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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.\" @(#)radixsort.3 8.2 (Berkeley) 1/27/94 33.\" $FreeBSD$ 34.\" 35.Dd January 27, 1994 36.Dt RADIXSORT 3 37.Os 38.Sh NAME 39.Nm radixsort 40.Nd radix sort 41.Sh SYNOPSIS 42.Fd #include <limits.h> 43.Fd #include <stdlib.h> 44.Ft int 45.Fn radixsort "const unsigned char **base" "int nmemb" "const unsigned char *table" "unsigned endbyte" 46.Ft int 47.Fn sradixsort "const unsigned char **base" "int nmemb" "const unsigned char *table" "unsigned endbyte" 48.Sh DESCRIPTION 49The 50.Fn radixsort 51and 52.Fn sradixsort 53functions 54are implementations of radix sort. 55.Pp 56These functions sort an array of pointers to byte strings, the initial 57member of which is referenced by 58.Fa base . 59The byte strings may contain any values; the end of each string 60is denoted by the user-specified value 61.Fa endbyte . 62.Pp 63Applications may specify a sort order by providing the 64.Fa table 65argument. 66If 67.Pf non- Dv NULL , 68.Fa table 69must reference an array of 70.Dv UCHAR_MAX 71+ 1 bytes which contains the sort 72weight of each possible byte value. 73The end-of-string byte must have a sort weight of 0 or 255 74(for sorting in reverse order). 75More than one byte may have the same sort weight. 76The 77.Fa table 78argument 79is useful for applications which wish to sort different characters 80equally, for example, providing a table with the same weights 81for A-Z as for a-z will result in a case-insensitive sort. 82If 83.Fa table 84is NULL, the contents of the array are sorted in ascending order 85according to the 86.Tn ASCII 87order of the byte strings they reference and 88.Fa endbyte 89has a sorting weight of 0. 90.Pp 91The 92.Fn sradixsort 93function is stable, that is, if two elements compare as equal, their 94order in the sorted array is unchanged. 95The 96.Fn sradixsort 97function uses additional memory sufficient to hold 98.Fa nmemb 99pointers. 100.Pp 101The 102.Fn radixsort 103function is not stable, but uses no additional memory. 104.Pp 105These functions are variants of most-significant-byte radix sorting; in 106particular, see D.E. Knuth's Algorithm R and section 5.2.5, exercise 10. 107They take linear time relative to the number of bytes in the strings. 108.Sh RETURN VALUES 109Upon successful completion 0 is returned. 110Otherwise, \-1 is returned and the global variable 111.Va errno 112is set to indicate the error. 113.Sh ERRORS 114.Bl -tag -width Er 115.It Bq Er EINVAL 116The value of the 117.Fa endbyte 118element of 119.Fa table 120is not 0 or 255. 121.El 122.Pp 123Additionally, the 124.Fn sradixsort 125function 126may fail and set 127.Va errno 128for any of the errors specified for the library routine 129.Xr malloc 3 . 130.Sh SEE ALSO 131.Xr sort 1 , 132.Xr qsort 3 133.Pp 134.Rs 135.%A Knuth, D.E. 136.%D 1968 137.%B "The Art of Computer Programming" 138.%T "Sorting and Searching" 139.%V Vol. 3 140.%P pp. 170-178 141.Re 142.Rs 143.%A Paige, R. 144.%D 1987 145.%T "Three Partition Refinement Algorithms" 146.%J "SIAM J. Comput." 147.%V Vol. 16 148.%N No. 6 149.Re 150.Rs 151.%A McIlroy, P. 152.%D 1993 153.%B "Engineering Radix Sort" 154.%T "Computing Systems" 155.%V Vol. 6:1 156.%P pp. 5-27 157.Re 158.Sh HISTORY 159The 160.Fn radixsort 161function first appeared in 162.Bx 4.4 . 163