add sradixsort

[unix-history] / usr / src / lib / libc / stdlib / radixsort.3

.\" Copyright (c) 1990, 1991 The Regents of the University of California.
.\" All rights reserved.
.\"
.\" %sccs.include.redist.man%
.\"
.\"     @(#)radixsort.3	5.8 (Berkeley) %G%
.\"
.Dd 
.Dt RADIXSORT 3
.Os
.Sh NAME
.Nm radixsort
.Nd radix sort
.Sh SYNOPSIS
.Fd #include <limits.h>
.Fd #include <stdlib.h>
.Ft int
.Fn radixsort "u_char **base" "int nmemb" "u_char *table" "u_int endbyte"
.Sh DESCRIPTION
The
.Fn radixsort
function
is a radix sort.
.Pp
The
.Fn radixsort
function sorts an array of
.Fa nmemb
pointers to byte strings, the initial member of which is referenced
by
.Fa base .
The byte strings may contain any values; the end of each string
is denoted by the user-specified value
.Fa endbyte .
The contents of the array are sorted in ascending order according
to the
.Tn ASCII
order of the byte strings they reference.
.Pp
Applications may specify a sort order by providing the
.Fa table
argument.
If
.Pf non- Dv NULL , 
.Fa table
must reference an array of
.Dv UCHAR_MAX
+ 1 bytes which contains the sort
weight of each possible byte value.
The end-of-string byte must have a sort weight of 0 or 255
(for sorting in reverse order).
More than one byte may have the same sort weight.
The
.Fa table
argument
is useful for applications which wish to sort different characters
equally; for example, providing a table with the same weights
for A-Z as for a-z will result in a case-insensitive sort.
If
.Fa table
is NULL,
ASCII weights are used and
.Fa endbyte
has a sorting weight of 0.
.Pp
The
.Fn radixsort
function
is stable, that is, if two elements compare as equal, their order in
the sorted array is unchanged.
.Pp
The
.Fn radixsort
function
is a variant of most-significant-byte radix sorting; in particular, see
D.E. Knuth's Algorithm R and section 5.2.5, exercise 10.
The
.Fn radixsort
function
takes linear time relative to the number of bytes in the strings.
.Sh RETURN VALUES
Upon successful completion 0 is returned.
Otherwise, \-1 is returned and the global variable 
.Va errno
is set to indicate the error.
.Sh ERRORS
.Bl -tag -width Er
.It Bq Er EINVAL
The value of the
.Fa endbyte
element of
.Fa table
is not 0 or 255.
.El
.Pp
Additionally, the
.Fn radixsort
function
may fail and set
.Va errno
for any of the errors specified for the library routine
.Xr malloc 3 .
.Sh SEE ALSO
.Xr sort 1 ,
.Xr qsort 3
.Pp
.Rs
.%A Knuth, D.E.
.%D 1968
.%B "The Art of Computer Programming"
.%T "Sorting and Searching"
.%V Vol. 3
.%P pp. 170-178
.Re
.Rs
.%A Paige, R.
.%D 1987
.%T "Three Partition Refinement Algorithms"
.%J "SIAM J. Comput."
.%V Vol. 16
.%N No. 6
.Re
.Sh HISTORY
The
.Fn radixsort
function is
.Ud .