New upstream version 8.1.0

fsck/source/database/Group.h

@@ -0,0 +1,131 @@
+#ifndef GROUP_H_
+#define GROUP_H_
+
+#include <boost/utility/result_of.hpp>
+
+#include <utility>
+
+/*
+ * requires Ops : struct {
+ *    typedef <key-type> KeyType;
+ *    typedef <proj-type> ProjType;
+ *    typedef <group-type> GroupType;
+ *
+ *    KeyType key(Source::ElementType&);
+ *    ProjType project(Source::ElementType&);
+ *    void step(Source::ElementType&);
+ *
+ *    GroupType finish();
+ * }
+ *
+ * yields sequence (Source::ElementType, <row-type>)
+ */
+template<typename Source, typename Ops>
+class Group
+{
+   private:
+      typedef typename Ops::KeyType KeyType;
+      typedef typename Ops::ProjType ProjType;
+      typedef typename Ops::GroupType GroupType;
+
+   public:
+      typedef std::pair<ProjType, GroupType> ElementType;
+      typedef typename Source::MarkerType MarkerType;
+
+   public:
+      Group(Source source, Ops ops)
+         : source(source), ops(ops), sourceIsActive(false)
+      {
+      }
+
+      bool step()
+      {
+         if(!this->sourceIsActive && !this->source.step() )
+            return false;
+
+         groupCurrentSet();
+         return true;
+      }
+
+      ElementType* get()
+      {
+         return &current;
+      }
+
+      MarkerType mark() const
+      {
+          return this->currentMark;
+      }
+
+      void restore(MarkerType mark)
+      {
+         this->source.restore(mark);
+         groupCurrentSet();
+      }
+
+   private:
+      void groupCurrentSet()
+      {
+         typename Source::ElementType* row = this->source.get();
+
+         this->currentMark = this->source.mark();
+         this->current.first = this->ops.project(*row);
+         this->ops.step(*row);
+
+         KeyType currentKey = this->ops.key(*row);
+
+         while(true)
+         {
+            if(!this->source.step() )
+            {
+               this->sourceIsActive = false;
+               break;
+            }
+
+            row = this->source.get();
+
+            if(!(currentKey == this->ops.key(*row) ) )
+            {
+               this->sourceIsActive = true;
+               break;
+            }
+
+            this->ops.step(*row);
+         }
+
+         this->current.second = this->ops.finish();
+      }
+
+   private:
+      Source source;
+      Ops ops;
+      ElementType current;
+      typename Source::MarkerType currentMark;
+      bool sourceIsActive;
+};
+
+
+namespace db {
+
+template<typename Ops>
+struct GroupOp
+{
+   Ops ops;
+
+   template<typename Source>
+   friend Group<Source, Ops> operator|(Source source, const GroupOp& fn)
+   {
+      return Group<Source, Ops>(source, fn.ops);
+   }
+};
+
+template<typename Ops>
+inline GroupOp<Ops> groupBy(Ops ops)
+{
+   GroupOp<Ops> result = {ops};
+   return result;
+}
+
+}
+
+#endif