Revert "Change mbbisearch to return the character range"

This reverts commit 78ab944.

After I had committed eb0d0d2 and 78ab944, I decided to add
a sanity check for a "can't happen" scenario just to be cautious.
It turned out that it already happened in the official Unicode source
data, namely that a character can be both wide and a combining
character. This fact renders the aforementioned commits unnecessary,
so revert both of them.

Discussion:
https://www.postgresql.org/message-id/CAFBsxsH5ejH4-1xaTLpSK8vWoK1m6fA1JBtTM6jmBsLfmDki1g%40mail.gmail.com

Author: j-naylor

src/common/unicode/generate-unicode_width_table.pl

@@ -17,7 +17,7 @@
 print
   "/* generated by src/common/unicode/generate-unicode_width_table.pl, do not edit */\n\n";
 
-print "static const struct mbinterval wcwidth[] = {\n";
+print "static const struct mbinterval combining[] = {\n";
 
 foreach my $line (<ARGV>)
 {
@@ -40,7 +40,7 @@
 		# not a combining character, print out previous range if any
 		if (defined($range_start))
 		{
-			printf "\t{0x%04X, 0x%04X, 0},\n", $range_start, $prev_codepoint;
+			printf "\t{0x%04X, 0x%04X},\n", $range_start, $prev_codepoint;
 			$range_start = undef;
 		}
 	}

src/common/wchar.c

@@ -585,18 +585,17 @@ struct mbinterval
 {
 	unsigned short first;
 	unsigned short last;
-	signed int	width;
 };
 
 /* auxiliary function for binary search in interval table */
-static const struct mbinterval *
+static int
 mbbisearch(pg_wchar ucs, const struct mbinterval *table, int max)
 {
 	int			min = 0;
 	int			mid;
 
 	if (ucs < table[0].first || ucs > table[max].last)
-		return NULL;
+		return 0;
 	while (max >= min)
 	{
 		mid = (min + max) / 2;
@@ -605,10 +604,10 @@ mbbisearch(pg_wchar ucs, const struct mbinterval *table, int max)
 		else if (ucs < table[mid].first)
 			max = mid - 1;
 		else
-			return &table[mid];
+			return 1;
 	}
 
-	return NULL;
+	return 0;
 }
 
 
@@ -647,21 +646,17 @@ ucs_wcwidth(pg_wchar ucs)
 {
 #include "common/unicode_width_table.h"
 
-	const struct mbinterval *range;
-
 	/* test for 8-bit control characters */
 	if (ucs == 0)
 		return 0;
 
 	if (ucs < 0x20 || (ucs >= 0x7f && ucs < 0xa0) || ucs > 0x0010ffff)
 		return -1;
 
-	/* binary search in table of character widths */
-	range = mbbisearch(ucs, wcwidth,
-					   sizeof(wcwidth) / sizeof(struct mbinterval) - 1);
-
-	if (range != NULL)
-		return range->width;
+	/* binary search in table of non-spacing characters */
+	if (mbbisearch(ucs, combining,
+				   sizeof(combining) / sizeof(struct mbinterval) - 1))
+		return 0;
 
 	/*
 	 * if we arrive here, ucs is not a combining or C0/C1 control character