diff options
Diffstat (limited to 'include/netlink')
-rw-r--r-- | include/netlink/hash.h | 69 |
1 files changed, 69 insertions, 0 deletions
diff --git a/include/netlink/hash.h b/include/netlink/hash.h new file mode 100644 index 0000000..8ca1f5b --- /dev/null +++ b/include/netlink/hash.h @@ -0,0 +1,69 @@ +/* + * This file was taken from http://ccodearchive.net/info/hash.html + * Changes to the original file include cleanups and removal of unwanted code + * and also code that depended on build_asert + */ +#ifndef CCAN_HASH_H +#define CCAN_HASH_H +#include <stdint.h> +#include <stdlib.h> +#include <endian.h> + +/* Stolen mostly from: lookup3.c, by Bob Jenkins, May 2006, Public Domain. + * + * http://burtleburtle.net/bob/c/lookup3.c + */ + +#ifdef __LITTLE_ENDIAN +# define HAVE_LITTLE_ENDIAN 1 +#elif __BIG_ENDIAN +# define HAVE_BIG_ENDIAN 1 +#else +#error Unknown endianness. Failure in endian.h +#endif + +/** + * hash - fast hash of an array for internal use + * @p: the array or pointer to first element + * @num: the number of elements to hash + * @base: the base number to roll into the hash (usually 0) + * + * The memory region pointed to by p is combined with the base to form + * a 32-bit hash. + * + * This hash will have different results on different machines, so is + * only useful for internal hashes (ie. not hashes sent across the + * network or saved to disk). + * + * It may also change with future versions: it could even detect at runtime + * what the fastest hash to use is. + * + * See also: hash64, hash_stable. + * + * Example: + * #include <ccan/hash/hash.h> + * #include <err.h> + * #include <stdio.h> + * #include <string.h> + * + * // Simple demonstration: idential strings will have the same hash, but + * // two different strings will probably not. + * int main(int argc, char *argv[]) + * { + * uint32_t hash1, hash2; + * + * if (argc != 3) + * err(1, "Usage: %s <string1> <string2>", argv[0]); + * + * hash1 = hash(argv[1], strlen(argv[1]), 0); + * hash2 = hash(argv[2], strlen(argv[2]), 0); + * printf("Hash is %s\n", hash1 == hash2 ? "same" : "different"); + * return 0; + * } + */ +#define hash(p, num, base) hash_any((p), (num)*sizeof(*(p)), (base)) + +/* Our underlying operations. */ +uint32_t hash_any(const void *key, size_t length, uint32_t base); + +#endif /* HASH_H */ |