Using predefined stream classes

The DataBlade API provides several predefined stream classes that you can access with the stream I/O interface.

To use a predefined stream class in your UDR:

Open a stream with the appropriate type-specific stream-open function.
The following table shows the predefined stream classes that the DataBlade API provides and their associated stream-open functions.
Predefined stream class Stream-open function

File stream mi_stream_open_fio()

String stream mi_stream_open_str()

Varying-length-data stream mi_stream_open_mi_lvarchar()

The mistrmtype.h header file declares these predefined stream-open functions.
Access the open stream with the appropriate stream I/O function.
Table 1 lists the stream I/O functions that the DataBlade API provides.

Predefined stream class	Stream-open function
File stream	mi_stream_open_fio()
String stream	mi_stream_open_str()
Varying-length-data stream	mi_stream_open_mi_lvarchar()

For example, the following code fragment reads 26 bytes of data from a string stream into a user-defined buffer named buf:

#define STRING_SIZE = 80

MI_STREAM *strm_desc;
mi_integer nbytes;
char buf[200];
char string_txt[STRING_SIZE] = 
   "A stream is a generic term for some object that can be\
 written to or read from."

strm_desc = mi_stream_open_str(NULL, string_txt, STRING_SIZE);
   if ( (nbytes = mi_stream_read(strm_desc, buf, 26)) != 26 )
      /* error in read */
mi_stream_close(strm_desc);

After this code fragment completes, the buf user-defined buffer contains the following character string:

A stream is a generic term

The following sections provide additional details on each of the predefined DataBlade API stream classes.