libnl: /data/src/libnl/include/netlink/hash.h Source File

libnl 3.12.0

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
9#include <stdint.h>
10#include <stdlib.h>
11#include <endian.h>
12
13/* Stolen mostly from: lookup3.c, by Bob Jenkins, May 2006, Public Domain.
14 *
15 * http://burtleburtle.net/bob/c/lookup3.c
16 */
17
18#ifdef __cplusplus
19extern "C" {
20#endif
21
22#ifdef __LITTLE_ENDIAN
23# define HAVE_LITTLE_ENDIAN 1
24#elif __BIG_ENDIAN
25# define HAVE_BIG_ENDIAN 1
26#else
27#error Unknown endianness. Failure in endian.h
28#endif
29
30/**
31 * hash - fast hash of an array for internal use
32 * @p: the array or pointer to first element
33 * @num: the number of elements to hash
34 * @base: the base number to roll into the hash (usually 0)
35 *
36 * The memory region pointed to by p is combined with the base to form
37 * a 32-bit hash.
38 *
39 * This hash will have different results on different machines, so is
40 * only useful for internal hashes (ie. not hashes sent across the
41 * network or saved to disk).
42 *
43 * It may also change with future versions: it could even detect at runtime
44 * what the fastest hash to use is.
45 *
46 * See also: hash64, hash_stable.
47 *
48 * Example:
49 * #include <ccan/hash/hash.h>
50 * #include <err.h>
51 * #include <stdio.h>
52 * #include <string.h>
53 *
54 * // Simple demonstration: idential strings will have the same hash, but
55 * // two different strings will probably not.
56 * int main(int argc, char *argv[])
57 * {
58 * uint32_t hash1, hash2;
59 *
60 * if (argc != 3)
61 * err(1, "Usage: %s <string1> <string2>", argv[0]);
62 *
63 * hash1 = __nl_hash(argv[1], strlen(argv[1]), 0);
64 * hash2 = __nl_hash(argv[2], strlen(argv[2]), 0);
65 * printf("Hash is %s\n", hash1 == hash2 ? "same" : "different");
66 * return 0;
67 * }
68 */
69#define __nl_hash(p, num, base) nl_hash_any((p), (num)*sizeof(*(p)), (base))
70
71/* Our underlying operations. */
72uint32_t nl_hash_any(const void *key, size_t length, uint32_t base);
73
74#ifdef __cplusplus
75}
76#endif
77
78#endif /* HASH_H */