70 lines
1.9 KiB
C
70 lines
1.9 KiB
C
|
/*
|
||
|
|
* 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 = __nl_hash(argv[1], strlen(argv[1]), 0);
|
||
|
|
* hash2 = __nl_hash(argv[2], strlen(argv[2]), 0);
|
||
|
|
* printf("Hash is %s\n", hash1 == hash2 ? "same" : "different");
|
||
|
|
* return 0;
|
||
|
|
* }
|
||
|
|
*/
|
||
|
|
#define __nl_hash(p, num, base) nl_hash_any((p), (num)*sizeof(*(p)), (base))
|
||
|
|
|
||
|
|
/* Our underlying operations. */
|
||
|
|
uint32_t nl_hash_any(const void *key, size_t length, uint32_t base);
|
||
|
|
|
||
|
|
#endif /* HASH_H */
|