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Add RB_REINSERT(3), a low overhead alternative to removing a node

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and reinserting it back with an updated key.

This is one of dependencies for the upcoming stats(3) code.

Reviewed by:	cem
Obtained from:	Netflix
MFC after:	2 weeks
Sponsored by:	Klara Inc, Netflix
Differential Revision:	https://reviews.freebsd.org/D21786
This commit is contained in:
trasz 2019-09-28 09:22:52 +00:00
parent 0216ab4d73
commit 253e3db566
3 changed files with 50 additions and 6 deletions
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1
share/man/man3/Makefile
View File

@ -324,6 +324,7 @@ MLINKS+= tree.3 RB_EMPTY.3 \
tree.3 RB_PROTOTYPE_REMOVE.3 \
tree.3 RB_PROTOTYPE_REMOVE_COLOR.3 \
tree.3 RB_PROTOTYPE_STATIC.3 \
tree.3 RB_REINSERT.3 \
tree.3 RB_REMOVE.3 \
tree.3 RB_RIGHT.3 \
tree.3 RB_ROOT.3 \

29
share/man/man3/tree.3
View File

@ -30,7 +30,7 @@
.\"
.\" $FreeBSD$
.\"
.Dd May 8, 2019
.Dd September 28, 2019
.Dt TREE 3
.Os
.Sh NAME
@ -62,6 +62,7 @@
.Nm RB_PROTOTYPE_NEXT ,
.Nm RB_PROTOTYPE_PREV ,
.Nm RB_PROTOTYPE_MINMAX ,
.Nm RB_PROTOTYPE_REINSERT ,
.Nm RB_GENERATE ,
.Nm RB_GENERATE_STATIC ,
.Nm RB_GENERATE_INSERT ,
@ -73,6 +74,7 @@
.Nm RB_GENERATE_NEXT ,
.Nm RB_GENERATE_PREV ,
.Nm RB_GENERATE_MINMAX ,
.Nm RB_GENERATE_REINSERT ,
.Nm RB_ENTRY ,
.Nm RB_HEAD ,
.Nm RB_INITIALIZER ,
@ -95,7 +97,8 @@
.Nm RB_FOREACH_REVERSE_SAFE ,
.Nm RB_INIT ,
.Nm RB_INSERT ,
.Nm RB_REMOVE
.Nm RB_REMOVE ,
.Nm RB_REINSERT
.Nd "implementations of splay and red-black trees"
.Sh SYNOPSIS
.In sys/tree.h
@ -138,6 +141,7 @@
.Fn RB_PROTOTYPE_NEXT NAME TYPE ATTR
.Fn RB_PROTOTYPE_PREV NAME TYPE ATTR
.Fn RB_PROTOTYPE_MINMAX NAME TYPE ATTR
.Fn RB_PROTOTYPE_REINSERT NAME TYPE ATTR
.Fn RB_GENERATE NAME TYPE FIELD CMP
.Fn RB_GENERATE_STATIC NAME TYPE FIELD CMP
.Fn RB_GENERATE_INSERT NAME TYPE FIELD CMP ATTR
@ -149,6 +153,7 @@
.Fn RB_GENERATE_NEXT NAME TYPE FIELD ATTR
.Fn RB_GENERATE_PREV NAME TYPE FIELD ATTR
.Fn RB_GENERATE_MINMAX NAME TYPE FIELD ATTR
.Fn RB_GENERATE_REINSERT NAME TYPE FIELD CMP ATTR
.Fn RB_ENTRY TYPE
.Fn RB_HEAD HEADNAME TYPE
.Fn RB_INITIALIZER "RB_HEAD *head"
@ -186,6 +191,8 @@
.Fn RB_INSERT NAME "RB_HEAD *head" "struct TYPE *elm"
.Ft "struct TYPE *"
.Fn RB_REMOVE NAME "RB_HEAD *head" "struct TYPE *elm"
.Ft "struct TYPE *"
.Fn RB_REINSERT NAME "RB_HEAD *head" "struct TYPE *elm"
.Sh DESCRIPTION
These macros define data structures for different types of trees:
splay trees and red-black trees.
@ -422,8 +429,9 @@ Individual prototypes can be declared with
.Fn RB_PROTOTYPE_NFIND ,
.Fn RB_PROTOTYPE_NEXT ,
.Fn RB_PROTOTYPE_PREV ,
.Fn RB_PROTOTYPE_MINMAX ,
and
.Fn RB_PROTOTYPE_MINMAX
.Fn RB_PROTOTYPE_REINSERT
in case not all functions are required.
The individual prototype macros expect
.Fa NAME ,
@ -456,8 +464,9 @@ As an alternative individual function bodies are generated with the
.Fn RB_GENERATE_NFIND ,
.Fn RB_GENERATE_NEXT ,
.Fn RB_GENERATE_PREV ,
.Fn RB_GENERATE_MINMAX ,
and
.Fn RB_GENERATE_MINMAX
.Fn RB_GENERATE_REINSERT
macros.
.Pp
Finally,
@ -559,6 +568,18 @@ and will be overwritten to provide safe traversal.
The
.Fn RB_EMPTY
macro should be used to check whether a red-black tree is empty.
.Pp
The
.Fn RB_REINSERT
macro updates the position of the element
.Fa elm
in the tree.
This must be called if a member of a
.Nm tree
is modified in a way that affects comparison, such as by modifying
a node's key.
This is a lower overhead alternative to removing the element
and reinserting it again.
.Sh EXAMPLES
The following example demonstrates how to declare a red-black tree
holding integers.

26
sys/sys/tree.h
View File

@ -393,7 +393,8 @@ struct { \
RB_PROTOTYPE_NFIND(name, type, attr); \
RB_PROTOTYPE_NEXT(name, type, attr); \
RB_PROTOTYPE_PREV(name, type, attr); \
RB_PROTOTYPE_MINMAX(name, type, attr);
RB_PROTOTYPE_MINMAX(name, type, attr); \
RB_PROTOTYPE_REINSERT(name, type, attr);
#define RB_PROTOTYPE_INSERT_COLOR(name, type, attr) \
attr void name##_RB_INSERT_COLOR(struct name *, struct type *)
#define RB_PROTOTYPE_REMOVE_COLOR(name, type, attr) \
@ -412,6 +413,8 @@ struct { \
attr struct type *name##_RB_PREV(struct type *)
#define RB_PROTOTYPE_MINMAX(name, type, attr) \
attr struct type *name##_RB_MINMAX(struct name *, int)
#define RB_PROTOTYPE_REINSERT(name, type, attr) \
attr struct type *name##_RB_REINSERT(struct name *, struct type *)
/* Main rb operation.
* Moves node close to the key of elm to top
@ -429,7 +432,9 @@ struct { \
RB_GENERATE_NFIND(name, type, field, cmp, attr) \
RB_GENERATE_NEXT(name, type, field, attr) \
RB_GENERATE_PREV(name, type, field, attr) \
RB_GENERATE_MINMAX(name, type, field, attr)
RB_GENERATE_MINMAX(name, type, field, attr) \
RB_GENERATE_REINSERT(name, type, field, cmp, attr)
#define RB_GENERATE_INSERT_COLOR(name, type, field, attr) \
attr void \
@ -758,6 +763,22 @@ name##_RB_MINMAX(struct name *head, int val) \
return (parent); \
}
#define RB_GENERATE_REINSERT(name, type, field, cmp, attr) \
attr struct type * \
name##_RB_REINSERT(struct name *head, struct type *elm) \
{ \
struct type *cmpelm; \
if (((cmpelm = RB_PREV(name, head, elm)) != NULL && \
cmp(cmpelm, elm) >= 0) || \
((cmpelm = RB_NEXT(name, head, elm)) != NULL && \
cmp(elm, cmpelm) >= 0)) { \
/* XXXLAS: Remove/insert is heavy handed. */ \
RB_REMOVE(name, head, elm); \
return (RB_INSERT(name, head, elm)); \
} \
return (NULL); \
} \
#define RB_NEGINF -1
#define RB_INF 1
@ -769,6 +790,7 @@ name##_RB_MINMAX(struct name *head, int val) \
#define RB_PREV(name, x, y) name##_RB_PREV(y)
#define RB_MIN(name, x) name##_RB_MINMAX(x, RB_NEGINF)
#define RB_MAX(name, x) name##_RB_MINMAX(x, RB_INF)
#define RB_REINSERT(name, x, y) name##_RB_REINSERT(x, y)
#define RB_FOREACH(x, name, head) \
for ((x) = RB_MIN(name, head); \