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31 lines
1 KiB
C
31 lines
1 KiB
C
#ident "Copyright (c) 2007, 2008 Tokutek Inc. All rights reserved."
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// FNV Hash: From an idea sent by Glenn Fowler and Phong Vo to the IEEE POSIX 1003.2 committee. Landon Curt Noll improved it.
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// See: http://isthe.com/chongo/tech/comp/fnv/
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static inline unsigned int hash_key (const unsigned char *key, unsigned long keylen) {
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unsigned long i;
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unsigned int hash=0;
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for (i=0; i<keylen; i++, key++) {
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hash *= 16777619;
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// GCC 4.1.2 -O2 and -O3 translates the following shifts back into the multiply shown on the line above here.
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// So much for optimizing this multiplication...
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//hash += (hash<<1) + (hash<<4) + (hash<<7) + (hash<<8) + (hash<<24);
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hash ^= *key;
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}
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return hash;
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}
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#if 0
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static unsigned int hash_key (const char *key, ITEMLEN keylen) {
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/* From Sedgewick. There are probably better hash functions. */
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unsigned int b = 378551;
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unsigned int a = 63689;
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unsigned int hash = 0;
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ITEMLEN i;
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for (i = 0; i < keylen; i++ ) {
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hash = hash * a + key[i];
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a *= b;
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}
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return hash;
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}
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#endif
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