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Change meaning of "bits" in FNV hash functions to bitlen instead of 32-bitlen. 

Do reduction like recommended by
http://www.isthe.com/chongo/tech/comp/fnv/index.html#xor-fold
This commit is contained in:
Jilles Tjoelker 2007-12-08 19:44:18 +01:00
parent 176489286d
commit 1cda7a9cb2
2 changed files with 12 additions and 8 deletions
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8
include/hash.h
View File

@ -44,19 +44,19 @@ extern struct Dictionary *nd_dict;
#define FNV1_32_INIT 0x811c9dc5UL
/* Client hash table size, used in hash.c/s_debug.c */
#define U_MAX_BITS (32-17)
#define U_MAX_BITS 17
#define U_MAX 131072 /* 2^17 */
/* Channel hash table size, hash.c/s_debug.c */
#define CH_MAX_BITS (32-16)
#define CH_MAX_BITS 16
#define CH_MAX 65536 /* 2^16 */
/* hostname hash table size */
#define HOST_MAX_BITS (32-17)
#define HOST_MAX_BITS 17
#define HOST_MAX 131072 /* 2^17 */
/* RESV/XLINE hash table size, used in hash.c */
#define R_MAX_BITS (32-10)
#define R_MAX_BITS 10
#define R_MAX 1024 /* 2^10 */

12
src/hash.c
View File

@ -109,7 +109,8 @@ fnv_hash_upper(const unsigned char *s, int bits)
h ^= ToUpper(*s++);
h += (h<<1) + (h<<4) + (h<<7) + (h << 8) + (h << 24);
}
h = (h >> bits) ^ (h & ((2^bits)-1));
if (bits < 32)
h = ((h >> bits) ^ h) & ((1<<bits)-1);
return h;
}
@ -123,7 +124,8 @@ fnv_hash(const unsigned char *s, int bits)
h ^= *s++;
h += (h<<1) + (h<<4) + (h<<7) + (h << 8) + (h << 24);
}
h = (h >> bits) ^ (h & ((2^bits)-1));
if (bits < 32)
h = ((h >> bits) ^ h) & ((1<<bits)-1);
return h;
}
@ -137,7 +139,8 @@ fnv_hash_len(const unsigned char *s, int bits, int len)
h ^= *s++;
h += (h<<1) + (h<<4) + (h<<7) + (h << 8) + (h << 24);
}
h = (h >> bits) ^ (h & ((2^bits)-1));
if (bits < 32)
h = ((h >> bits) ^ h) & ((1<<bits)-1);
return h;
}
@ -151,7 +154,8 @@ fnv_hash_upper_len(const unsigned char *s, int bits, int len)
h ^= ToUpper(*s++);
h += (h<<1) + (h<<4) + (h<<7) + (h << 8) + (h << 24);
}
h = (h >> bits) ^ (h & ((2^bits)-1));
if (bits < 32)
h = ((h >> bits) ^ h) & ((1<<bits)-1);
return h;
}
#endif