1/* 2 * Copyright (c) 1990 Regents of the University of California. 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. [rescinded 22 July 1999] 14 * 4. Neither the name of the University nor the names of its contributors 15 * may be used to endorse or promote products derived from this software 16 * without specific prior written permission. 17 * 18 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28 * SUCH DAMAGE. 29 */ 30 31/* 32 33@deftypefn Supplemental void* bsearch_r (const void *@var{key}, @ 34 const void *@var{base}, size_t @var{nmemb}, size_t @var{size}, @ 35 int (*@var{compar})(const void *, const void *, void *), void *@var{arg}) 36 37Performs a search over an array of @var{nmemb} elements pointed to by 38@var{base} for a member that matches the object pointed to by @var{key}. 39The size of each member is specified by @var{size}. The array contents 40should be sorted in ascending order according to the @var{compar} 41comparison function. This routine should take three arguments: the first 42two point to the @var{key} and to an array member, and the last is passed 43down unchanged from @code{bsearch_r}'s last argument. It should return an 44integer less than, equal to, or greater than zero if the @var{key} object 45is respectively less than, matching, or greater than the array member. 46 47@end deftypefn 48 49*/ 50 51#include "config.h" 52#include "ansidecl.h" 53#include <sys/types.h> /* size_t */ 54#include <stdio.h> 55 56/* 57 * Perform a binary search. 58 * 59 * The code below is a bit sneaky. After a comparison fails, we 60 * divide the work in half by moving either left or right. If lim 61 * is odd, moving left simply involves halving lim: e.g., when lim 62 * is 5 we look at item 2, so we change lim to 2 so that we will 63 * look at items 0 & 1. If lim is even, the same applies. If lim 64 * is odd, moving right again involes halving lim, this time moving 65 * the base up one item past p: e.g., when lim is 5 we change base 66 * to item 3 and make lim 2 so that we will look at items 3 and 4. 67 * If lim is even, however, we have to shrink it by one before 68 * halving: e.g., when lim is 4, we still looked at item 2, so we 69 * have to make lim 3, then halve, obtaining 1, so that we will only 70 * look at item 3. 71 */ 72void * 73bsearch_r (const void *key, const void *base0, 74 size_t nmemb, size_t size, 75 int (*compar)(const void *, const void *, void *), 76 void *arg) 77{ 78 const char *base = (const char *) base0; 79 int lim, cmp; 80 const void *p; 81 82 for (lim = nmemb; lim != 0; lim >>= 1) { 83 p = base + (lim >> 1) * size; 84 cmp = (*compar)(key, p, arg); 85 if (cmp == 0) 86 return (void *)p; 87 if (cmp > 0) { /* key > p: move right */ 88 base = (const char *)p + size; 89 lim--; 90 } /* else move left */ 91 } 92 return (NULL); 93} 94