Issue 7250 - Optimize third-party request check

lib/domain.js

Index: lib/domain.js
===================================================================
--- a/lib/domain.js
+++ b/lib/domain.js
@@ -14,16 +14,39 @@
  * 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");
 
+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.

+
+function buildPublicSuffixMap()
+{
+  let map = new Map();
+
+  for (let key in publicSuffixes)
+    map.set(key, publicSuffixes[key]);
+
+  return map;
+}
+
+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);
+  }
+}
+
 /**
  * Checks whether the given hostname is a domain.
  *
  * @param {string} hostname
  * @returns {boolean}
  */
 function isDomain(hostname)
 {
@@ -39,48 +62,60 @@
 /**
  * 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 bits = hostname.split(".");
-  let cutoff = bits.length - 2;
+  let slices = [];
+  let cutoff = null;
 
-  for (let i = 0; i < bits.length; i++)
+  for (let suffix of suffixes(hostname))
   {
-    let offset = publicSuffixes[bits.slice(i).join(".")];
+    slices.push(suffix);
+
+    let offset = publicSuffixMap.get(suffix);
 
     if (typeof offset != "undefined")
     {
-      cutoff = i - offset;
+      cutoff = slices.length - 1 - offset;
       break;
     }
   }
 
+  if (cutoff == null)
+    return slices.length > 2 ? slices[slices.length - 2] : hostname;
+
   if (cutoff <= 0)
     return hostname;
 
-  return bits.slice(cutoff).join(".");
+  return slices[cutoff];
 }
 
+exports.getDomain = getDomain;
+
 /**
  * Checks whether a request's origin is different from its document's origin.
  *
  * @param {URL} url The request URL.
  * @param {string} documentHostname The IDNA-encoded hostname of the document.
  *
  * @returns {boolean}
  */
 function isThirdParty(url, documentHostname)
 {
-  let requestHostname = url.hostname.replace(/\.+$/, "");
-  documentHostname = documentHostname.replace(/\.+$/, "");
+  let requestHostname = url.hostname;
+
+  if (requestHostname[requestHostname.length - 1] == ".")
+    requestHostname = requestHostname.replace(/\.+$/, "");
+
+  if (documentHostname[documentHostname.length - 1] == ".")
+    documentHostname = documentHostname.replace(/\.+$/, "");
 
   if (requestHostname == documentHostname)
     return false;
 
   if (!isDomain(requestHostname) || !isDomain(documentHostname))
     return true;
 
   return getDomain(requestHostname) != getDomain(documentHostname);