Implement download to temporary file

Instead of directly downloading into the target file, download to a
temporary file and move it to its final location/name when the download
is complete. This avoids leaving a partially downloaded file in its
final requested location and name.

Also provides a wait for waiting for the client to complete its
operation after stopping is requested.

Bump to version 1.0.4.

Signed-off-by: Maxime Petazzoni <mpetazzoni@turn.com>

build.xml

@@ -22,7 +22,7 @@
 	<property name="src.dir" location="src" />
 
 	<!-- Release version. -->
-	<property name="project.version" value="1.0.3" />
+	<property name="project.version" value="1.0.4" />
 
 	<path id="project.classpath">
 		<pathelement location="${build.dir}" />

src/com/turn/ttorrent/client/Client.java

@@ -221,11 +221,28 @@ public synchronized void share(int seed) {
 
 	/** Immediately but gracefully stop this client.
 	 */
-	public synchronized void stop() {
+	public void stop() {
+		this.stop(true);
+	}
+
+	/** Immediately but gracefully stop this client.
+	 *
+	 * @param wait Whether to wait for the client execution thread to complete
+	 * or not. This allows for the client's state to be settled down in one of
+	 * the <tt>DONE</tt> or <tt>ERROR</tt> states when this method returns.
+	 */
+	public void stop(boolean wait) {
 		this.stop = true;
 
 		if (this.thread != null && this.thread.isAlive()) {
 			this.thread.interrupt();
+			if (wait) {
+				try {
+					this.thread.join();
+				} catch (InterruptedException ie) {
+					// Ignore
+				}
+			}
 		}
 
 		this.thread = null;
@@ -316,6 +333,8 @@ public void run() {
 			peer.unbind(true);
 		}
 
+		this.torrent.close();
+
 		// Determine final state
 		if (this.torrent.isComplete()) {
 			this.setState(ClientState.DONE);

src/com/turn/ttorrent/client/SharedTorrent.java

@@ -237,6 +237,15 @@ public synchronized void init() throws IOException {
 				this.pieces.length + "].");
 	}
 
+	public synchronized void close() {
+		try {
+			this.bucket.close();
+		} catch (IOException ioe) {
+			logger.error("Error closing torrent byte storage: " +
+				ioe.getMessage());
+		}
+	}
+
 	/** Retrieve a piece object by index.
 	 *
 	 * @param index The index of the piece in this torrent.
@@ -506,6 +515,15 @@ public synchronized void handlePieceCompleted(SharingPeer peer, Piece piece) {
 			logger.warn("Downloaded piece " + piece + " was not valid ;-(");
 		}
 
+		if (this.isComplete()) {
+			try {
+				this.bucket.complete();
+			} catch (IOException ioe) {
+				logger.error("Could not move downloaded file(s) to their " +
+					"target location!", ioe);
+			}
+		}
+
 		logger.trace("We now have " + this.completedPieces.cardinality() +
 				" piece(s) and " + this.requestedPieces.cardinality() +
 				" outstanding request(s): " + this.requestedPieces + ".");

src/com/turn/ttorrent/client/TorrentByteStorage.java

@@ -21,21 +21,28 @@
 import java.nio.ByteBuffer;
 import java.nio.channels.FileChannel;
 
+import org.apache.commons.io.FileUtils;
 import org.apache.log4j.Logger;
 
 /** Torrent data storage.
  *
+ * <p>
  * A torrent, regardless of whether it contains multiple files or not, is
  * considered as one linear, contiguous byte array. As such, pieces can spread
  * across multiple files.
+ * </p>
  *
+ * <p>
  * Although this BitTorrent client currently only supports single-torrent
  * files, this TorrentByteStorage class provides an abstraction for the Piece
  * class to read and write to the torrent's data without having to care about
  * which file(s) a piece is on.
+ * </p>
  *
+ * <p>
  * The current implementation uses a RandomAccessFile FileChannel to expose
  * thread-safe read/write methods.
+ * </p>
  *
  * @author mpetazzoni
  */
@@ -44,29 +51,96 @@ public class TorrentByteStorage {
 	private static final Logger logger =
 		Logger.getLogger(TorrentByteStorage.class);
 
+	private static final String PARTIAL_FILE_NAME_SUFFIX = ".part";
+
+	private File target;
+	private File partial;
+	private File current;
+
+	private RandomAccessFile raf;
 	private FileChannel channel;
+	private long size;
+
+	public TorrentByteStorage(File file, long size) throws IOException {
+		this.target = file;
+		this.size = size;
+
+		this.partial = new File(this.target.getAbsolutePath() +
+			TorrentByteStorage.PARTIAL_FILE_NAME_SUFFIX);
 
-	public TorrentByteStorage(File file, int size) throws IOException {
-		RandomAccessFile raf = new RandomAccessFile(file, "rw");
+		if (this.partial.exists()) {
+			logger.info("Partial download found at " +
+				this.partial.getAbsolutePath() + ". Continuing...");
+			this.current = this.partial;
+		} else if (!this.target.exists()) {
+			logger.info("Downloading new file to " +
+				this.partial.getAbsolutePath() + "...");
+			this.current = this.partial;
+		} else {
+			logger.info("Using existing file " +
+				this.target.getAbsolutePath() + ".");
+			this.current = this.target;
+		}
+
+		this.raf = new RandomAccessFile(this.current, "rw");
 
 		// Set the file length to the appropriate size, eventually truncating
 		// or extending the file if it already exists with a different size.
-		raf.setLength(size);
+		this.raf.setLength(this.size);
 
 		this.channel = raf.getChannel();
 		logger.debug("Initialized torrent byte storage at " +
-				file.getAbsolutePath() + ".");
+			this.current.getAbsolutePath() + ".");
 	}
 
 	public ByteBuffer read(int offset, int length) throws IOException {
 		ByteBuffer data = ByteBuffer.allocate(length);
-		int bytes = channel.read(data, offset);
+		int bytes = this.channel.read(data, offset);
 		data.clear();
 		data.limit(bytes >= 0 ? bytes : 0);
 		return data;
 	}
 
 	public void write(ByteBuffer block, int offset) throws IOException {
-		channel.write(block, offset);
+		this.channel.write(block, offset);
+	}
+
+	/** Move the partial file to its final location.
+	 *
+	 * <p>
+	 * This method needs to make sure reads can still happen seemlessly during
+	 * the operation. The partial is first flushed to the storage device before
+	 * being copied to its target location. The {@link FileChannel} is then
+	 * switched to this new file before the partial is removed.
+	 * </p>
+	 */
+	public synchronized void complete() throws IOException {
+		this.channel.force(true);
+
+		// Nothing more to do if we're already on the target file.
+		if (this.current.equals(this.target)) {
+			return;
+		}
+
+		FileUtils.deleteQuietly(this.target);
+		FileUtils.copyFile(this.current, this.target);
+
+		logger.debug("Re-opening torrent byte storage at " +
+				this.target.getAbsolutePath() + ".");
+
+		RandomAccessFile raf = new RandomAccessFile(this.target, "rw");
+		raf.setLength(this.size);
+
+		this.channel = raf.getChannel();
+		this.raf.close();
+		this.raf = raf;
+		this.current = this.target;
+
+		FileUtils.deleteQuietly(this.partial);
+	}
+
+	public synchronized void close() throws IOException {
+		this.channel.force(true);
+		this.raf.close();
 	}
 }