DatabaseComponent.generateBatch() now returns a boolean.

This allows a connection to know whether to try writing another batch
immediately, or to wait for an event from the DB.

api/net/sf/briar/api/db/DatabaseComponent.java

@@ -73,17 +73,21 @@ public interface DatabaseComponent {
 	void generateAck(ContactId c, AckWriter a) throws DbException,
 	IOException;
 
-	/** Generates a batch of messages for the given contact. */
+	/**
-	void generateBatch(ContactId c, BatchWriter b) throws DbException,
+	 * Generates a batch of messages for the given contact.
+	 * @return True if any messages were added to tbe batch.
+	 */
+	boolean generateBatch(ContactId c, BatchWriter b) throws DbException,
 	IOException;
 
 	/**
 	 * Generates a batch of messages for the given contact from the given
-	 * collection of requested messages, and returns the IDs of any messages
+	 * collection of requested messages. Any messages that were either added to
-	 * that were either added to the batch, or were considered for inclusion
+	 * the batch, or were considered but are no longer sendable to the contact,
-	 * but are no longer sendable to the contact.
+	 * are removed from the collection of requested messages before returning.
+	 * @return True if any messages were added to the batch.
 	 */
-	Collection<MessageId> generateBatch(ContactId c, BatchWriter b,
+	boolean generateBatch(ContactId c, BatchWriter b,
 			Collection<MessageId> requested) throws DbException, IOException;
 
 	/**

components/net/sf/briar/db/DatabaseComponentImpl.java

@@ -408,29 +408,26 @@ DatabaseCleaner.Callback {
 		}
 	}
 
-	public void generateBatch(ContactId c, BatchWriter b) throws DbException,
+	public boolean generateBatch(ContactId c, BatchWriter b) throws DbException,
 	IOException {
 		contactLock.readLock().lock();
 		try {
 			if(!containsContact(c)) throw new NoSuchContactException();
 			messageLock.readLock().lock();
 			try {
-				Collection<MessageId> sent;
+				Collection<MessageId> sent = new ArrayList<MessageId>();
-				int bytesSent = 0;
 				messageStatusLock.readLock().lock();
 				try {
 					subscriptionLock.readLock().lock();
 					try {
 						T txn = db.startTransaction();
 						try {
-							sent = new ArrayList<MessageId>();
 							int capacity = b.getCapacity();
 							Collection<MessageId> sendable =
 								db.getSendableMessages(txn, c, capacity);
 							for(MessageId m : sendable) {
 								byte[] raw = db.getMessage(txn, m);
 								if(!b.writeMessage(raw)) break;
-								bytesSent += raw.length;
 								sent.add(m);
 							}
 							db.commitTransaction(txn);
@@ -448,7 +445,7 @@ DatabaseCleaner.Callback {
 					messageStatusLock.readLock().unlock();
 				}
 				// Record the contents of the batch, unless it's empty
-				if(sent.isEmpty()) return;
+				if(sent.isEmpty()) return false;
 				BatchId id = b.finish();
 				messageStatusLock.writeLock().lock();
 				try {
@@ -456,6 +453,7 @@ DatabaseCleaner.Callback {
 					try {
 						db.addOutstandingBatch(txn, c, id, sent);
 						db.commitTransaction(txn);
+						return true;
 					} catch(DbException e) {
 						db.abortTransaction(txn);
 						throw e;
@@ -471,24 +469,23 @@ DatabaseCleaner.Callback {
 		}
 	}
 
-	public Collection<MessageId> generateBatch(ContactId c, BatchWriter b,
+	public boolean generateBatch(ContactId c, BatchWriter b,
 			Collection<MessageId> requested) throws DbException, IOException {
 		contactLock.readLock().lock();
 		try {
 			if(!containsContact(c)) throw new NoSuchContactException();
 			messageLock.readLock().lock();
 			try {
-				Collection<MessageId> sent, considered;
+				Collection<MessageId> sent = new ArrayList<MessageId>();
 				messageStatusLock.readLock().lock();
 				try{
 					subscriptionLock.readLock().lock();
 					try {
 						T txn = db.startTransaction();
 						try {
-							sent = new ArrayList<MessageId>();
+							Iterator<MessageId> it = requested.iterator();
-							considered = new ArrayList<MessageId>();
+							while(it.hasNext()) {
-							int bytesSent = 0;
+								MessageId m = it.next();
-							for(MessageId m : requested) {
 								byte[] raw = db.getMessageIfSendable(txn, c, m);
 								// If the message is still sendable, try to add
 								// it to the batch. If the batch is full, don't
@@ -496,10 +493,9 @@ DatabaseCleaner.Callback {
 								// try to add any further messages.
 								if(raw != null) {
 									if(!b.writeMessage(raw)) break;
-									bytesSent += raw.length;
 									sent.add(m);
 								}
-								considered.add(m);
+								it.remove();
 							}
 							db.commitTransaction(txn);
 						} catch(DbException e) {
@@ -516,7 +512,7 @@ DatabaseCleaner.Callback {
 					messageStatusLock.readLock().unlock();
 				}
 				// Record the contents of the batch, unless it's empty
-				if(sent.isEmpty()) return considered;
+				if(sent.isEmpty()) return false;
 				BatchId id = b.finish();
 				messageStatusLock.writeLock().lock();
 				try {
@@ -524,7 +520,7 @@ DatabaseCleaner.Callback {
 					try {
 						db.addOutstandingBatch(txn, c, id, sent);
 						db.commitTransaction(txn);
-						return considered;
+						return true;
 					} catch(DbException e) {
 						db.abortTransaction(txn);
 						throw e;

components/net/sf/briar/protocol/writers/BatchWriterImpl.java

@@ -41,8 +41,8 @@ class BatchWriterImpl implements BatchWriter {
 			started = true;
 		}
 		// Allow one byte for the list end tag
-		int capacity = ProtocolConstants.MAX_PACKET_LENGTH
+		int capacity =
-		- (int) w.getBytesWritten() - 1;
+			ProtocolConstants.MAX_PACKET_LENGTH - (int) w.getBytesWritten() - 1;
 		if(capacity < message.length) return false;
 		// Bypass the writer and write each raw message directly
 		out.write(message);