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- /*
- * 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 [rescinded 22 July 1999]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_r (const void *@var{key}, @
- const void *@var{base}, size_t @var{nmemb}, size_t @var{size}, @
- int (*@var{compar})(const void *, const void *, void *), void *@var{arg})
- 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 three arguments: the first
- two point to the @var{key} and to an array member, and the last is passed
- down unchanged from @code{bsearch_r}'s last argument. It 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_r (const void *key, const void *base0,
- size_t nmemb, size_t size,
- int (*compar)(const void *, const void *, void *),
- void *arg)
- {
- 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, arg);
- if (cmp == 0)
- return (void *)p;
- if (cmp > 0) { /* key > p: move right */
- base = (const char *)p + size;
- lim--;
- } /* else move left */
- }
- return (NULL);
- }
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