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    /*	$OpenBSD: bsearch.c,v 1.8 2016/10/22 19:19:34 tb Exp $ */  | 
    
    
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    /*  | 
    
    
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     * Copyright (c) 1990 Regents of the University of California.  | 
    
    
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     * All rights reserved.  | 
    
    
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     *  | 
    
    
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     * Redistribution and use in source and binary forms, with or without  | 
    
    
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     * modification, are permitted provided that the following conditions  | 
    
    
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     * are met:  | 
    
    
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     * 1. Redistributions of source code must retain the above copyright  | 
    
    
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     *    notice, this list of conditions and the following disclaimer.  | 
    
    
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     * 2. Redistributions in binary form must reproduce the above copyright  | 
    
    
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     *    notice, this list of conditions and the following disclaimer in the  | 
    
    
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     *    documentation and/or other materials provided with the distribution.  | 
    
    
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     * 3. Neither the name of the University nor the names of its contributors  | 
    
    
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     *    may be used to endorse or promote products derived from this software  | 
    
    
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     *    without specific prior written permission.  | 
    
    
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     *  | 
    
    
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     * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND  | 
    
    
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     * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE  | 
    
    
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     * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE  | 
    
    
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     * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE  | 
    
    
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     * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL  | 
    
    
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     * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS  | 
    
    
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     * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)  | 
    
    
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     * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT  | 
    
    
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     * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY  | 
    
    
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     * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF  | 
    
    
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     * SUCH DAMAGE.  | 
    
    
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     */  | 
    
    
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    #include <stdlib.h>  | 
    
    
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    /*  | 
    
    
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     * Perform a binary search.  | 
    
    
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     *  | 
    
    
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     * The code below is a bit sneaky.  After a comparison fails, we  | 
    
    
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     * divide the work in half by moving either left or right. If lim  | 
    
    
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     * is odd, moving left simply involves halving lim: e.g., when lim  | 
    
    
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     * is 5 we look at item 2, so we change lim to 2 so that we will  | 
    
    
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     * look at items 0 & 1.  If lim is even, the same applies.  If lim  | 
    
    
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     * is odd, moving right again involves halving lim, this time moving  | 
    
    
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     * the base up one item past p: e.g., when lim is 5 we change base  | 
    
    
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     * to item 3 and make lim 2 so that we will look at items 3 and 4.  | 
    
    
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     * If lim is even, however, we have to shrink it by one before  | 
    
    
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     * halving: e.g., when lim is 4, we still looked at item 2, so we  | 
    
    
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     * have to make lim 3, then halve, obtaining 1, so that we will only  | 
    
    
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     * look at item 3.  | 
    
    
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     */  | 
    
    
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    void *  | 
    
    
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    bsearch(const void *key, const void *base0, size_t nmemb, size_t size,  | 
    
    
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        int (*compar)(const void *, const void *))  | 
    
    
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    { | 
    
    
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    	const char *base = base0;  | 
    
    
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    	int lim, cmp;  | 
    
    
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    	const void *p;  | 
    
    
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    ✓✓ | 
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    	for (lim = nmemb; lim != 0; lim >>= 1) { | 
    
    
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    		p = base + (lim >> 1) * size;  | 
    
    
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    		cmp = (*compar)(key, p);  | 
    
    
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    ✓✓ | 
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    		if (cmp == 0)  | 
    
    
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    			return ((void *)p);  | 
    
    
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    ✓✓ | 
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    		if (cmp > 0) {	/* key > p: move right */ | 
    
    
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    			base = (char *)p + size;  | 
    
    
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    			lim--;  | 
    
    
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    		} /* else move left */  | 
    
    
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    	}  | 
    
    
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    	return (NULL);  | 
    
    
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    }  |