Issue 116 - Document the libadblockplus API

include/AdblockPlus/ReferrerMapping.h

 /*
  * 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/>.
  */
 
 #ifndef ADBLOCK_PLUS_REFERRER_MAPPING_H
 #define ADBLOCK_PLUS_REFERRER_MAPPING_H
 
 #include <list>
 #include <map>
 #include <string>
 #include <vector>
 
 namespace AdblockPlus
 {
+  /**
+   * Stores a mapping between URLs and their referrers.
+   * This can be used to build a chain of referrers for any URL
+   * (see `BuildReferrerChain()`), which approximates the frame structure, see
+   * FilterEngine::Matches().
+   */
   class ReferrerMapping
   {
   public:
+    /**
+     * Constructor.
+     * @param maxCachedUrls Number of URL mappings to store. The higher the
+     *        better - clients typically cache requests, and a single cached
+     *        request will break the referrer chain.
+     */
     ReferrerMapping(const int maxCachedUrls = 5000);
+
+    /**
+     * Records the refferer for a URL.
+     * @param url Request URL.
+     * @param referrer Request referrer.
+     */
     void Add(const std::string& url, const std::string& referrer);
+
+    /**
+     * Builds a chain of referrers for the supplied URL.
+     * This should reconstruct a document's parent frame URLs.
+     * @param url URL to build the chain for.
+     * @return List of URLs, starting with `url`.
+     */
     std::vector<std::string> BuildReferrerChain(const std::string& url) const;
 
   private:
     const int maxCachedUrls;
     std::map<std::string, std::string> mapping;
     std::list<std::string> cachedUrls;
   };
 }
 
 #endif