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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 [rescinded 22 July 1999]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 (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 "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 (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);
+}