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/*
Interval Trees
(C) 2012 Michel Lespinasse <walken@google.com>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
include/linux/interval_tree_tmpl.h
*/
/*
* Template for implementing interval trees
*
* ITSTRUCT: struct type of the interval tree nodes
* ITRB: name of struct rb_node field within ITSTRUCT
* ITTYPE: type of the interval endpoints
* ITSUBTREE: name of ITTYPE field within ITSTRUCT holding last-in-subtree
* ITSTART(n): start endpoint of ITSTRUCT node n
* ITLAST(n): last endpoing of ITSTRUCT node n
* ITSTATIC: 'static' or empty
* ITPREFIX: prefix to use for the inline tree definitions
*/
/* IT(name) -> ITPREFIX_name */
#define _ITNAME(prefix, name) prefix ## _ ## name
#define ITNAME(prefix, name) _ITNAME(prefix, name)
#define IT(name) ITNAME(ITPREFIX, name)
/* Callbacks for augmented rbtree insert and remove */
static inline ITTYPE IT(compute_subtree_last)(ITSTRUCT *node)
{
ITTYPE max = ITLAST(node), subtree_last;
if (node->ITRB.rb_left) {
subtree_last = rb_entry(node->ITRB.rb_left,
ITSTRUCT, ITRB)->ITSUBTREE;
if (max < subtree_last)
max = subtree_last;
}
if (node->ITRB.rb_right) {
subtree_last = rb_entry(node->ITRB.rb_right,
ITSTRUCT, ITRB)->ITSUBTREE;
if (max < subtree_last)
max = subtree_last;
}
return max;
}
static void IT(augment_propagate)(struct rb_node *rb, struct rb_node *stop)
{
while (rb != stop) {
ITSTRUCT *node = rb_entry(rb, ITSTRUCT, ITRB);
ITTYPE subtree_last = IT(compute_subtree_last)(node);
if (node->ITSUBTREE == subtree_last)
break;
node->ITSUBTREE = subtree_last;
rb = rb_parent(&node->ITRB);
}
}
static void IT(augment_copy)(struct rb_node *rb_old, struct rb_node *rb_new)
{
ITSTRUCT *old = rb_entry(rb_old, ITSTRUCT, ITRB);
ITSTRUCT *new = rb_entry(rb_new, ITSTRUCT, ITRB);
new->ITSUBTREE = old->ITSUBTREE;
}
static void IT(augment_rotate)(struct rb_node *rb_old, struct rb_node *rb_new)
{
ITSTRUCT *old = rb_entry(rb_old, ITSTRUCT, ITRB);
ITSTRUCT *new = rb_entry(rb_new, ITSTRUCT, ITRB);
new->ITSUBTREE = old->ITSUBTREE;
old->ITSUBTREE = IT(compute_subtree_last)(old);
}
static const struct rb_augment_callbacks IT(augment_callbacks) = {
IT(augment_propagate), IT(augment_copy), IT(augment_rotate)
};
/* Insert / remove interval nodes from the tree */
ITSTATIC void IT(insert)(ITSTRUCT *node, struct rb_root *root)
{
struct rb_node **link = &root->rb_node, *rb_parent = NULL;
ITTYPE start = ITSTART(node), last = ITLAST(node);
ITSTRUCT *parent;
while (*link) {
rb_parent = *link;
parent = rb_entry(rb_parent, ITSTRUCT, ITRB);
if (parent->ITSUBTREE < last)
parent->ITSUBTREE = last;
if (start < ITSTART(parent))
link = &parent->ITRB.rb_left;
else
link = &parent->ITRB.rb_right;
}
node->ITSUBTREE = last;
rb_link_node(&node->ITRB, rb_parent, link);
rb_insert_augmented(&node->ITRB, root, &IT(augment_callbacks));
}
ITSTATIC void IT(remove)(ITSTRUCT *node, struct rb_root *root)
{
rb_erase_augmented(&node->ITRB, root, &IT(augment_callbacks));
}
/*
* Iterate over intervals intersecting [start;last]
*
* Note that a node's interval intersects [start;last] iff:
* Cond1: ITSTART(node) <= last
* and
* Cond2: start <= ITLAST(node)
*/
static ITSTRUCT *IT(subtree_search)(ITSTRUCT *node, ITTYPE start, ITTYPE last)
{
while (true) {
/*
* Loop invariant: start <= node->ITSUBTREE
* (Cond2 is satisfied by one of the subtree nodes)
*/
if (node->ITRB.rb_left) {
ITSTRUCT *left = rb_entry(node->ITRB.rb_left,
ITSTRUCT, ITRB);
if (start <= left->ITSUBTREE) {
/*
* Some nodes in left subtree satisfy Cond2.
* Iterate to find the leftmost such node N.
* If it also satisfies Cond1, that's the match
* we are looking for. Otherwise, there is no
* matching interval as nodes to the right of N
* can't satisfy Cond1 either.
*/
node = left;
continue;
}
}
if (ITSTART(node) <= last) { /* Cond1 */
if (start <= ITLAST(node)) /* Cond2 */
return node; /* node is leftmost match */
if (node->ITRB.rb_right) {
node = rb_entry(node->ITRB.rb_right,
ITSTRUCT, ITRB);
if (start <= node->ITSUBTREE)
continue;
}
}
return NULL; /* No match */
}
}
ITSTATIC ITSTRUCT *IT(iter_first)(struct rb_root *root,
ITTYPE start, ITTYPE last)
{
ITSTRUCT *node;
if (!root->rb_node)
return NULL;
node = rb_entry(root->rb_node, ITSTRUCT, ITRB);
if (node->ITSUBTREE < start)
return NULL;
return IT(subtree_search)(node, start, last);
}
ITSTATIC ITSTRUCT *IT(iter_next)(ITSTRUCT *node, ITTYPE start, ITTYPE last)
{
struct rb_node *rb = node->ITRB.rb_right, *prev;
while (true) {
/*
* Loop invariants:
* Cond1: ITSTART(node) <= last
* rb == node->ITRB.rb_right
*
* First, search right subtree if suitable
*/
if (rb) {
ITSTRUCT *right = rb_entry(rb, ITSTRUCT, ITRB);
if (start <= right->ITSUBTREE)
return IT(subtree_search)(right, start, last);
}
/* Move up the tree until we come from a node's left child */
do {
rb = rb_parent(&node->ITRB);
if (!rb)
return NULL;
prev = &node->ITRB;
node = rb_entry(rb, ITSTRUCT, ITRB);
rb = node->ITRB.rb_right;
} while (prev == rb);
/* Check if the node intersects [start;last] */
if (last < ITSTART(node)) /* !Cond1 */
return NULL;
else if (start <= ITLAST(node)) /* Cond2 */
return node;
}
}
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