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32 * @(#)hash_func.c 8.2 (Berkeley) 2/21/94
33 * $DragonFly: src/lib/libc/db/hash/hash_func.c,v 1.8 2005/11/19 20:46:32 swildner Exp $
36 #include <sys/types.h>
43 static u_int32_t hash1 (const void *, size_t) __unused;
44 static u_int32_t hash2 (const void *, size_t) __unused;
45 static u_int32_t hash3 (const void *, size_t) __unused;
46 static u_int32_t hash4 (const void *, size_t);
48 /* Global default hash function */
49 u_int32_t (*__default_hash) (const void *, size_t) = hash4;
54 * Assume that we've already split the bucket to which this key hashes,
55 * calculate that bucket, and check that in fact we did already split it.
57 * This came from ejb's hsearch.
61 #define PRIME2 1048583
64 hash1(const void *keyarg, size_t len)
69 /* Convert string to integer */
70 for (key = keyarg, h = 0; len--;)
71 h = h * PRIME1 ^ (*key++ - ' ');
77 * Phong's linear congruential hash
79 #define dcharhash(h, c) ((h) = 0x63c63cd9*(h) + 0x9c39c33d + (c))
82 hash2(const void *keyarg, size_t len)
84 const u_char *e, *key;
90 for (h = 0; key != e;) {
100 * This is INCREDIBLY ugly, but fast. We break the string up into 8 byte
101 * units. On the first time through the loop we get the "leftover bytes"
102 * (strlen % 8). On every other iteration, we perform 8 HASHC's so we handle
103 * all 8 bytes. Essentially, this saves us 7 cmp & branch instructions. If
104 * this routine is heavily used enough, it's worth the ugly coding.
106 * OZ's original sdbm hash
109 hash3(const void *keyarg, size_t len)
115 #define HASHC h = *key++ + 65599 * h
120 loop = (len + 8 - 1) >> 3;
122 switch (len & (8 - 1)) {
153 /* Hash function from Chris Torek. */
155 hash4(const void *keyarg, size_t len)
161 #define HASH4a h = (h << 5) - h + *key++;
162 #define HASH4b h = (h << 5) + h + *key++;
168 loop = (len + 8 - 1) >> 3;
170 switch (len & (8 - 1)) {