Patchwork [Ada] Test for common parent before testing for sibling

login
register
mail settings
Submitter Arnaud Charlet
Date Aug. 29, 2011, 10:02 a.m.
Message ID <20110829100224.GA19600@adacore.com>
Download mbox | patch
Permalink /patch/112006/
State New
Headers show

Comments

Arnaud Charlet - Aug. 29, 2011, 10:02 a.m.
Splice_Subtree specifies a position in the target container to which the source
subtree should be moved. The target position is a 2-tuple comprising the new
parent of the subtree and its new (next) sibling (parameter Before).

Before attempting to move the subtree, the implementation must perform two
tests. If the Subtree node is the same as the Before node, then the operation
does nothing. If the Subtree node's next sibling is the same as Before, then
there is nothing else to do. If neither of these conditions hold, then the
subtree is moved from the source to the target.

However, these tests are only appropriate if the Subtree node and the Before
node have the same parent. The bug was that the sibling tests were performed
without also testing the parent. The fix is to test the sibling only after also
testing the parent.

There is one additional change for the bounded from of the tree
container. Instead of moving the subtree (which does not make sense for a
bounded form), that container first copies the subtree from the source to the
target, and then deletes the subtree from the source. There was a bug in which
only the children of the source subtree were deleted from the source (the root
node of the subtree was not deleted). The fix is to remove all of the subtree
node and its children from the source tree.

Tested on x86_64-pc-linux-gnu, committed on trunk

2011-08-29  Matthew Heaney  <heaney@adacore.com>

	* a-comutr.adb, a-cimutr.adb, a-cbmutr.adb (Splice_Subtree): Only check
	for sibling when common parent.

Patch

Index: a-cimutr.adb
===================================================================
--- a-cimutr.adb	(revision 178159)
+++ a-cimutr.adb	(working copy)
@@ -2101,10 +2101,14 @@ 
       end if;
 
       if Target'Address = Source'Address then
-         if Position.Node = Before.Node
-           or else Position.Node.Next = Before.Node
-         then
-            return;
+         if Position.Node.Parent = Parent.Node then
+            if Position.Node = Before.Node then
+               return;
+            end if;
+
+            if Position.Node.Next = Before.Node then
+               return;
+            end if;
          end if;
 
          if Target.Busy > 0 then
@@ -2199,10 +2203,14 @@ 
          raise Constraint_Error with "Position cursor designates root";
       end if;
 
-      if Position.Node = Before.Node
-        or else Position.Node.Next = Before.Node
-      then
-         return;
+      if Position.Node.Parent = Parent.Node then
+         if Position.Node = Before.Node then
+            return;
+         end if;
+
+         if Position.Node.Next = Before.Node then
+            return;
+         end if;
       end if;
 
       if Container.Busy > 0 then
Index: a-comutr.adb
===================================================================
--- a-comutr.adb	(revision 178159)
+++ a-comutr.adb	(working copy)
@@ -2147,10 +2147,14 @@ 
       end if;
 
       if Target'Address = Source'Address then
-         if Position.Node = Before.Node
-           or else Position.Node.Next = Before.Node
-         then
-            return;
+         if Position.Node.Parent = Parent.Node then
+            if Position.Node = Before.Node then
+               return;
+            end if;
+
+            if Position.Node.Next = Before.Node then
+               return;
+            end if;
          end if;
 
          if Target.Busy > 0 then
@@ -2245,10 +2249,14 @@ 
          raise Constraint_Error with "Position cursor designates root";
       end if;
 
-      if Position.Node = Before.Node
-        or else Position.Node.Next = Before.Node
-      then
-         return;
+      if Position.Node.Parent = Parent.Node then
+         if Position.Node = Before.Node then
+            return;
+         end if;
+
+         if Position.Node.Next = Before.Node then
+            return;
+         end if;
       end if;
 
       if Container.Busy > 0 then
Index: a-cbmutr.adb
===================================================================
--- a-cbmutr.adb	(revision 178159)
+++ a-cbmutr.adb	(working copy)
@@ -2676,13 +2676,18 @@ 
       end if;
 
       if Target'Address = Source'Address then
-         if Before = No_Element then
-            if Target.Nodes (Position.Node).Next <= 0 then  -- last child
+         if Target.Nodes (Position.Node).Parent = Parent.Node then
+            if Before = No_Element then
+               if Target.Nodes (Position.Node).Next <= 0 then  -- last child
+                  return;
+               end if;
+
+            elsif Position.Node = Before.Node then
                return;
+
+            elsif Target.Nodes (Position.Node).Next = Before.Node then
+               return;
             end if;
-
-         elsif Position.Node = Before.Node then
-            return;
          end if;
 
          if Target.Busy > 0 then
@@ -2769,13 +2774,18 @@ 
          raise Constraint_Error with "Position cursor designates root";
       end if;
 
-      if Before = No_Element then
-         if Container.Nodes (Position.Node).Next <= 0 then  -- last child
+      if Container.Nodes (Position.Node).Parent = Parent.Node then
+         if Before = No_Element then
+            if Container.Nodes (Position.Node).Next <= 0 then  -- last child
+               return;
+            end if;
+
+         elsif Position.Node = Before.Node then
             return;
+
+         elsif Container.Nodes (Position.Node).Next = Before.Node then
+            return;
          end if;
-
-      elsif Position.Node = Before.Node then
-         return;
       end if;
 
       if Container.Busy > 0 then
@@ -2809,6 +2819,11 @@ 
       Target_Count   : Count_Type;
 
    begin
+      --  This is a utility operation to do the heavy lifting associated with
+      --  splicing a subtree from one tree to another. Note that "splicing"
+      --  is a bit of a misnomer here in the case of a bounded tree, because
+      --  the elements must be copied from the source to the target.
+
       if Target.Count > Target.Capacity - Source_Count then
          raise Capacity_Error  -- ???
            with "Source count exceeds available storage on Target";
@@ -2830,6 +2845,8 @@ 
 
       pragma Assert (Target_Count = Source_Count);
 
+      --  Now link the newly-allocated subtree into the target.
+
       Insert_Subtree_Node
         (Container => Target,
          Subtree   => Target_Subtree,
@@ -2838,6 +2855,11 @@ 
 
       Target.Count := Target.Count + Target_Count;
 
+      --  The manipulation of the Target container is complete. Now we remove
+      --  the subtree from the Source container.
+
+      Remove_Subtree (Source, Position);  -- unlink the subtree
+
       --  As with Copy_Subtree, operation Deallocate_Subtree returns a count of
       --  the number of nodes it deallocates, but it works by incrementing the
       --  value passed in. We must therefore initialize the count before
@@ -2845,7 +2867,7 @@ 
 
       Source_Count := 0;
 
-      Deallocate_Children (Source, Position, Source_Count);
+      Deallocate_Subtree (Source, Position, Source_Count);
       pragma Assert (Source_Count = Target_Count);
 
       Source.Count := Source.Count - Source_Count;