From 5e45211a64149b3c659b90ff2de6fa982a5a93ed Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sat, 4 May 2024 14:17:33 +0200 Subject: Adding upstream version 15.5. Signed-off-by: Daniel Baumann --- src/port/bsearch_arg.c | 78 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 78 insertions(+) create mode 100644 src/port/bsearch_arg.c (limited to 'src/port/bsearch_arg.c') diff --git a/src/port/bsearch_arg.c b/src/port/bsearch_arg.c new file mode 100644 index 0000000..a74c588 --- /dev/null +++ b/src/port/bsearch_arg.c @@ -0,0 +1,78 @@ +/* + * bsearch_arg.c: bsearch variant with a user-supplied pointer + * + * Copyright (c) 2021-2022, PostgreSQL Global Development Group + * 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 [rescinded 22 July 1999] + * 4.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. + * + * src/port/bsearch_arg.c + */ + +#include "c.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 involves 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_arg(const void *key, const void *base0, + size_t nmemb, size_t size, + int (*compar) (const void *, const void *, void *), + void *arg) +{ + const char *base = (const char *) base0; + int lim, + cmp; + const void *p; + + for (lim = nmemb; lim != 0; lim >>= 1) + { + p = base + (lim >> 1) * size; + cmp = (*compar) (key, p, arg); + if (cmp == 0) + return (void *) p; + if (cmp > 0) + { /* key > p: move right */ + base = (const char *) p + size; + lim--; + } /* else move left */ + } + return (NULL); +} -- cgit v1.2.3