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