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suricata/src/interval-tree.h

564 lines
45 KiB
C

/* $NetBSD: interval-tree.h,v 1.8 2004/03/28 19:38:30 provos Exp $ */
/* $OpenBSD: interval-tree.h,v 1.7 2002/10/17 21:51:54 art Exp $ */
/* $FreeBSD$ */
/* This is a COPY of the in-tree tree.h modified to accomodate interval
* tree operations */
/*-
* SPDX-License-Identifier: BSD-2-Clause-FreeBSD
*
* Copyright 2002 Niels Provos <provos@citi.umich.edu>
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef _SYS_INTERVALTREE_H_
#define _SYS_INTERVALTREE_H_
#if defined(__clang_analyzer__)
#define _T_ASSERT(a) assert((a))
#else
#define _T_ASSERT(a)
#endif
/*
* This file defines data structures for interval trees which are
* implemented using red-black trees.
*
* A red-black tree is a binary search tree with the node color as an
* extra attribute. It fulfills a set of conditions:
* - every search path from the root to a leaf consists of the
* same number of black nodes,
* - each red node (except for the root) has a black parent,
* - each leaf node is black.
*
* Every operation on a red-black tree is bounded as O(lg n).
* The maximum height of a red-black tree is 2lg (n+1).
*/
/* Macros that define a red-black tree */
#define IRB_HEAD(name, type) \
struct name { \
struct type *rbh_root; /* root of the tree */ \
}
#define IRB_INITIALIZER(root) \
{ \
NULL \
}
#define IRB_INIT(root) \
do { \
(root)->rbh_root = NULL; \
} while (/*CONSTCOND*/ 0)
#define IRB_BLACK 0
#define IRB_RED 1
#define IRB_ENTRY(type) \
struct { \
struct type *rbe_left; /* left element */ \
struct type *rbe_right; /* right element */ \
struct type *rbe_parent; /* parent element */ \
int rbe_color; /* node color */ \
}
#define IRB_LEFT(elm, field) (elm)->field.rbe_left
#define IRB_RIGHT(elm, field) (elm)->field.rbe_right
#define IRB_PARENT(elm, field) (elm)->field.rbe_parent
#define IRB_COLOR(elm, field) (elm)->field.rbe_color
#define IRB_ROOT(head) (head)->rbh_root
#define IRB_EMPTY(head) (IRB_ROOT(head) == NULL)
#define IRB_SET(elm, parent, field) \
do { \
IRB_PARENT(elm, field) = parent; \
IRB_LEFT(elm, field) = IRB_RIGHT(elm, field) = NULL; \
IRB_COLOR(elm, field) = IRB_RED; \
} while (/*CONSTCOND*/ 0)
#define IRB_SET_BLACKRED(black, red, field) \
do { \
IRB_COLOR(black, field) = IRB_BLACK; \
IRB_COLOR(red, field) = IRB_RED; \
} while (/*CONSTCOND*/ 0)
/*
* The implementation of the following macro has been updated.
* In order to incorporte it properly, the call sites of this
* function have also been updated compared to the standard
* Red Black tree implementation in tree.h of BSD */
#ifndef IRB_AUGMENT
#define IRB_AUGMENT(x, field) \
do { \
if (x != NULL) { \
x->max = x->port2; \
if (IRB_LEFT(x, field) != NULL) { \
x->max = MAX(x->max, IRB_LEFT(x, field)->max); \
} \
if (IRB_RIGHT(x, field) != NULL) { \
x->max = MAX(x->max, IRB_RIGHT(x, field)->max); \
} \
} \
} while (0)
#endif
#define IRB_ROTATE_LEFT(head, elm, tmp, field) \
do { \
(tmp) = IRB_RIGHT(elm, field); \
if ((IRB_RIGHT(elm, field) = IRB_LEFT(tmp, field)) != NULL) { \
IRB_PARENT(IRB_LEFT(tmp, field), field) = (elm); \
} \
if ((IRB_PARENT(tmp, field) = IRB_PARENT(elm, field)) != NULL) { \
if ((elm) == IRB_LEFT(IRB_PARENT(elm, field), field)) \
IRB_LEFT(IRB_PARENT(elm, field), field) = (tmp); \
else \
IRB_RIGHT(IRB_PARENT(elm, field), field) = (tmp); \
} else \
(head)->rbh_root = (tmp); \
IRB_LEFT(tmp, field) = (elm); \
IRB_PARENT(elm, field) = (tmp); \
IRB_AUGMENT(elm, field); \
IRB_AUGMENT(tmp, field); \
if ((IRB_PARENT(tmp, field))) \
IRB_AUGMENT(IRB_PARENT(tmp, field), field); \
} while (/*CONSTCOND*/ 0)
#define IRB_ROTATE_RIGHT(head, elm, tmp, field) \
do { \
(tmp) = IRB_LEFT(elm, field); \
if ((IRB_LEFT(elm, field) = IRB_RIGHT(tmp, field)) != NULL) { \
IRB_PARENT(IRB_RIGHT(tmp, field), field) = (elm); \
} \
if ((IRB_PARENT(tmp, field) = IRB_PARENT(elm, field)) != NULL) { \
if ((elm) == IRB_LEFT(IRB_PARENT(elm, field), field)) \
IRB_LEFT(IRB_PARENT(elm, field), field) = (tmp); \
else \
IRB_RIGHT(IRB_PARENT(elm, field), field) = (tmp); \
} else \
(head)->rbh_root = (tmp); \
IRB_RIGHT(tmp, field) = (elm); \
IRB_PARENT(elm, field) = (tmp); \
IRB_AUGMENT(elm, field); \
IRB_AUGMENT(tmp, field); \
if ((IRB_PARENT(tmp, field))) \
IRB_AUGMENT(IRB_PARENT(tmp, field), field); \
} while (/*CONSTCOND*/ 0)
/* Generates prototypes and inline functions */
#define IRB_PROTOTYPE(name, type, field, cmp) IRB_PROTOTYPE_INTERNAL(name, type, field, cmp, )
#define IRB_PROTOTYPE_STATIC(name, type, field, cmp) \
IRB_PROTOTYPE_INTERNAL(name, type, field, cmp, __unused static)
#define IRB_PROTOTYPE_INTERNAL(name, type, field, cmp, attr) \
IRB_PROTOTYPE_INSERT_COLOR(name, type, attr); \
IRB_PROTOTYPE_REMOVE_COLOR(name, type, attr); \
IRB_PROTOTYPE_INSERT(name, type, attr); \
IRB_PROTOTYPE_REMOVE(name, type, attr); \
IRB_PROTOTYPE_FIND(name, type, attr); \
IRB_PROTOTYPE_NFIND(name, type, attr); \
IRB_PROTOTYPE_NEXT(name, type, attr); \
IRB_PROTOTYPE_PREV(name, type, attr); \
IRB_PROTOTYPE_MINMAX(name, type, attr);
#define IRB_PROTOTYPE_INSERT_COLOR(name, type, attr) \
attr void name##_IRB_INSERT_COLOR(struct name *, struct type *)
#define IRB_PROTOTYPE_REMOVE_COLOR(name, type, attr) \
attr void name##_IRB_REMOVE_COLOR(struct name *, struct type *, struct type *)
#define IRB_PROTOTYPE_REMOVE(name, type, attr) \
attr struct type *name##_IRB_REMOVE(struct name *, struct type *)
#define IRB_PROTOTYPE_INSERT(name, type, attr) \
attr struct type *name##_IRB_INSERT(struct name *, struct type *)
#define IRB_PROTOTYPE_FIND(name, type, attr) \
attr struct type *name##_IRB_FIND(struct name *, struct type *)
#define IRB_PROTOTYPE_NFIND(name, type, attr) \
attr struct type *name##_IRB_NFIND(struct name *, struct type *)
#define IRB_PROTOTYPE_NEXT(name, type, attr) attr struct type *name##_IRB_NEXT(struct type *)
#define IRB_PROTOTYPE_PREV(name, type, attr) attr struct type *name##_IRB_PREV(struct type *)
#define IRB_PROTOTYPE_MINMAX(name, type, attr) \
attr struct type *name##_IRB_MINMAX(struct name *, int)
/* Main rb operation.
* Moves node close to the key of elm to top
*/
#define IRB_GENERATE(name, type, field, cmp) IRB_GENERATE_INTERNAL(name, type, field, cmp, )
#define IRB_GENERATE_STATIC(name, type, field, cmp) \
IRB_GENERATE_INTERNAL(name, type, field, cmp, __unused static)
#define IRB_GENERATE_INTERNAL(name, type, field, cmp, attr) \
IRB_GENERATE_INSERT_COLOR(name, type, field, attr) \
IRB_GENERATE_REMOVE_COLOR(name, type, field, attr) \
IRB_GENERATE_INSERT(name, type, field, cmp, attr) \
IRB_GENERATE_REMOVE(name, type, field, attr) \
IRB_GENERATE_FIND(name, type, field, cmp, attr) \
IRB_GENERATE_NFIND(name, type, field, cmp, attr) \
IRB_GENERATE_NEXT(name, type, field, attr) \
IRB_GENERATE_PREV(name, type, field, attr) \
IRB_GENERATE_MINMAX(name, type, field, attr)
#define IRB_GENERATE_INSERT_COLOR(name, type, field, attr) \
attr void name##_IRB_INSERT_COLOR(struct name *head, struct type *elm) \
{ \
struct type *parent, *gparent, *tmp; \
while ((parent = IRB_PARENT(elm, field)) != NULL && IRB_COLOR(parent, field) == IRB_RED) { \
gparent = IRB_PARENT(parent, field); \
_T_ASSERT(gparent); \
if (parent == IRB_LEFT(gparent, field)) { \
tmp = IRB_RIGHT(gparent, field); \
if (tmp && IRB_COLOR(tmp, field) == IRB_RED) { \
IRB_COLOR(tmp, field) = IRB_BLACK; \
IRB_SET_BLACKRED(parent, gparent, field); \
elm = gparent; \
continue; \
} \
if (IRB_RIGHT(parent, field) == elm) { \
IRB_ROTATE_LEFT(head, parent, tmp, field); \
tmp = parent; \
parent = elm; \
elm = tmp; \
} \
IRB_SET_BLACKRED(parent, gparent, field); \
IRB_ROTATE_RIGHT(head, gparent, tmp, field); \
} else { \
tmp = IRB_LEFT(gparent, field); \
if (tmp && IRB_COLOR(tmp, field) == IRB_RED) { \
IRB_COLOR(tmp, field) = IRB_BLACK; \
IRB_SET_BLACKRED(parent, gparent, field); \
elm = gparent; \
continue; \
} \
if (IRB_LEFT(parent, field) == elm) { \
IRB_ROTATE_RIGHT(head, parent, tmp, field); \
tmp = parent; \
parent = elm; \
elm = tmp; \
} \
IRB_SET_BLACKRED(parent, gparent, field); \
IRB_ROTATE_LEFT(head, gparent, tmp, field); \
} \
} \
IRB_COLOR(head->rbh_root, field) = IRB_BLACK; \
}
#define IRB_GENERATE_REMOVE_COLOR(name, type, field, attr) \
attr void name##_IRB_REMOVE_COLOR(struct name *head, struct type *parent, struct type *elm) \
{ \
struct type *tmp; \
while ((elm == NULL || IRB_COLOR(elm, field) == IRB_BLACK) && elm != IRB_ROOT(head)) { \
if (IRB_LEFT(parent, field) == elm) { \
tmp = IRB_RIGHT(parent, field); \
if (IRB_COLOR(tmp, field) == IRB_RED) { \
IRB_SET_BLACKRED(tmp, parent, field); \
IRB_ROTATE_LEFT(head, parent, tmp, field); \
tmp = IRB_RIGHT(parent, field); \
} \
_T_ASSERT(tmp); \
if ((IRB_LEFT(tmp, field) == NULL || \
IRB_COLOR(IRB_LEFT(tmp, field), field) == IRB_BLACK) && \
(IRB_RIGHT(tmp, field) == NULL || \
IRB_COLOR(IRB_RIGHT(tmp, field), field) == IRB_BLACK)) { \
IRB_COLOR(tmp, field) = IRB_RED; \
elm = parent; \
parent = IRB_PARENT(elm, field); \
} else { \
if (IRB_RIGHT(tmp, field) == NULL || \
IRB_COLOR(IRB_RIGHT(tmp, field), field) == IRB_BLACK) { \
struct type *oleft; \
if ((oleft = IRB_LEFT(tmp, field)) != NULL) \
IRB_COLOR(oleft, field) = IRB_BLACK; \
IRB_COLOR(tmp, field) = IRB_RED; \
IRB_ROTATE_RIGHT(head, tmp, oleft, field); \
tmp = IRB_RIGHT(parent, field); \
} \
IRB_COLOR(tmp, field) = IRB_COLOR(parent, field); \
IRB_COLOR(parent, field) = IRB_BLACK; \
if (IRB_RIGHT(tmp, field)) \
IRB_COLOR(IRB_RIGHT(tmp, field), field) = IRB_BLACK; \
IRB_ROTATE_LEFT(head, parent, tmp, field); \
elm = IRB_ROOT(head); \
break; \
} \
} else { \
tmp = IRB_LEFT(parent, field); \
if (IRB_COLOR(tmp, field) == IRB_RED) { \
IRB_SET_BLACKRED(tmp, parent, field); \
IRB_ROTATE_RIGHT(head, parent, tmp, field); \
tmp = IRB_LEFT(parent, field); \
} \
_T_ASSERT(tmp); \
if ((IRB_LEFT(tmp, field) == NULL || \
IRB_COLOR(IRB_LEFT(tmp, field), field) == IRB_BLACK) && \
(IRB_RIGHT(tmp, field) == NULL || \
IRB_COLOR(IRB_RIGHT(tmp, field), field) == IRB_BLACK)) { \
IRB_COLOR(tmp, field) = IRB_RED; \
elm = parent; \
parent = IRB_PARENT(elm, field); \
} else { \
if (IRB_LEFT(tmp, field) == NULL || \
IRB_COLOR(IRB_LEFT(tmp, field), field) == IRB_BLACK) { \
struct type *oright; \
if ((oright = IRB_RIGHT(tmp, field)) != NULL) \
IRB_COLOR(oright, field) = IRB_BLACK; \
IRB_COLOR(tmp, field) = IRB_RED; \
IRB_ROTATE_LEFT(head, tmp, oright, field); \
tmp = IRB_LEFT(parent, field); \
} \
IRB_COLOR(tmp, field) = IRB_COLOR(parent, field); \
IRB_COLOR(parent, field) = IRB_BLACK; \
if (IRB_LEFT(tmp, field)) \
IRB_COLOR(IRB_LEFT(tmp, field), field) = IRB_BLACK; \
IRB_ROTATE_RIGHT(head, parent, tmp, field); \
elm = IRB_ROOT(head); \
break; \
} \
} \
} \
if (elm) \
IRB_COLOR(elm, field) = IRB_BLACK; \
}
#define IRB_GENERATE_REMOVE(name, type, field, attr) \
attr struct type *name##_IRB_REMOVE(struct name *head, struct type *elm) \
{ \
struct type *child, *parent, *old = elm; \
int color; \
if (IRB_LEFT(elm, field) == NULL) \
child = IRB_RIGHT(elm, field); \
else if (IRB_RIGHT(elm, field) == NULL) \
child = IRB_LEFT(elm, field); \
else { \
struct type *left; \
elm = IRB_RIGHT(elm, field); \
while ((left = IRB_LEFT(elm, field)) != NULL) \
elm = left; \
child = IRB_RIGHT(elm, field); \
parent = IRB_PARENT(elm, field); \
color = IRB_COLOR(elm, field); \
if (child) \
IRB_PARENT(child, field) = parent; \
if (parent) { \
if (IRB_LEFT(parent, field) == elm) \
IRB_LEFT(parent, field) = child; \
else \
IRB_RIGHT(parent, field) = child; \
IRB_AUGMENT(parent, field); \
} else \
IRB_ROOT(head) = child; \
if (IRB_PARENT(elm, field) == old) \
parent = elm; \
_T_ASSERT((old)); \
(elm)->field = (old)->field; \
if (IRB_PARENT(old, field)) { \
if (IRB_LEFT(IRB_PARENT(old, field), field) == old) \
IRB_LEFT(IRB_PARENT(old, field), field) = elm; \
else \
IRB_RIGHT(IRB_PARENT(old, field), field) = elm; \
IRB_AUGMENT(IRB_PARENT(old, field), field); \
} else \
IRB_ROOT(head) = elm; \
_T_ASSERT(old); \
_T_ASSERT(IRB_LEFT(old, field)); \
IRB_PARENT(IRB_LEFT(old, field), field) = elm; \
if (IRB_RIGHT(old, field)) \
IRB_PARENT(IRB_RIGHT(old, field), field) = elm; \
if (parent) { \
left = parent; \
do { \
IRB_AUGMENT(left, field); \
} while ((left = IRB_PARENT(left, field)) != NULL); \
} \
goto color; \
} \
parent = IRB_PARENT(elm, field); \
color = IRB_COLOR(elm, field); \
if (child) \
IRB_PARENT(child, field) = parent; \
if (parent) { \
if (IRB_LEFT(parent, field) == elm) \
IRB_LEFT(parent, field) = child; \
else \
IRB_RIGHT(parent, field) = child; \
IRB_AUGMENT(parent, field); \
} else \
IRB_ROOT(head) = child; \
color: \
if (color == IRB_BLACK) \
name##_IRB_REMOVE_COLOR(head, parent, child); \
return (old); \
}
#define IRB_GENERATE_INSERT(name, type, field, cmp, attr) \
/* Inserts a node into the IRB tree */ \
attr struct type *name##_IRB_INSERT(struct name *head, struct type *elm) \
{ \
struct type *tmp; \
struct type *parent = NULL; \
int comp = 0; \
tmp = IRB_ROOT(head); \
while (tmp) { \
parent = tmp; \
comp = (cmp)(elm, parent); \
if (comp < 0) { \
tmp = IRB_LEFT(tmp, field); \
} else if (comp > 0) { \
tmp = IRB_RIGHT(tmp, field); \
} else \
return (tmp); \
} \
IRB_SET(elm, parent, field); \
if (parent != NULL) { \
if (comp < 0) \
IRB_LEFT(parent, field) = elm; \
else \
IRB_RIGHT(parent, field) = elm; \
} else \
IRB_ROOT(head) = elm; \
IRB_AUGMENT(elm, field); \
name##_IRB_INSERT_COLOR(head, elm); \
return (NULL); \
}
#define IRB_GENERATE_FIND(name, type, field, cmp, attr) \
/* Finds the node with the same key as elm */ \
attr struct type *name##_IRB_FIND(struct name *head, struct type *elm) \
{ \
struct type *tmp = IRB_ROOT(head); \
int comp; \
while (tmp) { \
comp = cmp(elm, tmp); \
if (comp < 0) \
tmp = IRB_LEFT(tmp, field); \
else if (comp > 0) \
tmp = IRB_RIGHT(tmp, field); \
else \
return (tmp); \
} \
return (NULL); \
}
#define IRB_GENERATE_NFIND(name, type, field, cmp, attr) \
/* Finds the first node greater than or equal to the search key */ \
attr struct type *name##_IRB_NFIND(struct name *head, struct type *elm) \
{ \
struct type *tmp = IRB_ROOT(head); \
struct type *res = NULL; \
int comp; \
while (tmp) { \
comp = cmp(elm, tmp); \
if (comp < 0) { \
res = tmp; \
tmp = IRB_LEFT(tmp, field); \
} else if (comp > 0) \
tmp = IRB_RIGHT(tmp, field); \
else \
return (tmp); \
} \
return (res); \
}
#define IRB_GENERATE_NEXT(name, type, field, attr) \
/* ARGSUSED */ \
attr struct type *name##_IRB_NEXT(struct type *elm) \
{ \
if (IRB_RIGHT(elm, field)) { \
elm = IRB_RIGHT(elm, field); \
while (IRB_LEFT(elm, field)) \
elm = IRB_LEFT(elm, field); \
} else { \
if (IRB_PARENT(elm, field) && (elm == IRB_LEFT(IRB_PARENT(elm, field), field))) \
elm = IRB_PARENT(elm, field); \
else { \
while (IRB_PARENT(elm, field) && \
(elm == IRB_RIGHT(IRB_PARENT(elm, field), field))) \
elm = IRB_PARENT(elm, field); \
elm = IRB_PARENT(elm, field); \
} \
} \
return (elm); \
}
#define IRB_GENERATE_PREV(name, type, field, attr) \
/* ARGSUSED */ \
attr struct type *name##_IRB_PREV(struct type *elm) \
{ \
if (IRB_LEFT(elm, field)) { \
elm = IRB_LEFT(elm, field); \
while (IRB_RIGHT(elm, field)) \
elm = IRB_RIGHT(elm, field); \
} else { \
if (IRB_PARENT(elm, field) && (elm == IRB_RIGHT(IRB_PARENT(elm, field), field))) \
elm = IRB_PARENT(elm, field); \
else { \
while (IRB_PARENT(elm, field) && (elm == IRB_LEFT(IRB_PARENT(elm, field), field))) \
elm = IRB_PARENT(elm, field); \
elm = IRB_PARENT(elm, field); \
} \
} \
return (elm); \
}
#define IRB_GENERATE_MINMAX(name, type, field, attr) \
attr struct type *name##_IRB_MINMAX(struct name *head, int val) \
{ \
struct type *tmp = IRB_ROOT(head); \
struct type *parent = NULL; \
while (tmp) { \
parent = tmp; \
if (val < 0) \
tmp = IRB_LEFT(tmp, field); \
else \
tmp = IRB_RIGHT(tmp, field); \
} \
return (parent); \
}
#define IRB_NEGINF -1
#define IRB_INF 1
#define IRB_INSERT(name, x, y) name##_IRB_INSERT(x, y)
#define IRB_REMOVE(name, x, y) name##_IRB_REMOVE(x, y)
#define IRB_FIND(name, x, y) name##_IRB_FIND(x, y)
#define IRB_NFIND(name, x, y) name##_IRB_NFIND(x, y)
#define IRB_NEXT(name, x, y) name##_IRB_NEXT(y)
#define IRB_PREV(name, x, y) name##_IRB_PREV(y)
#define IRB_MIN(name, x) name##_IRB_MINMAX(x, IRB_NEGINF)
#define IRB_MAX(name, x) name##_IRB_MINMAX(x, IRB_INF)
#define IRB_FOREACH(x, name, head) \
for ((x) = IRB_MIN(name, head); (x) != NULL; (x) = name##_IRB_NEXT(x))
#define IRB_FOREACH_FROM(x, name, y) \
for ((x) = (y); ((x) != NULL) && ((y) = name##_IRB_NEXT(x), (x) != NULL); (x) = (y))
#define IRB_FOREACH_SAFE(x, name, head, y) \
for ((x) = IRB_MIN(name, head); ((x) != NULL) && ((y) = name##_IRB_NEXT(x), (x) != NULL); \
(x) = (y))
#define IRB_FOREACH_REVERSE(x, name, head) \
for ((x) = IRB_MAX(name, head); (x) != NULL; (x) = name##_IRB_PREV(x))
#define IRB_FOREACH_REVERSE_FROM(x, name, y) \
for ((x) = (y); ((x) != NULL) && ((y) = name##_IRB_PREV(x), (x) != NULL); (x) = (y))
#define IRB_FOREACH_REVERSE_SAFE(x, name, head, y) \
for ((x) = IRB_MAX(name, head); ((x) != NULL) && ((y) = name##_IRB_PREV(x), (x) != NULL); \
(x) = (y))
#endif /* _SYS_INTERVALTREE_H_ */