1.\" Copyright (c) 1990, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" $OpenBSD: radixsort.3,v 1.9 2003/06/02 20:18:38 millert Exp $ 29.\" 30.Dd January 27, 1994 31.Dt RADIXSORT 3 32.Os 33.Sh NAME 34.Nm radixsort , 35.Nm sradixsort 36.Nd radix sort 37.Sh SYNOPSIS 38.Fd #include <limits.h> 39.Fd #include <stdlib.h> 40.Ft int 41.Fn radixsort "const u_char **base" "int nmemb" "const u_char *table" "u_int endbyte" 42.Ft int 43.Fn sradixsort "const u_char **base" "int nmemb" "const u_char *table" "u_int endbyte" 44.Sh DESCRIPTION 45The 46.Fn radixsort 47and 48.Fn sradixsort 49functions are implementations of radix sort. 50.Pp 51These functions sort an array of 52.Fa nmemb 53pointers to byte strings. 54The initial member is referenced by 55.Fa base . 56The byte strings may contain any values; the end of each string 57is denoted by the user-specified value 58.Fa endbyte . 59.Pp 60Applications may specify a sort order by providing the 61.Fa table 62argument. 63If non-null, 64.Fa table 65must reference an array of 66.Dv UCHAR_MAX 67+ 1 bytes which contains the sort weight of each possible byte value. 68The end-of-string byte must have a sort weight of 0 or 255 69(for sorting in reverse order). 70More than one byte may have the same sort weight. 71The 72.Fa table 73argument is useful for applications which wish to sort different characters 74equally, for example, providing a table with the same weights 75for A-Z as for a-z will result in a case-insensitive sort. 76If 77.Fa table 78is 79.Dv NULL , 80the contents of the array are sorted in ascending order according to the 81.Tn ASCII 82order of the byte strings they reference and 83.Fa endbyte 84has a sorting weight of 0. 85.Pp 86The 87.Fn sradixsort 88function is stable; that is, if two elements compare as equal, their 89order in the sorted array is unchanged. 90The 91.Fn sradixsort 92function uses additional memory sufficient to hold 93.Fa nmemb 94pointers. 95.Pp 96The 97.Fn radixsort 98function is not stable, but uses no additional memory. 99.Pp 100These functions are variants of most-significant-byte radix sorting; in 101particular, see D.E. Knuth's Algorithm R and section 5.2.5, exercise 10. 102They take linear time relative to the number of bytes in the strings. 103.Sh RETURN VALUES 104Upon successful completion 0 is returned. 105Otherwise, \-1 is returned and the global variable 106.Va errno 107is set to indicate the error. 108.Sh ERRORS 109.Bl -tag -width Er 110.It Bq Er EINVAL 111The value of the 112.Fa endbyte 113element of 114.Fa table 115is not 0 or 255. 116.El 117.Pp 118Additionally, the 119.Fn sradixsort 120function may fail and set 121.Va errno 122for any of the errors specified for the library routine 123.Xr malloc 3 . 124.Sh SEE ALSO 125.Xr sort 1 , 126.Xr qsort 3 127.Rs 128.%A Knuth, D.E. 129.%D 1968 130.%B "The Art of Computer Programming" 131.%T "Sorting and Searching" 132.%V Vol. 3 133.%P pp. 170-178 134.Re 135.Rs 136.%A Paige, R. 137.%D 1987 138.%T "Three Partition Refinement Algorithms" 139.%J "SIAM J. Comput." 140.%V Vol. 16 141.%N No. 6 142.Re 143.Rs 144.%A McIlroy, P. 145.%D 1993 146.%B "Engineering Radix Sort" 147.%T "Computing Systems" 148.%V Vol. 6:1 149.%P pp. 5-27 150.Re 151.Sh HISTORY 152The 153.Fn radixsort 154function first appeared in 155.Bx 4.4 . 156