Move bsearch_arg to src/port

tvondra · tvondra · commit bfa2cee78412 · 2021-03-23T00:11:22.000+01:00
Until now the bsearch_arg function was used only in extended statistics
code, so it was defined in that code.  But we already have qsort_arg in
src/port, so let's move it next to it.
diff --git a/src/backend/statistics/extended_stats.c b/src/backend/statistics/extended_stats.c
@@ -659,37 +659,6 @@ compare_datums_simple(Datum a, Datum b, SortSupport ssup)
 	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.
diff --git a/src/include/port.h b/src/include/port.h
@@ -508,6 +508,11 @@ typedef int (*qsort_arg_comparator) (const void *a, const void *b, void *arg);
 extern void qsort_arg(void *base, size_t nel, size_t elsize,
 					  qsort_arg_comparator cmp, void *arg);
 
+extern void *bsearch_arg(const void *key, const void *base,
+						 size_t nmemb, size_t size,
+						 int (*compar) (const void *, const void *, void *),
+						 void *arg);
+
 /* port/chklocale.c */
 extern int	pg_get_encoding_from_locale(const char *ctype, bool write_message);
 
diff --git a/src/include/statistics/extended_stats_internal.h b/src/include/statistics/extended_stats_internal.h
@@ -85,11 +85,6 @@ extern int	multi_sort_compare_dims(int start, int end, const SortItem *a,
 extern int	compare_scalars_simple(const void *a, const void *b, void *arg);
 extern int	compare_datums_simple(Datum a, Datum b, SortSupport ssup);
 
-extern void *bsearch_arg(const void *key, const void *base,
-						 size_t nmemb, size_t size,
-						 int (*compar) (const void *, const void *, void *),
-						 void *arg);
-
 extern AttrNumber *build_attnums_array(Bitmapset *attrs, int *numattrs);
 
 extern SortItem *build_sorted_items(int numrows, int *nitems, HeapTuple *rows,
diff --git a/src/port/Makefile b/src/port/Makefile
@@ -40,6 +40,7 @@ LIBS += $(PTHREAD_LIBS)
 OBJS = \
 	$(LIBOBJS) \
 	$(PG_CRC32C_OBJS) \
+	bsearch_arg.o \
 	chklocale.o \
 	erand48.o \
 	inet_net_ntop.o \
diff --git a/src/port/bsearch_arg.c b/src/port/bsearch_arg.c
@@ -0,0 +1,78 @@
+/*
+ * 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);
+}
diff --git a/src/tools/msvc/Mkvcbuild.pm b/src/tools/msvc/Mkvcbuild.pm
@@ -103,7 +103,7 @@ sub mkvcbuild
 	  dirent.c dlopen.c getopt.c getopt_long.c link.c
 	  pread.c preadv.c pwrite.c pwritev.c pg_bitutils.c
 	  pg_strong_random.c pgcheckdir.c pgmkdirp.c pgsleep.c pgstrcasecmp.c
-	  pqsignal.c mkdtemp.c qsort.c qsort_arg.c quotes.c system.c
+	  pqsignal.c mkdtemp.c qsort.c qsort_arg.c bsearch_arg.c quotes.c system.c
 	  strerror.c tar.c thread.c
 	  win32env.c win32error.c win32security.c win32setlocale.c win32stat.c);
 
