| /* |
| * Copyright (c) 1990 Regents of the University of California. |
| * All rights reserved. |
| * |
| * 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. [rescinded 22 July 1999] |
| * 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. |
| */ |
| |
| #include "config.h" |
| #include "ansidecl.h" |
| #include <sys/types.h> /* size_t */ |
| #include <stdio.h> |
| |
| /* |
| * Perform a binary search. |
| * |
| * The code below is a bit sneaky. After a comparison fails, we |
| * divide the work in half by moving either left or right. If lim |
| * is odd, moving left simply involves halving lim: e.g., when lim |
| * is 5 we look at item 2, so we change lim to 2 so that we will |
| * look at items 0 & 1. If lim is even, the same applies. If lim |
| * is odd, moving right again involes halving lim, this time moving |
| * the base up one item past p: e.g., when lim is 5 we change base |
| * to item 3 and make lim 2 so that we will look at items 3 and 4. |
| * If lim is even, however, we have to shrink it by one before |
| * halving: e.g., when lim is 4, we still looked at item 2, so we |
| * have to make lim 3, then halve, obtaining 1, so that we will only |
| * look at item 3. |
| */ |
| void * |
| bsearch(key, base0, nmemb, size, compar) |
| register void *key; |
| void *base0; |
| size_t nmemb; |
| register size_t size; |
| register int (*compar)(); |
| { |
| register char *base = base0; |
| register int lim, cmp; |
| register void *p; |
| |
| for (lim = nmemb; lim != 0; lim >>= 1) { |
| p = base + (lim >> 1) * size; |
| cmp = (*compar)(key, p); |
| if (cmp == 0) |
| return (p); |
| if (cmp > 0) { /* key > p: move right */ |
| base = (char *)p + size; |
| lim--; |
| } /* else move left */ |
| } |
| return (NULL); |
| } |