1 /* $OpenBSD: hash_func.c,v 1.11 2016/05/29 20:47:49 guenther Exp $ */ 2 3 /*- 4 * Copyright (c) 1990, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * This code is derived from software contributed to Berkeley by 8 * Margo Seltzer. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. Neither the name of the University nor the names of its contributors 19 * may be used to endorse or promote products derived from this software 20 * without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 */ 34 35 #include <sys/types.h> 36 37 #include <db.h> 38 39 /* Chris Torek's hash function. */ 40 u_int32_t 41 __default_hash(const void *key, size_t len) 42 { 43 u_int32_t h, loop; 44 u_int8_t *k; 45 46 #define HASH4a h = (h << 5) - h + *k++; 47 #define HASH4b h = (h << 5) + h + *k++; 48 #define HASH4 HASH4b 49 50 h = 0; 51 k = (u_int8_t *)key; 52 if (len > 0) { 53 loop = (len + 8 - 1) >> 3; 54 55 switch (len & (8 - 1)) { 56 case 0: 57 do { /* All fall throughs */ 58 HASH4; 59 case 7: 60 HASH4; 61 case 6: 62 HASH4; 63 case 5: 64 HASH4; 65 case 4: 66 HASH4; 67 case 3: 68 HASH4; 69 case 2: 70 HASH4; 71 case 1: 72 HASH4; 73 } while (--loop); 74 } 75 76 } 77 return (h); 78 } 79