RADIXSORT(3) BSD 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 userspecified value
endbyte.
Applications may specify a sort order by providing the table argument.
If nonNULL, table must reference an array of UCHAR_MAX + 1 bytes which
contains the sort weight of each possible byte value. The endofstring
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 AZ as for az
will result in a caseinsensitive 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 mostsignificantbyte 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. 170178, 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.
527, 1993.
HISTORY
The radixsort() function first appeared in 4.4BSD.
4.4BSD January 27, 1994 2
