git: d0354fa7b6b1 - main - rb_tree: reduce duplication in balancing code
- Go to: [ bottom of page ] [ top of archives ] [ this month ]
Date: Thu, 08 Sep 2022 04:49:11 UTC
The branch main has been updated by dougm:
URL: https://cgit.FreeBSD.org/src/commit/?id=d0354fa7b6b1931afe1806bd0bfe3ba83e2aeb00
commit d0354fa7b6b1931afe1806bd0bfe3ba83e2aeb00
Author: Doug Moore <dougm@FreeBSD.org>
AuthorDate: 2022-09-08 04:46:19 +0000
Commit: Doug Moore <dougm@FreeBSD.org>
CommitDate: 2022-09-08 04:46:19 +0000
rb_tree: reduce duplication in balancing code
Change RB_INSERT_COLOR and RB_REMOVE_COLOR so that the blocks of code
that are identical except for left and right being exchanged are made
only one block with a variable to indicate left- or right-handedness.
Rename RB macros so that those not intended for external use begin
with an underscore.
Add comments to the balancing code so that another might understand it.
Reviewed by: alc, kib
MFC after: 3 weeks
Differential Revision: https://reviews.freebsd.org/D36393
---
sys/compat/linuxkpi/common/include/linux/rbtree.h | 12 +-
sys/kern/subr_stats.c | 4 +-
sys/sys/tree.h | 437 +++++++++++-----------
3 files changed, 223 insertions(+), 230 deletions(-)
diff --git a/sys/compat/linuxkpi/common/include/linux/rbtree.h b/sys/compat/linuxkpi/common/include/linux/rbtree.h
index 1db9b1d4fa21..1f337d59545c 100644
--- a/sys/compat/linuxkpi/common/include/linux/rbtree.h
+++ b/sys/compat/linuxkpi/common/include/linux/rbtree.h
@@ -41,8 +41,8 @@
struct rb_node {
RB_ENTRY(rb_node) __entry;
};
-#define rb_left __entry.rbe_left
-#define rb_right __entry.rbe_right
+#define rb_left __entry.rbe_link[_RB_L]
+#define rb_right __entry.rbe_link[_RB_R]
/*
* We provide a false structure that has the same bit pattern as tree.h
@@ -134,10 +134,10 @@ rb_replace_node(struct rb_node *victim, struct rb_node *new,
RB_SWAP_CHILD((struct linux_root *)root, rb_parent(victim),
victim, new, __entry);
- if (victim->rb_left)
- RB_SET_PARENT(victim->rb_left, new, __entry);
- if (victim->rb_right)
- RB_SET_PARENT(victim->rb_right, new, __entry);
+ if (RB_LEFT(victim, __entry))
+ RB_SET_PARENT(RB_LEFT(victim, __entry), new, __entry);
+ if (RB_RIGHT(victim, __entry))
+ RB_SET_PARENT(RB_RIGHT(victim, __entry), new, __entry);
*new = *victim;
}
diff --git a/sys/kern/subr_stats.c b/sys/kern/subr_stats.c
index 0984d2a21014..ff8ddbac4d81 100644
--- a/sys/kern/subr_stats.c
+++ b/sys/kern/subr_stats.c
@@ -3411,8 +3411,8 @@ stats_v1_vsd_tdgst_add(enum vsd_dtype vs_dtype, struct voistatdata_tdgst *tdgst,
int rb_color =
parent == NULL ? 0 :
RB_LEFT(parent, rblnk) == rbctd64 ?
- (RB_BITS(parent, rblnk) & RB_RED_L) != 0 :
- (RB_BITS(parent, rblnk) & RB_RED_R) != 0;
+ (_RB_BITSUP(parent, rblnk) & _RB_L) != 0 :
+ (_RB_BITSUP(parent, rblnk) & _RB_R) != 0;
printf(" RB ctd=%3d p=%3d l=%3d r=%3d c=%2d "
"mu=%s\n",
(int)ARB_SELFIDX(ctd64tree, rbctd64),
diff --git a/sys/sys/tree.h b/sys/sys/tree.h
index 74f1f23d3576..e0ab4449bd35 100644
--- a/sys/sys/tree.h
+++ b/sys/sys/tree.h
@@ -56,9 +56,11 @@
* the same, and defines the rank of that node. The rank of the null node
* is -1.
*
- * Different additional conditions define different sorts of balanced
- * trees, including "red-black" and "AVL" trees. The set of conditions
- * applied here are the "weak-AVL" conditions of Haeupler, Sen and Tarjan:
+ * Different additional conditions define different sorts of balanced trees,
+ * including "red-black" and "AVL" trees. The set of conditions applied here
+ * are the "weak-AVL" conditions of Haeupler, Sen and Tarjan presented in in
+ * "Rank Balanced Trees", ACM Transactions on Algorithms Volume 11 Issue 4 June
+ * 2015 Article No.: 30pp 1–26 https://doi.org/10.1145/2689412 (the HST paper):
* - every rank-difference is 1 or 2.
* - the rank of any leaf is 1.
*
@@ -318,14 +320,9 @@ struct name { \
#define RB_ENTRY(type) \
struct { \
- struct type *rbe_left; /* left element */ \
- struct type *rbe_right; /* right element */ \
- struct type *rbe_parent; /* parent element */ \
+ struct type *rbe_link[3]; \
}
-#define RB_LEFT(elm, field) (elm)->field.rbe_left
-#define RB_RIGHT(elm, field) (elm)->field.rbe_right
-
/*
* With the expectation that any object of struct type has an
* address that is a multiple of 4, and that therefore the
@@ -333,27 +330,29 @@ struct { \
* always zero, this implementation sets those bits to indicate
* that the left or right child of the tree node is "red".
*/
-#define RB_UP(elm, field) (elm)->field.rbe_parent
-#define RB_BITS(elm, field) (*(__uintptr_t *)&RB_UP(elm, field))
-#define RB_RED_L ((__uintptr_t)1)
-#define RB_RED_R ((__uintptr_t)2)
-#define RB_RED_MASK ((__uintptr_t)3)
-#define RB_FLIP_LEFT(elm, field) (RB_BITS(elm, field) ^= RB_RED_L)
-#define RB_FLIP_RIGHT(elm, field) (RB_BITS(elm, field) ^= RB_RED_R)
-#define RB_FLIP_ALL(elm, field) (RB_BITS(elm, field) ^= RB_RED_MASK)
-#define _RB_PARENT_ONLY(elm) (__typeof(elm)) \
- ((__uintptr_t)elm & ~RB_RED_MASK)
-#define RB_PARENT(elm, field) _RB_PARENT_ONLY(RB_UP(elm, field))
+#define _RB_LINK(elm, dir, field) (elm)->field.rbe_link[dir]
+#define _RB_UP(elm, field) _RB_LINK(elm, 0, field)
+#define _RB_L ((__uintptr_t)1)
+#define _RB_R ((__uintptr_t)2)
+#define _RB_LR ((__uintptr_t)3)
+#define _RB_BITS(elm) (*(__uintptr_t *)&elm)
+#define _RB_BITSUP(elm, field) _RB_BITS(_RB_UP(elm, field))
+#define _RB_PTR(elm) (__typeof(elm)) \
+ ((__uintptr_t)elm & ~_RB_LR)
+
+#define RB_PARENT(elm, field) _RB_PTR(_RB_UP(elm, field))
+#define RB_LEFT(elm, field) _RB_LINK(elm, _RB_L, field)
+#define RB_RIGHT(elm, field) _RB_LINK(elm, _RB_R, field)
#define RB_ROOT(head) (head)->rbh_root
#define RB_EMPTY(head) (RB_ROOT(head) == NULL)
#define RB_SET_PARENT(dst, src, field) do { \
- RB_BITS(dst, field) = (__uintptr_t)src | \
- (RB_BITS(dst, field) & RB_RED_MASK); \
+ _RB_BITSUP(dst, field) = (__uintptr_t)src | \
+ (_RB_BITSUP(dst, field) & _RB_LR); \
} while (/*CONSTCOND*/ 0)
#define RB_SET(elm, parent, field) do { \
- RB_UP(elm, field) = parent; \
+ _RB_UP(elm, field) = parent; \
RB_LEFT(elm, field) = RB_RIGHT(elm, field) = NULL; \
} while (/*CONSTCOND*/ 0)
@@ -382,31 +381,20 @@ struct { \
} while (/*CONSTCOND*/ 0)
/*
- * RB_ROTATE macros partially restructure the tree to improve
- * balance. The ROTATE_RIGHT case is just a reflection of the
- * ROTATE_LEFT case. Initially, tmp is a right child of elm. After
- * rotation, elm is a left child of tmp, and the subtree that
- * represented the items between them, which formerly hung to the left
- * of tmp now hangs to the right of elm. The parent-child
- * relationship between elm and its former parent is not changed;
- * where this macro once updated those fields, that is now left to the
- * caller of RB_ROTATE to clean up, so that a pair of rotations does
- * not twice update the same pair of pointer fields with distinct
- * values.
+ * RB_ROTATE macro partially restructures the tree to improve balance. In the
+ * case when dir is _RB_L, tmp is a right child of elm. After rotation, elm
+ * is a left child of tmp, and the subtree that represented the items between
+ * them, which formerly hung to the left of tmp now hangs to the right of elm.
+ * The parent-child relationship between elm and its former parent is not
+ * changed; where this macro once updated those fields, that is now left to the
+ * caller of RB_ROTATE to clean up, so that a pair of rotations does not twice
+ * update the same pair of pointer fields with distinct values.
*/
-#define RB_ROTATE_LEFT(elm, tmp, field) do { \
- if ((RB_RIGHT(elm, field) = RB_LEFT(tmp, field)) != NULL) { \
- RB_SET_PARENT(RB_RIGHT(elm, field), elm, field); \
- } \
- RB_LEFT(tmp, field) = (elm); \
- RB_SET_PARENT(elm, tmp, field); \
-} while (/*CONSTCOND*/ 0)
-
-#define RB_ROTATE_RIGHT(elm, tmp, field) do { \
- if ((RB_LEFT(elm, field) = RB_RIGHT(tmp, field)) != NULL) { \
- RB_SET_PARENT(RB_LEFT(elm, field), elm, field); \
- } \
- RB_RIGHT(tmp, field) = (elm); \
+#define RB_ROTATE(elm, tmp, dir, field) do { \
+ if ((_RB_LINK(elm, dir ^ _RB_LR, field) = \
+ _RB_LINK(tmp, dir, field)) != NULL) \
+ RB_SET_PARENT(_RB_LINK(tmp, dir, field), elm, field); \
+ _RB_LINK(tmp, dir, field) = (elm); \
RB_SET_PARENT(elm, tmp, field); \
} while (/*CONSTCOND*/ 0)
@@ -484,17 +472,18 @@ struct { \
attr int \
name##_RB_RANK(struct type *elm) \
{ \
- struct type *left, *right; \
+ struct type *left, *right, *up; \
int left_rank, right_rank; \
- __uintptr_t bits; \
\
if (elm == NULL) \
return (0); \
- bits = RB_BITS(elm, field); \
+ up = _RB_UP(elm, field); \
left = RB_LEFT(elm, field); \
- left_rank = ((bits & RB_RED_L) ? 2 : 1) + name##_RB_RANK(left); \
+ left_rank = ((_RB_BITS(up) & _RB_L) ? 2 : 1) + \
+ name##_RB_RANK(left); \
right = RB_RIGHT(elm, field); \
- right_rank = ((bits & RB_RED_R) ? 2 : 1) + name##_RB_RANK(right); \
+ right_rank = ((_RB_BITS(up) & _RB_R) ? 2 : 1) + \
+ name##_RB_RANK(right); \
if (left_rank != right_rank || \
(left_rank == 2 && left == NULL && right == NULL)) \
return (-1); \
@@ -518,72 +507,82 @@ name##_RB_INSERT_COLOR(struct name *head, struct type *elm) \
* uninitialized 'child', and a later iteration can only happen \
* when a value has been assigned to 'child' in the previous \
* one. \
- */ \
- struct type *child, *gpar = RB_UP(elm, field), *parent; \
- __uintptr_t red; \
+ */ \
+ struct type *child, *child_up, *gpar, *parent; \
+ __uintptr_t elmdir, sibdir; \
\
+ gpar = _RB_UP(elm, field); \
while ((parent = gpar) != NULL) { \
- red = RB_BITS(parent, field); \
- gpar = RB_UP(parent, field); \
- if (RB_LEFT(parent, field) == elm) { \
- if (red & RB_RED_L) { \
- RB_FLIP_LEFT(parent, field); \
- return; \
- } \
- RB_FLIP_RIGHT(parent, field); \
- if ((red & RB_RED_MASK) == 0) { \
- child = elm; \
- elm = parent; \
- continue; \
- } \
- red = RB_BITS(elm, field); \
- if (red & RB_RED_R) \
- child = elm; \
- else { \
- /* coverity[uninit_use] */ \
- RB_ROTATE_LEFT(elm, child, field); \
- red = RB_BITS(child, field); \
- if (red & RB_RED_R) \
- RB_FLIP_LEFT(parent, field); \
- if (red & RB_RED_L) \
- RB_FLIP_ALL(elm, field); \
- else \
- RB_FLIP_LEFT(elm, field); \
- if ((red & RB_RED_MASK) == 0) \
- elm = child; \
- } \
- RB_ROTATE_RIGHT(parent, child, field); \
- } else { \
- if (red & RB_RED_R) { \
- RB_FLIP_RIGHT(parent, field); \
- return; \
- } \
- RB_FLIP_LEFT(parent, field); \
- if ((red & RB_RED_MASK) == 0) { \
- child = elm; \
- elm = parent; \
- continue; \
- } \
- red = RB_BITS(elm, field); \
- if (red & RB_RED_L) \
- child = elm; \
- else { \
- /* coverity[uninit_use] */ \
- RB_ROTATE_RIGHT(elm, child, field); \
- red = RB_BITS(child, field); \
- if (red & RB_RED_L) \
- RB_FLIP_RIGHT(parent, field); \
- if (red & RB_RED_R) \
- RB_FLIP_ALL(elm, field); \
- else \
- RB_FLIP_RIGHT(elm, field); \
- if ((red & RB_RED_MASK) == 0) \
- elm = child; \
- } \
- RB_ROTATE_LEFT(parent, child, field); \
+ /* the rank of the tree rooted at elm grew */ \
+ gpar = _RB_UP(parent, field); \
+ elmdir = RB_RIGHT(parent, field) == elm ? _RB_R : _RB_L; \
+ if (_RB_BITS(gpar) & elmdir) { \
+ /* shorten the parent-elm edge to rebalance */ \
+ _RB_BITSUP(parent, field) ^= elmdir; \
+ return; \
+ } \
+ sibdir = elmdir ^ _RB_LR; \
+ /* the other edge must change length */ \
+ _RB_BITSUP(parent, field) ^= sibdir; \
+ if ((_RB_BITS(gpar) & _RB_LR) == 0) { \
+ /* both edges now short, retry from parent */ \
+ child = elm; \
+ elm = parent; \
+ continue; \
} \
- gpar = _RB_PARENT_ONLY(gpar); \
- RB_UP(child, field) = gpar; \
+ _RB_UP(parent, field) = gpar = _RB_PTR(gpar); \
+ if (_RB_BITSUP(elm, field) & elmdir) { \
+ /* \
+ * Exactly one of the edges descending from elm \
+ * is long. The long one is in the same \
+ * direction as the edge from parent to elm, \
+ * so change that by rotation. The edge from \
+ * parent to z was shortened above. Shorten \
+ * the long edge down from elm, and adjust \
+ * other edge lengths based on the downward \
+ * edges from 'child'. \
+ * \
+ * par par \
+ * / \ / \ \
+ * elm z / z \
+ * / \ child \
+ * / child / \ \
+ * / / \ elm \ \
+ * w / \ / \ y \
+ * x y w \ \
+ * x \
+ */ \
+ RB_ROTATE(elm, child, elmdir, field); \
+ child_up = _RB_UP(child, field); \
+ if (_RB_BITS(child_up) & sibdir) \
+ _RB_BITSUP(parent, field) ^= elmdir; \
+ if (_RB_BITS(child_up) & elmdir) \
+ _RB_BITSUP(elm, field) ^= _RB_LR; \
+ else \
+ _RB_BITSUP(elm, field) ^= elmdir; \
+ /* if child is a leaf, don't augment elm, \
+ * since it is restored to be a leaf again. */ \
+ if ((_RB_BITS(child_up) & _RB_LR) == 0) \
+ elm = child; \
+ } else \
+ child = elm; \
+ \
+ /* \
+ * The long edge descending from 'child' points back \
+ * in the direction of 'parent'. Rotate to make \
+ * 'parent' a child of 'child', then make both edges \
+ * of 'child' short to rebalance. \
+ * \
+ * par child \
+ * / \ / \ \
+ * / z x par \
+ * child / \ \
+ * / \ / z \
+ * x \ y \
+ * y \
+ */ \
+ RB_ROTATE(parent, child, sibdir, field); \
+ _RB_UP(child, field) = gpar; \
RB_SWAP_CHILD(head, gpar, parent, child, field); \
if (elm != child) \
RB_AUGMENT(elm); \
@@ -608,120 +607,112 @@ attr void \
name##_RB_REMOVE_COLOR(struct name *head, \
struct type *parent, struct type *elm) \
{ \
- struct type *gpar, *sib; \
- __uintptr_t red; \
+ struct type *gpar, *sib, *up; \
+ __uintptr_t elmdir, sibdir; \
\
- if (RB_LEFT(parent, field) == elm && \
- RB_RIGHT(parent, field) == elm) { \
- RB_BITS(parent, field) &= ~RB_RED_MASK; \
+ if (RB_RIGHT(parent, field) == elm && \
+ RB_LEFT(parent, field) == elm) { \
+ /* Deleting a leaf that is an only-child creates a \
+ * rank-2 leaf. Demote that leaf. */ \
+ _RB_UP(parent, field) = _RB_PTR(_RB_UP(parent, field)); \
elm = parent; \
- parent = RB_PARENT(elm, field); \
- if (parent == NULL) \
+ if ((parent = _RB_UP(elm, field)) == NULL) \
return; \
} \
do { \
- red = RB_BITS(parent, field); \
- gpar = RB_UP(parent, field); \
- if (RB_LEFT(parent, field) == elm) { \
- if (~red & RB_RED_L) { \
- RB_FLIP_LEFT(parent, field); \
- return; \
- } \
- if ((~red & RB_RED_MASK) == 0) { \
- RB_FLIP_RIGHT(parent, field); \
- elm = parent; \
- continue; \
- } \
- sib = RB_RIGHT(parent, field); \
- red = RB_BITS(sib, field); \
- switch (red & RB_RED_MASK) { \
- case RB_RED_MASK: \
- RB_FLIP_ALL(sib, field); \
- elm = parent; \
- continue; \
- case RB_RED_R: \
- elm = RB_LEFT(sib, field); \
- RB_ROTATE_RIGHT(sib, elm, field); \
- red = RB_BITS(elm, field); \
- if (red & RB_RED_L) \
- RB_FLIP_ALL(parent, field); \
- else \
- RB_FLIP_LEFT(parent, field); \
- if (red & RB_RED_R) \
- RB_FLIP_ALL(sib, field); \
- else \
- RB_FLIP_RIGHT(sib, field); \
- RB_BITS(elm, field) |= RB_RED_MASK; \
- break; \
- case RB_RED_L: \
- if (RB_STRICT_HST && elm != NULL) { \
- RB_FLIP_RIGHT(parent, field); \
- RB_FLIP_ALL(sib, field); \
- elm = sib; \
- break; \
- } \
- RB_FLIP_LEFT(parent, field); \
- /* FALLTHROUGH */ \
- default: \
- RB_FLIP_RIGHT(sib, field); \
- elm = sib; \
- break; \
- } \
- RB_ROTATE_LEFT(parent, elm, field); \
+ /* the rank of the tree rooted at elm shrank */ \
+ gpar = _RB_UP(parent, field); \
+ elmdir = RB_RIGHT(parent, field) == elm ? _RB_R : _RB_L; \
+ _RB_BITS(gpar) ^= elmdir; \
+ if (_RB_BITS(gpar) & elmdir) { \
+ /* lengthen the parent-elm edge to rebalance */ \
+ _RB_UP(parent, field) = gpar; \
+ return; \
+ } \
+ if (_RB_BITS(gpar) & _RB_LR) { \
+ /* shorten other edge, retry from parent */ \
+ _RB_BITS(gpar) ^= _RB_LR; \
+ _RB_UP(parent, field) = gpar; \
+ gpar = _RB_PTR(gpar); \
+ continue; \
+ } \
+ sibdir = elmdir ^ _RB_LR; \
+ sib = _RB_LINK(parent, sibdir, field); \
+ up = _RB_UP(sib, field); \
+ _RB_BITS(up) ^= _RB_LR; \
+ if ((_RB_BITS(up) & _RB_LR) == 0) { \
+ /* shorten edges descending from sib, retry */ \
+ _RB_UP(sib, field) = up; \
+ continue; \
+ } \
+ if ((_RB_BITS(up) & sibdir) == 0) { \
+ /* \
+ * The edge descending from 'sib' away from \
+ * 'parent' is long. The short edge descending \
+ * from 'sib' toward 'parent' points to 'elm*' \
+ * Rotate to make 'sib' a child of 'elm*' \
+ * then adjust the lengths of the edges \
+ * descending from 'sib' and 'elm*'. \
+ * \
+ * par par \
+ * / \ / \ \
+ * / sib elm \ \
+ * / / \ elm* \
+ * elm elm* \ / \ \
+ * / \ \ / \ \
+ * / \ z / \ \
+ * x y x sib \
+ * / \ \
+ * / z \
+ * y \
+ */ \
+ elm = _RB_LINK(sib, elmdir, field); \
+ /* elm is a 1-child. First rotate at elm. */ \
+ RB_ROTATE(sib, elm, sibdir, field); \
+ up = _RB_UP(elm, field); \
+ _RB_BITSUP(parent, field) ^= \
+ (_RB_BITS(up) & elmdir) ? _RB_LR : elmdir; \
+ _RB_BITSUP(sib, field) ^= \
+ (_RB_BITS(up) & sibdir) ? _RB_LR : sibdir; \
+ _RB_BITSUP(elm, field) |= _RB_LR; \
} else { \
- if (~red & RB_RED_R) { \
- RB_FLIP_RIGHT(parent, field); \
- return; \
- } \
- if ((~red & RB_RED_MASK) == 0) { \
- RB_FLIP_LEFT(parent, field); \
- elm = parent; \
- continue; \
- } \
- sib = RB_LEFT(parent, field); \
- red = RB_BITS(sib, field); \
- switch (red & RB_RED_MASK) { \
- case RB_RED_MASK: \
- RB_FLIP_ALL(sib, field); \
- elm = parent; \
- continue; \
- case RB_RED_L: \
- elm = RB_RIGHT(sib, field); \
- RB_ROTATE_LEFT(sib, elm, field); \
- red = RB_BITS(elm, field); \
- if (red & RB_RED_R) \
- RB_FLIP_ALL(parent, field); \
- else \
- RB_FLIP_RIGHT(parent, field); \
- if (red & RB_RED_L) \
- RB_FLIP_ALL(sib, field); \
- else \
- RB_FLIP_LEFT(sib, field); \
- RB_BITS(elm, field) |= RB_RED_MASK; \
- break; \
- case RB_RED_R: \
- if (RB_STRICT_HST && elm != NULL) { \
- RB_FLIP_LEFT(parent, field); \
- RB_FLIP_ALL(sib, field); \
- elm = sib; \
- break; \
- } \
- RB_FLIP_RIGHT(parent, field); \
- /* FALLTHROUGH */ \
- default: \
- RB_FLIP_LEFT(sib, field); \
- elm = sib; \
- break; \
- } \
- RB_ROTATE_RIGHT(parent, elm, field); \
+ if ((_RB_BITS(up) & elmdir) == 0 && \
+ RB_STRICT_HST && elm != NULL) { \
+ /* if parent does not become a leaf, \
+ do not demote parent yet. */ \
+ _RB_BITSUP(parent, field) ^= sibdir; \
+ _RB_BITSUP(sib, field) ^= _RB_LR; \
+ } else if ((_RB_BITS(up) & elmdir) == 0) { \
+ /* demote parent. */ \
+ _RB_BITSUP(parent, field) ^= elmdir; \
+ _RB_BITSUP(sib, field) ^= sibdir; \
+ } else \
+ _RB_BITSUP(sib, field) ^= sibdir; \
+ elm = sib; \
} \
- gpar = _RB_PARENT_ONLY(gpar); \
+ \
+ /* \
+ * The edge descending from 'elm' away from 'parent' \
+ * is short. Rotate to make 'parent' a child of 'elm', \
+ * then lengthen the short edges descending from \
+ * 'parent' and 'elm' to rebalance. \
+ * \
+ * par elm \
+ * / \ / \ \
+ * e \ / \ \
+ * elm / \ \
+ * / \ par s \
+ * / \ / \ \
+ * / \ e \ \
+ * x s x \
+ */ \
+ RB_ROTATE(parent, elm, elmdir, field); \
RB_SET_PARENT(elm, gpar, field); \
RB_SWAP_CHILD(head, gpar, parent, elm, field); \
if (sib != elm) \
RB_AUGMENT(sib); \
break; \
- } while ((parent = _RB_PARENT_ONLY(gpar)) != NULL); \
+ } while (elm = parent, (parent = gpar) != NULL); \
}
#define RB_GENERATE_REMOVE(name, type, field, attr) \
@@ -732,10 +723,10 @@ name##_RB_REMOVE(struct name *head, struct type *out) \
\
child = RB_LEFT(out, field); \
in = RB_RIGHT(out, field); \
- opar = RB_UP(out, field); \
+ opar = _RB_UP(out, field); \
if (in == NULL || child == NULL) { \
in = child = in == NULL ? child : in; \
- parent = opar = _RB_PARENT_ONLY(opar); \
+ parent = opar = _RB_PTR(opar); \
} else { \
parent = in; \
while (RB_LEFT(in, field)) \
@@ -749,14 +740,16 @@ name##_RB_REMOVE(struct name *head, struct type *out) \
parent = RB_PARENT(in, field); \
RB_LEFT(parent, field) = child; \
} \
- RB_UP(in, field) = opar; \
- opar = _RB_PARENT_ONLY(opar); \
+ _RB_UP(in, field) = opar; \
+ opar = _RB_PTR(opar); \
} \
RB_SWAP_CHILD(head, opar, out, in, field); \
if (child != NULL) \
- RB_UP(child, field) = parent; \
+ _RB_UP(child, field) = parent; \
if (parent != NULL) { \
name##_RB_REMOVE_COLOR(head, parent, child); \
+ /* if rotation has made 'parent' the root of the same \
+ * subtree as before, don't re-augment it. */ \
if (parent == in && RB_LEFT(parent, field) == NULL) \
parent = RB_PARENT(parent, field); \
RB_UPDATE_AUGMENT(parent, field); \