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Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" $OpenBSD: radixsort.3,v 1.7 2001/08/06 10:42:26 mpech Exp $ 33.\" 34.Dd January 27, 1994 35.Dt RADIXSORT 3 36.Os 37.Sh NAME 38.Nm radixsort 39.Nd radix sort 40.Sh SYNOPSIS 41.Fd #include <limits.h> 42.Fd #include <stdlib.h> 43.Ft int 44.Fn radixsort "const u_char **base" "int nmemb" "const u_char *table" "u_int endbyte" 45.Ft int 46.Fn sradixsort "const u_char **base" "int nmemb" "const u_char *table" "u_int endbyte" 47.Sh DESCRIPTION 48The 49.Fn radixsort 50and 51.Fn sradixsort 52functions are implementations of radix sort. 53.Pp 54These functions sort an array of pointers to byte strings, the initial 55member of which is referenced by 56.Fa base . 57The byte strings may contain any values; the end of each string 58is denoted by the user-specified value 59.Fa endbyte . 60.Pp 61Applications may specify a sort order by providing the 62.Fa table 63argument. 64If non-null, 65.Fa table 66must reference an array of 67.Dv UCHAR_MAX 68+ 1 bytes which contains the sort weight of each possible byte value. 69The end-of-string byte must have a sort weight of 0 or 255 70(for sorting in reverse order). 71More than one byte may have the same sort weight. 72The 73.Fa table 74argument is 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 80.Dv NULL , 81the contents of the array are sorted in ascending order according to the 82.Tn ASCII 83order of the byte strings they reference and 84.Fa endbyte 85has a sorting weight of 0. 86.Pp 87The 88.Fn sradixsort 89function is stable, that is, if two elements compare as equal, their 90order in the sorted array is unchanged. 91The 92.Fn sradixsort 93function uses additional memory sufficient to hold 94.Fa nmemb 95pointers. 96.Pp 97The 98.Fn radixsort 99function is not stable, but uses no additional memory. 100.Pp 101These functions are variants of most-significant-byte radix sorting; in 102particular, see D.E. Knuth's Algorithm R and section 5.2.5, exercise 10. 103They take linear time relative to the number of bytes in the strings. 104.Sh RETURN VALUES 105Upon successful completion 0 is returned. 106Otherwise, \-1 is returned and the global variable 107.Va errno 108is set to indicate the error. 109.Sh ERRORS 110.Bl -tag -width Er 111.It Bq Er EINVAL 112The value of the 113.Fa endbyte 114element of 115.Fa table 116is not 0 or 255. 117.El 118.Pp 119Additionally, the 120.Fn sradixsort 121function may 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.Rs 129.%A Knuth, D.E. 130.%D 1968 131.%B "The Art of Computer Programming" 132.%T "Sorting and Searching" 133.%V Vol. 3 134.%P pp. 170-178 135.Re 136.Rs 137.%A Paige, R. 138.%D 1987 139.%T "Three Partition Refinement Algorithms" 140.%J "SIAM J. Comput." 141.%V Vol. 16 142.%N No. 6 143.Re 144.Rs 145.%A McIlroy, P. 146.%D 1993 147.%B "Engineering Radix Sort" 148.%T "Computing Systems" 149.%V Vol. 6:1 150.%P pp. 5-27 151.Re 152.Sh HISTORY 153The 154.Fn radixsort 155function first appeared in 156.Bx 4.4 . 157