summaryrefslogtreecommitdiff
path: root/db/hash/hash_func.c
diff options
context:
space:
mode:
authorRoland McGrath <roland@gnu.org>1996-01-02 08:57:42 +0000
committerRoland McGrath <roland@gnu.org>1996-01-02 08:57:42 +0000
commit71733723fb421bd54467d1a27096463ed1dcc2ed (patch)
treef304556d491722c797d876911834dc4afbfa2740 /db/hash/hash_func.c
parentfc4026d8e43407ba2739e493878d1ce259500059 (diff)
downloadglibc-cvs/libc-960102.tar.gz
* hurd/hurd/signal.h (struct hurd_sigstate): New member `preempters'.cvs/libc-960102
(hurd_preempt_signals, hurd_unpreempt_signals): Decls removed. * hurd/hurd/sigpreempt.h: New file. * hurd/preempt-sig.c: Rewritten with new interface. * sysdeps/mach/hurd/jmp-unwind.c (_longjmp_unwind): Remove local signal preempters being unwound past. * db: New directory, 4.4 BSD db package incorporated from BSD db-1.85 release. * sysdeps/unix/sysv/linux/sys/param.h: Several new macros for BSD compatibility.
Diffstat (limited to 'db/hash/hash_func.c')
-rw-r--r--db/hash/hash_func.c212
1 files changed, 212 insertions, 0 deletions
diff --git a/db/hash/hash_func.c b/db/hash/hash_func.c
new file mode 100644
index 0000000000..a5ec434ee9
--- /dev/null
+++ b/db/hash/hash_func.c
@@ -0,0 +1,212 @@
+/*-
+ * 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.
+ */
+
+#if defined(LIBC_SCCS) && !defined(lint)
+static char sccsid[] = "@(#)hash_func.c 8.2 (Berkeley) 2/21/94";
+#endif /* LIBC_SCCS and not lint */
+
+#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);
+}