RADIXSORT(3) MachTen Programmer’s Manual RADIXSORT(3)
NAME
radixsort - radix sort
SYNOPSIS
#include <limits.h>
#include <stdlib.h>
int
radixsort(u_char **base, int nmemb, u_char *table, u_int
endbyte)
int
sradixsort(u_char **base, int nmemb, u_char *table, u_int
endbyte)
DESCRIPTION
The radixsort() and sradixsort() functions are
implementations of radix
sort.
These functions sort an array of
pointers to byte strings, the initial
member of which is referenced by base. The byte strings may
contain any
values; the end of each string is denoted by the
user-specified value
endbyte.
Applications may specify a sort
order by providing the table argument.
If non-NULL, table must reference an array of 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 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 table is NULL,
the contents
of the array are sorted in ascending order according to the
ASCII order
of the byte strings they reference and endbyte has a sorting
weight of 0.
The sradixsort() function is
stable, that is, if two elements compare as
equal, their order in the sorted array is unchanged. The
sradixsort()
function uses additional memory sufficient to hold nmemb
pointers.
The radixsort() function is not stable, but uses no additional memory.
These functions are variants of
most-significant-byte radix sorting; in
particular, see D.E. Knuth’s Algorithm R and section
5.2.5, exercise 10.
They take linear time relative to the number of bytes in the
strings.
RETURN VALUES
Upon successful completion 0 is returned. Otherwise, -1 is
returned and
the global variable errno is set to indicate the error.
ERRORS
[EINVAL] The value of the endbyte element of table is not 0
or 255.
Additionally, the sradixsort()
function may fail and set errno for any of
the errors specified for the library routine malloc(3).
SEE ALSO
sort(1), qsort(3)
Knuth, D.E., "Sorting and
Searching", The Art of Computer Programming,
Vol. 3, pp. 170-178, 1968.
Paige, R., "Three Partition
Refinement Algorithms", SIAM J. Comput., No.
6, Vol. 16, 1987.
McIlroy, P., "Computing
Systems", Engineering Radix Sort, Vol. 6:1, pp.
5-27, 1993.
HISTORY
The radixsort() function first appeared in 4.4BSD.
4.4BSD January 27, 1994 2