[Bf-blender-cvs] SVN commit: /data/svn/bf-blender [42127] trunk/blender/source/blender/ blenlib/intern/DLRB_tree.c: (See http://codereview.appspot.com/5431064/ for review of patch)

[Konrad Kleine]

Revision: 42127
          http://projects.blender.org/scm/viewvc.php?view=rev&root=bf-blender&revision=42127
Author:   kwk
Date:     2011-11-24 14:58:42 +0000 (Thu, 24 Nov 2011)
Log Message:
-----------
(See http://codereview.appspot.com/5431064/ for review of patch)

I've written a convenient function that returns the sibling of a node in the
red-black tree implementation originally implemented by Joshua Leung.

I want to use this get_sibling() function in the future to implement the missing
removal function of the red-black tree implementation.

For now the get_sibling() function just simplifies the get_uncle() function.

Just like the rest of the red-black tree implementation this diff is based on
Wikipedia: http://en.wikipedia.org/wiki/Red%E2%80%93black_tree#Removal

Modified Paths:
--------------
    trunk/blender/source/blender/blenlib/intern/DLRB_tree.c

Modified: trunk/blender/source/blender/blenlib/intern/DLRB_tree.c
===================================================================
--- trunk/blender/source/blender/blenlib/intern/DLRB_tree.c	2011-11-24 14:30:37 UTC (rev 42126)
+++ trunk/blender/source/blender/blenlib/intern/DLRB_tree.c	2011-11-24 14:58:42 UTC (rev 42127)
@@ -287,20 +287,28 @@
 		return NULL;
 }
 
+/* get the sibling node (e.g. if node is left child of parent, return right child of parent) */
+static DLRBT_Node *get_sibling(DLRBT_Node *node)
+{
+	if (node && node->parent) {
+		if (node == node->parent->left)
+			return node->parent->right;
+		else
+			return node->parent->left;
+	}
+
+	/* sibling not found */
+	return NULL;
+}
+
 /* get the 'uncle' - the sibling of the parent - of the given node */
 static DLRBT_Node *get_uncle (DLRBT_Node *node)
 {
-	DLRBT_Node *gpn= get_grandparent(node);
+	if (node)
+		/* return the child of the grandparent which isn't the node's parent */
+		return get_sibling(node->parent);
 	
-	/* return the child of the grandparent which isn't the node's parent */
-	if (gpn) {
-		if (gpn->left == node->parent)
-			return gpn->right;
-		else
-			return gpn->left;
-	}
-	
-	/* not found */
+	/* uncle not found */
 	return NULL;
 }