mirror of https://github.com/mkerrisk/man-pages
158 lines
5.3 KiB
Groff
158 lines
5.3 KiB
Groff
.\" Copyright (c) 1993
|
|
.\" The Regents of the University of California. All rights reserved.
|
|
.\" and Copyright (c) 2020 by Alejandro Colomar <colomar.6.4.3@gmail.com>
|
|
.\"
|
|
.\" %%%LICENSE_START(BSD_3_CLAUSE_UCB)
|
|
.\" 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.
|
|
.\" %%%LICENSE_END
|
|
.\"
|
|
.\"
|
|
.TH QUEUE 7 2021-03-22 "GNU" "Linux Programmer's Manual"
|
|
.SH NAME
|
|
queue \- implementations of linked lists and queues
|
|
.SH DESCRIPTION
|
|
The
|
|
.I <sys/queue.h>
|
|
header file provides a set of macros that
|
|
define and operate on the following data structures:
|
|
.IP * 3
|
|
singly linked lists (SLIST)
|
|
.IP *
|
|
doubly linked lists (LIST)
|
|
.IP *
|
|
singly linked tail queues (STAILQ)
|
|
.IP *
|
|
doubly linked tail queues (TAILQ)
|
|
.IP *
|
|
doubly linked circular queues (CIRCLEQ)
|
|
.PP
|
|
All structures support the following functionality:
|
|
.IP * 3
|
|
Insertion of a new entry at the head of the list.
|
|
.IP *
|
|
Insertion of a new entry after any element in the list.
|
|
.IP *
|
|
O(1) removal of an entry from the head of the list.
|
|
.IP *
|
|
Forward traversal through the list.
|
|
.\".IP *
|
|
.\" Swapping the contents of two lists.
|
|
.PP
|
|
Code size and execution time
|
|
depend on the complexity of the data structure being used,
|
|
so programmers should take care to choose the appropriate one.
|
|
.SS Singly linked lists (SLIST)
|
|
Singly linked lists are the simplest
|
|
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.
|
|
Singly linked lists add the following functionality:
|
|
.IP * 3
|
|
O(n) removal of any entry in the list.
|
|
.SS Singly linked tail queues (STAILQ)
|
|
Singly linked tail queues add the following functionality:
|
|
.IP * 3
|
|
Entries can be added at the end of a list.
|
|
.IP *
|
|
O(n) removal of any entry in the list.
|
|
.IP *
|
|
They may be concatenated.
|
|
.PP
|
|
However:
|
|
.IP * 3
|
|
All list insertions must specify the head of the list.
|
|
.IP *
|
|
Each head entry requires two pointers rather than one.
|
|
.PP
|
|
Singly linked tail queues are ideal for applications with
|
|
large datasets and few or no removals,
|
|
or for implementing a FIFO queue.
|
|
.SS Doubly linked data structures
|
|
All doubly linked types of data structures (lists and tail queues)
|
|
additionally allow:
|
|
.IP * 3
|
|
Insertion of a new entry before any element in the list.
|
|
.IP *
|
|
O(1) removal of any entry in the list.
|
|
.PP
|
|
However:
|
|
.IP * 3
|
|
Each element requires two pointers rather than one.
|
|
.SS Doubly linked lists (LIST)
|
|
Linked lists are the simplest of the doubly linked data structures.
|
|
They add the following functionality over the above:
|
|
.IP * 3
|
|
They may be traversed backwards.
|
|
.PP
|
|
However:
|
|
.IP * 3
|
|
To traverse backwards, an entry to begin the traversal and the list in
|
|
which it is contained must be specified.
|
|
.SS Doubly linked tail queues (TAILQ)
|
|
Tail queues add the following functionality:
|
|
.IP * 3
|
|
Entries can be added at the end of a list.
|
|
.IP *
|
|
They may be traversed backwards, from tail to head.
|
|
.IP *
|
|
They may be concatenated.
|
|
.PP
|
|
However:
|
|
.IP * 3
|
|
All list insertions and removals must specify the head of the list.
|
|
.IP *
|
|
Each head entry requires two pointers rather than one.
|
|
.SS Doubly linked circular queues (CIRCLEQ)
|
|
Circular queues add the following functionality over the above:
|
|
.IP * 3
|
|
The first and last entries are connected.
|
|
.PP
|
|
However:
|
|
.IP * 3
|
|
The termination condition for traversal is more complex.
|
|
.SH CONFORMING TO
|
|
Not in POSIX.1, POSIX.1-2001, or POSIX.1-2008.
|
|
Present on the BSDs.
|
|
.I <sys/queue.h>
|
|
macros first appeared in 4.4BSD.
|
|
.SH NOTES
|
|
Some BSDs provide SIMPLEQ instead of STAILQ.
|
|
They are identical, but for historical reasons
|
|
they were named differently on different BSDs.
|
|
STAILQ originated on FreeBSD, and SIMPLEQ originated on NetBSD.
|
|
For compatibility reasons, some systems provide both sets of macros.
|
|
Glibc provides both STAILQ and SIMPLEQ,
|
|
which are identical except for a missing SIMPLEQ equivalent to
|
|
.BR STAILQ_CONCAT ().
|
|
.SH SEE ALSO
|
|
.BR circleq (3),
|
|
.BR insque (3),
|
|
.BR list (3),
|
|
.BR slist (3),
|
|
.BR stailq (3),
|
|
.BR tailq (3)
|
|
.\" .BR tree (3)
|