feature_impl: key/value forward iterator

include/mapnik/feature_kv_iterator.hpp

@@ -0,0 +1,75 @@
+/*****************************************************************************
+ *
+ * This file is part of Mapnik (c++ mapping toolkit)
+ *
+ * Copyright (C) 2012 Artem Pavlenko
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ *
+ *****************************************************************************/
+
+#ifndef MAPNIK_FEATURE_KV_ITERATOR_HPP
+#define MAPNIK_FEATURE_KV_ITERATOR_HPP
+
+#include <boost/tuple/tuple.hpp>
+#include <boost/iterator/iterator_facade.hpp>
+
+#include "feature.hpp"
+
+
+namespace mapnik { 
+
+class feature_kv_iterator :
+        public boost::iterator_facade<feature_kv_iterator,
+                                      boost::tuple<std::string , value> const,
+                                      boost::forward_traversal_tag>
+{
+public:
+    typedef boost::tuple<std::string,value> value_type;
+    
+    feature_kv_iterator (feature const& f, bool begin = false)
+        : f_(f),
+          itr_( begin ? f_.ctx_->begin() : f_.ctx_->end())  {}
+    
+private:
+    friend class boost::iterator_core_access;
+    
+    void increment()
+    {        
+        ++itr_;
+    }
+    
+    bool equal( feature_kv_iterator const& other) const
+    {
+        return ( itr_ == other.itr_);        
+    }
+    
+    value_type const& dereference() const
+    {
+        boost::get<0>(kv_) = itr_->first;
+        boost::get<1>(kv_) = f_.get(itr_->first);
+        return kv_;
+    }
+    
+    feature const& f_;
+    map_type::const_iterator itr_;
+    mutable value_type kv_;
+    
+};
+
+}
+
+#endif // MAPNIK_FEATURE_KV_ITERATOR_HPP
+