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Diffstat (limited to 'lib/libc/stdlib/bsearch.c')
| -rw-r--r-- | lib/libc/stdlib/bsearch.c | 96 |
1 files changed, 96 insertions, 0 deletions
diff --git a/lib/libc/stdlib/bsearch.c b/lib/libc/stdlib/bsearch.c new file mode 100644 index 000000000000..4a1dd525a67d --- /dev/null +++ b/lib/libc/stdlib/bsearch.c @@ -0,0 +1,96 @@ +/* + * 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. 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("$FreeBSD$"); + +#include <stddef.h> +#include <stdlib.h> + +#ifdef I_AM_BSEARCH_B +#include "block_abi.h" +#define COMPAR(x,y) CALL_BLOCK(compar, x, y) +#else +#define COMPAR(x,y) compar(x, y) +#endif + +/* + * 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. + */ +#ifdef I_AM_BSEARCH_B +void * +bsearch_b(key, base0, nmemb, size, compar) + const void *key; + const void *base0; + size_t nmemb; + size_t size; + DECLARE_BLOCK(int, compar, const void *, const void *); +#else +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 *); +#endif +{ + 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); +} |