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Diffstat (limited to 'lib/libc/db/hash/hash_func.c')
| -rw-r--r-- | lib/libc/db/hash/hash_func.c | 191 |
1 files changed, 191 insertions, 0 deletions
diff --git a/lib/libc/db/hash/hash_func.c b/lib/libc/db/hash/hash_func.c new file mode 100644 index 000000000000..e4e8fcbe0fdc --- /dev/null +++ b/lib/libc/db/hash/hash_func.c @@ -0,0 +1,191 @@ +/*- + * 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 8.1 (Berkeley) 6/4/93"; +#endif /* LIBC_SCCS and not lint */ + +#include <sys/types.h> + +#include <db.h> +#include "hash.h" +#include "page.h" +#include "extern.h" + +static int hash1 __P((u_char *, int)); +static int hash2 __P((u_char *, int)); +static int hash3 __P((u_char *, int)); +static int hash4 __P((u_char *, int)); + +/* Global default hash function */ +int (*__default_hash) __P((u_char *, int)) = 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 int +hash1(key, len) + register u_char *key; + register int len; +{ + register int h; + + h = 0; + /* Convert string to integer */ + while (len--) + h = h * PRIME1 ^ (*key++ - ' '); + h %= PRIME2; + return (h); +} + +/* + * Phong's linear congruential hash + */ +#define dcharhash(h, c) ((h) = 0x63c63cd9*(h) + 0x9c39c33d + (c)) + +static int +hash2(key, len) + register u_char *key; + int len; +{ + register u_char *e, c; + register int h; + + 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 int +hash3(key, len) + register u_char *key; + register int len; +{ + register int n, loop; + +#define HASHC n = *key++ + 65599 * n + + n = 0; + if (len > 0) { + loop = (len + 8 - 1) >> 3; + + switch (len & (8 - 1)) { + case 0: + do { /* All fall throughs */ + HASHC; + case 7: + HASHC; + case 6: + HASHC; + case 5: + HASHC; + case 4: + HASHC; + case 3: + HASHC; + case 2: + HASHC; + case 1: + HASHC; + } while (--loop); + } + + } + return (n); +} + +/* Hash function from Chris Torek. */ +static int +hash4(key, len) + register u_char *key; + register int len; +{ + register int h, loop; + +#define HASH4a h = (h << 5) - h + *key++; +#define HASH4b h = (h << 5) + h + *key++; +#define HASH4 HASH4b + + h = 0; + if (len > 0) { + loop = (len + 8 - 1) >> 3; + + switch (len & (8 - 1)) { + case 0: + do { /* All fall throughs */ + HASH4; + case 7: + HASH4; + case 6: + HASH4; + case 5: + HASH4; + case 4: + HASH4; + case 3: + HASH4; + case 2: + HASH4; + case 1: + HASH4; + } while (--loop); + } + + } + return (h); +} |