Get the amount of buffering that the stream has. The buffering is defined as the number of bytes that the stream has buffered, excluding the number of bytes that is currently granted to the user (with GetBuffer()).
- AK_DataReady: Some data has been buffered (out_uNumBytesAvailable is greater than 0).
- AK_NoDataReady: No data is available, and the end of file has not been reached.
- AK_NoMoreData: Some or no data is available, but the end of file has been reached. The stream will not buffer any more data.
- AK_Fail: The stream is invalid due to an I/O error.
||Number of bytes available in the stream's buffer(s).