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Diffstat (limited to 'lib/libc/stdlib/qsort.3')
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diff --git a/lib/libc/stdlib/qsort.3 b/lib/libc/stdlib/qsort.3 new file mode 100644 index 000000000000..03f1b8d4ef44 --- /dev/null +++ b/lib/libc/stdlib/qsort.3 @@ -0,0 +1,168 @@ +.\" Copyright (c) 1990, 1991 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. +.\" +.\" @(#)qsort.3 6.7 (Berkeley) 6/29/91 +.\" +.Dd June 29, 1991 +.Dt QSORT 3 +.Os +.Sh NAME +.Nm qsort, heapsort +.Nd sort functions +.Sh SYNOPSIS +.Fd #include <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 *)" +.Sh DESCRIPTION +The +.Fn qsort +function is a modified partition-exchange sort, or quicksort. +The +.Fn heapsort +function is a modified selection sort. +.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 . +.Pp +The contents of the array are sorted in ascending order according to +a comparison function pointed to by +.Fa compar , +which is called with two arguments that point 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. +.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 the traditional +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 no additional memory. +.Sh RETURN VALUES +The +.Fn qsort +function +returns no value. +.Pp +Upon successful completion, +.Fn heapsort +returns 0. +Otherwise, it returns \-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. +.Sh COMPATIBILITY +Previous versions of +.Fn qsort +did not permit the comparison routine to itself call +.Fn qsort 3 . +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 +.Sh STANDARDS +The +.Fn qsort +function +conforms to +.St -ansiC . |