1.\" Copyright (c) 1990, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" %sccs.include.redist.man% 5.\" 6.\" @(#)radixsort.3 8.2 (Berkeley) 01/27/94 7.\" 8.Dd 9.Dt RADIXSORT 3 10.Os 11.Sh NAME 12.Nm radixsort 13.Nd radix sort 14.Sh SYNOPSIS 15.Fd #include <limits.h> 16.Fd #include <stdlib.h> 17.Ft int 18.Fn radixsort "u_char **base" "int nmemb" "u_char *table" "u_int endbyte" 19.Ft int 20.Fn sradixsort "u_char **base" "int nmemb" "u_char *table" "u_int endbyte" 21.Sh DESCRIPTION 22The 23.Fn radixsort 24and 25.Fn sradixsort 26functions 27are implementations of radix sort. 28.Pp 29These functions sort an array of pointers to byte strings, the initial 30member of which is referenced by 31.Fa base . 32The byte strings may contain any values; the end of each string 33is denoted by the user-specified value 34.Fa endbyte . 35.Pp 36Applications may specify a sort order by providing the 37.Fa table 38argument. 39If 40.Pf non- Dv NULL , 41.Fa table 42must reference an array of 43.Dv UCHAR_MAX 44+ 1 bytes which contains the sort 45weight of each possible byte value. 46The end-of-string byte must have a sort weight of 0 or 255 47(for sorting in reverse order). 48More than one byte may have the same sort weight. 49The 50.Fa table 51argument 52is useful for applications which wish to sort different characters 53equally, for example, providing a table with the same weights 54for A-Z as for a-z will result in a case-insensitive sort. 55If 56.Fa table 57is NULL, the contents of the array are sorted in ascending order 58according to the 59.Tn ASCII 60order of the byte strings they reference and 61.Fa endbyte 62has a sorting weight of 0. 63.Pp 64The 65.Fn sradixsort 66function is stable, that is, if two elements compare as equal, their 67order in the sorted array is unchanged. 68The 69.Fn sradixsort 70function uses additional memory sufficient to hold 71.Fa nmemb 72pointers. 73.Pp 74The 75.Fn radixsort 76function is not stable, but uses no additional memory. 77.Pp 78These functions are variants of most-significant-byte radix sorting; in 79particular, see D.E. Knuth's Algorithm R and section 5.2.5, exercise 10. 80They take linear time relative to the number of bytes in the strings. 81.Sh RETURN VALUES 82Upon successful completion 0 is returned. 83Otherwise, \-1 is returned and the global variable 84.Va errno 85is set to indicate the error. 86.Sh ERRORS 87.Bl -tag -width Er 88.It Bq Er EINVAL 89The value of the 90.Fa endbyte 91element of 92.Fa table 93is not 0 or 255. 94.El 95.Pp 96Additionally, the 97.Fn sradixsort 98function 99may fail and set 100.Va errno 101for any of the errors specified for the library routine 102.Xr malloc 3 . 103.Sh SEE ALSO 104.Xr sort 1 , 105.Xr qsort 3 106.Pp 107.Rs 108.%A Knuth, D.E. 109.%D 1968 110.%B "The Art of Computer Programming" 111.%T "Sorting and Searching" 112.%V Vol. 3 113.%P pp. 170-178 114.Re 115.Rs 116.%A Paige, R. 117.%D 1987 118.%T "Three Partition Refinement Algorithms" 119.%J "SIAM J. Comput." 120.%V Vol. 16 121.%N No. 6 122.Re 123.Rs 124.%A McIlroy, P. 125.%D 1993 126.%B "Engineering Radix Sort" 127.%T "Computing Systems" 128.%V Vol. 6:1 129.%P pp. 5-27 130.Re 131.Sh HISTORY 132The 133.Fn radixsort 134function first appeared in 4.4BSD. 135