NAME

       radixsort, sradixsort — radix sort

LIBRARY

       Utility functions from BSD systems (libbsd, -lbsd)

SYNOPSIS

       #include <limits.h>
       #include <stdlib.h>
       (See libbsd(7) for include usage.)

       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 nmemb element array of pointers to byte strings, with the initial member of which
       is  referenced by base.  The byte strings may contain any values.  End of strings is denoted by character
       which has same weight as user specified value endbyte.  endbyte has to be between 0 and 255.

       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

       The radixsort() function returns the value 0 if successful; otherwise the value -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.

Debian                                          January 27, 1994                                 radixsort(3bsd)