void _RBTree_Iterate(
const RBTree_Control *rbtree,
RBTree_Visitor visitor,
void *visitor_arg
)
{
const RBTree_Node *current = _RBTree_Minimum( rbtree );
bool stop = false;
while ( !stop && current != NULL ) {
stop = ( *visitor )( current, visitor_arg );
current = _RBTree_Successor( current );
}
}
void _RBTree_Extract(
RBTree_Control *the_rbtree,
RBTree_Node *the_node
)
{
RBTree_Node *leaf, *target;
RBTree_Color victim_color;
RBTree_Direction dir;
/* check if min needs to be updated */
if ( the_node == the_rbtree->first[ RBT_LEFT ] ) {
RBTree_Node *next;
next = _RBTree_Successor( the_node );
the_rbtree->first[ RBT_LEFT ] = next;
}
/* Check if max needs to be updated. min=max for 1 element trees so
* do not use else if here. */
if ( the_node == the_rbtree->first[ RBT_RIGHT ] ) {
RBTree_Node *previous;
previous = _RBTree_Predecessor( the_node );
the_rbtree->first[ RBT_RIGHT ] = previous;
}
/* if the_node has at most one non-null child then it is safe to proceed
* check if both children are non-null, if so then we must find a target node
* either max in node->child[RBT_LEFT] or min in node->child[RBT_RIGHT],
* and replace the_node with the target node. This maintains the binary
* search tree property, but may violate the red-black properties.
*/
if ( the_node->child[ RBT_LEFT ] && the_node->child[ RBT_RIGHT ] ) {
target = the_node->child[ RBT_LEFT ]; /* find max in node->child[RBT_LEFT] */
while ( target->child[ RBT_RIGHT ] )
target = target->child[ RBT_RIGHT ];
/* if the target node has a child, need to move it up the tree into
* target's position (target is the right child of target->parent)
* when target vacates it. if there is no child, then target->parent
* should become NULL. This may cause the coloring to be violated.
* For now we store the color of the node being deleted in victim_color.
*/
leaf = target->child[ RBT_LEFT ];
if ( leaf ) {
leaf->parent = target->parent;
} else {
/* fix the tree here if the child is a null leaf. */
_RBTree_Extract_validate( target );
}
victim_color = target->color;
dir = target != target->parent->child[ 0 ];
target->parent->child[ dir ] = leaf;
/* now replace the_node with target */
dir = the_node != the_node->parent->child[ 0 ];
the_node->parent->child[ dir ] = target;
/* set target's new children to the original node's children */
target->child[ RBT_RIGHT ] = the_node->child[ RBT_RIGHT ];
if ( the_node->child[ RBT_RIGHT ] )
the_node->child[ RBT_RIGHT ]->parent = target;
target->child[ RBT_LEFT ] = the_node->child[ RBT_LEFT ];
if ( the_node->child[ RBT_LEFT ] )
the_node->child[ RBT_LEFT ]->parent = target;
/* finally, update the parent node and recolor. target has completely
* replaced the_node, and target's child has moved up the tree if needed.
* the_node is no longer part of the tree, although it has valid pointers
* still.
*/
target->parent = the_node->parent;
target->color = the_node->color;
} else {
/* the_node has at most 1 non-null child. Move the child in to
* the_node's location in the tree. This may cause the coloring to be
* violated. We will fix it later.
* For now we store the color of the node being deleted in victim_color.
*/
leaf = the_node->child[ RBT_LEFT ] ?
the_node->child[ RBT_LEFT ] : the_node->child[ RBT_RIGHT ];
if ( leaf ) {
leaf->parent = the_node->parent;
} else {
/* fix the tree here if the child is a null leaf. */
_RBTree_Extract_validate( the_node );
}
victim_color = the_node->color;
/* remove the_node from the tree */
dir = the_node != the_node->parent->child[ 0 ];
the_node->parent->child[ dir ] = leaf;
}
/* fix coloring. leaf has moved up the tree. The color of the deleted
* node is in victim_color. There are two cases:
* 1. Deleted a red node, its child must be black. Nothing must be done.
* 2. Deleted a black node, its child must be red. Paint child black.
*/
if ( victim_color == RBT_BLACK ) { /* eliminate case 1 */
if ( leaf ) {
leaf->color = RBT_BLACK; /* case 2 */
}
}
/* set root to black, if it exists */
if ( the_rbtree->root )
the_rbtree->root->color = RBT_BLACK;
}
