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.Dd January 27, 1994 29.Dt RADIXSORT 3 30.Os 31.Sh NAME 32.Nm radixsort , sradixsort 33.Nd radix sort 34.Sh LIBRARY 35.Lb libc 36.Sh SYNOPSIS 37.In limits.h 38.In stdlib.h 39.Ft int 40.Fn radixsort "const unsigned char **base" "int nmemb" "const unsigned char *table" "unsigned endbyte" 41.Ft int 42.Fn sradixsort "const unsigned char **base" "int nmemb" "const unsigned char *table" "unsigned endbyte" 43.Sh DESCRIPTION 44The 45.Fn radixsort 46and 47.Fn sradixsort 48functions 49are implementations of radix sort. 50.Pp 51These functions sort an array of pointers to byte strings, the initial 52member of which is referenced by 53.Fa base . 54The byte strings may contain any values; the end of each string 55is denoted by the user-specified value 56.Fa endbyte . 57.Pp 58Applications may specify a sort order by providing the 59.Fa table 60argument. 61If 62.Pf non- Dv NULL , 63.Fa table 64must reference an array of 65.Dv UCHAR_MAX 66+ 1 bytes which contains the sort 67weight 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 74is useful for applications which wish to sort different characters 75equally, for example, providing a table with the same weights 76for A-Z as for a-z will result in a case-insensitive sort. 77If 78.Fa table 79is NULL, the contents of the array are sorted in ascending order 80according to the 81.Tn ASCII 82order of the byte strings they reference and 83.Fa endbyte 84has a sorting weight of 0. 85.Pp 86The 87.Fn sradixsort 88function is stable, that is, if two elements compare as equal, their 89order in the sorted array is unchanged. 90The 91.Fn sradixsort 92function uses additional memory sufficient to hold 93.Fa nmemb 94pointers. 95.Pp 96The 97.Fn radixsort 98function is not stable, but uses no additional memory. 99.Pp 100These functions are variants of most-significant-byte radix sorting; in 101particular, see 102.An "D.E. Knuth" Ns 's 103.%T "Algorithm R" 104and section 5.2.5, exercise 10. 105They take linear time relative to the number of bytes in the strings. 106.Sh RETURN VALUES 107.Rv -std radixsort 108.Sh ERRORS 109.Bl -tag -width Er 110.It Bq Er EINVAL 111The value of the 112.Fa endbyte 113element of 114.Fa table 115is not 0 or 255. 116.El 117.Pp 118Additionally, the 119.Fn sradixsort 120function 121may fail and set 122.Va errno 123for any of the errors specified for the library routine 124.Xr malloc 3 . 125.Sh SEE ALSO 126.Xr sort 1 , 127.Xr qsort 3 128.Pp 129.Rs 130.%A Knuth, D.E. 131.%D 1968 132.%B "The Art of Computer Programming" 133.%T "Sorting and Searching" 134.%V Vol. 3 135.%P pp. 170-178 136.Re 137.Rs 138.%A Paige, R. 139.%D 1987 140.%T "Three Partition Refinement Algorithms" 141.%J "SIAM J. Comput." 142.%V Vol. 16 143.%N No. 6 144.Re 145.Rs 146.%A McIlroy, P. 147.%D 1993 148.%B "Engineering Radix Sort" 149.%T "Computing Systems" 150.%V Vol. 6:1 151.%P pp. 5-27 152.Re 153.Sh HISTORY 154The 155.Fn radixsort 156function first appeared in 157.Bx 4.4 . 158