1.\" $NetBSD: radixsort.3,v 1.6 1998/02/05 18:50:13 perry 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 "u_char **base" "int nmemb" "u_char *table" "u_int endbyte" 49.Ft int 50.Fn sradixsort "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; the end of each string 63is denoted by the user-specified value 64.Fa endbyte . 65.Pp 66Applications may specify a sort order by providing the 67.Fa table 68argument. 69If 70.Pf non- Dv NULL , 71.Fa table 72must reference an array of 73.Dv UCHAR_MAX 74+ 1 bytes which contains the sort 75weight of each possible byte value. 76The end-of-string byte must have a sort weight of 0 or 255 77(for sorting in reverse order). 78More than one byte may have the same sort weight. 79The 80.Fa table 81argument 82is useful for applications which wish to sort different characters 83equally, for example, providing a table with the same weights 84for A-Z as for a-z will result in a case-insensitive sort. 85If 86.Fa table 87is NULL, the contents of the array are sorted in ascending order 88according to the 89.Tn ASCII 90order of the byte strings they reference and 91.Fa endbyte 92has a sorting weight of 0. 93.Pp 94The 95.Fn sradixsort 96function is stable, that is, if two elements compare as equal, their 97order in the sorted array is unchanged. 98The 99.Fn sradixsort 100function uses additional memory sufficient to hold 101.Fa nmemb 102pointers. 103.Pp 104The 105.Fn radixsort 106function is not stable, but uses no additional memory. 107.Pp 108These functions are variants of most-significant-byte radix sorting; in 109particular, see D.E. Knuth's Algorithm R and section 5.2.5, exercise 10. 110They take linear time relative to the number of bytes in the strings. 111.Sh RETURN VALUES 112Upon successful completion 0 is returned. 113Otherwise, \-1 is returned and the global variable 114.Va errno 115is set to indicate the error. 116.Sh ERRORS 117.Bl -tag -width Er 118.It Bq Er EINVAL 119The value of the 120.Fa endbyte 121element of 122.Fa table 123is not 0 or 255. 124.El 125.Pp 126Additionally, the 127.Fn sradixsort 128function 129may fail and set 130.Va errno 131for any of the errors specified for the library routine 132.Xr malloc 3 . 133.Sh SEE ALSO 134.Xr sort 1 , 135.Xr qsort 3 136.Pp 137.Rs 138.%A Knuth, D.E. 139.%D 1968 140.%B "The Art of Computer Programming" 141.%T "Sorting and Searching" 142.%V Vol. 3 143.%P pp. 170-178 144.Re 145.Rs 146.%A Paige, R. 147.%D 1987 148.%T "Three Partition Refinement Algorithms" 149.%J "SIAM J. Comput." 150.%V Vol. 16 151.%N No. 6 152.Re 153.Rs 154.%A McIlroy, P. 155.%D 1993 156.%B "Engineering Radix Sort" 157.%T "Computing Systems" 158.%V Vol. 6:1 159.%P pp. 5-27 160.Re 161.Sh HISTORY 162The 163.Fn radixsort 164function first appeared in 165.Bx 4.4 . 166