2fe8fb192f
There is important information about booting non-ack images in docs/UPDATING. ack/aout-format images can't be built any more, and booting clang/ELF-format ones is a little different. Updating to the new boot monitor is recommended. Changes in this commit: . drop boot monitor -> allowing dropping ack support . facility to copy ELF boot files to /boot so that old boot monitor can still boot fairly easily, see UPDATING . no more ack-format libraries -> single-case libraries . some cleanup of OBJECT_FMT, COMPILER_TYPE, etc cases . drop several ack toolchain commands, but not all support commands (e.g. aal is gone but acksize is not yet). . a few libc files moved to netbsd libc dir . new /bin/date as minix date used code in libc/ . test compile fix . harmonize includes . /usr/lib is no longer special: without ack, /usr/lib plays no kind of special bootstrapping role any more and bootstrapping is done exclusively through packages, so releases depend even less on the state of the machine making them now. . rename nbsd_lib* to lib* . reduce mtree
238 lines
5.9 KiB
Groff
238 lines
5.9 KiB
Groff
.\" $NetBSD: qsort.3,v 1.13 2003/08/07 16:43:42 agc 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. 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
|
|
.Os
|
|
.Sh NAME
|
|
.Nm qsort ,
|
|
.Nm heapsort ,
|
|
.Nm mergesort
|
|
.Nd sort functions
|
|
.Sh LIBRARY
|
|
.Lb libc
|
|
.Sh SYNOPSIS
|
|
.In stdlib.h
|
|
.Ft void
|
|
.Fn qsort "void *base" "size_t nmemb" "size_t size" "int (*compar)(const void *, const void *)"
|
|
.Ft int
|
|
.Fn heapsort "void *base" "size_t nmemb" "size_t size" "int (*compar)(const void *, const void *)"
|
|
.Ft int
|
|
.Fn mergesort "void *base" "size_t nmemb" "size_t size" "int (*compar)(const void *, const void *)"
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Fn qsort
|
|
function is a modified partition-exchange sort, or quicksort.
|
|
The
|
|
.Fn heapsort
|
|
function is a modified selection sort.
|
|
The
|
|
.Fn mergesort
|
|
function is a modified merge sort with exponential search
|
|
intended for sorting data with pre-existing order.
|
|
.Pp
|
|
The
|
|
.Fn qsort
|
|
and
|
|
.Fn heapsort
|
|
functions sort an array of
|
|
.Fa nmemb
|
|
objects, the initial member of which is pointed to by
|
|
.Fa base .
|
|
The size of each object is specified by
|
|
.Fa size .
|
|
.Fn mergesort
|
|
behaves similarly, but
|
|
.Em requires
|
|
that
|
|
.Fa size
|
|
be greater than
|
|
.Dq "sizeof(void *) / 2" .
|
|
.Pp
|
|
The contents of the array
|
|
.Fa base
|
|
are sorted in ascending order according to
|
|
a comparison function pointed to by
|
|
.Fa compar ,
|
|
which requires two arguments pointing to the objects being
|
|
compared.
|
|
.Pp
|
|
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.
|
|
.Pp
|
|
The functions
|
|
.Fn qsort
|
|
and
|
|
.Fn heapsort
|
|
are
|
|
.Em not
|
|
stable, that is, if two members compare as equal, their order in
|
|
the sorted array is undefined.
|
|
The function
|
|
.Fn mergesort
|
|
is stable.
|
|
.Pp
|
|
The
|
|
.Fn qsort
|
|
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
|
|
Algorithm Q.
|
|
.Fn qsort
|
|
takes O N lg N average time.
|
|
This implementation uses median selection to avoid its
|
|
O N**2 worst-case behavior.
|
|
.Pp
|
|
The
|
|
.Fn heapsort
|
|
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.
|
|
.Fn heapsort
|
|
takes O N lg N worst-case time.
|
|
Its
|
|
.Em only
|
|
advantage over
|
|
.Fn qsort
|
|
is that it uses almost no additional memory; while
|
|
.Fn qsort
|
|
does not allocate memory, it is implemented using recursion.
|
|
.Pp
|
|
The function
|
|
.Fn mergesort
|
|
requires additional memory of size
|
|
.Fa nmemb *
|
|
.Fa size
|
|
bytes; it should be used only when space is not at a premium.
|
|
.Fn mergesort
|
|
is optimized for data with pre-existing order; its worst case
|
|
time is O N lg N; its best case is O N.
|
|
.Pp
|
|
Normally,
|
|
.Fn qsort
|
|
is faster than
|
|
.Fn mergesort
|
|
is faster than
|
|
.Fn heapsort .
|
|
Memory availability and pre-existing order in the data can make this
|
|
untrue.
|
|
.Sh RETURN VALUES
|
|
The
|
|
.Fn qsort
|
|
function
|
|
returns no value.
|
|
.Pp
|
|
Upon successful completion,
|
|
.Fn heapsort
|
|
and
|
|
.Fn mergesort
|
|
return 0.
|
|
Otherwise, they return \-1 and the global variable
|
|
.Va errno
|
|
is set to indicate the error.
|
|
.Sh ERRORS
|
|
The
|
|
.Fn heapsort
|
|
function succeeds unless:
|
|
.Bl -tag -width Er
|
|
.It Bq Er EINVAL
|
|
The
|
|
.Fa size
|
|
argument is zero, or,
|
|
the
|
|
.Fa size
|
|
argument to
|
|
.Fn mergesort
|
|
is less than
|
|
.Dq "sizeof(void *) / 2" .
|
|
.It Bq Er ENOMEM
|
|
.Fn heapsort
|
|
or
|
|
.Fn mergesort
|
|
were unable to allocate memory.
|
|
.El
|
|
.Sh COMPATIBILITY
|
|
Previous versions of
|
|
.Fn qsort
|
|
did not permit the comparison routine itself to call
|
|
.Fn qsort .
|
|
This is no longer true.
|
|
.Sh SEE ALSO
|
|
.Xr sort 1 ,
|
|
.Xr radixsort 3
|
|
.Rs
|
|
.%A Hoare, C.A.R.
|
|
.%D 1962
|
|
.%T "Quicksort"
|
|
.%J "The Computer Journal"
|
|
.%V 5:1
|
|
.%P pp. 10-15
|
|
.Re
|
|
.Rs
|
|
.%A Williams, J.W.J
|
|
.%D 1964
|
|
.%T "Heapsort"
|
|
.%J "Communications of the ACM"
|
|
.%V 7:1
|
|
.%P pp. 347-348
|
|
.Re
|
|
.Rs
|
|
.%A Knuth, D.E.
|
|
.%D 1968
|
|
.%B "The Art of Computer Programming"
|
|
.%V Vol. 3
|
|
.%T "Sorting and Searching"
|
|
.%P pp. 114-123, 145-149
|
|
.Re
|
|
.Rs
|
|
.%A McIlroy, P.M.
|
|
.%D 1993
|
|
.%T "Optimistic Sorting and Information Theoretic Complexity"
|
|
.%J "Proceedings of the Fourth Annual ACM-SIAM Symposium on Discrete Algorithms"
|
|
.%P pp. 467-474
|
|
.Re
|
|
.Rs
|
|
.%A Bentley, J.L. and McIlroy, M.D.
|
|
.%D 1993
|
|
.%T "Engineering a Sort Function"
|
|
.%J "Software-Practice and Experience"
|
|
.%V Vol. 23
|
|
.%P pp. 1249-1265
|
|
.Re
|
|
.Sh STANDARDS
|
|
The
|
|
.Fn qsort
|
|
function
|
|
conforms to
|
|
.St -ansiC .
|