1.\" $NetBSD: radixsort.3,v 1.8 2001/01/12 19:23:11 jdolecek 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 array of pointers to byte strings, the initial 60member of which is referenced by 61.Fa base . 62The byte strings may contain any values. End of strings is denoted 63by character which has same weight as user specified value 64.Fa endbyte . 65.Fa endbyte 66has to be between 0 and 255. 67.Pp 68Applications may specify a sort order by providing the 69.Fa table 70argument. 71If 72.Pf non- Dv NULL , 73.Fa table 74must reference an array of 75.Dv UCHAR_MAX 76+ 1 bytes which contains the sort 77weight of each possible byte value. 78The end-of-string byte must have a sort weight of 0 or 255 79(for sorting in reverse order). 80More than one byte may have the same sort weight. 81The 82.Fa table 83argument 84is useful for applications which wish to sort different characters 85equally, for example, providing a table with the same weights 86for A-Z as for a-z will result in a case-insensitive sort. 87If 88.Fa table 89is NULL, the contents of the array are sorted in ascending order 90according to the 91.Tn ASCII 92order of the byte strings they reference and 93.Fa endbyte 94has a sorting weight of 0. 95.Pp 96The 97.Fn sradixsort 98function is stable, that is, if two elements compare as equal, their 99order in the sorted array is unchanged. 100The 101.Fn sradixsort 102function uses additional memory sufficient to hold 103.Fa nmemb 104pointers. 105.Pp 106The 107.Fn radixsort 108function is not stable, but uses no additional memory. 109.Pp 110These functions are variants of most-significant-byte radix sorting; in 111particular, see D.E. Knuth's Algorithm R and section 5.2.5, exercise 10. 112They take linear time relative to the number of bytes in the strings. 113.Sh RETURN VALUES 114Upon successful completion 0 is returned. 115Otherwise, \-1 is returned and the global variable 116.Va errno 117is set to indicate the error. 118.Sh ERRORS 119.Bl -tag -width Er 120.It Bq Er EINVAL 121The value of the 122.Fa endbyte 123element of 124.Fa table 125is not 0 or 255. 126.El 127.Pp 128Additionally, the 129.Fn sradixsort 130function 131may fail and set 132.Va errno 133for any of the errors specified for the library routine 134.Xr malloc 3 . 135.Sh SEE ALSO 136.Xr sort 1 , 137.Xr qsort 3 138.Pp 139.Rs 140.%A Knuth, D.E. 141.%D 1968 142.%B "The Art of Computer Programming" 143.%T "Sorting and Searching" 144.%V Vol. 3 145.%P pp. 170-178 146.Re 147.Rs 148.%A Paige, R. 149.%D 1987 150.%T "Three Partition Refinement Algorithms" 151.%J "SIAM J. Comput." 152.%V Vol. 16 153.%N No. 6 154.Re 155.Rs 156.%A McIlroy, P. 157.%D 1993 158.%B "Engineering Radix Sort" 159.%T "Computing Systems" 160.%V Vol. 6:1 161.%P pp. 5-27 162.Re 163.Sh HISTORY 164The 165.Fn radixsort 166function first appeared in 167.Bx 4.4 . 168