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1 /*
2  * This file was taken from http://ccodearchive.net/info/hash.html
3  * Changes to the original file include cleanups and removal of unwanted code
4  * and also code that depended on build_asert
5  */
6 #ifndef CCAN_HASH_H
7 #define CCAN_HASH_H
8 #include <stdint.h>
9 #include <stdlib.h>
10 #include <endian.h>
11 
12 /* Stolen mostly from: lookup3.c, by Bob Jenkins, May 2006, Public Domain.
13  *
14  * http://burtleburtle.net/bob/c/lookup3.c
15  */
16 
17 #ifdef __LITTLE_ENDIAN
18 #   define HAVE_LITTLE_ENDIAN 1
19 #elif __BIG_ENDIAN
20 #   define HAVE_BIG_ENDIAN 1
21 #else
22 #error Unknown endianness.  Failure in endian.h
23 #endif
24 
25 /**
26  * hash - fast hash of an array for internal use
27  * @p: the array or pointer to first element
28  * @num: the number of elements to hash
29  * @base: the base number to roll into the hash (usually 0)
30  *
31  * The memory region pointed to by p is combined with the base to form
32  * a 32-bit hash.
33  *
34  * This hash will have different results on different machines, so is
35  * only useful for internal hashes (ie. not hashes sent across the
36  * network or saved to disk).
37  *
38  * It may also change with future versions: it could even detect at runtime
39  * what the fastest hash to use is.
40  *
41  * See also: hash64, hash_stable.
42  *
43  * Example:
44  *	#include <ccan/hash/hash.h>
45  *	#include <err.h>
46  *	#include <stdio.h>
47  *	#include <string.h>
48  *
49  *	// Simple demonstration: idential strings will have the same hash, but
50  *	// two different strings will probably not.
51  *	int main(int argc, char *argv[])
52  *	{
53  *		uint32_t hash1, hash2;
54  *
55  *		if (argc != 3)
56  *			err(1, "Usage: %s <string1> <string2>", argv[0]);
57  *
58  *		hash1 = __nl_hash(argv[1], strlen(argv[1]), 0);
59  *		hash2 = __nl_hash(argv[2], strlen(argv[2]), 0);
60  *		printf("Hash is %s\n", hash1 == hash2 ? "same" : "different");
61  *		return 0;
62  *	}
63  */
64 #define __nl_hash(p, num, base) nl_hash_any((p), (num)*sizeof(*(p)), (base))
65 
66 /* Our underlying operations. */
67 uint32_t nl_hash_any(const void *key, size_t length, uint32_t base);
68 
69 #endif /* HASH_H */
70