2 * Copyright (c) 1990, 1993
3 * The Regents of the University of California. All rights reserved.
5 * This code is derived from software contributed to Berkeley by
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
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12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 * 3. ***REMOVED*** - see
17 * ftp://ftp.cs.berkeley.edu/pub/4bsd/README.Impt.License.Change
18 * 4. Neither the name of the University nor the names of its contributors
19 * may be used to endorse or promote products derived from this software
20 * without specific prior written permission.
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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35 #if defined(LIBC_SCCS) && !defined(lint)
36 static char sccsid
[] = "@(#)hash_func.c 8.2 (Berkeley) 2/21/94";
37 #endif /* LIBC_SCCS and not lint */
40 #include <sys/types.h>
45 /* #include "extern.h" */
48 static uint32 hash1
__P((const void *, size_t));
49 static uint32 hash2
__P((const void *, size_t));
50 static uint32 hash3
__P((const void *, size_t));
52 static uint32 hash4
__P((const void *, size_t));
54 /* Global default hash function */
55 uint32 (*__default_hash
) __P((const void *, size_t)) = hash4
;
60 * Assume that we've already split the bucket to which this key hashes,
61 * calculate that bucket, and check that in fact we did already split it.
63 * This came from ejb's hsearch.
67 #define PRIME2 1048583
71 hash1(const void *keyarg
, register size_t len
)
73 register const uint8
*key
;
76 /* Convert string to integer */
77 for (key
= (const uint8
*)keyarg
, h
= 0; len
--;)
78 h
= h
* PRIME1
^ (*key
++ - ' ');
84 * Phong's linear congruential hash
86 #define dcharhash(h, c) ((h) = 0x63c63cd9*(h) + 0x9c39c33d + (c))
89 hash2(const void *keyarg
, size_t len
)
91 register const uint8
*e
, *key
;
95 key
= (const uint8
*)keyarg
;
97 for (h
= 0; key
!= e
;) {
107 * This is INCREDIBLY ugly, but fast. We break the string up into 8 byte
108 * units. On the first time through the loop we get the "leftover bytes"
109 * (strlen % 8). On every other iteration, we perform 8 HASHC's so we handle
110 * all 8 bytes. Essentially, this saves us 7 cmp & branch instructions. If
111 * this routine is heavily used enough, it's worth the ugly coding.
113 * OZ's original sdbm hash
116 hash3(const void *keyarg
, register size_t len
)
118 register const uint8
*key
;
119 register size_t loop
;
122 #define HASHC h = *key++ + 65599 * h
125 key
= (const uint8
*)keyarg
;
127 loop
= (len
+ 8 - 1) >> 3;
129 switch (len
& (8 - 1)) {
161 /* Hash function from Chris Torek. */
163 hash4(const void *keyarg
, register size_t len
)
165 register const uint8
*key
;
166 register size_t loop
;
169 #define HASH4a h = (h << 5) - h + *key++;
170 #define HASH4b h = (h << 5) + h + *key++;
174 key
= (const uint8
*)keyarg
;
176 loop
= (len
+ 8 - 1) >> 3;
178 switch (len
& (8 - 1)) {