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Michel Lespinasse
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Linus Torvalds
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Oct 9, 2012
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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 | ||
*/ | ||
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/* | ||
* 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 | ||
*/ | ||
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/* IT(name) -> ITPREFIX_name */ | ||
#define _ITNAME(prefix, name) prefix ## _ ## name | ||
#define ITNAME(prefix, name) _ITNAME(prefix, name) | ||
#define IT(name) ITNAME(ITPREFIX, name) | ||
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/* Callbacks for augmented rbtree insert and remove */ | ||
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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; | ||
} | ||
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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); | ||
} | ||
} | ||
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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); | ||
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new->ITSUBTREE = old->ITSUBTREE; | ||
} | ||
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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); | ||
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new->ITSUBTREE = old->ITSUBTREE; | ||
old->ITSUBTREE = IT(compute_subtree_last)(old); | ||
} | ||
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static const struct rb_augment_callbacks IT(augment_callbacks) = { | ||
IT(augment_propagate), IT(augment_copy), IT(augment_rotate) | ||
}; | ||
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/* Insert / remove interval nodes from the tree */ | ||
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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; | ||
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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; | ||
} | ||
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node->ITSUBTREE = last; | ||
rb_link_node(&node->ITRB, rb_parent, link); | ||
rb_insert_augmented(&node->ITRB, root, &IT(augment_callbacks)); | ||
} | ||
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ITSTATIC void IT(remove)(ITSTRUCT *node, struct rb_root *root) | ||
{ | ||
rb_erase_augmented(&node->ITRB, root, &IT(augment_callbacks)); | ||
} | ||
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/* | ||
* 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) | ||
*/ | ||
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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 */ | ||
} | ||
} | ||
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ITSTATIC ITSTRUCT *IT(iter_first)(struct rb_root *root, | ||
ITTYPE start, ITTYPE last) | ||
{ | ||
ITSTRUCT *node; | ||
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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); | ||
} | ||
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ITSTATIC ITSTRUCT *IT(iter_next)(ITSTRUCT *node, ITTYPE start, ITTYPE last) | ||
{ | ||
struct rb_node *rb = node->ITRB.rb_right, *prev; | ||
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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); | ||
} | ||
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/* 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); | ||
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/* 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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