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.