any colons to exclude IPv6 addresses.
   return hostname.indexOf(":") == -1;
 }
 
 /**
  * Gets the base domain for the given hostname.
  *
  * @param {string} hostname
  * @returns {string}
  */
 function getDomain(hostname)

[Manish Jethani, 2019/01/31 10:14:15]

At least twice as fast as the previous implementation.

 {
   let slices = [];
-  let cutoff = null;
+  let cutoff = NaN;
 
   for (let suffix of suffixes(hostname))
   {
     slices.push(suffix);
 
     let offset = publicSuffixMap.get(suffix);
 
     if (typeof offset != "undefined")
     {
       cutoff = slices.length - 1 - offset;
       break;
     }
   }
 
-  if (cutoff == null)
+  if (isNaN(cutoff))
     return slices.length > 2 ? slices[slices.length - 2] : hostname;
 
   if (cutoff <= 0)
     return hostname;
 
   return slices[cutoff];
 }
 
 exports.getDomain = getDomain;
 
@@ skipping 18 matching lines @@
   if (requestHostname == documentHostname)
     return false;
 
   if (!isDomain(requestHostname) || !isDomain(documentHostname))
     return true;
 
   return getDomain(requestHostname) != getDomain(documentHostname);
 }
 
 exports.isThirdParty = isThirdParty;