When this method is called, the buffer previously returned from next method is no longer
used. Thus implementation of this method can safely discard it.
If the input is already closed then invoking
this method has no effect.
Attributes
Throws:
Exception
when IO error occurred when closing the data source
This method should return a ReadBuffer instance that has data filled in.
When this method is called twice, the previously returned buffer is no longer used. Thus implementation of this
method can safely discard it. This is useful when it uses a memory pool.
Attributes
Returns:
the next input ReadBuffer, or return None if no more buffer is available.