RADIXSORT(3)						   BSD Library Functions Manual 					      RADIXSORT(3)

NAME

     radixsort, sradixsort -- radix sort

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <limits.h>
     #include <stdlib.h>

     int
     radixsort(const unsigned char **base, int nmemb, const unsigned char *table, unsigned endbyte);

     int
     sradixsort(const unsigned char **base, int nmemb, const unsigned char *table, unsigned 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 differ-
     ent 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

     The radixsort() function returns the value 0 if successful; otherwise the value -1 is returned and the global variable errno is set to indi-
     cate 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.

BSD
								 January 27, 1994							       BSD