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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 refer-ence reference
     ence 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 sort-ing sorting
     ing 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.

BSD                            January 27, 1994                            BSD

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