|File: [cvs.NetBSD.org] / src / lib / libc / stdlib / qsort.3 (download)
Revision 1.9, Thu Feb 7 07:00:30 2002 UTC (18 years ago) by ross
CVS Tags: netbsd-1-6-base, netbsd-1-6-RELEASE, netbsd-1-6-RC3, netbsd-1-6-RC2, netbsd-1-6-RC1, netbsd-1-6-PATCH002-RELEASE, netbsd-1-6-PATCH002-RC4, netbsd-1-6-PATCH002-RC3, netbsd-1-6-PATCH002-RC2, netbsd-1-6-PATCH002-RC1, netbsd-1-6-PATCH002, netbsd-1-6-PATCH001-RELEASE, netbsd-1-6-PATCH001-RC3, netbsd-1-6-PATCH001-RC2, netbsd-1-6-PATCH001-RC1, netbsd-1-6-PATCH001, netbsd-1-6, nathanw_sa_before_merge, nathanw_sa_base, fvdl_fs64_base
Changes since 1.8: +2 -2
Generate <>& symbolically.
.\" $NetBSD: qsort.3,v 1.9 2002/02/07 07:00:30 ross Exp $
.\" Copyright (c) 1990, 1991, 1993
.\" The Regents of the University of California. All rights reserved.
.\" This code is derived from software contributed to Berkeley by
.\" the American National Standards Committee X3, on Information
.\" Processing Systems.
.\" 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. All advertising materials mentioning features or use of this software
.\" must display the following acknowledgement:
.\" This product includes software developed by the University of
.\" California, Berkeley and its contributors.
.\" 4. 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.
.\" from: @(#)qsort.3 8.1 (Berkeley) 6/4/93
.Dd June 4, 1993
.Dt QSORT 3
.Nm qsort ,
.Nm heapsort ,
.Nd sort functions
.Fd #include \*[Lt]stdlib.h\*[Gt]
.Fn qsort "void *base" "size_t nmemb" "size_t size" "int (*compar)(const void *, const void *)"
.Fn heapsort "void *base" "size_t nmemb" "size_t size" "int (*compar)(const void *, const void *)"
.Fn mergesort "void *base" "size_t nmemb" "size_t size" "int (*compar)(const void *, const void *)"
function is a modified partition-exchange sort, or quicksort.
function is a modified selection sort.
function is a modified merge sort with exponential search
intended for sorting data with pre-existing order.
functions sort an array of
objects, the initial member of which is pointed to by
.Fa base .
The size of each object is specified by
.Fa size .
behaves similarly, but
be greater than
.Dq "sizeof(void *) / 2" .
The contents of the array
are sorted in ascending order according to
a comparison function pointed to by
.Fa compar ,
which requires two arguments pointing to the objects being
The comparison function must return an integer less than, equal to, or
greater than zero if the first argument is considered to be respectively
less than, equal to, or greater than the second.
stable, that is, if two members compare as equal, their order in
the sorted array is undefined.
function is an implementation of C.A.R. Hoare's ``quicksort'' algorithm,
a variant of partition-exchange sorting; in particular, see D.E. Knuth's
takes O N lg N average time.
This implementation uses median selection to avoid its
O N**2 worst-case behavior.
function is an implementation of J.W.J. William's ``heapsort'' algorithm,
a variant of selection sorting; in particular, see D.E. Knuth's Algorithm H.
takes O N lg N worst-case time.
is that it uses almost no additional memory; while
does not allocate memory, it is implemented using recursion.
requires additional memory of size
.Fa nmemb *
bytes; it should be used only when space is not at a premium.
is optimized for data with pre-existing order; its worst case
time is O N lg N; its best case is O N.
is faster than
is faster than
.Fn heapsort .
Memory availability and pre-existing order in the data can make this
.Sh RETURN VALUES
returns no value.
Upon successful completion,
Otherwise, they return \-1 and the global variable
is set to indicate the error.
function succeeds unless:
.Bl -tag -width Er
.It Bq Er EINVAL
argument is zero, or,
is less than
.Dq "sizeof(void *) / 2" .
.It Bq Er ENOMEM
were unable to allocate memory.
Previous versions of
did not permit the comparison routine itself to call
.Fn qsort 3 .
This is no longer true.
.Sh SEE ALSO
.Xr sort 1 ,
.Xr radixsort 3
.%A Hoare, C.A.R.
.%J "The Computer Journal"
.%P pp. 10-15
.%A Williams, J.W.J
.%J "Communications of the ACM"
.%P pp. 347-348
.%A Knuth, D.E.
.%B "The Art of Computer Programming"
.%V Vol. 3
.%T "Sorting and Searching"
.%P pp. 114-123, 145-149
.%A Mcilroy, P.M.
.%T "Optimistic Sorting and Information Theoretic Complexity"
.%J "Fourth Annual ACM-SIAM Symposium on Discrete Algorithms"
.%V January 1992
.%A Bentley, J.L.
.%T "Engineering a Sort Function"
.%V January 1992
.St -ansiC .