return ApplySortComparator(a, false, b, false, ssup);
}
-/* simple counterpart to qsort_arg */
-void *
-bsearch_arg(const void *key, const void *base, size_t nmemb, size_t size,
- int (*compar) (const void *, const void *, void *),
- void *arg)
-{
- size_t l,
- u,
- idx;
- const void *p;
- int comparison;
-
- l = 0;
- u = nmemb;
- while (l < u)
- {
- idx = (l + u) / 2;
- p = (void *) (((const char *) base) + (idx * size));
- comparison = (*compar) (key, p, arg);
-
- if (comparison < 0)
- u = idx;
- else if (comparison > 0)
- l = idx + 1;
- else
- return (void *) p;
- }
-
- return NULL;
-}
-
/*
* build_attnums_array
* Transforms a bitmap into an array of AttrNumber values.
--- /dev/null
+/*
+ * bsearch_arg.c: bsearch variant with a user-supplied pointer
+ *
+ * Copyright (c) 2021, 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 [rescinded 22 July 1999]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 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_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);
+}
projects / users / gsingh / postgres.git / commitdiff