RADIXSORT(3) BSD Library Functions Manual RADIXSORT(3)
radixsort, sradixsort -- radix sort
Standard C Library (libc, -lc)
radixsort(const u_char **base, int nmemb, u_char *table, u_int endbyte);
sradixsort(const u_char **base, int nmemb, u_char *table, u_int endbyte);
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 possi-
ble 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, pro-
viding 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 suffi-
cient 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.
Upon successful completion 0 is returned. Otherwise, -1 is returned and the global variable
errno is set to indicate the error.
[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 speci-
fied for the library routine malloc(3).
Knuth, D.E., "Sorting and Searching", The Art of Computer Programming, Vol. 3, pp. 170-178,
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.
The radixsort() function first appeared in 4.4BSD.
BSD January 27, 1994 BSD