/** @brief Validate and fix-up tree properties for a new insert/colored node
*
* This routine checks and fixes the Red-Black Tree properties based on
* @a the_node being just added to the tree.
*
* @note It does NOT disable interrupts to ensure the atomicity of the
* append operation.
*/
static void _RBTree_Validate_insert( RBTree_Node *the_node )
{
RBTree_Node *parent = _RBTree_Parent( the_node );
RBTree_Color parentcolor;
RBTree_Node *grandparent = _RBTree_Parent_and_color( parent, &parentcolor );
/* note: the insert root case is handled already */
/* if the parent is black, nothing needs to be done
* otherwise may need to loop a few times */
while ( parentcolor == RBT_RED ) {
/* The root is black, so the grandparent must exist */
RBTree_Node *uncle = _RBTree_Sibling( parent, grandparent );
RBTree_Node *grandgrandparent = _RBTree_Parent( grandparent );
/*
* If uncle exists and is red, repaint uncle/parent black and grandparent
* red.
*/
if ( uncle != NULL && _RBTree_Color( uncle ) == RBT_RED ) {
_RBTree_Set_parent_and_color( parent, grandparent, RBT_BLACK );
_RBTree_Set_parent_and_color( uncle, grandparent, RBT_BLACK );
_RBTree_Set_parent_and_color( grandparent, grandgrandparent, RBT_RED );
the_node = grandparent;
parent = grandgrandparent;
grandparent = _RBTree_Parent_and_color( parent, &parentcolor );
if ( grandparent == NULL )
break;
} else { /* If uncle does not exist or is black */
RBTree_Direction dir = _RBTree_Direction( the_node, parent );
RBTree_Direction parentdir = _RBTree_Direction( parent, grandparent );
/* ensure node is on the same branch direction as parent */
if ( dir != parentdir ) {
RBTree_Node *oldparent = parent;
parent = the_node;
the_node = oldparent;
_RBTree_Rotate( oldparent, parentdir );
}
_RBTree_Set_color( parent, RBT_BLACK );
_RBTree_Set_parent_and_color( grandparent, grandgrandparent, RBT_RED );
/* now rotate grandparent in the other branch direction (toward uncle) */
_RBTree_Rotate( grandparent, _RBTree_Opposite_direction( parentdir ) );
grandparent = _RBTree_Parent( parent );
break;
}
}
if ( grandparent == NULL )
_RBTree_Set_parent_and_color( the_node, parent, RBT_BLACK );
}
void _RBTree_Iterate_unprotected(
const RBTree_Control *rbtree,
RBTree_Direction dir,
RBTree_Visitor visitor,
void *visitor_arg
)
{
RBTree_Direction opp_dir = _RBTree_Opposite_direction( dir );
const RBTree_Node *current = _RBTree_First( rbtree, opp_dir );
bool stop = false;
while ( !stop && current != NULL ) {
stop = (*visitor)( current, dir, visitor_arg );
current = _RBTree_Next_unprotected( current, dir );
}
}
/** @brief Validate and fix-up tree properties after deleting a node
*
* This routine is called on a black node, @a the_node, after its deletion.
* This function maintains the properties of the red-black tree.
*
* @note It does NOT disable interrupts to ensure the atomicity
* of the extract operation.
*/
static void _RBTree_Extract_validate( RBTree_Node *the_node )
{
RBTree_Node *parent;
parent = the_node->parent;
if ( !parent->parent )
return;
/* continue to correct tree as long as the_node is black and not the root */
while ( !_RBTree_Is_red( the_node ) && parent->parent ) {
RBTree_Node *sibling = _RBTree_Sibling( the_node, parent );
/* if sibling is red, switch parent (black) and sibling colors,
* then rotate parent left, making the sibling be the_node's grandparent.
* Now the_node has a black sibling and red parent. After rotation,
* update sibling pointer.
*/
if ( _RBTree_Is_red( sibling ) ) {
RBTree_Direction dir = _RBTree_Direction( the_node, parent );
RBTree_Direction opp_dir = _RBTree_Opposite_direction( dir );
parent->color = RBT_RED;
sibling->color = RBT_BLACK;
_RBTree_Rotate( parent, dir );
sibling = parent->child[ opp_dir ];
}
/* sibling is black, see if both of its children are also black. */
if ( !_RBTree_Is_red( sibling->child[ RBT_RIGHT ] ) &&
!_RBTree_Is_red( sibling->child[ RBT_LEFT ] ) ) {
sibling->color = RBT_RED;
if ( _RBTree_Is_red( parent ) ) {
parent->color = RBT_BLACK;
break;
}
the_node = parent; /* done if parent is red */
parent = the_node->parent;
} else {
/* at least one of sibling's children is red. we now proceed in two
* cases, either the_node is to the left or the right of the parent.
* In both cases, first check if one of sibling's children is black,
* and if so rotate in the proper direction and update sibling pointer.
* Then switch the sibling and parent colors, and rotate through parent.
*/
RBTree_Direction dir = _RBTree_Direction( the_node, parent );
RBTree_Direction opp_dir = _RBTree_Opposite_direction( dir );
if (
!_RBTree_Is_red( sibling->child[ opp_dir ] )
) {
sibling->color = RBT_RED;
sibling->child[ dir ]->color = RBT_BLACK;
_RBTree_Rotate( sibling, opp_dir );
sibling = parent->child[ opp_dir ];
}
sibling->color = parent->color;
parent->color = RBT_BLACK;
sibling->child[ opp_dir ]->color = RBT_BLACK;
_RBTree_Rotate( parent, dir );
break; /* done */
}
} /* while */
if ( !the_node->parent->parent )
the_node->color = RBT_BLACK;
}
/** @brief Validate and fix-up tree properties after deleting a node
*
* This routine is called on a black node, @a the_node, after its deletion.
* This function maintains the properties of the red-black tree.
*/
static void rtems_rbtree_extract_validate( RBTree_Node *the_node )
{
RBTree_Color color;
RBTree_Node *parent = _RBTree_Parent_and_color( the_node, &color );
RBTree_Color parentcolor;
RBTree_Node *grandparent = _RBTree_Parent_and_color( parent, &parentcolor );
if ( grandparent == NULL )
return;
/* continue to correct tree as long as the_node is black and not the root */
while ( grandparent != NULL && color == RBT_BLACK ) {
RBTree_Node *sibling = _RBTree_Sibling( the_node, parent );
/* if sibling is red, switch parent (black) and sibling colors,
* then rotate parent left, making the sibling be the_node's grandparent.
* Now the_node has a black sibling and red parent. After rotation,
* update sibling pointer.
*/
if ( _RBTree_Color( sibling ) == RBT_RED ) {
RBTree_Direction dir = _RBTree_Direction( the_node, parent );
RBTree_Direction opp_dir = _RBTree_Opposite_direction( dir );
parentcolor = RBT_RED;
_RBTree_Set_parent_and_color( parent, grandparent, parentcolor );
_RBTree_Set_parent_and_color( sibling, parent, RBT_BLACK );
_RBTree_Rotate( parent, dir );
grandparent = sibling;
sibling = parent->child[ opp_dir ];
}
/* sibling is black, see if both of its children are also black. */
if ( _RBTree_Is_null_or_black( sibling->child[ RBT_RIGHT ] ) &&
_RBTree_Is_null_or_black( sibling->child[ RBT_LEFT ] ) ) {
_RBTree_Set_parent_and_color( sibling, parent, RBT_RED );
if ( parentcolor == RBT_RED ) {
_RBTree_Set_parent_and_color( parent, grandparent, RBT_BLACK );
break;
}
the_node = parent; /* done if parent is red */
parent = grandparent;
grandparent = _RBTree_Parent_and_color( parent, &parentcolor );
} else {
/* at least one of sibling's children is red. we now proceed in two
* cases, either the_node is to the left or the right of the parent.
* In both cases, first check if one of sibling's children is black,
* and if so rotate in the proper direction and update sibling pointer.
* Then switch the sibling and parent colors, and rotate through parent.
*/
RBTree_Direction dir = _RBTree_Direction( the_node, parent );
RBTree_Direction opp_dir = _RBTree_Opposite_direction( dir );
if ( _RBTree_Is_null_or_black( sibling->child[ opp_dir ] ) ) {
_RBTree_Set_parent_and_color( sibling, parent, RBT_RED );
_RBTree_Set_parent_and_color(
sibling->child[ dir ],
sibling,
RBT_BLACK
);
_RBTree_Rotate( sibling, opp_dir );
sibling = parent->child[ opp_dir ];
}
_RBTree_Set_parent_and_color( sibling, parent, parentcolor );
_RBTree_Set_parent_and_color( parent, grandparent, RBT_BLACK );
_RBTree_Set_parent_and_color(
sibling->child[ opp_dir ],
sibling,
RBT_BLACK
);
_RBTree_Rotate( parent, dir );
grandparent = sibling;
break; /* done */
}
} /* while */
if ( grandparent == NULL )
_RBTree_Set_parent_and_color( the_node, parent, RBT_BLACK );
}