private long addBlock(Block block, List<BlockWithLocations> results) {
final List<String> machineSet = getValidLocations(block);
if(machineSet.size() == 0) {
return 0;
} else {
results.add(new BlockWithLocations(block,
machineSet.toArray(new String[machineSet.size()])));
return block.getNumBytes();
}
}