Expose quote_literal_cstr() from core.

This eliminates the need for inefficient implementions of this
functionality in both contrib/dblink and contrib/tablefunc, so remove
them.  The upcoming patch implementing an in-core format() function
will also require this functionality.

In passing, add some regression tests.

4 files changed, 75 insertions, 22 deletions

diff --git a/src/backend/utils/adt/quote.c b/src/backend/utils/adt/quote.c
index 70e98cad84b..af07443f7df 100644
--- a/src/backend/utils/adt/quote.c
+++ b/src/backend/utils/adt/quote.c
@@ -33,8 +33,8 @@ quote_ident(PG_FUNCTION_ARGS)
 }
 
 /*
- * quote_literal -
- *	  returns a properly quoted literal
+ * quote_literal_internal -
+ *	  helper function for quote_literal and quote_literal_cstr
  *
  * NOTE: think not to make this function's behavior change with
  * standard_conforming_strings.  We don't know where the result
@@ -42,6 +42,37 @@ quote_ident(PG_FUNCTION_ARGS)
  * will work with either setting.  Take a look at what dblink
  * uses this for before thinking you know better.
  */
+static size_t
+quote_literal_internal(char *dst, char *src, size_t len)
+{
+	char	   *s;
+	char	   *savedst = dst;
+
+	for (s = src; s < src + len; s++)
+	{
+		if (*s == '\\')
+		{
+			*dst++ = ESCAPE_STRING_SYNTAX;
+			break;
+		}
+	}
+
+	*dst++ = '\'';
+	while (len-- > 0)
+	{
+		if (SQL_STR_DOUBLE(*src, true))
+			*dst++ = *src;
+		*dst++ = *src++;
+	}
+	*dst++ = '\'';
+
+	return dst - savedst;
+}
+
+/*
+ * quote_literal -
+ *	  returns a properly quoted literal
+ */
 Datum
 quote_literal(PG_FUNCTION_ARGS)
 {
@@ -58,30 +89,30 @@ quote_literal(PG_FUNCTION_ARGS)
 	cp1 = VARDATA(t);
 	cp2 = VARDATA(result);
 
-	for (; len-- > 0; cp1++)
-	{
-		if (*cp1 == '\\')
-		{
-			*cp2++ = ESCAPE_STRING_SYNTAX;
-			break;
-		}
-	}
+	SET_VARSIZE(result, VARHDRSZ + quote_literal_internal(cp2, cp1, len));
 
-	len = VARSIZE(t) - VARHDRSZ;
-	cp1 = VARDATA(t);
+	PG_RETURN_TEXT_P(result);
+}
 
-	*cp2++ = '\'';
-	while (len-- > 0)
-	{
-		if (SQL_STR_DOUBLE(*cp1, true))
-			*cp2++ = *cp1;
-		*cp2++ = *cp1++;
-	}
-	*cp2++ = '\'';
+/*
+ * quote_literal_cstr -
+ *	  returns a properly quoted literal
+ */
+char *
+quote_literal_cstr(char *rawstr)
+{
+	char	   *result;
+	int			len;
+	int			newlen;
 
-	SET_VARSIZE(result, cp2 - ((char *) result));
+	len = strlen(rawstr);
+	/* We make a worst-case result area; wasting a little space is OK */
+	result = palloc(len * 2 + 3);
 
-	PG_RETURN_TEXT_P(result);
+	newlen = quote_literal_internal(result, rawstr, len);
+	result[newlen] = '\0';
+
+	return result;
 }
 
 /*
diff --git a/src/include/utils/builtins.h b/src/include/utils/builtins.h
index 7b1bb235383..ae267ab17ad 100644
--- a/src/include/utils/builtins.h
+++ b/src/include/utils/builtins.h
@@ -977,6 +977,7 @@ extern int32 type_maximum_size(Oid type_oid, int32 typemod);
 /* quote.c */
 extern Datum quote_ident(PG_FUNCTION_ARGS);
 extern Datum quote_literal(PG_FUNCTION_ARGS);
+extern char *quote_literal_cstr(char *rawstr);
 extern Datum quote_nullable(PG_FUNCTION_ARGS);
 
 /* guc.c */
diff --git a/src/test/regress/expected/text.out b/src/test/regress/expected/text.out
index 84f4a5cda8b..0b0014a6e25 100644
--- a/src/test/regress/expected/text.out
+++ b/src/test/regress/expected/text.out
@@ -118,3 +118,21 @@ select i, left('ahoj', i), right('ahoj', i) from generate_series(-5, 5) t(i) ord
   5 | ahoj | ahoj
 (11 rows)
 
+select quote_literal('');
+ quote_literal 
+---------------
+ ''
+(1 row)
+
+select quote_literal('abc''');
+ quote_literal 
+---------------
+ 'abc'''
+(1 row)
+
+select quote_literal(e'\\');
+ quote_literal 
+---------------
+ E'\\'
+(1 row)
+
diff --git a/src/test/regress/sql/text.sql b/src/test/regress/sql/text.sql
index a8768ee81aa..50c3033d9eb 100644
--- a/src/test/regress/sql/text.sql
+++ b/src/test/regress/sql/text.sql
@@ -41,3 +41,6 @@ select concat_ws('',10,20,null,30);
 select concat_ws(NULL,10,20,null,30) is null;
 select reverse('abcde');
 select i, left('ahoj', i), right('ahoj', i) from generate_series(-5, 5) t(i) order by i;
+select quote_literal('');
+select quote_literal('abc''');
+select quote_literal(e'\\');