180 lines
4.7 KiB
C
180 lines
4.7 KiB
C
/*-
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* Copyright (c) 1990 The Regents of the University of California.
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* All rights reserved.
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*
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* This code is derived from software contributed to Berkeley by
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* Margo Seltzer.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#if defined(LIBC_SCCS) && !defined(lint)
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static char sccsid[] = "@(#)hfunc.c 5.1 (Berkeley) 2/12/91";
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#endif /* LIBC_SCCS and not lint */
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/* Global default hash function */
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static int hash1();
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static int hash2();
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static int hash3();
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static int hash4();
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int (*default_hash)() = hash4;
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/******************************* HASH FUNCTIONS **************************/
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/*
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Assume that we've already split the bucket to which this
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key hashes, calculate that bucket, and check that in fact
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we did already split it.
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This came from ejb's hsearch.
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*/
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# define PRIME1 37
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# define PRIME2 1048583
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static int
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hash1(key,len)
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char *key;
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int len;
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{
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register int h;
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register int l = len;
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register unsigned char *k = (unsigned char *) key;
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h = 0;
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/*
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* Convert string to integer
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*/
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while (l--) h = h * PRIME1 ^ (*k++ - ' ');
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h %= PRIME2;
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return (h);
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}
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/*
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Phong's linear congruential hash
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*/
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#define dcharhash(h, c) ((h) = 0x63c63cd9*(h) + 0x9c39c33d + (c))
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static int
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hash2(str, n)
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register unsigned char *str;
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int n;
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{
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register unsigned char *e, c;
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register int h;
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e = str + n;
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for (h = 0; str != e;) {
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c = *str++;
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if (!c && str > e)
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break;
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dcharhash(h,c);
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}
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return(h);
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}
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/*
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* This is INCREDIBLY ugly, but fast.
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* We break the string up into 8 byte units. On the first time
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* through the loop we get the "leftover bytes" (strlen % 8).
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* On every other iteration, we perform 8 HASHC's so we handle
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* all 8 bytes. Essentially, this saves us 7 cmp & branch
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* instructions. If this routine is heavily used enough, it's
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* worth the ugly coding
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*
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* OZ's original sdbm hash
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*/
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static int
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hash3(key,nbytes)
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char *key;
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int nbytes;
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{
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register int n = 0;
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register char *str = key;
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register int loop;
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register int len = nbytes;
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#define HASHC n = *str++ + 65599 * n
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if (len > 0) {
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loop = (len + 8 - 1) >> 3;
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switch(len & (8 - 1)) {
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case 0: do { /* All fall throughs */
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HASHC;
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case 7: HASHC;
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case 6: HASHC;
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case 5: HASHC;
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case 4: HASHC;
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case 3: HASHC;
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case 2: HASHC;
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case 1: HASHC;
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} while (--loop);
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}
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}
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return(n);
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}
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/* Hash function from Chris Torek */
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static int
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hash4(key,nbytes)
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char *key;
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int nbytes;
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{
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register int h = 0;
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register char *p = key;
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register int loop;
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register int len = nbytes;
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#define HASH4a h = (h << 5) - h + *p++;
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#define HASH4b h = (h << 5) + h + *p++;
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#define HASH4 HASH4b
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if (len > 0) {
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loop = (len + 8 - 1) >> 3;
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switch(len & (8 - 1)) {
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case 0: do { /* All fall throughs */
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HASH4;
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case 7: HASH4;
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case 6: HASH4;
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case 5: HASH4;
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case 4: HASH4;
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case 3: HASH4;
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case 2: HASH4;
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case 1: HASH4;
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} while (--loop);
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}
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}
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return(h);
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}
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