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Add documentation for tree.h and queue.h.

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.\" $OpenBSD: queue.3,v 1.60 2014/09/13 01:09:31 guenther Exp $
.\" $NetBSD: queue.3,v 1.4 1995/07/03 00:25:36 mycroft Exp $
.\"
.\" Copyright (c) 1993 The Regents of the University of California.
.\" 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.
.\" 3. Neither the name of the University nor the names of its contributors
.\" may be used to endorse or promote products derived from this software
.\" without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``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 REGENTS OR CONTRIBUTORS 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.
.\"
.\" @(#)queue.3 8.1 (Berkeley) 12/13/93
.\"
.Dd $Mdocdate: September 13 2014 $
.Dt QUEUE 3
.Os
.Sh NAME
.Nm SLIST_ENTRY ,
.Nm SLIST_HEAD ,
.Nm SLIST_HEAD_INITIALIZER ,
.Nm SLIST_FIRST ,
.Nm SLIST_NEXT ,
.Nm SLIST_EMPTY ,
.Nm SLIST_FOREACH ,
.Nm SLIST_FOREACH_SAFE ,
.Nm SLIST_INIT ,
.Nm SLIST_INSERT_AFTER ,
.Nm SLIST_INSERT_HEAD ,
.Nm SLIST_REMOVE_AFTER ,
.Nm SLIST_REMOVE_HEAD ,
.Nm SLIST_REMOVE ,
.Nm LIST_ENTRY ,
.Nm LIST_HEAD ,
.Nm LIST_HEAD_INITIALIZER ,
.Nm LIST_FIRST ,
.Nm LIST_NEXT ,
.Nm LIST_EMPTY ,
.Nm LIST_FOREACH ,
.Nm LIST_FOREACH_SAFE ,
.Nm LIST_INIT ,
.Nm LIST_INSERT_AFTER ,
.Nm LIST_INSERT_BEFORE ,
.Nm LIST_INSERT_HEAD ,
.Nm LIST_REMOVE ,
.Nm LIST_REPLACE ,
.Nm SIMPLEQ_ENTRY ,
.Nm SIMPLEQ_HEAD ,
.Nm SIMPLEQ_HEAD_INITIALIZER ,
.Nm SIMPLEQ_FIRST ,
.Nm SIMPLEQ_NEXT ,
.Nm SIMPLEQ_EMPTY ,
.Nm SIMPLEQ_FOREACH ,
.Nm SIMPLEQ_FOREACH_SAFE ,
.Nm SIMPLEQ_INIT ,
.Nm SIMPLEQ_INSERT_AFTER ,
.Nm SIMPLEQ_INSERT_HEAD ,
.Nm SIMPLEQ_INSERT_TAIL ,
.Nm SIMPLEQ_REMOVE_AFTER ,
.Nm SIMPLEQ_REMOVE_HEAD ,
.Nm TAILQ_ENTRY ,
.Nm TAILQ_HEAD ,
.Nm TAILQ_HEAD_INITIALIZER ,
.Nm TAILQ_FIRST ,
.Nm TAILQ_NEXT ,
.Nm TAILQ_LAST ,
.Nm TAILQ_PREV ,
.Nm TAILQ_EMPTY ,
.Nm TAILQ_FOREACH ,
.Nm TAILQ_FOREACH_SAFE ,
.Nm TAILQ_FOREACH_REVERSE ,
.Nm TAILQ_FOREACH_REVERSE_SAFE ,
.Nm TAILQ_INIT ,
.Nm TAILQ_INSERT_AFTER ,
.Nm TAILQ_INSERT_BEFORE ,
.Nm TAILQ_INSERT_HEAD ,
.Nm TAILQ_INSERT_TAIL ,
.Nm TAILQ_REMOVE ,
.Nm TAILQ_REPLACE
.Nd implementations of singly-linked lists, doubly-linked lists, simple queues, and tail queues
.Sh SYNOPSIS
.In sys/queue.h
.Pp
.Fn SLIST_ENTRY "TYPE"
.Fn SLIST_HEAD "HEADNAME" "TYPE"
.Fn SLIST_HEAD_INITIALIZER "SLIST_HEAD head"
.Ft "struct TYPE *"
.Fn SLIST_FIRST "SLIST_HEAD *head"
.Ft "struct TYPE *"
.Fn SLIST_NEXT "struct TYPE *listelm" "FIELDNAME"
.Ft int
.Fn SLIST_EMPTY "SLIST_HEAD *head"
.Fn SLIST_FOREACH "VARNAME" "SLIST_HEAD *head" "FIELDNAME"
.Fn SLIST_FOREACH_SAFE "VARNAME" "SLIST_HEAD *head" "FIELDNAME" "TEMP_VARNAME"
.Ft void
.Fn SLIST_INIT "SLIST_HEAD *head"
.Ft void
.Fn SLIST_INSERT_AFTER "struct TYPE *listelm" "struct TYPE *elm" "FIELDNAME"
.Ft void
.Fn SLIST_INSERT_HEAD "SLIST_HEAD *head" "struct TYPE *elm" "FIELDNAME"
.Ft void
.Fn SLIST_REMOVE_AFTER "struct TYPE *elm" "FIELDNAME"
.Ft void
.Fn SLIST_REMOVE_HEAD "SLIST_HEAD *head" "FIELDNAME"
.Ft void
.Fn SLIST_REMOVE "SLIST_HEAD *head" "struct TYPE *elm" "TYPE" "FIELDNAME"
.Pp
.Fn LIST_ENTRY "TYPE"
.Fn LIST_HEAD "HEADNAME" "TYPE"
.Fn LIST_HEAD_INITIALIZER "LIST_HEAD head"
.Ft "struct TYPE *"
.Fn LIST_FIRST "LIST_HEAD *head"
.Ft "struct TYPE *"
.Fn LIST_NEXT "struct TYPE *listelm" "FIELDNAME"
.Ft int
.Fn LIST_EMPTY "LIST_HEAD *head"
.Fn LIST_FOREACH "VARNAME" "LIST_HEAD *head" "FIELDNAME"
.Fn LIST_FOREACH_SAFE "VARNAME" "LIST_HEAD *head" "FIELDNAME" "TEMP_VARNAME"
.Ft void
.Fn LIST_INIT "LIST_HEAD *head"
.Ft void
.Fn LIST_INSERT_AFTER "struct TYPE *listelm" "struct TYPE *elm" "FIELDNAME"
.Ft void
.Fn LIST_INSERT_BEFORE "struct TYPE *listelm" "struct TYPE *elm" "FIELDNAME"
.Ft void
.Fn LIST_INSERT_HEAD "LIST_HEAD *head" "struct TYPE *elm" "FIELDNAME"
.Ft void
.Fn LIST_REMOVE "struct TYPE *elm" "FIELDNAME"
.Ft void
.Fn LIST_REPLACE "struct TYPE *elm" "struct TYPE *elm2" "FIELDNAME"
.Pp
.Fn SIMPLEQ_ENTRY "TYPE"
.Fn SIMPLEQ_HEAD "HEADNAME" "TYPE"
.Fn SIMPLEQ_HEAD_INITIALIZER "SIMPLEQ_HEAD head"
.Ft "struct TYPE *"
.Fn SIMPLEQ_FIRST "SIMPLEQ_HEAD *head"
.Ft "struct TYPE *"
.Fn SIMPLEQ_NEXT "struct TYPE *listelm" "FIELDNAME"
.Ft int
.Fn SIMPLEQ_EMPTY "SIMPLEQ_HEAD *head"
.Fn SIMPLEQ_FOREACH "VARNAME" "SIMPLEQ_HEAD *head" "FIELDNAME"
.Fn SIMPLEQ_FOREACH_SAFE "VARNAME" "SIMPLEQ_HEAD *head" "FIELDNAME" "TEMP_VARNAME"
.Ft void
.Fn SIMPLEQ_INIT "SIMPLEQ_HEAD *head"
.Ft void
.Fn SIMPLEQ_INSERT_AFTER "SIMPLEQ_HEAD *head" "struct TYPE *listelm" "struct TYPE *elm" "FIELDNAME"
.Ft void
.Fn SIMPLEQ_INSERT_HEAD "SIMPLEQ_HEAD *head" "struct TYPE *elm" "FIELDNAME"
.Ft void
.Fn SIMPLEQ_INSERT_TAIL "SIMPLEQ_HEAD *head" "struct TYPE *elm" "FIELDNAME"
.Ft void
.Fn SIMPLEQ_REMOVE_AFTER "SIMPLEQ_HEAD *head" "struct TYPE *elm" "FIELDNAME"
.Ft void
.Fn SIMPLEQ_REMOVE_HEAD "SIMPLEQ_HEAD *head" "FIELDNAME"
.Pp
.Fn TAILQ_ENTRY "TYPE"
.Fn TAILQ_HEAD "HEADNAME" "TYPE"
.Fn TAILQ_HEAD_INITIALIZER "TAILQ_HEAD head"
.Ft "struct TYPE *"
.Fn TAILQ_FIRST "TAILQ_HEAD *head"
.Ft "struct TYPE *"
.Fn TAILQ_NEXT "struct TYPE *listelm" "FIELDNAME"
.Ft "struct TYPE *"
.Fn TAILQ_LAST "TAILQ_HEAD *head" "HEADNAME"
.Ft "struct TYPE *"
.Fn TAILQ_PREV "struct TYPE *listelm" "HEADNAME" "FIELDNAME"
.Ft int
.Fn TAILQ_EMPTY "TAILQ_HEAD *head"
.Fn TAILQ_FOREACH "VARNAME" "TAILQ_HEAD *head" "FIELDNAME"
.Fn TAILQ_FOREACH_SAFE "VARNAME" "TAILQ_HEAD *head" "FIELDNAME" "TEMP_VARNAME"
.Fn TAILQ_FOREACH_REVERSE "VARNAME" "TAILQ_HEAD *head" "HEADNAME" "FIELDNAME"
.Fn TAILQ_FOREACH_REVERSE_SAFE "VARNAME" "TAILQ_HEAD *head" "HEADNAME" "FIELDNAME" "TEMP_VARNAME"
.Ft void
.Fn TAILQ_INIT "TAILQ_HEAD *head"
.Ft void
.Fn TAILQ_INSERT_AFTER "TAILQ_HEAD *head" "struct TYPE *listelm" "struct TYPE *elm" "FIELDNAME"
.Ft void
.Fn TAILQ_INSERT_BEFORE "struct TYPE *listelm" "struct TYPE *elm" "FIELDNAME"
.Ft void
.Fn TAILQ_INSERT_HEAD "TAILQ_HEAD *head" "struct TYPE *elm" "FIELDNAME"
.Ft void
.Fn TAILQ_INSERT_TAIL "TAILQ_HEAD *head" "struct TYPE *elm" "FIELDNAME"
.Ft void
.Fn TAILQ_REMOVE "TAILQ_HEAD *head" "struct TYPE *elm" "FIELDNAME"
.Ft void
.Fn TAILQ_REPLACE "TAILQ_HEAD *head" "struct TYPE *elm" "struct TYPE *elm2" "FIELDNAME"
.Sh DESCRIPTION
These macros define and operate on four types of data structures:
singly-linked lists, simple queues, lists, and tail queues.
All four structures support the following functionality:
.Pp
.Bl -enum -compact -offset indent
.It
Insertion of a new entry at the head of the list.
.It
Insertion of a new entry after any element in the list.
.It
Removal of an entry from the head of the list.
.It
Forward traversal through the list.
.El
.Pp
Singly-linked lists are the simplest of the four data structures
and support only the above functionality.
Singly-linked lists are ideal for applications with large datasets
and few or no removals, or for implementing a LIFO queue.
.Pp
Simple queues add the following functionality:
.Pp
.Bl -enum -compact -offset indent
.It
Entries can be added at the end of a list.
.El
.Pp
However:
.Pp
.Bl -enum -compact -offset indent
.It
All list insertions must specify the head of the list.
.It
Each head entry requires two pointers rather than one.
.It
Code size is about 15% greater and operations run about 20% slower
than singly-linked lists.
.El
.Pp
Simple queues are ideal for applications with large datasets and
few or no removals, or for implementing a FIFO queue.
.Pp
All doubly linked types of data structures (lists and tail queues)
additionally allow:
.Pp
.Bl -enum -compact -offset indent
.It
Insertion of a new entry before any element in the list.
.It
Removal of any entry in the list.
.El
.Pp
However:
.Pp
.Bl -enum -compact -offset indent
.It
Each element requires two pointers rather than one.
.It
Code size and execution time of operations (except for removal) is about
twice that of the singly-linked data-structures.
.El
.Pp
Lists are the simplest of the doubly linked data structures and support
only the above functionality over singly-linked lists.
.Pp
Tail queues add the following functionality:
.Pp
.Bl -enum -compact -offset indent
.It
Entries can be added at the end of a list.
.It
They may be traversed backwards, at a cost.
.El
.Pp
However:
.Pp
.Bl -enum -compact -offset indent
.It
All list insertions and removals must specify the head of the list.
.It
Each head entry requires two pointers rather than one.
.It
Code size is about 15% greater and operations run about 20% slower
than singly-linked lists.
.El
.Pp
An additional type of data structure, circular queues, violated the C
language aliasing rules and were miscompiled as a result.
All code using them should be converted to another structure;
tail queues are usually the easiest to convert to.
.Pp
In the macro definitions,
.Fa TYPE
is the name tag of a user defined structure that must contain a field of type
.Li SLIST_ENTRY ,
.Li LIST_ENTRY ,
.Li SIMPLEQ_ENTRY ,
or
.Li TAILQ_ENTRY ,
named
.Fa FIELDNAME .
The argument
.Fa HEADNAME
is the name tag of a user defined structure that must be declared
using the macros
.Fn SLIST_HEAD ,
.Fn LIST_HEAD ,
.Fn SIMPLEQ_HEAD ,
or
.Fn TAILQ_HEAD .
See the examples below for further explanation of how these macros are used.
.Sh SINGLY-LINKED LISTS
A singly-linked list is headed by a structure defined by the
.Fn SLIST_HEAD
macro.
This structure contains a single pointer to the first element on the list.
The elements are singly linked for minimum space and pointer manipulation
overhead at the expense of O(n) removal for arbitrary elements.
New elements can be added to the list after an existing element or
at the head of the list.
A
.Fa SLIST_HEAD
structure is declared as follows:
.Bd -literal -offset indent
SLIST_HEAD(HEADNAME, TYPE) head;
.Ed
.Pp
where
.Fa HEADNAME
is the name of the structure to be defined, and struct
.Fa TYPE
is the type of the elements to be linked into the list.
A pointer to the head of the list can later be declared as:
.Bd -literal -offset indent
struct HEADNAME *headp;
.Ed
.Pp
(The names
.Li head
and
.Li headp
are user selectable.)
.Pp
The
.Fa HEADNAME
facility is often not used, leading to the following bizarre code:
.Bd -literal -offset indent
SLIST_HEAD(, TYPE) head, *headp;
.Ed
.Pp
The
.Fn SLIST_ENTRY
macro declares a structure that connects the elements in the list.
.Pp
The
.Fn SLIST_INIT
macro initializes the list referenced by
.Fa head .
.Pp
The list can also be initialized statically by using the
.Fn SLIST_HEAD_INITIALIZER
macro like this:
.Bd -literal -offset indent
SLIST_HEAD(HEADNAME, TYPE) head = SLIST_HEAD_INITIALIZER(head);
.Ed
.Pp
The
.Fn SLIST_INSERT_HEAD
macro inserts the new element
.Fa elm
at the head of the list.
.Pp
The
.Fn SLIST_INSERT_AFTER
macro inserts the new element
.Fa elm
after the element
.Fa listelm .
.Pp
The
.Fn SLIST_REMOVE_HEAD
macro removes the first element of the list pointed by
.Fa head .
.Pp
The
.Fn SLIST_REMOVE_AFTER
macro removes the list element immediately following
.Fa elm .
.Pp
The
.Fn SLIST_REMOVE
macro removes the element
.Fa elm
of the list pointed by
.Fa head .
.Pp
The
.Fn SLIST_FIRST
and
.Fn SLIST_NEXT
macros can be used to traverse the list:
.Bd -literal -offset indent
for (np = SLIST_FIRST(&head); np != NULL; np = SLIST_NEXT(np, FIELDNAME))
.Ed
.Pp
Or, for simplicity, one can use the
.Fn SLIST_FOREACH
macro:
.Bd -literal -offset indent
SLIST_FOREACH(np, head, FIELDNAME)
.Ed
.Pp
The macro
.Fn SLIST_FOREACH_SAFE
traverses the list referenced by head in a
forward direction, assigning each element in turn to var.
However, unlike
.Fn SLIST_FOREACH
it is permitted to remove var as well
as free it from within the loop safely without interfering with the traversal.
.Pp
The
.Fn SLIST_EMPTY
macro should be used to check whether a simple list is empty.
.Sh SINGLY-LINKED LIST EXAMPLE
.Bd -literal
SLIST_HEAD(listhead, entry) head;
struct entry {
...
SLIST_ENTRY(entry) entries; /* Simple list. */
...
} *n1, *n2, *np;
SLIST_INIT(&head); /* Initialize simple list. */
n1 = malloc(sizeof(struct entry)); /* Insert at the head. */
SLIST_INSERT_HEAD(&head, n1, entries);
n2 = malloc(sizeof(struct entry)); /* Insert after. */
SLIST_INSERT_AFTER(n1, n2, entries);
SLIST_FOREACH(np, &head, entries) /* Forward traversal. */
np-> ...
while (!SLIST_EMPTY(&head)) { /* Delete. */
n1 = SLIST_FIRST(&head);
SLIST_REMOVE_HEAD(&head, entries);
free(n1);
}
.Ed
.Sh LISTS
A list is headed by a structure defined by the
.Fn LIST_HEAD
macro.
This structure contains a single pointer to the first element on the list.
The elements are doubly linked so that an arbitrary element can be
removed without traversing the list.
New elements can be added to the list after an existing element,
before an existing element, or at the head of the list.
A
.Fa LIST_HEAD
structure is declared as follows:
.Bd -literal -offset indent
LIST_HEAD(HEADNAME, TYPE) head;
.Ed
.Pp
where
.Fa HEADNAME
is the name of the structure to be defined, and struct
.Fa TYPE
is the type of the elements to be linked into the list.
A pointer to the head of the list can later be declared as:
.Bd -literal -offset indent
struct HEADNAME *headp;
.Ed
.Pp
(The names
.Li head
and
.Li headp
are user selectable.)
.Pp
The
.Fa HEADNAME
facility is often not used, leading to the following bizarre code:
.Bd -literal -offset indent
LIST_HEAD(, TYPE) head, *headp;
.Ed
.Pp
The
.Fn LIST_ENTRY
macro declares a structure that connects the elements in the list.
.Pp
The
.Fn LIST_INIT
macro initializes the list referenced by
.Fa head .
.Pp
The list can also be initialized statically by using the
.Fn LIST_HEAD_INITIALIZER
macro like this:
.Bd -literal -offset indent
LIST_HEAD(HEADNAME, TYPE) head = LIST_HEAD_INITIALIZER(head);
.Ed
.Pp
The
.Fn LIST_INSERT_HEAD
macro inserts the new element
.Fa elm
at the head of the list.
.Pp
The
.Fn LIST_INSERT_AFTER
macro inserts the new element
.Fa elm
after the element
.Fa listelm .
.Pp
The
.Fn LIST_INSERT_BEFORE
macro inserts the new element
.Fa elm
before the element
.Fa listelm .
.Pp
The
.Fn LIST_REMOVE
macro removes the element
.Fa elm
from the list.
.Pp
The
.Fn LIST_REPLACE
macro replaces the list element
.Fa elm
with the new element
.Fa elm2 .
.Pp
The
.Fn LIST_FIRST
and
.Fn LIST_NEXT
macros can be used to traverse the list:
.Bd -literal -offset indent
for (np = LIST_FIRST(&head); np != NULL; np = LIST_NEXT(np, FIELDNAME))
.Ed
.Pp
Or, for simplicity, one can use the
.Fn LIST_FOREACH
macro:
.Bd -literal -offset indent
LIST_FOREACH(np, head, FIELDNAME)
.Ed
.Pp
The macro
.Fn LIST_FOREACH_SAFE
traverses the list referenced by head in a
forward direction, assigning each element in turn to var.
However, unlike
.Fn LIST_FOREACH
it is permitted to remove var as well
as free it from within the loop safely without interfering with the traversal.
.Pp
The
.Fn LIST_EMPTY
macro should be used to check whether a list is empty.
.Sh LIST EXAMPLE
.Bd -literal
LIST_HEAD(listhead, entry) head;
struct entry {
...
LIST_ENTRY(entry) entries; /* List. */
...
} *n1, *n2, *np;
LIST_INIT(&head); /* Initialize list. */
n1 = malloc(sizeof(struct entry)); /* Insert at the head. */
LIST_INSERT_HEAD(&head, n1, entries);
n2 = malloc(sizeof(struct entry)); /* Insert after. */
LIST_INSERT_AFTER(n1, n2, entries);
n2 = malloc(sizeof(struct entry)); /* Insert before. */
LIST_INSERT_BEFORE(n1, n2, entries);
/* Forward traversal. */
LIST_FOREACH(np, &head, entries)
np-> ...
while (!LIST_EMPTY(&head)) /* Delete. */
n1 = LIST_FIRST(&head);
LIST_REMOVE(n1, entries);
free(n1);
}
.Ed
.Sh SIMPLE QUEUES
A simple queue is headed by a structure defined by the
.Fn SIMPLEQ_HEAD
macro.
This structure contains a pair of pointers, one to the first element in the
simple queue and the other to the last element in the simple queue.
The elements are singly linked.
New elements can be added to the queue after an existing element,
at the head of the queue or at the tail of the queue.
A
.Fa SIMPLEQ_HEAD
structure is declared as follows:
.Bd -literal -offset indent
SIMPLEQ_HEAD(HEADNAME, TYPE) head;
.Ed
.Pp
where
.Fa HEADNAME
is the name of the structure to be defined, and struct
.Fa TYPE
is the type of the elements to be linked into the queue.
A pointer to the head of the queue can later be declared as:
.Bd -literal -offset indent
struct HEADNAME *headp;
.Ed
.Pp
(The names
.Li head
and
.Li headp
are user selectable.)
.Pp
The
.Fn SIMPLEQ_ENTRY
macro declares a structure that connects the elements in
the queue.
.Pp
The
.Fn SIMPLEQ_INIT
macro initializes the queue referenced by
.Fa head .
.Pp
The queue can also be initialized statically by using the
.Fn SIMPLEQ_HEAD_INITIALIZER
macro like this:
.Bd -literal -offset indent
SIMPLEQ_HEAD(HEADNAME, TYPE) head = SIMPLEQ_HEAD_INITIALIZER(head);
.Ed
.Pp
The
.Fn SIMPLEQ_INSERT_AFTER
macro inserts the new element
.Fa elm
after the element
.Fa listelm .
.Pp
The
.Fn SIMPLEQ_INSERT_HEAD
macro inserts the new element
.Fa elm
at the head of the queue.
.Pp
The
.Fn SIMPLEQ_INSERT_TAIL
macro inserts the new element
.Fa elm
at the end of the queue.
.Pp
The
.Fn SIMPLEQ_REMOVE_AFTER
macro removes the queue element immediately following
.Fa elm .
.Pp
The
.Fn SIMPLEQ_REMOVE_HEAD
macro removes the first element
from the queue.
.Pp
The
.Fn SIMPLEQ_FIRST
and
.Fn SIMPLEQ_NEXT
macros can be used to traverse the queue.
The
.Fn SIMPLEQ_FOREACH
is used for queue traversal:
.Bd -literal -offset indent
SIMPLEQ_FOREACH(np, head, FIELDNAME)
.Ed
.Pp
The macro
.Fn SIMPLEQ_FOREACH_SAFE
traverses the queue referenced by head in a
forward direction, assigning each element in turn to var.
However, unlike
.Fn SIMPLEQ_FOREACH
it is permitted to remove var as well
as free it from within the loop safely without interfering with the traversal.
.Pp
The
.Fn SIMPLEQ_EMPTY
macro should be used to check whether a list is empty.
.Sh SIMPLE QUEUE EXAMPLE
.Bd -literal
SIMPLEQ_HEAD(listhead, entry) head = SIMPLEQ_HEAD_INITIALIZER(head);
struct entry {
...
SIMPLEQ_ENTRY(entry) entries; /* Simple queue. */
...
} *n1, *n2, *np;
n1 = malloc(sizeof(struct entry)); /* Insert at the head. */
SIMPLEQ_INSERT_HEAD(&head, n1, entries);
n2 = malloc(sizeof(struct entry)); /* Insert after. */
SIMPLEQ_INSERT_AFTER(&head, n1, n2, entries);
n2 = malloc(sizeof(struct entry)); /* Insert at the tail. */
SIMPLEQ_INSERT_TAIL(&head, n2, entries);
/* Forward traversal. */
SIMPLEQ_FOREACH(np, &head, entries)
np-> ...
/* Delete. */
while (!SIMPLEQ_EMPTY(&head)) {
n1 = SIMPLEQ_FIRST(&head);
SIMPLEQ_REMOVE_HEAD(&head, entries);
free(n1);
}
.Ed
.Sh TAIL QUEUES
A tail queue is headed by a structure defined by the
.Fn TAILQ_HEAD
macro.
This structure contains a pair of pointers,
one to the first element in the tail queue and the other to
the last element in the tail queue.
The elements are doubly linked so that an arbitrary element can be
removed without traversing the tail queue.
New elements can be added to the queue after an existing element,
before an existing element, at the head of the queue, or at the end
of the queue.
A
.Fa TAILQ_HEAD
structure is declared as follows:
.Bd -literal -offset indent
TAILQ_HEAD(HEADNAME, TYPE) head;
.Ed
.Pp
where
.Fa HEADNAME
is the name of the structure to be defined, and struct
.Fa TYPE
is the type of the elements to be linked into the tail queue.
A pointer to the head of the tail queue can later be declared as:
.Bd -literal -offset indent
struct HEADNAME *headp;
.Ed
.Pp
(The names
.Li head
and
.Li headp
are user selectable.)
.Pp
The
.Fn TAILQ_ENTRY
macro declares a structure that connects the elements in
the tail queue.
.Pp
The
.Fn TAILQ_INIT
macro initializes the tail queue referenced by
.Fa head .
.Pp
The tail queue can also be initialized statically by using the
.Fn TAILQ_HEAD_INITIALIZER
macro.
.Pp
The
.Fn TAILQ_INSERT_HEAD
macro inserts the new element
.Fa elm
at the head of the tail queue.
.Pp
The
.Fn TAILQ_INSERT_TAIL
macro inserts the new element
.Fa elm
at the end of the tail queue.
.Pp
The
.Fn TAILQ_INSERT_AFTER
macro inserts the new element
.Fa elm
after the element
.Fa listelm .
.Pp
The
.Fn TAILQ_INSERT_BEFORE
macro inserts the new element
.Fa elm
before the element
.Fa listelm .
.Pp
The
.Fn TAILQ_REMOVE
macro removes the element
.Fa elm
from the tail queue.
.Pp
The
.Fn TAILQ_REPLACE
macro replaces the list element
.Fa elm
with the new element
.Fa elm2 .
.Pp
.Fn TAILQ_FOREACH
and
.Fn TAILQ_FOREACH_REVERSE
are used for traversing a tail queue.
.Fn TAILQ_FOREACH
starts at the first element and proceeds towards the last.
.Fn TAILQ_FOREACH_REVERSE
starts at the last element and proceeds towards the first.
.Bd -literal -offset indent
TAILQ_FOREACH(np, &head, FIELDNAME)
TAILQ_FOREACH_REVERSE(np, &head, HEADNAME, FIELDNAME)
.Ed
.Pp
The macros
.Fn TAILQ_FOREACH_SAFE
and
.Fn TAILQ_FOREACH_REVERSE_SAFE
traverse the list referenced by head
in a forward or reverse direction respectively,
assigning each element in turn to var.
However, unlike their unsafe counterparts,
they permit both the removal of var
as well as freeing it from within the loop safely
without interfering with the traversal.
.Pp
The
.Fn TAILQ_FIRST ,
.Fn TAILQ_NEXT ,
.Fn TAILQ_LAST
and
.Fn TAILQ_PREV
macros can be used to manually traverse a tail queue or an arbitrary part of
one.
.Pp
The
.Fn TAILQ_EMPTY
macro should be used to check whether a tail queue is empty.
.Sh TAIL QUEUE EXAMPLE
.Bd -literal
TAILQ_HEAD(tailhead, entry) head;
struct entry {
...
TAILQ_ENTRY(entry) entries; /* Tail queue. */
...
} *n1, *n2, *np;
TAILQ_INIT(&head); /* Initialize queue. */
n1 = malloc(sizeof(struct entry)); /* Insert at the head. */
TAILQ_INSERT_HEAD(&head, n1, entries);
n1 = malloc(sizeof(struct entry)); /* Insert at the tail. */
TAILQ_INSERT_TAIL(&head, n1, entries);
n2 = malloc(sizeof(struct entry)); /* Insert after. */
TAILQ_INSERT_AFTER(&head, n1, n2, entries);
n2 = malloc(sizeof(struct entry)); /* Insert before. */
TAILQ_INSERT_BEFORE(n1, n2, entries);
/* Forward traversal. */
TAILQ_FOREACH(np, &head, entries)
np-> ...
/* Manual forward traversal. */
for (np = n2; np != NULL; np = TAILQ_NEXT(np, entries))
np-> ...
/* Delete. */
while ((np = TAILQ_FIRST(&head))) {
TAILQ_REMOVE(&head, np, entries);
free(np);
}
.Ed
.Sh NOTES
It is an error to assume the next and previous fields are preserved
after an element has been removed from a list or queue.
Using any macro (except the various forms of insertion) on an element
removed from a list or queue is incorrect.
An example of erroneous usage is removing the same element twice.
.Pp
The
.Fn SLIST_END ,
.Fn LIST_END ,
.Fn SIMPLEQ_END
and
.Fn TAILQ_END
macros are deprecated; they provided symmetry with the historical
.Fn CIRCLEQ_END
and just expand to
.Dv NULL .
.Pp
Trying to free a list in the following way is a common error:
.Bd -literal -offset indent
LIST_FOREACH(var, head, entry)
free(var);
free(head);
.Ed
.Pp
Since
.Va var
is free'd, the FOREACH macros refer to a pointer that may have been
reallocated already.
A similar situation occurs when the current element is deleted
from the list.
In cases like these the data structure's FOREACH_SAFE macros should be used
instead.
.Sh HISTORY
The
.Nm queue
functions first appeared in
.Bx 4.4 .
The historical circle queue macros were deprecated in
.Ox 5.5 .

2
queue.h
View File

@ -1,3 +1,5 @@
/* man ./queue.3 to see documentation on how to use this! */
/* $OpenBSD: queue.h,v 1.38 2013/07/03 15:05:21 fgsch Exp $ */
/* $NetBSD: queue.h,v 1.11 1996/05/16 05:17:14 mycroft Exp $ */

577
tree.3 Normal file
View File

@ -0,0 +1,577 @@
.\" $OpenBSD: tree.3,v 1.26 2014/09/08 01:27:55 schwarze Exp $
.\"/*
.\" * 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.
.\" */
.Dd $Mdocdate: September 8 2014 $
.Dt TREE 3
.Os
.Sh NAME
.Nm SPLAY_PROTOTYPE ,
.Nm SPLAY_GENERATE ,
.Nm SPLAY_ENTRY ,
.Nm SPLAY_HEAD ,
.Nm SPLAY_INITIALIZER ,
.Nm SPLAY_ROOT ,
.Nm SPLAY_EMPTY ,
.Nm SPLAY_NEXT ,
.Nm SPLAY_MIN ,
.Nm SPLAY_MAX ,
.Nm SPLAY_FIND ,
.Nm SPLAY_LEFT ,
.Nm SPLAY_RIGHT ,
.Nm SPLAY_FOREACH ,
.Nm SPLAY_INIT ,
.Nm SPLAY_INSERT ,
.Nm SPLAY_REMOVE ,
.Nm RB_PROTOTYPE ,
.Nm RB_PROTOTYPE_STATIC ,
.Nm RB_GENERATE ,
.Nm RB_GENERATE_STATIC ,
.Nm RB_ENTRY ,
.Nm RB_HEAD ,
.Nm RB_INITIALIZER ,
.Nm RB_ROOT ,
.Nm RB_EMPTY ,
.Nm RB_NEXT ,
.Nm RB_PREV ,
.Nm RB_MIN ,
.Nm RB_MAX ,
.Nm RB_FIND ,
.Nm RB_NFIND ,
.Nm RB_LEFT ,
.Nm RB_RIGHT ,
.Nm RB_PARENT ,
.Nm RB_FOREACH ,
.Nm RB_FOREACH_SAFE ,
.Nm RB_FOREACH_REVERSE ,
.Nm RB_FOREACH_REVERSE_SAFE ,
.Nm RB_INIT ,
.Nm RB_INSERT ,
.Nm RB_REMOVE
.Nd implementations of splay and red-black trees
.Sh SYNOPSIS
.In sys/tree.h
.Pp
.Fn SPLAY_PROTOTYPE "NAME" "TYPE" "FIELD" "CMP"
.Fn SPLAY_GENERATE "NAME" "TYPE" "FIELD" "CMP"
.Fn SPLAY_ENTRY "TYPE"
.Fn SPLAY_HEAD "HEADNAME" "TYPE"
.Ft "struct TYPE *"
.Fn SPLAY_INITIALIZER "SPLAY_HEAD *head"
.Fn SPLAY_ROOT "SPLAY_HEAD *head"
.Ft "int"
.Fn SPLAY_EMPTY "SPLAY_HEAD *head"
.Ft "struct TYPE *"
.Fn SPLAY_NEXT "NAME" "SPLAY_HEAD *head" "struct TYPE *elm"
.Ft "struct TYPE *"
.Fn SPLAY_MIN "NAME" "SPLAY_HEAD *head"
.Ft "struct TYPE *"
.Fn SPLAY_MAX "NAME" "SPLAY_HEAD *head"
.Ft "struct TYPE *"
.Fn SPLAY_FIND "NAME" "SPLAY_HEAD *head" "struct TYPE *elm"
.Ft "struct TYPE *"
.Fn SPLAY_LEFT "struct TYPE *elm" "SPLAY_ENTRY NAME"
.Ft "struct TYPE *"
.Fn SPLAY_RIGHT "struct TYPE *elm" "SPLAY_ENTRY NAME"
.Fn SPLAY_FOREACH "VARNAME" "NAME" "SPLAY_HEAD *head"
.Ft void
.Fn SPLAY_INIT "SPLAY_HEAD *head"
.Ft "struct TYPE *"
.Fn SPLAY_INSERT "NAME" "SPLAY_HEAD *head" "struct TYPE *elm"
.Ft "struct TYPE *"
.Fn SPLAY_REMOVE "NAME" "SPLAY_HEAD *head" "struct TYPE *elm"
.Pp
.Fn RB_PROTOTYPE "NAME" "TYPE" "FIELD" "CMP"
.Fn RB_PROTOTYPE_STATIC "NAME" "TYPE" "FIELD" "CMP"
.Fn RB_GENERATE "NAME" "TYPE" "FIELD" "CMP"
.Fn RB_GENERATE_STATIC "NAME" "TYPE" "FIELD" "CMP"
.Fn RB_ENTRY "TYPE"
.Fn RB_HEAD "HEADNAME" "TYPE"
.Fn RB_INITIALIZER "RB_HEAD *head"
.Ft "struct TYPE *"
.Fn RB_ROOT "RB_HEAD *head"
.Ft "int"
.Fn RB_EMPTY "RB_HEAD *head"
.Ft "struct TYPE *"
.Fn RB_NEXT "NAME" "RB_HEAD *head" "struct TYPE *elm"
.Ft "struct TYPE *"
.Fn RB_PREV "NAME" "RB_HEAD *head" "struct TYPE *elm"
.Ft "struct TYPE *"
.Fn RB_MIN "NAME" "RB_HEAD *head"
.Ft "struct TYPE *"
.Fn RB_MAX "NAME" "RB_HEAD *head"
.Ft "struct TYPE *"
.Fn RB_FIND "NAME" "RB_HEAD *head" "struct TYPE *elm"
.Ft "struct TYPE *"
.Fn RB_NFIND "NAME" "RB_HEAD *head" "struct TYPE *elm"
.Ft "struct TYPE *"
.Fn RB_LEFT "struct TYPE *elm" "RB_ENTRY NAME"
.Ft "struct TYPE *"
.Fn RB_RIGHT "struct TYPE *elm" "RB_ENTRY NAME"
.Ft "struct TYPE *"
.Fn RB_PARENT "struct TYPE *elm" "RB_ENTRY NAME"
.Fn RB_FOREACH "VARNAME" "NAME" "RB_HEAD *head"
.Fn RB_FOREACH_SAFE "VARNAME" "NAME" "RB_HEAD *head" "TEMP_VARNAME"
.Fn RB_FOREACH_REVERSE "VARNAME" "NAME" "RB_HEAD *head"
.Fn RB_FOREACH_REVERSE_SAFE "VARNAME" "NAME" "RB_HEAD *head" "TEMP_VARNAME"
.Ft void
.Fn RB_INIT "RB_HEAD *head"
.Ft "struct TYPE *"
.Fn RB_INSERT "NAME" "RB_HEAD *head" "struct TYPE *elm"
.Ft "struct TYPE *"
.Fn RB_REMOVE "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.
.Pp
In the macro definitions,
.Fa TYPE
is the name tag of a user defined structure that must contain a field named
.Fa FIELD ,
of type
.Li SPLAY_ENTRY
or
.Li RB_ENTRY .
The argument
.Fa HEADNAME
is the name tag of a user defined structure that must be declared
using the macros
.Fn SPLAY_HEAD
or
.Fn RB_HEAD .
The argument
.Fa NAME
has to be a unique name prefix for every tree that is defined.
.Pp
The function prototypes are declared with
.Li SPLAY_PROTOTYPE ,
.Li RB_PROTOTYPE ,
or
.Li RB_PROTOTYPE_STATIC .
The function bodies are generated with
.Li SPLAY_GENERATE ,
.Li RB_GENERATE ,
or
.Li RB_GENERATE_STATIC .
See the examples below for further explanation of how these macros are used.
.Sh SPLAY TREES
A splay tree is a self-organizing data structure.
Every operation on the tree causes a splay to happen.
The splay moves the requested node to the root of the tree and partly
rebalances it.
.Pp
This has the benefit that request locality causes faster lookups as
the requested nodes move to the top of the tree.
On the other hand, every lookup causes memory writes.
.Pp
The Balance Theorem bounds the total access time for m operations
and n inserts on an initially empty tree as O((m + n)lg n).
The amortized cost for a sequence of m accesses to a splay tree is O(lg n).
.Pp
A splay tree is headed by a structure defined by the
.Fn SPLAY_HEAD
macro.
A
.Fa SPLAY_HEAD
structure is declared as follows:
.Bd -literal -offset indent
SPLAY_HEAD(HEADNAME, TYPE) head;
.Ed
.Pp
where
.Fa HEADNAME
is the name of the structure to be defined, and struct
.Fa TYPE
is the type of the elements to be inserted into the tree.
.Pp
The
.Fn SPLAY_ENTRY
macro declares a structure that allows elements to be connected in the tree.
.Pp
In order to use the functions that manipulate the tree structure,
their prototypes need to be declared with the
.Fn SPLAY_PROTOTYPE
macro,
where
.Fa NAME
is a unique identifier for this particular tree.
The
.Fa TYPE
argument is the type of the structure that is being managed
by the tree.
The
.Fa FIELD
argument is the name of the element defined by
.Fn SPLAY_ENTRY .
.Pp
The function bodies are generated with the
.Fn SPLAY_GENERATE
macro.
It takes the same arguments as the
.Fn SPLAY_PROTOTYPE
macro, but should be used only once.
.Pp
Finally,
the
.Fa CMP
argument is the name of a function used to compare trees' nodes
with each other.
The function takes two arguments of type
.Fa "struct TYPE *" .
If the first argument is smaller than the second, the function returns a
value smaller than zero.
If they are equal, the function returns zero.
Otherwise, it should return a value greater than zero.
The compare function defines the order of the tree elements.
.Pp
The
.Fn SPLAY_INIT
macro initializes the tree referenced by
.Fa head .
.Pp
The splay tree can also be initialized statically by using the
.Fn SPLAY_INITIALIZER
macro like this:
.Bd -literal -offset indent
SPLAY_HEAD(HEADNAME, TYPE) head = SPLAY_INITIALIZER(&head);
.Ed
.Pp
The
.Fn SPLAY_INSERT
macro inserts the new element
.Fa elm
into the tree.
Upon success,
.Va NULL
is returned.
If a matching element already exists in the tree, the insertion is
aborted, and a pointer to the existing element is returned.
.Pp
The
.Fn SPLAY_REMOVE
macro removes the element
.Fa elm
from the tree pointed by
.Fa head .
Upon success, a pointer to the removed element is returned.
.Va NULL
is returned if
.Fa elm
is not present in the tree.
.Pp
The
.Fn SPLAY_FIND
macro can be used to find a particular element in the tree.
.Bd -literal -offset indent
struct TYPE find, *res;
find.key = 30;
res = SPLAY_FIND(NAME, &head, &find);
.Ed
.Pp
The
.Fn SPLAY_ROOT ,
.Fn SPLAY_MIN ,
.Fn SPLAY_MAX ,
and
.Fn SPLAY_NEXT
macros can be used to traverse the tree:
.Bd -literal -offset indent
for (np = SPLAY_MIN(NAME, &head); np != NULL; np = SPLAY_NEXT(NAME, &head, np))
.Ed
.Pp
Or, for simplicity, one can use the
.Fn SPLAY_FOREACH
macro:
.Bd -literal -offset indent
SPLAY_FOREACH(np, NAME, &head)
.Ed
.Pp
The
.Fn SPLAY_EMPTY
macro should be used to check whether a splay tree is empty.
.Sh 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:
.Pp
.Bl -enum -compact -offset indent
.It
every search path from the root to a leaf consists of the same number of
black nodes,
.It
each red node (except for the root) has a black parent,
.It
each leaf node is black.
.El
.Pp
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).
.Pp
A red-black tree is headed by a structure defined by the
.Fn RB_HEAD
macro.
A
.Fa RB_HEAD
structure is declared as follows:
.Bd -literal -offset indent
RB_HEAD(HEADNAME, TYPE) head;
.Ed
.Pp
where
.Fa HEADNAME
is the name of the structure to be defined, and struct
.Fa TYPE
is the type of the elements to be inserted into the tree.
.Pp
The
.Fn RB_ENTRY
macro declares a structure that allows elements to be connected in the tree.
.Pp
In order to use the functions that manipulate the tree structure,
their prototypes need to be declared with the
.Fn RB_PROTOTYPE
or
.Fn RB_PROTOTYPE_STATIC
macros,
where
.Fa NAME
is a unique identifier for this particular tree.
The
.Fa TYPE
argument is the type of the structure that is being managed
by the tree.
The
.Fa FIELD
argument is the name of the element defined by
.Fn RB_ENTRY .
.Pp
The function bodies are generated with the
.Fn RB_GENERATE
or
.Fn RB_GENERATE_STATIC
macros.
These macros take the same arguments as the
.Fn RB_PROTOTYPE
and
.Fn RB_PROTOTYPE_STATIC
macros, but should be used only once.
.Pp
Finally,
the
.Fa CMP
argument is the name of a function used to compare trees' nodes
with each other.
The function takes two arguments of type
.Fa "struct TYPE *" .
If the first argument is smaller than the second, the function returns a
value smaller than zero.
If they are equal, the function returns zero.
Otherwise, it should return a value greater than zero.
The compare function defines the order of the tree elements.
.Pp
The
.Fn RB_INIT
macro initializes the tree referenced by
.Fa head .
.Pp
The red-black tree can also be initialized statically by using the
.Fn RB_INITIALIZER
macro like this:
.Bd -literal -offset indent
RB_HEAD(HEADNAME, TYPE) head = RB_INITIALIZER(&head);
.Ed
.Pp
The
.Fn RB_INSERT
macro inserts the new element
.Fa elm
into the tree.
Upon success,
.Va NULL
is returned.
If a matching element already exists in the tree, the insertion is
aborted, and a pointer to the existing element is returned.
.Pp
The
.Fn RB_REMOVE
macro removes the element
.Fa elm
from the tree pointed by
.Fa head .
.Fn RB_REMOVE
returns
.Fa elm .
.Pp
The
.Fn RB_FIND
and
.Fn RB_NFIND
macros can be used to find a particular element in the tree.
.Fn RB_FIND
finds the node with the same key as
.Fa elm .
.Fn RB_NFIND
finds the first node greater than or equal to the search key.
.Bd -literal -offset indent
struct TYPE find, *res;
find.key = 30;
res = RB_FIND(NAME, &head, &find);
.Ed
.Pp
The
.Fn RB_ROOT ,
.Fn RB_MIN ,
.Fn RB_MAX ,
.Fn RB_NEXT ,
and
.Fn RB_PREV
macros can be used to traverse the tree:
.Bd -literal -offset indent
for (np = RB_MIN(NAME, &head); np != NULL; np = RB_NEXT(NAME, &head, np))
.Ed
.Pp
Or, for simplicity, one can use the
.Fn RB_FOREACH
or
.Fn RB_FOREACH_REVERSE
macros:
.Bd -literal -offset indent
RB_FOREACH(np, NAME, &head)
.Ed
.Pp
The macros
.Fn RB_FOREACH_SAFE
and
.Fn RB_FOREACH_REVERSE_SAFE
traverse the tree referenced by head
in a forward or reverse direction respectively,
assigning each element in turn to np.
However, unlike their unsafe counterparts,
they permit both the removal of np
as well as freeing it from within the loop safely
without interfering with the traversal.
.Pp
The
.Fn RB_EMPTY
macro should be used to check whether a red-black tree is empty.
.Sh EXAMPLES
The following example demonstrates how to declare a red-black tree
holding integers.
Values are inserted into it and the contents of the tree are printed
in order.
Lastly, the internal structure of the tree is printed.
.Bd -literal -offset 3n
#include <sys/tree.h>
#include <err.h>
#include <stdio.h>
#include <stdlib.h>
struct node {
RB_ENTRY(node) entry;
int i;
};
int
intcmp(struct node *e1, struct node *e2)
{
return (e1->i < e2->i ? -1 : e1->i > e2->i);
}
RB_HEAD(inttree, node) head = RB_INITIALIZER(&head);
RB_GENERATE(inttree, node, entry, intcmp)
int testdata[] = {
20, 16, 17, 13, 3, 6, 1, 8, 2, 4, 10, 19, 5, 9, 12, 15, 18,
7, 11, 14
};
void
print_tree(struct node *n)
{
struct node *left, *right;
if (n == NULL) {
printf("nil");
return;
}
left = RB_LEFT(n, entry);
right = RB_RIGHT(n, entry);
if (left == NULL && right == NULL)
printf("%d", n->i);
else {
printf("%d(", n->i);
print_tree(left);
printf(",");
print_tree(right);
printf(")");
}
}
int
main()
{
int i;
struct node *n;
for (i = 0; i < sizeof(testdata) / sizeof(testdata[0]); i++) {
if ((n = malloc(sizeof(struct node))) == NULL)
err(1, NULL);
n->i = testdata[i];
RB_INSERT(inttree, &head, n);
}
RB_FOREACH(n, inttree, &head) {
printf("%d\en", n->i);
}
print_tree(RB_ROOT(&head));
printf("\en");
return (0);
}
.Ed
.Sh NOTES
Trying to free a tree in the following way is a common error:
.Bd -literal -offset indent
SPLAY_FOREACH(var, NAME, &head) {
SPLAY_REMOVE(NAME, &head, var);
free(var);
}
free(head);
.Ed
.Pp
Since
.Va var
is free'd, the
.Fn FOREACH
macro refers to a pointer that may have been reallocated already.
Proper code needs a second variable.
.Bd -literal -offset indent
for (var = SPLAY_MIN(NAME, &head); var != NULL; var = nxt) {
nxt = SPLAY_NEXT(NAME, &head, var);
SPLAY_REMOVE(NAME, &head, var);
free(var);
}
.Ed
.Sh AUTHORS
The author of the tree macros is
.An Niels Provos .

2
tree.h
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@ -1,3 +1,5 @@
/* man ./tree.3 to see documentation on how to use this! */
/* $OpenBSD: tree.h,v 1.13 2011/07/09 00:19:45 pirofti Exp $ */
/*
* Copyright 2002 Niels Provos <provos@citi.umich.edu>