New upstream version 8.1.0

fsck/source/database/Distinct.h

@@ -0,0 +1,88 @@
+#ifndef DISTINCT_H_
+#define DISTINCT_H_
+
+#include <boost/type_traits/decay.hpp>
+#include <boost/utility/result_of.hpp>
+
+template<typename Source, typename KeyExtract>
+class Distinct
+{
+   private:
+      typedef typename boost::decay<
+            typename boost::result_of<KeyExtract(typename Source::ElementType&)>::type
+         >::type KeyType;
+
+   public:
+      typedef typename Source::ElementType ElementType;
+      typedef typename Source::MarkerType MarkerType;
+
+   public:
+      Distinct(Source source, KeyExtract keyExtract)
+         : source(source), keyExtract(keyExtract), hasKey(false)
+      {}
+
+      bool step()
+      {
+         if(!this->source.step() )
+            return false;
+
+         while(this->hasKey && this->key == this->keyExtract(*this->source.get() ) )
+         {
+            if(!this->source.step() )
+               return false;
+         }
+
+         this->hasKey = true;
+         this->key = this->keyExtract(*this->source.get() );
+         return true;
+      }
+
+      ElementType* get()
+      {
+         return this->source.get();
+      }
+
+      MarkerType mark() const
+      {
+         return this->source.mark();
+      }
+
+      void restore(MarkerType mark)
+      {
+         this->source.restore(mark);
+         this->hasKey = true;
+         this->key = this->keyExtract(*this->source.get() );
+      }
+
+   private:
+      Source source;
+      KeyType key;
+      KeyExtract keyExtract;
+      bool hasKey;
+};
+
+
+namespace db {
+
+template<typename KeyExtract>
+struct DistinctOp
+{
+   KeyExtract keyExtract;
+
+   template<typename Source>
+   friend Distinct<Source, KeyExtract> operator|(Source source, const DistinctOp& op)
+   {
+      return Distinct<Source, KeyExtract>(source, op.keyExtract);
+   }
+};
+
+template<typename KeyExtract>
+inline DistinctOp<KeyExtract> distinctBy(KeyExtract keyExtract)
+{
+   DistinctOp<KeyExtract> result = {keyExtract};
+   return result;
+}
+
+}
+
+#endif