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 1.14 2022/08/04 06:20:24 jsg Exp $ 29.\" 30.Dd $Mdocdate: August 4 2022 $ 31.Dt RADIXSORT 3 32.Os 33.Sh NAME 34.Nm radixsort , 35.Nm sradixsort 36.Nd radix sort 37.Sh SYNOPSIS 38.In limits.h 39.In 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 81ASCII order of the byte strings they reference and 82.Fa endbyte 83has a sorting weight of 0. 84.Pp 85The 86.Fn sradixsort 87function is stable; that is, if two elements compare as equal, their 88order in the sorted array is unchanged. 89The 90.Fn sradixsort 91function uses additional memory sufficient to hold 92.Fa nmemb 93pointers. 94.Pp 95The 96.Fn radixsort 97function is not stable, but uses no additional memory. 98.Pp 99These functions are variants of most-significant-byte radix sorting; in 100particular, see D.E. Knuth's Algorithm R and section 5.2.5, exercise 10. 101They take linear time relative to the number of bytes in the strings. 102.Sh RETURN VALUES 103.Rv -std 104.Sh ERRORS 105.Bl -tag -width Er 106.It Bq Er EINVAL 107The value of the 108.Fa endbyte 109element of 110.Fa table 111is not 0 or 255. 112.El 113.Pp 114Additionally, the 115.Fn sradixsort 116function may fail and set 117.Va errno 118for any of the errors specified for the library routine 119.Xr malloc 3 . 120.Sh SEE ALSO 121.Xr sort 1 , 122.Xr qsort 3 123.Rs 124.%A Knuth, D.E. 125.%D 1968 126.%B "The Art of Computer Programming" 127.%T "Sorting and Searching" 128.%V Vol. 3 129.%P pp. 170-178 130.Re 131.Rs 132.%A Paige, R. 133.%D 1987 134.%T "Three Partition Refinement Algorithms" 135.%J "SIAM J. Comput." 136.%V Vol. 16 137.%N No. 6 138.Re 139.Rs 140.%A McIlroy, P. 141.%D 1993 142.%B "Engineering Radix Sort" 143.%T "Computing Systems" 144.%V Vol. 6:1 145.%P pp. 5-27 146.Re 147.Sh HISTORY 148The 149.Fn radixsort 150function first appeared in 151.Bx 4.3 Net/2 . 152