		/*
     * 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 [rescinded 22 July 1999]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 <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 (register const void *key, const void *base0,
             size_t nmemb, register size_t size,
             register int (*compar)(const void *, const void *))
    {
            register const char *base = (const char *) base0;
            register int lim, cmp;
            register 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);
    }
	