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File: [cvs.NetBSD.org] / src / lib / libc / db / hash / hash_func.c (download)

Revision 1.13, Wed Sep 10 17:52:35 2008 UTC (15 years, 6 months ago) by joerg
Branch: MAIN
CVS Tags: yamt-pagecache-tag8, yamt-pagecache-base9, yamt-pagecache-base8, yamt-pagecache-base7, yamt-pagecache-base6, yamt-pagecache-base5, yamt-pagecache-base4, yamt-pagecache-base3, yamt-pagecache-base2, yamt-pagecache-base, yamt-pagecache, wrstuden-revivesa-base-3, tls-maxphys-base, tls-maxphys, tls-earlyentropy-base, tls-earlyentropy, riastradh-xf86-video-intel-2-7-1-pre-2-21-15, riastradh-drm2-base3, riastradh-drm2-base2, riastradh-drm2-base1, riastradh-drm2-base, riastradh-drm2, prg-localcount2-base3, prg-localcount2-base2, prg-localcount2-base1, prg-localcount2-base, prg-localcount2, phil-wifi-base, phil-wifi-20200421, phil-wifi-20200411, phil-wifi-20200406, phil-wifi-20191119, phil-wifi-20190609, phil-wifi, pgoyette-localcount-base, pgoyette-localcount-20170426, pgoyette-localcount-20170320, pgoyette-localcount-20170107, pgoyette-localcount-20161104, pgoyette-localcount-20160806, pgoyette-localcount-20160726, pgoyette-localcount, pgoyette-compat-merge-20190127, pgoyette-compat-base, pgoyette-compat-20190127, pgoyette-compat-20190118, pgoyette-compat-1226, pgoyette-compat-1126, pgoyette-compat-1020, pgoyette-compat-0930, pgoyette-compat-0906, pgoyette-compat-0728, pgoyette-compat-0625, pgoyette-compat-0521, pgoyette-compat-0502, pgoyette-compat-0422, pgoyette-compat-0415, pgoyette-compat-0407, pgoyette-compat-0330, pgoyette-compat-0322, pgoyette-compat-0315, pgoyette-compat, perseant-stdc-iso10646-base, perseant-stdc-iso10646, netbsd-9-base, netbsd-9-3-RELEASE, netbsd-9-2-RELEASE, netbsd-9-1-RELEASE, netbsd-9-0-RELEASE, netbsd-9-0-RC2, netbsd-9-0-RC1, netbsd-9, netbsd-8-base, netbsd-8-2-RELEASE, netbsd-8-1-RELEASE, netbsd-8-1-RC1, netbsd-8-0-RELEASE, netbsd-8-0-RC2, netbsd-8-0-RC1, netbsd-8, netbsd-7-nhusb-base-20170116, netbsd-7-nhusb-base, netbsd-7-nhusb, netbsd-7-base, netbsd-7-2-RELEASE, netbsd-7-1-RELEASE, netbsd-7-1-RC2, netbsd-7-1-RC1, netbsd-7-1-2-RELEASE, netbsd-7-1-1-RELEASE, netbsd-7-1, netbsd-7-0-RELEASE, netbsd-7-0-RC3, netbsd-7-0-RC2, netbsd-7-0-RC1, netbsd-7-0-2-RELEASE, netbsd-7-0-1-RELEASE, netbsd-7-0, netbsd-7, netbsd-6-base, netbsd-6-1-RELEASE, netbsd-6-1-RC4, netbsd-6-1-RC3, netbsd-6-1-RC2, netbsd-6-1-RC1, netbsd-6-1-5-RELEASE, netbsd-6-1-4-RELEASE, netbsd-6-1-3-RELEASE, netbsd-6-1-2-RELEASE, netbsd-6-1-1-RELEASE, netbsd-6-1, netbsd-6-0-RELEASE, netbsd-6-0-RC2, netbsd-6-0-RC1, netbsd-6-0-6-RELEASE, netbsd-6-0-5-RELEASE, netbsd-6-0-4-RELEASE, netbsd-6-0-3-RELEASE, netbsd-6-0-2-RELEASE, netbsd-6-0-1-RELEASE, netbsd-6-0, netbsd-6, netbsd-5-base, netbsd-5-2-RELEASE, netbsd-5-2-RC1, netbsd-5-2-3-RELEASE, netbsd-5-2-2-RELEASE, netbsd-5-2-1-RELEASE, netbsd-5-2, netbsd-5-1-RELEASE, netbsd-5-1-RC4, netbsd-5-1-RC3, netbsd-5-1-RC2, netbsd-5-1-RC1, netbsd-5-1-5-RELEASE, netbsd-5-1-4-RELEASE, netbsd-5-1-3-RELEASE, netbsd-5-1-2-RELEASE, netbsd-5-1-1-RELEASE, netbsd-5-1, netbsd-5-0-RELEASE, netbsd-5-0-RC4, netbsd-5-0-RC3, netbsd-5-0-RC2, netbsd-5-0-RC1, netbsd-5-0-2-RELEASE, netbsd-5-0-1-RELEASE, netbsd-5-0, netbsd-5, netbsd-10-base, netbsd-10-0-RELEASE, netbsd-10-0-RC6, netbsd-10-0-RC5, netbsd-10-0-RC4, netbsd-10-0-RC3, netbsd-10-0-RC2, netbsd-10-0-RC1, netbsd-10, matt-premerge-20091211, matt-nb8-mediatek-base, matt-nb8-mediatek, matt-nb6-plus-nbase, matt-nb6-plus-base, matt-nb6-plus, matt-nb5-pq3-base, matt-nb5-pq3, matt-nb5-mips64-u2-k2-k4-k7-k8-k9, matt-nb5-mips64-u1-k1-k5, matt-nb5-mips64-premerge-20101231, matt-nb5-mips64-premerge-20091211, matt-nb5-mips64-k15, matt-nb5-mips64, matt-nb4-mips64-k7-u2a-k9b, matt-mips64-premerge-20101231, matt-mips64-base2, localcount-20160914, jym-xensuspend-nbase, jym-xensuspend-base, jym-xensuspend, is-mlppp-base, is-mlppp, cjep_sun2x-base1, cjep_sun2x-base, cjep_sun2x, cjep_staticlib_x-base1, cjep_staticlib_x-base, cjep_staticlib_x, christos-time_t-nbase, christos-time_t-base, cherry-xenmp-base, cherry-xenmp, bouyer-socketcan-base1, bouyer-socketcan-base, bouyer-socketcan, bouyer-quota2-nbase, bouyer-quota2-base, bouyer-quota2, agc-symver-base, agc-symver, HEAD
Branch point for: christos-time_t
Changes since 1.12: +2 -8 lines

In preparation for providing a db fallback in libnbcompat, remove
sccsid and conditionals around __RCSID. lint understands __RCSID enough
to ignore it, undefining LIBC_SCCS is superseded by MKSTRIPIDENT.
No functional changes.

/*	$NetBSD: hash_func.c,v 1.13 2008/09/10 17:52:35 joerg Exp $	*/

/*-
 * 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. 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.
 */

#if HAVE_NBTOOL_CONFIG_H
#include "nbtool_config.h"
#endif

#include <sys/cdefs.h>
__RCSID("$NetBSD: hash_func.c,v 1.13 2008/09/10 17:52:35 joerg Exp $");

#include <sys/types.h>

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

#if 0
static uint32_t hash1(const void *, size_t) __attribute__((__unused__));
static uint32_t hash2(const void *, size_t) __attribute__((__unused__));
static uint32_t hash3(const void *, size_t) __attribute__((__unused__));
#endif
static uint32_t hash4(const void *, size_t) __attribute__((__unused__));

/* Global default hash function */
uint32_t (*__default_hash)(const void *, size_t) = hash4;
#if 0
/*
 * 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 uint32_t
hash1(const void *keyarg, size_t len)
{
	const uint8_t *key;
	uint32_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 uint32_t
hash2(const void *keyarg, size_t len)
{
	const uint8_t *e, *key;
	uint32_t h;
	uint8_t 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 uint32_t
hash3(const void *keyarg, size_t len)
{
	const uint8_t *key;
	size_t loop;
	uint32_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);
}
#endif

/* Hash function from Chris Torek. */
static uint32_t
hash4(const void *keyarg, size_t len)
{
	const uint8_t *key;
	size_t loop;
	uint32_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);
}