RADIXSORT(3) BSD Programmer's Manual RADIXSORT(3)

radixsort,sradixsort- radix sort

#include <limits.h>#include <stdlib.h>intradixsort(const u_char **base,int nmemb,const u_char *table,u_int endbyte);intsradixsort(const u_char **base,int nmemb,const u_char *table,u_int endbyte);

Theradixsort() andsradixsort() functions are implementations of radix sort. These functions sort an array ofnmembpointers to byte strings. The ini- tial member is referenced bybase. The byte strings may contain any values; the end of each string is denoted by the user-specified valueendbyte. Applications may specify a sort order by providing thetableargument. If non-null,tablemust reference an array of UCHAR_MAX + 1 bytes which con- tains 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. Thetableargument is useful for applications which wish to sort different characters equally; for ex- ample, providing a table with the same weights for A-Z as for a-z will result in a case-insensitive sort. Iftableis NULL, the contents of the array are sorted in ascending order according to the ASCII order of the byte strings they reference andendbytehas a sorting weight of 0. Thesradixsort() function is stable; that is, if two elements compare as equal, their order in the sorted array is unchanged. Thesradixsort() function uses additional memory sufficient to holdnmembpointers. Theradixsort() 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 variableerrnois set to indicate the error.

[EINVAL] The value of theendbyteelement oftableis not 0 or 255. Additionally, thesradixsort() function may fail and seterrnofor any of the errors specified for the library routine malloc(3).

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.

Theradixsort() function first appeared in 4.4BSD. MirOS BSD #10-current January 27, 1994 1

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