+/*
+ * Copyright (c) 1990, 1993
+ * The 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. All advertising materials mentioning features or use of this software
+ * must display the following acknowledgement:
+ * This product includes software developed by the University of
+ * California, Berkeley and its contributors.
+ * 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.
+ */
+
+#if defined(LIBC_SCCS) && !defined(lint)
+static char sccsid[] = "@(#)bsearch.c 8.1 (Berkeley) 6/4/93";
+#endif /* LIBC_SCCS and not lint */
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD: src/lib/libc/stdlib/bsearch.c,v 1.3 2002/03/21 22:48:41 obrien Exp $");
+
+#include <stddef.h>
+#include <stdlib.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(key, base0, nmemb, size, compar)
+ const void *key;
+ const void *base0;
+ size_t nmemb;
+ size_t size;
+ int (*compar)(const void *, const void *);
+{
+ const char *base = base0;
+ size_t lim;
+ int cmp;
+ 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 = (char *)p + size;
+ lim--;
+ } /* else move left */
+ }
+ return (NULL);
+}
+
+#ifdef __BLOCKS__
+void *
+bsearch_b(key, base0, nmemb, size, compar)
+ const void *key;
+ const void *base0;
+ size_t nmemb;
+ size_t size;
+ int (^compar)(const void *, const void *);
+{
+ const char *base = base0;
+ size_t lim;
+ int cmp;
+ 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 = (char *)p + size;
+ lim--;
+ } /* else move left */
+ }
+ return (NULL);
+}
+#endif /* __BLOCKS__ */
projects / apple / libc.git / blobdiff