Fortunately there is no "ignore all these" rows method.
So the only option left to forcefully stop the transformation is to actually call stopAll();
I find the use-case a bit dubious though. How would you know that you read all the lookup data and where to stop? That's just one question I would have in this situation.
I think that instead you just need to make sure you depleted all the steps from a specific (what we call) info-step before starting to read from all other steps. From StreamLookup.java:
RowSet rowSet = findInputRowSet( data.infoStream.getStepname() );
Object[] rowData = getRowFrom( rowSet ); // rows are originating from "lookup_from"
while ( rowData != null ) {
... do something....
rowData = getRowFrom( rowSet );
}
and only then call getRow() as before.
Good luck!
Matt