libnl 3.5.0

hash.h
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 */