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 19 extern "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. */ 72 uint32_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 */ 79