1/* Licensed to the Apache Software Foundation (ASF) under one or more 2 * contributor license agreements. See the NOTICE file distributed with 3 * this work for additional information regarding copyright ownership. 4 * The ASF licenses this file to You under the Apache License, Version 2.0 5 * (the "License"); you may not use this file except in compliance with 6 * the License. You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17/* 18 * sdbm - ndbm work-alike hashed database library 19 * based on Per-Aake Larson's Dynamic Hashing algorithms. BIT 18 (1978). 20 * author: oz@nexus.yorku.ca 21 * status: ex-public domain. keep it that way. 22 * 23 * hashing routine 24 */ 25 26#include "apr_sdbm.h" 27#include "sdbm_private.h" 28 29/* 30 * polynomial conversion ignoring overflows 31 * [this seems to work remarkably well, in fact better 32 * then the ndbm hash function. Replace at your own risk] 33 * use: 65599 nice. 34 * 65587 even better. 35 */ 36long sdbm_hash(const char *str, int len) 37{ 38 register unsigned long n = 0; 39 40#define DUFF /* go ahead and use the loop-unrolled version */ 41#ifdef DUFF 42 43#define HASHC n = *str++ + 65599 * n 44 45 if (len > 0) { 46 register int loop = (len + 8 - 1) >> 3; 47 48 switch(len & (8 - 1)) { 49 case 0: do { 50 HASHC; case 7: HASHC; 51 case 6: HASHC; case 5: HASHC; 52 case 4: HASHC; case 3: HASHC; 53 case 2: HASHC; case 1: HASHC; 54 } while (--loop); 55 } 56 57 } 58#else 59 while (len--) 60 n = *str++ + 65599 * n; 61#endif 62 return n; 63} 64