* @param in the InputStream to be used
* @return the 'augmented' InputStream using the given stream as the underlying InputStream
*/
protected synchronized InputStream setCurrentInputStream(InputStream in) {
if(tlin==null) {
tlin = new ThroughputLimitInputStream(new CounterInputStream(in, currentFileByteCounter), throughputLimit);
}
else {
tlin.setUnderlyingInputStream(new CounterInputStream(in, currentFileByteCounter));
}