Informix DataBlade API Programmer's Manual DataBlade API Function Descriptions

The mi_cast_get() function looks up a registered function by the type identifiers of its source and target data types and returns its function descriptor.

MI_FUNC_DESC *mi_cast_get(conn, source_type, target_type, cast_status)

MI_CONNECTION *conn;

MI_TYPEID *source_type;

MI_TYPEID *target_type;

mi_char *cast_status;

conn	is a pointer to the connection descriptor that a previous call to mi_open(), mi_server_connect(), or mi_server_reconnect() established.
source_type	is a pointer to the type identifier of the source data type of the cast.
target_type	is a pointer to the type identifier of the target data type of the cast.
cast_status	is a pointer to the status flag that mi_cast_get() sets to indicate the kind of cast function that it locates or the cause of an error.

Valid in Client LIBMI Application?	Valid in User-Defined Routine?
Yes	Yes

The mi_cast_get() function whose source and target data types the source_type and target_type arguments references. It accepts source and target data types as pointers to type identifiers. This function is one of the functions of the Fastpath interface. It is a constructor function for the function descriptor.

The mi_cast_get() function performs the following tasks:

1. Looks in the syscasts system catalog table for the cast function that casts from the source_type data type to the target_type data type.
2. Allocates a function descriptor for the cast function and saves the routine sequence in this descriptor.
3. Allocates an MI_FPARAM structure for the cast function and saves the argument and return-value information in this structure.
4. Sets the cast_status output parameter to provide status information about the cast function.
5. Returns a pointer to the function descriptor that it allocates for the cast function.

The mi_cast_get() function allocates a new function descriptor in the PER_COMMAND memory duration.

The cast_status flag can have one of the following constant values.

The following call to mi_cast_get() looks for a cast function that converts from an INTEGER to an opaque data type called percent:

MI_TYPEID *src_type, *trgt_type;
mi_char cast_stat;
MI_FUNC_DESC *func_desc;
MI_CONNECTION *conn;
...
src_type = mi_typestring_to_id(conn, "INTEGER");
trgt_type = mi_typestring_to_id(conn, "percent");
func_desc = mi_cast_get(conn, &src_type, &trgt_type,

	&cast_stat);
if ( func_desc == NULL )
	{
	switch ( cast_stat )
		{
		case MI_NO_CAST:
			mi_db_error_raise(NULL, MI_EXCEPTION, 
				"No cast function found");
			break;
		case MI_ERROR_CAST:
			mi_db_error_raise(NULL, MI_EXCEPTION, 
				"Error in mi_cast_get() function");
			break;
		case MI_NOP_CAST:

			mi_db_error_raise(NULL, MI_EXCEPTION, 
				"No cast function needed");
			break;
		...

See the descriptions of the following functions: mi_fparam_get(), mi_routine_get(), mi_routine_exec(), mi_routine_end(), and mi_td_cast_get().

For more information on the use of the Fastpath interface, see Calling UDRs with the Fastpath Interface.