Added wrapper around XML functions to support OPENXML without WITH clause (#622)

To add support for OPENXML without WITH clause in Babelfish, we need following functions xml_parse(...),
pg_xmlCharStrndup(...) and parse_xml_decl(...).

Although these functions are defined as static on engine side. And in order to facilitate support for OPENXML without
WITH clause, This commit added wrapper functions.

Extension PR: babelfish-for-postgresql/babelfish_extensions#4091

Task: BABEL-6046
Signed-off-by: Rohit Bhagat <[email protected]>

Author: rohit01010

src/backend/utils/adt/xml.c

@@ -5114,3 +5114,28 @@ XmlTableDestroyOpaque(TableFuncScanState *state)
 	NO_XML_SUPPORT();
 #endif							/* not USE_LIBXML */
 }
+
+#ifdef USE_LIBXML
+xmlDocPtr
+xml_parse_wrapper(text *data, XmlOptionType xmloption_arg,
+		  bool preserve_whitespace, int encoding,
+		  XmlOptionType *parsed_xmloptiontype, xmlNodePtr *parsed_nodes,
+		  Node *escontext)
+{
+	return xml_parse(data, xmloption_arg, preserve_whitespace,
+					encoding, parsed_xmloptiontype, parsed_nodes, escontext);
+}
+
+xmlChar *
+pg_xmlCharStrndup_wrapper(const char *str, size_t len)
+{
+	return pg_xmlCharStrndup(str, len);
+}
+
+int
+parse_xml_decl_wrapper(const xmlChar *str, size_t *lenp,
+						   xmlChar **version, xmlChar **encoding, int *standalone)
+{
+	return parse_xml_decl(str, lenp, version, encoding, standalone);
+}
+#endif							/* USE_LIBXML */

src/include/utils/xml.h

@@ -19,6 +19,9 @@
 #include "fmgr.h"
 #include "nodes/execnodes.h"
 #include "nodes/primnodes.h"
+#ifdef USE_LIBXML
+#include <libxml/tree.h>
+#endif
 
 typedef struct varlena xmltype;
 
@@ -85,6 +88,16 @@ extern char *map_sql_identifier_to_xml_name(const char *ident, bool fully_escape
 extern char *map_xml_name_to_sql_identifier(const char *name);
 extern char *map_sql_value_to_xml_value(Datum value, Oid type, bool xml_escape_strings);
 
+#ifdef USE_LIBXML
+extern xmlDocPtr xml_parse_wrapper(text *data, XmlOptionType xmloption_arg,
+							bool preserve_whitespace, int encoding,
+							XmlOptionType *parsed_xmloptiontype, xmlNodePtr *parsed_nodes,
+							Node *escontext);
+extern xmlChar *pg_xmlCharStrndup_wrapper(const char *str, size_t len);
+extern int parse_xml_decl_wrapper(const xmlChar *str, size_t *lenp,
+						   xmlChar **version, xmlChar **encoding, int *standalone);
+#endif							/* USE_LIBXML */
+
 extern PGDLLIMPORT int xmlbinary;	/* XmlBinaryType, but int for guc enum */
 
 extern PGDLLIMPORT int xmloption;	/* XmlOptionType, but int for guc enum */