Issue 984 - port referrer mapping from Android

src/ReferrerMapping.cpp

Index: src/ReferrerMapping.cpp
===================================================================
new file mode 100644
--- /dev/null
+++ b/src/ReferrerMapping.cpp
@@ -0,0 +1,60 @@
+/*
+ * 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)
+{
+  if (mapping.find(url) != mapping.end())
+    cachedUrls.remove(url);
+  cachedUrls.push_back(url);
+  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& currentUrl = currentEntry->second;
+    referrerChain.insert(referrerChain.begin(), currentUrl);
+    currentEntry = mapping.find(currentUrl);
+  }
+  return referrerChain;
+}