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.\" @(#)radixsort.3 8.2 (Berkeley) 1/27/94 29.\" 30.Dd January 27, 1994 31.Dt RADIXSORT 3 32.Os 33.Sh NAME 34.Nm radixsort , sradixsort 35.Nd radix sort 36.Sh LIBRARY 37.Lb libc 38.Sh SYNOPSIS 39.In limits.h 40.In stdlib.h 41.Ft int 42.Fn radixsort "const unsigned char **base" "int nmemb" "const unsigned char *table" "unsigned endbyte" 43.Ft int 44.Fn sradixsort "const unsigned char **base" "int nmemb" "const unsigned char *table" "unsigned endbyte" 45.Sh DESCRIPTION 46The 47.Fn radixsort 48and 49.Fn sradixsort 50functions 51are implementations of radix sort. 52.Pp 53These functions sort an array of pointers to byte strings, the initial 54member of which 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 64.Pf non- Dv NULL , 65.Fa table 66must reference an array of 67.Dv UCHAR_MAX 68+ 1 bytes which contains the sort 69weight of each possible byte value. 70The end-of-string byte must have a sort weight of 0 or 255 71(for sorting in reverse order). 72More than one byte may have the same sort weight. 73The 74.Fa table 75argument 76is useful for applications which wish to sort different characters 77equally, for example, providing a table with the same weights 78for A-Z as for a-z will result in a case-insensitive sort. 79If 80.Fa table 81is NULL, the contents of the array are sorted in ascending order 82according to the 83.Tn ASCII 84order of the byte strings they reference and 85.Fa endbyte 86has a sorting weight of 0. 87.Pp 88The 89.Fn sradixsort 90function is stable, that is, if two elements compare as equal, their 91order in the sorted array is unchanged. 92The 93.Fn sradixsort 94function uses additional memory sufficient to hold 95.Fa nmemb 96pointers. 97.Pp 98The 99.Fn radixsort 100function is not stable, but uses no additional memory. 101.Pp 102These functions are variants of most-significant-byte radix sorting; in 103particular, see 104.An "D.E. Knuth" Ns 's 105.%T "Algorithm R" 106and section 5.2.5, exercise 10. 107They take linear time relative to the number of bytes in the strings. 108.Sh RETURN VALUES 109.Rv -std radixsort 110.Sh ERRORS 111.Bl -tag -width Er 112.It Bq Er EINVAL 113The value of the 114.Fa endbyte 115element of 116.Fa table 117is not 0 or 255. 118.El 119.Pp 120Additionally, the 121.Fn sradixsort 122function 123may fail and set 124.Va errno 125for any of the errors specified for the library routine 126.Xr malloc 3 . 127.Sh SEE ALSO 128.Xr sort 1 , 129.Xr qsort 3 130.Pp 131.Rs 132.%A Knuth, D.E. 133.%D 1968 134.%B "The Art of Computer Programming" 135.%T "Sorting and Searching" 136.%V Vol. 3 137.%P pp. 170-178 138.Re 139.Rs 140.%A Paige, R. 141.%D 1987 142.%T "Three Partition Refinement Algorithms" 143.%J "SIAM J. Comput." 144.%V Vol. 16 145.%N No. 6 146.Re 147.Rs 148.%A McIlroy, P. 149.%D 1993 150.%B "Engineering Radix Sort" 151.%T "Computing Systems" 152.%V Vol. 6:1 153.%P pp. 5-27 154.Re 155.Sh HISTORY 156The 157.Fn radixsort 158function first appeared in 159.Bx 4.4 . 160