Issue 984 - port referrer mapping from Android

src/ReferrerMapping.cpp

 /*
  * This file is part of Adblock Plus <http://adblockplus.org/>,
  * Copyright (C) 2006-2014 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/>.
  */
 
 #include <AdblockPlus/ReferrerMapping.h>
 
 using namespace AdblockPlus;
 
 ReferrerMapping::ReferrerMapping(const int maxCachedUrls)
   : maxCachedUrls(maxCachedUrls)
 {
 }
 
 void ReferrerMapping::Add(const std::string& url, const std::string& referrer)
 {
-  mapping[url] = referrer;
-  if (std::find(cachedUrls.begin(), cachedUrls.end(), url) != cachedUrls.end())
+  if (mapping.find(url) != mapping.end())
     cachedUrls.remove(url);
   cachedUrls.push_back(url);
-  while (cachedUrls.size() > maxCachedUrls)
+  mapping[url] = referrer;
+
+  const int urlsToPop = cachedUrls.size() - maxCachedUrls;
+  for (int i = 0; i < urlsToPop; i++)
   {
     const std::string poppedUrl = cachedUrls.front();
     cachedUrls.pop_front();
     mapping.erase(poppedUrl);
   }
 }
 
 std::vector<std::string> ReferrerMapping::BuildReferrerChain(
   const std::string& url) const
 {
   std::vector<std::string> referrerChain;
   referrerChain.push_back(url);
   // We need to limit the chain length to ensure we don't block indefinitely
   // if there's a referrer loop.
   const int maxChainLength = 10;
   std::map<std::string, std::string>::const_iterator currentEntry =
     mapping.find(url);
   for (int i = 0; i < maxChainLength && currentEntry != mapping.end(); i++)
   {
-    const std::string url = currentEntry->second;

[René Jeschke, 2014/07/16 08:57:07]

Shouldn't this 
1) be a reference here?
2) be renamed as it's shadowing the method argument 'url'?

[Felix Dahlke, 2014/07/16 09:05:22]

Done.

-    referrerChain.insert(referrerChain.begin(), url);
-    currentEntry = mapping.find(url);
+    const std::string& currentUrl = currentEntry->second;
+    referrerChain.insert(referrerChain.begin(), currentUrl);
+    currentEntry = mapping.find(currentUrl);
   }
   return referrerChain;
 }