.\" Copyright (c) 1990, 1991, 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. .\" 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. .\" .\" @(#)radixsort.3 8.2 (Berkeley) 1/27/94 .\" $FreeBSD: src/lib/libc/stdlib/radixsort.3,v 1.12 2007/01/09 00:28:10 imp Exp $ .\" .Dd January 27, 1994 .Dt RADIXSORT 3 .Os .Sh NAME .Nm radixsort , sradixsort .Nd radix sort .Sh LIBRARY .Lb libc .Sh SYNOPSIS .In limits.h .In stdlib.h .Ft int .Fn radixsort "const unsigned char **base" "int nmemb" "const unsigned char *table" "unsigned endbyte" .Ft int .Fn sradixsort "const unsigned char **base" "int nmemb" "const unsigned char *table" "unsigned endbyte" .Sh DESCRIPTION The .Fn radixsort and .Fn sradixsort functions are implementations of radix sort. .Pp These functions sort an array of pointers to byte strings, the initial member of which is referenced by .Fa base . The byte strings may contain any values; the end of each string is denoted by the user-specified value .Fa endbyte . .Pp Applications may specify a sort order by providing the .Fa table argument. If .Pf non- Dv NULL , .Fa table must reference an array of .Dv UCHAR_MAX + 1 bytes which contains the sort weight of each possible byte value. The end-of-string byte must have a sort weight of 0 or 255 (for sorting in reverse order). More than one byte may have the same sort weight. The .Fa table argument is useful for applications which wish to sort different characters equally, for example, providing a table with the same weights for A-Z as for a-z will result in a case-insensitive sort. If .Fa table is NULL, the contents of the array are sorted in ascending order according to the .Tn ASCII order of the byte strings they reference and .Fa endbyte has a sorting weight of 0. .Pp The .Fn sradixsort function is stable, that is, if two elements compare as equal, their order in the sorted array is unchanged. The .Fn sradixsort function uses additional memory sufficient to hold .Fa nmemb pointers. .Pp The .Fn radixsort function is not stable, but uses no additional memory. .Pp These functions are variants of most-significant-byte radix sorting; in particular, see .An "D.E. Knuth" Ns 's .%T "Algorithm R" and section 5.2.5, exercise 10. They take linear time relative to the number of bytes in the strings. .Sh RETURN VALUES .Rv -std radixsort .Sh ERRORS .Bl -tag -width Er .It Bq Er EINVAL The value of the .Fa endbyte element of .Fa table is not 0 or 255. .El .Pp Additionally, the .Fn sradixsort function may fail and set .Va errno for any of the errors specified for the library routine .Xr malloc 3 . .Sh SEE ALSO .Xr sort 1 , .Xr qsort 3 .Pp .Rs .%A Knuth, D.E. .%D 1968 .%B "The Art of Computer Programming" .%T "Sorting and Searching" .%V Vol. 3 .%P pp. 170-178 .Re .Rs .%A Paige, R. .%D 1987 .%T "Three Partition Refinement Algorithms" .%J "SIAM J. Comput." .%V Vol. 16 .%N No. 6 .Re .Rs .%A McIlroy, P. .%D 1993 .%B "Engineering Radix Sort" .%T "Computing Systems" .%V Vol. 6:1 .%P pp. 5-27 .Re .Sh HISTORY The .Fn radixsort function first appeared in .Bx 4.4 .