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package bjc.utils.ioutils.blocks;
import java.io.IOException;
import java.util.Deque;
/**
* Provides a means of concatenating two block readers.
*
* @author bjculkin
*
*/
public class SerialBlockReader implements BlockReader {
private Deque<BlockReader> readerQueue;
private int blockNo;
/**
* Create a new serial block reader.
*
* @param readers
* The readers to pull from, in the order to pull from them.
*/
public SerialBlockReader(final BlockReader... readers) {
for(final BlockReader reader : readers) {
readerQueue.add(reader);
}
}
@Override
public boolean hasNextBlock() {
if(readerQueue.isEmpty()) return false;
/*
* Attempt to get a block from the first reader.
*/
boolean hasBlock = readerQueue.peek().hasNextBlock();
boolean cont = hasBlock || readerQueue.isEmpty();
/*
* Close/dispose of readers until we get an open one.
*/
while(!cont) {
try {
readerQueue.pop().close();
} catch(final IOException ioex) {
throw new IllegalStateException("Exception thrown by discarded reader", ioex);
}
hasBlock = readerQueue.peek().hasNextBlock();
cont = hasBlock || readerQueue.isEmpty();
}
return hasBlock;
}
@Override
public Block getBlock() {
if(readerQueue.isEmpty()) {
return null;
}
return readerQueue.peek().getBlock();
}
@Override
public boolean nextBlock() {
if(readerQueue.isEmpty()) return false;
boolean gotBlock = readerQueue.peek().nextBlock();
boolean cont = gotBlock || readerQueue.isEmpty();
while(!cont) {
try {
readerQueue.pop().close();
} catch(final IOException ioex) {
throw new IllegalStateException("Exception thrown by discarded reader", ioex);
}
gotBlock = readerQueue.peek().nextBlock();
cont = gotBlock || readerQueue.isEmpty();
}
if(cont) {
blockNo += 1;
}
return cont;
}
@Override
public int getBlockCount() {
return blockNo;
}
@Override
public void close() throws IOException {
while(!readerQueue.isEmpty()) {
final BlockReader reader = readerQueue.pop();
reader.close();
}
}
}
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