cc65/libsrc/common/bsearch.c

/*
 * bsearch.c
 *
 * Ullrich von Bassewitz, 17.06.1998
 */



#include <stdlib.h>



void* bsearch (const void* key, const void* base, size_t n, size_t size, 
	       int (*cmp) (const void*, const void*))
{
    int current;
    int result;
    int found = 0;
    int first = 0;
    int last = n - 1;

    /* Binary search */
    while (first <= last) {

	/* Set current to mid of range */
	current = (last + first) / 2;

	/* Do a compare */
       	result = cmp ((void*) (((int) base) + current*size), key);
        if (result < 0) {
	    first = current + 1;
	} else {
	    last = current - 1;
 	    if (result == 0) {
	 	/* Found one entry that matches the search key. However there may be
	 	 * more than one entry with the same key value and ANSI guarantees
	 	 * that we return the first of a row of items with the same key.
	 	 */
	 	found = 1;
	    }
	}
    }

    /* Did we find the entry? */
    return (void*) (found? ((int) base) + first*size : 0);
}