| /* |
| * 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 [rescinded 22 July 1999] |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. |
| */ |
| |
| /* |
| |
| @deftypefn Supplemental void* bsearch (const void *@var{key}, @ |
| const void *@var{base}, size_t @var{nmemb}, size_t @var{size}, @ |
| int (*@var{compar})(const void *, const void *)) |
| |
| Performs a search over an array of @var{nmemb} elements pointed to by |
| @var{base} for a member that matches the object pointed to by @var{key}. |
| The size of each member is specified by @var{size}. The array contents |
| should be sorted in ascending order according to the @var{compar} |
| comparison function. This routine should take two arguments pointing to |
| the @var{key} and to an array member, in that order, and should return an |
| integer less than, equal to, or greater than zero if the @var{key} object |
| is respectively less than, matching, or greater than the array member. |
| |
| @end deftypefn |
| |
| */ |
| |
| #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 (const void *key, const void *base0, |
| size_t nmemb, size_t size, |
| int (*compar)(const void *, const void *)) |
| { |
| const char *base = (const char *) base0; |
| int lim, cmp; |
| const void *p; |
| |
| for (lim = nmemb; lim != 0; lim >>= 1) { |
| p = base + (lim >> 1) * size; |
| cmp = (*compar)(key, p); |
| if (cmp == 0) |
| return (void *)p; |
| if (cmp > 0) { /* key > p: move right */ |
| base = (const char *)p + size; |
| lim--; |
| } /* else move left */ |
| } |
| return (NULL); |
| } |