New upstream version 8.1.0

fsck/source/database/Union.h

@@ -0,0 +1,130 @@
+#ifndef UNION_H_
+#define UNION_H_
+
+#include <utility>
+
+template<typename Left, typename Right, typename KeyExtract>
+class Union
+{
+   public:
+      typedef typename Left::ElementType ElementType;
+
+      struct MarkerType
+      {
+         typename Left::MarkerType leftMark;
+         typename Right::MarkerType rightMark;
+         bool leftEnded;
+         bool rightEnded;
+         bool nextStepLeft;
+      };
+
+   public:
+      Union(Left left, Right right, KeyExtract keyExtract):
+         left(left), right(right), keyExtract(keyExtract), leftEnded(false), nextStepLeft(true),
+         currentAtLeft(false)
+      {
+         this->rightEnded = !this->right.step();
+      }
+
+      bool step()
+      {
+         if(this->leftEnded && this->rightEnded)
+            return false;
+
+         if(this->leftEnded)
+         {
+            this->rightEnded = !this->right.step();
+            return resetCurrent();
+         }
+
+         if(this->rightEnded)
+         {
+            this->leftEnded = !this->left.step();
+            return resetCurrent();
+         }
+
+         if(this->nextStepLeft)
+            this->leftEnded = !this->left.step();
+         else
+            this->rightEnded = !this->right.step();
+
+         return resetCurrent();
+      }
+
+      ElementType* get()
+      {
+         if(this->currentAtLeft)
+            return this->left.get();
+         else
+            return this->right.get();
+      }
+
+      MarkerType mark() const
+      {
+         MarkerType result = { this->left.mark(), this->right.mark(), this->leftEnded,
+            this->rightEnded, this->nextStepLeft };
+         return result;
+      }
+
+      void restore(MarkerType mark)
+      {
+         this->leftEnded = mark.leftEnded;
+         this->rightEnded = mark.rightEnded;
+         this->nextStepLeft = mark.nextStepLeft;
+
+         if(!this->leftEnded)
+            this->left.restore(mark.leftMark);
+
+         if(!this->rightEnded)
+            this->right.restore(mark.rightMark);
+
+         resetCurrent();
+      }
+
+   private:
+      bool resetCurrent()
+      {
+         if(this->leftEnded && this->rightEnded)
+            return false;
+
+         if(this->leftEnded)
+            this->currentAtLeft = false;
+         else
+         if(this->rightEnded)
+            this->currentAtLeft = true;
+         else
+         if(this->keyExtract(*this->left.get() ) < this->keyExtract(*this->right.get() ) )
+         {
+            this->currentAtLeft = true;
+            this->nextStepLeft = true;
+         }
+         else
+         {
+            this->currentAtLeft = false;
+            this->nextStepLeft = false;
+         }
+
+         return true;
+      }
+
+   private:
+      Left left;
+      Right right;
+      KeyExtract keyExtract;
+      bool leftEnded;
+      bool rightEnded;
+      bool nextStepLeft;
+      bool currentAtLeft;
+};
+
+namespace db {
+
+template<typename KeyExtract, typename Left, typename Right>
+inline Union<Left, Right, KeyExtract> unionBy(KeyExtract keyExtract, Left left, Right right)
+{
+   return Union<Left, Right, KeyExtract>(left, right, keyExtract);
+}
+
+}
+
+#endif