readFromSource( )

Format

readFromSource(

ctx IN OUT RAW,

startPos IN INTEGER,

numBytes IN OUT INTEGER,

buffer OUT RAW);

Description

Lets you read a buffer of n bytes from a source beginning at a start position.

Parameters

ctx

The source plug-in context information. This should be allocated and initialized to NULL. If you are using a user-defined source plug-in, you should call the openSource( ) method. See the introduction to this chapter for more information.

startPos

The start position in the data source.

numBytes

The number of bytes to be read from the data source.

buffer

The buffer into which the data will be read.

Usage Notes

This method is not supported for HTTP sources.

To successfully read HTTP source types, you must request that the entire URL source be read. If you want to implement a read method for an HTTP source type, you must provide your own implementation for this method in the modified source plug-in for the HTTP source type.

Pragmas

None.

Exceptions

ORDSourceExceptions.INCOMPLETE_SOURCE_INFORMATION

This exception is raised if you call the readFromSource( ) method and the value of the source.srcType attribute is NULL.

ORDSourceExceptions.NULL_SOURCE

This exception is raised if you call the readFromSource( ) method and the value of source.local is 1 or NULL (TRUE), but the value of the source.localData attribute is NULL.

ORDSourceExceptions.METHOD_NOT_SUPPORTED

This exception is raised if you call the readFromSource( ) method and this method is not supported by the source plug-in being used.

ORDSourceExceptions.SOURCE_PLUGIN_EXCEPTION

This exception is raised if you call the readFromSource( ) method and the source plug-in raises an exception.

See Appendix F for more information about these exceptions.

Examples

Read a buffer from the source:

DECLARE
 obj ORDSYS.ORDAudio;
 buffer RAW(4000);
 i INTEGER;
 ctx RAW(64) :=NULL;
BEGIN
 i := 20;
 SELECT p.product_audio into obj from pm.online_media p 
  WHERE p.product_id = 1733;
 obj.readFromSource(ctx,1,i,buffer);
 DBMS_OUTPUT.PUT_LINE('Length is ' || TO_CHAR(obj.getContentLength(ctx)));
 COMMIT;
 EXCEPTION
 WHEN ORDSYS.ORDSourceExceptions.METHOD_NOT_SUPPORTED THEN
   DBMS_OUTPUT.PUT_LINE('ORDSourceExceptions.METHOD_NOT_SUPPORTED caught');
 WHEN ORDSYS.ORDSourceExceptions.INCOMPLETE_SOURCE_INFORMATION THEN
   DBMS_OUTPUT.PUT_LINE('ORDSourceExceptions.INCOMPLETE_SOURCE_INFORMATION
 caught');
 WHEN ORDSYS.ORDSourceExceptions.NULL_SOURCE THEN
   DBMS_OUTPUT.PUT_LINE('ORDSourceExceptions.NULL_SOURCE caught');
 WHEN ORDSYS.ORDSourceExceptions.SOURCE_PLUGIN_EXCEPTION THEN
   DBMS_OUTPUT.PUT_LINE('ORDSourceExceptions.SOURCE_PLUGIN_EXCEPTION caught');
 WHEN OTHERS THEN
   DBMS_OUTPUT.PUT_LINE('EXCEPTION caught');
END;
/