## table of contents

RADIXSORT(3bsd) | 3bsd | RADIXSORT(3bsd) |

# NAME¶

`radixsort`

,
`sradixsort`

— radix
sort

# LIBRARY¶

library “libbsd”

# 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¶

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.

January 27, 1994 | Debian |