Implement more BlockReader types

Adds additional useful block reader types.

* LayeredBlockReader, which represents priority

* SerialBlockReader, which concatenates readers

1 files changed, 98 insertions, 0 deletions

diff --git a/BJC-Utils2/src/main/java/bjc/utils/ioutils/SerialBlockReader.java b/BJC-Utils2/src/main/java/bjc/utils/ioutils/SerialBlockReader.java
new file mode 100644
index 0000000..0ae969d
--- /dev/null
+++ b/BJC-Utils2/src/main/java/bjc/utils/ioutils/SerialBlockReader.java
@@ -0,0 +1,98 @@
+package bjc.utils.ioutils;
+
+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(BlockReader... readers) {
+		for (BlockReader reader : readers) {
+			readerQueue.add(reader);
+		}
+	}
+
+	@Override
+	public boolean hasNextBlock() {
+		if (readerQueue.isEmpty()) return false;
+
+		boolean hasBlock = readerQueue.peek().hasNextBlock();
+
+		boolean cont = hasBlock || readerQueue.isEmpty();
+
+		while (!cont) {
+			try {
+				readerQueue.pop().close();
+			} catch (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;
+		else 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 (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()) {
+			BlockReader reader = readerQueue.pop();
+
+			reader.close();
+		}
+	}
+}
\ No newline at end of file