70 lines
1.9 KiB
C
70 lines
1.9 KiB
C
/*
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* This file was taken from http://ccodearchive.net/info/hash.html
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* Changes to the original file include cleanups and removal of unwanted code
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* and also code that depended on build_asert
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*/
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#ifndef CCAN_HASH_H
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#define CCAN_HASH_H
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#include <stdint.h>
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#include <stdlib.h>
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#include <endian.h>
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/* Stolen mostly from: lookup3.c, by Bob Jenkins, May 2006, Public Domain.
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*
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* http://burtleburtle.net/bob/c/lookup3.c
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*/
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#ifdef __LITTLE_ENDIAN
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# define HAVE_LITTLE_ENDIAN 1
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#elif __BIG_ENDIAN
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# define HAVE_BIG_ENDIAN 1
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#else
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#error Unknown endianness. Failure in endian.h
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#endif
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/**
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* hash - fast hash of an array for internal use
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* @p: the array or pointer to first element
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* @num: the number of elements to hash
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* @base: the base number to roll into the hash (usually 0)
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*
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* The memory region pointed to by p is combined with the base to form
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* a 32-bit hash.
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*
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* This hash will have different results on different machines, so is
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* only useful for internal hashes (ie. not hashes sent across the
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* network or saved to disk).
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*
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* It may also change with future versions: it could even detect at runtime
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* what the fastest hash to use is.
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*
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* See also: hash64, hash_stable.
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*
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* Example:
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* #include <ccan/hash/hash.h>
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* #include <err.h>
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* #include <stdio.h>
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* #include <string.h>
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*
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* // Simple demonstration: idential strings will have the same hash, but
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* // two different strings will probably not.
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* int main(int argc, char *argv[])
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* {
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* uint32_t hash1, hash2;
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*
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* if (argc != 3)
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* err(1, "Usage: %s <string1> <string2>", argv[0]);
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*
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* hash1 = __nl_hash(argv[1], strlen(argv[1]), 0);
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* hash2 = __nl_hash(argv[2], strlen(argv[2]), 0);
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* printf("Hash is %s\n", hash1 == hash2 ? "same" : "different");
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* return 0;
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* }
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*/
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#define __nl_hash(p, num, base) nl_hash_any((p), (num)*sizeof(*(p)), (base))
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/* Our underlying operations. */
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uint32_t nl_hash_any(const void *key, size_t length, uint32_t base);
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#endif /* HASH_H */
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