1 files changed, 139 insertions, 0 deletions
diff --git a/src/backend/commands/conversioncmds.c b/src/backend/commands/conversioncmds.c
new file mode 100644
index 0000000..5fed97a
--- /dev/null
+++ b/src/backend/commands/conversioncmds.c
@@ -0,0 +1,139 @@
+/*-------------------------------------------------------------------------
+ *
+ * conversioncmds.c
+ *	  conversion creation command support code
+ *
+ * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  src/backend/commands/conversioncmds.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/htup_details.h"
+#include "catalog/dependency.h"
+#include "catalog/indexing.h"
+#include "catalog/pg_conversion.h"
+#include "catalog/pg_type.h"
+#include "commands/alter.h"
+#include "commands/conversioncmds.h"
+#include "mb/pg_wchar.h"
+#include "miscadmin.h"
+#include "parser/parse_func.h"
+#include "utils/acl.h"
+#include "utils/builtins.h"
+#include "utils/lsyscache.h"
+#include "utils/rel.h"
+#include "utils/syscache.h"
+
+/*
+ * CREATE CONVERSION
+ */
+ObjectAddress
+CreateConversionCommand(CreateConversionStmt *stmt)
+{
+	Oid			namespaceId;
+	char	   *conversion_name;
+	AclResult	aclresult;
+	int			from_encoding;
+	int			to_encoding;
+	Oid			funcoid;
+	const char *from_encoding_name = stmt->for_encoding_name;
+	const char *to_encoding_name = stmt->to_encoding_name;
+	List	   *func_name = stmt->func_name;
+	static const Oid funcargs[] = {INT4OID, INT4OID, CSTRINGOID, INTERNALOID, INT4OID, BOOLOID};
+	char		result[1];
+	Datum		funcresult;
+
+	/* Convert list of names to a name and namespace */
+	namespaceId = QualifiedNameGetCreationNamespace(stmt->conversion_name,
+													&conversion_name);
+
+	/* Check we have creation rights in target namespace */
+	aclresult = pg_namespace_aclcheck(namespaceId, GetUserId(), ACL_CREATE);
+	if (aclresult != ACLCHECK_OK)
+		aclcheck_error(aclresult, OBJECT_SCHEMA,
+					   get_namespace_name(namespaceId));
+
+	/* Check the encoding names */
+	from_encoding = pg_char_to_encoding(from_encoding_name);
+	if (from_encoding < 0)
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("source encoding \"%s\" does not exist",
+						from_encoding_name)));
+
+	to_encoding = pg_char_to_encoding(to_encoding_name);
+	if (to_encoding < 0)
+		ereport(ERROR,
+				(errcode(ERRCODE_UNDEFINED_OBJECT),
+				 errmsg("destination encoding \"%s\" does not exist",
+						to_encoding_name)));
+
+	/*
+	 * We consider conversions to or from SQL_ASCII to be meaningless.  (If
+	 * you wish to change this, note that pg_do_encoding_conversion() and its
+	 * sister functions have hard-wired fast paths for any conversion in which
+	 * the source or target encoding is SQL_ASCII, so that an encoding
+	 * conversion function declared for such a case will never be used.)
+	 */
+	if (from_encoding == PG_SQL_ASCII || to_encoding == PG_SQL_ASCII)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("encoding conversion to or from \"SQL_ASCII\" is not supported")));
+
+	/*
+	 * Check the existence of the conversion function. Function name could be
+	 * a qualified name.
+	 */
+	funcoid = LookupFuncName(func_name, sizeof(funcargs) / sizeof(Oid),
+							 funcargs, false);
+
+	/* Check it returns int4, else it's probably the wrong function */
+	if (get_func_rettype(funcoid) != INT4OID)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("encoding conversion function %s must return type %s",
+						NameListToString(func_name), "integer")));
+
+	/* Check we have EXECUTE rights for the function */
+	aclresult = pg_proc_aclcheck(funcoid, GetUserId(), ACL_EXECUTE);
+	if (aclresult != ACLCHECK_OK)
+		aclcheck_error(aclresult, OBJECT_FUNCTION,
+					   NameListToString(func_name));
+
+	/*
+	 * Check that the conversion function is suitable for the requested source
+	 * and target encodings. We do that by calling the function with an empty
+	 * string; the conversion function should throw an error if it can't
+	 * perform the requested conversion.
+	 */
+	funcresult = OidFunctionCall6(funcoid,
+								  Int32GetDatum(from_encoding),
+								  Int32GetDatum(to_encoding),
+								  CStringGetDatum(""),
+								  CStringGetDatum(result),
+								  Int32GetDatum(0),
+								  BoolGetDatum(false));
+
+	/*
+	 * The function should return 0 for empty input. Might as well check that,
+	 * too.
+	 */
+	if (DatumGetInt32(funcresult) != 0)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
+				 errmsg("encoding conversion function %s returned incorrect result for empty input",
+						NameListToString(func_name))));
+
+	/*
+	 * All seem ok, go ahead (possible failure would be a duplicate conversion
+	 * name)
+	 */
+	return ConversionCreate(conversion_name, namespaceId, GetUserId(),
+							from_encoding, to_encoding, funcoid, stmt->def);
+}