1.\" $NetBSD: radixsort.3,v 1.9 2001/03/16 07:47:29 fair Exp $ 2.\" 3.\" Copyright (c) 1990, 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. All advertising materials mentioning features or use of this software 15.\" must display the following acknowledgement: 16.\" This product includes software developed by the University of 17.\" California, Berkeley and its contributors. 18.\" 4. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.\" from: @(#)radixsort.3 8.2 (Berkeley) 1/27/94 35.\" 36.Dd January 27, 1994 37.Dt RADIXSORT 3 38.Os 39.Sh NAME 40.Nm radixsort 41.Nd radix sort 42.Sh LIBRARY 43.Lb libc 44.Sh SYNOPSIS 45.Fd #include <limits.h> 46.Fd #include <stdlib.h> 47.Ft int 48.Fn radixsort "const u_char **base" "int nmemb" "u_char *table" "u_int endbyte" 49.Ft int 50.Fn sradixsort "const u_char **base" "int nmemb" "u_char *table" "u_int endbyte" 51.Sh DESCRIPTION 52The 53.Fn radixsort 54and 55.Fn sradixsort 56functions 57are implementations of radix sort. 58.Pp 59These functions sort an 60.Fa nmemb 61element array of pointers to byte strings, with 62the initial member of which is referenced by 63.Fa base . 64The byte strings may contain any values. 65End of strings is denoted 66by character which has same weight as user specified value 67.Fa endbyte . 68.Fa endbyte 69has to be between 0 and 255. 70.Pp 71Applications may specify a sort order by providing the 72.Fa table 73argument. 74If 75.Pf non- Dv NULL , 76.Fa table 77must reference an array of 78.Dv UCHAR_MAX 79+ 1 bytes which contains the sort 80weight of each possible byte value. 81The end-of-string byte must have a sort weight of 0 or 255 82(for sorting in reverse order). 83More than one byte may have the same sort weight. 84The 85.Fa table 86argument 87is useful for applications which wish to sort different characters 88equally, for example, providing a table with the same weights 89for A-Z as for a-z will result in a case-insensitive sort. 90If 91.Fa table 92is NULL, the contents of the array are sorted in ascending order 93according to the 94.Tn ASCII 95order of the byte strings they reference and 96.Fa endbyte 97has a sorting weight of 0. 98.Pp 99The 100.Fn sradixsort 101function is stable, that is, if two elements compare as equal, their 102order in the sorted array is unchanged. 103The 104.Fn sradixsort 105function uses additional memory sufficient to hold 106.Fa nmemb 107pointers. 108.Pp 109The 110.Fn radixsort 111function is not stable, but uses no additional memory. 112.Pp 113These functions are variants of most-significant-byte radix sorting; in 114particular, see D.E. Knuth's Algorithm R and section 5.2.5, exercise 10. 115They take linear time relative to the number of bytes in the strings. 116.Sh RETURN VALUES 117Upon successful completion 0 is returned. 118Otherwise, \-1 is returned and the global variable 119.Va errno 120is set to indicate the error. 121.Sh ERRORS 122.Bl -tag -width Er 123.It Bq Er EINVAL 124The value of the 125.Fa endbyte 126element of 127.Fa table 128is not 0 or 255. 129.El 130.Pp 131Additionally, the 132.Fn sradixsort 133function 134may fail and set 135.Va errno 136for any of the errors specified for the library routine 137.Xr malloc 3 . 138.Sh SEE ALSO 139.Xr sort 1 , 140.Xr qsort 3 141.Pp 142.Rs 143.%A Knuth, D.E. 144.%D 1968 145.%B "The Art of Computer Programming" 146.%T "Sorting and Searching" 147.%V Vol. 3 148.%P pp. 170-178 149.Re 150.Rs 151.%A Paige, R. 152.%D 1987 153.%T "Three Partition Refinement Algorithms" 154.%J "SIAM J. Comput." 155.%V Vol. 16 156.%N No. 6 157.Re 158.Rs 159.%A McIlroy, P. 160.%D 1993 161.%B "Engineering Radix Sort" 162.%T "Computing Systems" 163.%V Vol. 6:1 164.%P pp. 5-27 165.Re 166.Sh HISTORY 167The 168.Fn radixsort 169function first appeared in 170.Bx 4.4 . 171