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/*
 *	BSEARCH - binary search
 *
 *	Copyright (C) 1987 by Ian Macky, SRI International
 */

#include "stdio.h"

char *bsearch(key, base, count, size, compar)
char *key, *base;
unsigned count;
int size;
int (*compar)();
{
    int result, first, last, middle;
    char *current;

    if (size < 1 || count < 1) return NULL;	/* minor arg checking */
    first = 0;					/* initial range is whole */
    last = --count;				/* array, first & last */
    for (;;) {
	middle = first + ((last - first) / 2);	/* compute center of range */
	current = base + (middle * size);	/* turn into ptr to member */
	result = (*compar)(key, current);	/* do the user comparison */
	if (!result) return current;		/* got a match! */
	if (first >= last) return NULL;		/* narrowed to nothing */
	if (result < 0) last = --middle;	/* key is before midpoint */
	else first = ++middle;			/* else key after midpoint */
    }
}