radixsort(3bsd) 3bsd radixsort(3bsd)

# [NAME](#NAME)

`radixsort`, `sradixsort` — radix sort

# [LIBRARY](#LIBRARY)

library “libbsd”

# [SYNOPSIS](#SYNOPSIS)

`#include <limits.h>`  
`#include <stdlib.h>` (See [libbsd(7)](/man/os/libbsd/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](#DESCRIPTION)

The [`radixsort`](#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`](#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`](#radixsort~2)() 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](#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](#ERRORS)

\[[`EINVAL`](#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)](/man/os/libbsd/malloc.3).

# [SEE ALSO](#SEE_ALSO)

[sort(1)](/man/os/libbsd/sort.1), [qsort(3)](/man/os/libbsd/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](#HISTORY)

The `radixsort`() function first appeared in 4.4BSD.

January 27, 1994 Linux 4.19.0-gvisor

---

Document: radixsort(3bsd) from libbsd 0.12.2-r11 (Chainguard OS)
Source: https://gitlab.freedesktop.org/libbsd/libbsd