[apple/libc.git] / db / hash / hash_func.c

/*
 * Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * Copyright (c) 1999-2003 Apple Computer, Inc.  All Rights Reserved.
 * 
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this
 * file.
 * 
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 * 
 * @APPLE_LICENSE_HEADER_END@
 */
/*
 * Copyright (c) 1990, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Margo Seltzer.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */


#include <sys/types.h>

#include <db.h>
#include "hash.h"
#include "page.h"
#include "extern.h"

static u_int32_t hash1 __P((const void *, size_t));
static u_int32_t hash2 __P((const void *, size_t));
static u_int32_t hash3 __P((const void *, size_t));
static u_int32_t hash4 __P((const void *, size_t));

/* Global default hash function */
u_int32_t (*__default_hash) __P((const void *, size_t)) = hash4;

/*
 * HASH FUNCTIONS
 *
 * Assume that we've already split the bucket to which this key hashes,
 * calculate that bucket, and check that in fact we did already split it.
 *
 * This came from ejb's hsearch.
 */

#define PRIME1		37
#define PRIME2		1048583

static u_int32_t
hash1(keyarg, len)
	const void *keyarg;
	register size_t len;
{
	register const u_char *key;
	register u_int32_t h;

	/* Convert string to integer */
	for (key = keyarg, h = 0; len--;)
		h = h * PRIME1 ^ (*key++ - ' ');
	h %= PRIME2;
	return (h);
}

/*
 * Phong's linear congruential hash
 */
#define dcharhash(h, c)	((h) = 0x63c63cd9*(h) + 0x9c39c33d + (c))

static u_int32_t
hash2(keyarg, len)
	const void *keyarg;
	size_t len;
{
	register const u_char *e, *key;
	register u_int32_t h;
	register u_char c;

	key = keyarg;
	e = key + len;
	for (h = 0; key != e;) {
		c = *key++;
		if (!c && key > e)
			break;
		dcharhash(h, c);
	}
	return (h);
}

/*
 * This is INCREDIBLY ugly, but fast.  We break the string up into 8 byte
 * units.  On the first time through the loop we get the "leftover bytes"
 * (strlen % 8).  On every other iteration, we perform 8 HASHC's so we handle
 * all 8 bytes.  Essentially, this saves us 7 cmp & branch instructions.  If
 * this routine is heavily used enough, it's worth the ugly coding.
 *
 * OZ's original sdbm hash
 */
static u_int32_t
hash3(keyarg, len)
	const void *keyarg;
	register size_t len;
{
	register const u_char *key;
	register size_t loop;
	register u_int32_t h;

#define HASHC   h = *key++ + 65599 * h

	h = 0;
	key = keyarg;
	if (len > 0) {
		loop = (len + 8 - 1) >> 3;

		switch (len & (8 - 1)) {
		case 0:
			do {
				HASHC;
				/* FALLTHROUGH */
		case 7:
				HASHC;
				/* FALLTHROUGH */
		case 6:
				HASHC;
				/* FALLTHROUGH */
		case 5:
				HASHC;
				/* FALLTHROUGH */
		case 4:
				HASHC;
				/* FALLTHROUGH */
		case 3:
				HASHC;
				/* FALLTHROUGH */
		case 2:
				HASHC;
				/* FALLTHROUGH */
		case 1:
				HASHC;
			} while (--loop);
		}
	}
	return (h);
}

/* Hash function from Chris Torek. */
static u_int32_t
hash4(keyarg, len)
	const void *keyarg;
	register size_t len;
{
	register const u_char *key;
	register size_t loop;
	register u_int32_t h;

#define HASH4a   h = (h << 5) - h + *key++;
#define HASH4b   h = (h << 5) + h + *key++;
#define HASH4 HASH4b

	h = 0;
	key = keyarg;
	if (len > 0) {
		loop = (len + 8 - 1) >> 3;

		switch (len & (8 - 1)) {
		case 0:
			do {
				HASH4;
				/* FALLTHROUGH */
		case 7:
				HASH4;
				/* FALLTHROUGH */
		case 6:
				HASH4;
				/* FALLTHROUGH */
		case 5:
				HASH4;
				/* FALLTHROUGH */
		case 4:
				HASH4;
				/* FALLTHROUGH */
		case 3:
				HASH4;
				/* FALLTHROUGH */
		case 2:
				HASH4;
				/* FALLTHROUGH */
		case 1:
				HASH4;
			} while (--loop);
		}
	}
	return (h);
}
Commit	Line	Data
e9ce8d39 A	1	/*
	2	* Copyright (c) 1999 Apple Computer, Inc. All rights reserved.
	3	*
	4	* @APPLE_LICENSE_HEADER_START@
	5	*
734aad71	6	* Copyright (c) 1999-2003 Apple Computer, Inc. All Rights Reserved.
e9ce8d39	7	*
734aad71 A	8	* This file contains Original Code and/or Modifications of Original Code
	9	* as defined in and that are subject to the Apple Public Source License
	10	* Version 2.0 (the 'License'). You may not use this file except in
	11	* compliance with the License. Please obtain a copy of the License at
	12	* http://www.opensource.apple.com/apsl/ and read it before using this
	13	* file.
	14	*
	15	* The Original Code and all software distributed under the License are
	16	* distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
e9ce8d39 A	17	* EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
e9ce8d39 A	18	* INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
734aad71 A	19	* FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
	20	* Please see the License for the specific language governing rights and
	21	* limitations under the License.
e9ce8d39 A	22	*
	23	* @APPLE_LICENSE_HEADER_END@
	24	*/
	25	/*
	26	* Copyright (c) 1990, 1993
	27	* The Regents of the University of California. All rights reserved.
	28	*
	29	* This code is derived from software contributed to Berkeley by
	30	* Margo Seltzer.
	31	*
	32	* Redistribution and use in source and binary forms, with or without
	33	* modification, are permitted provided that the following conditions
	34	* are met:
	35	* 1. Redistributions of source code must retain the above copyright
	36	* notice, this list of conditions and the following disclaimer.
	37	* 2. Redistributions in binary form must reproduce the above copyright
	38	* notice, this list of conditions and the following disclaimer in the
	39	* documentation and/or other materials provided with the distribution.
	40	* 3. All advertising materials mentioning features or use of this software
	41	* must display the following acknowledgement:
	42	* This product includes software developed by the University of
	43	* California, Berkeley and its contributors.
	44	* 4. Neither the name of the University nor the names of its contributors
	45	* may be used to endorse or promote products derived from this software
	46	* without specific prior written permission.
	47	*
	48	* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	49	* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	50	* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	51	* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	52	* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	53	* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	54	* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	55	* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	56	* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	57	* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	58	* SUCH DAMAGE.
	59	*/
	60
	61
	62	#include <sys/types.h>
	63
	64	#include <db.h>
	65	#include "hash.h"
	66	#include "page.h"
	67	#include "extern.h"
	68
	69	static u_int32_t hash1 __P((const void *, size_t));
	70	static u_int32_t hash2 __P((const void *, size_t));
	71	static u_int32_t hash3 __P((const void *, size_t));
	72	static u_int32_t hash4 __P((const void *, size_t));
	73
	74	/* Global default hash function */
	75	u_int32_t (__default_hash) __P((const void , size_t)) = hash4;
	76
	77	/*
	78	* HASH FUNCTIONS
	79	*
	80	* Assume that we've already split the bucket to which this key hashes,
	81	* calculate that bucket, and check that in fact we did already split it.
	82	*
	83	* This came from ejb's hsearch.
	84	*/
	85
86	#define PRIME1 37
87	#define PRIME2 1048583
88
89	static u_int32_t
90	hash1(keyarg, len)
91	const void *keyarg;
92	register size_t len;
93	{
94	register const u_char *key;
95	register u_int32_t h;
96
97	/* Convert string to integer */
98	for (key = keyarg, h = 0; len--;)
99	h = h * PRIME1 ^ (*key++ - ' ');
100	h %= PRIME2;
101	return (h);
102	}
103
104	/*
105	* Phong's linear congruential hash
106	*/
107	#define dcharhash(h, c) ((h) = 0x63c63cd9*(h) + 0x9c39c33d + (c))
108
109	static u_int32_t
110	hash2(keyarg, len)
111	const void *keyarg;
112	size_t len;
113	{
114	register const u_char e, key;
115	register u_int32_t h;
116	register u_char c;
117
118	key = keyarg;
119	e = key + len;
120	for (h = 0; key != e;) {
121	c = *key++;
122	if (!c && key > e)
123	break;
124	dcharhash(h, c);
125	}
126	return (h);
127	}
128
129	/*
130	* This is INCREDIBLY ugly, but fast. We break the string up into 8 byte
131	* units. On the first time through the loop we get the "leftover bytes"
132	* (strlen % 8). On every other iteration, we perform 8 HASHC's so we handle
133	* all 8 bytes. Essentially, this saves us 7 cmp & branch instructions. If
134	* this routine is heavily used enough, it's worth the ugly coding.
135	*
136	* OZ's original sdbm hash
137	*/
138	static u_int32_t
139	hash3(keyarg, len)
140	const void *keyarg;
141	register size_t len;
142	{
143	register const u_char *key;
144	register size_t loop;
145	register u_int32_t h;
146
147	#define HASHC h = key++ + 65599 h
148
149	h = 0;
150	key = keyarg;
151	if (len > 0) {
152	loop = (len + 8 - 1) >> 3;
153
154	switch (len & (8 - 1)) {
155	case 0:
156	do {
157	HASHC;
158	/* FALLTHROUGH */
159	case 7:
160	HASHC;
161	/* FALLTHROUGH */
162	case 6:
163	HASHC;
164	/* FALLTHROUGH */
165	case 5:
166	HASHC;
167	/* FALLTHROUGH */
168	case 4:
169	HASHC;
170	/* FALLTHROUGH */
171	case 3:
172	HASHC;
173	/* FALLTHROUGH */
174	case 2:
175	HASHC;
176	/* FALLTHROUGH */
177	case 1:
178	HASHC;
179	} while (--loop);
180	}
181	}
182	return (h);
183	}
184
185	/* Hash function from Chris Torek. */
186	static u_int32_t
187	hash4(keyarg, len)
188	const void *keyarg;
189	register size_t len;
190	{
191	register const u_char *key;
192	register size_t loop;
193	register u_int32_t h;
194
195	#define HASH4a h = (h << 5) - h + *key++;
196	#define HASH4b h = (h << 5) + h + *key++;
197	#define HASH4 HASH4b
198
199	h = 0;
200	key = keyarg;
201	if (len > 0) {
202	loop = (len + 8 - 1) >> 3;
203
204	switch (len & (8 - 1)) {
205	case 0:
206	do {
207	HASH4;
208	/* FALLTHROUGH */
209	case 7:
210	HASH4;
211	/* FALLTHROUGH */
212	case 6:
213	HASH4;
214	/* FALLTHROUGH */
215	case 5:
216	HASH4;
217	/* FALLTHROUGH */
218	case 4:
219	HASH4;
220	/* FALLTHROUGH */
221	case 3:
222	HASH4;
223	/* FALLTHROUGH */
224	case 2:
225	HASH4;
226	/* FALLTHROUGH */
227	case 1:
228	HASH4;
229	} while (--loop);
230	}
231	}
232	return (h);
233	}