Added interfaces for reading and writing packets and recognising which

contact originated an incoming connection, and an implementation of
the PacketWriter interface.

api/net/sf/briar/api/crypto/CryptoComponent.java

@@ -4,13 +4,19 @@ import java.security.KeyPair;
 import java.security.MessageDigest;
 import java.security.Signature;
 
+import javax.crypto.Mac;
+import javax.crypto.SecretKey;
 
 public interface CryptoComponent {
 
 	KeyPair generateKeyPair();
 
+	SecretKey generateSecretKey();
+
 	KeyParser getKeyParser();
 
+	Mac getMac();
+
 	MessageDigest getMessageDigest();
 
 	Signature getSignature();

api/net/sf/briar/api/transport/ConnectionRecogniser.java

@@ -0,0 +1,16 @@
+package net.sf.briar.api.transport;
+
+import net.sf.briar.api.ContactId;
+
+/**
+ * Maintains a transport plugin's connection reordering window and decides
+ * whether incoming connections should be accepted or rejected.
+ */
+public interface ConnectionRecogniser {
+
+	/**
+	 * Returns the ID of the contact who created the tag if the connection
+	 * should be accepted, or null if the connection should be rejected.
+	 */
+	ContactId acceptConnection(byte[] tag);
+}

api/net/sf/briar/api/transport/PacketReader.java

@@ -0,0 +1,37 @@
+package net.sf.briar.api.transport;
+
+import java.io.IOException;
+
+import net.sf.briar.api.protocol.Ack;
+import net.sf.briar.api.protocol.Batch;
+import net.sf.briar.api.protocol.Offer;
+import net.sf.briar.api.protocol.Request;
+import net.sf.briar.api.protocol.SubscriptionUpdate;
+import net.sf.briar.api.protocol.TransportUpdate;
+
+/**
+ * Reads unencrypted packets from an underlying input stream and authenticates
+ * them.
+ */
+public interface PacketReader {
+
+	boolean eof() throws IOException;
+
+	boolean hasAck() throws IOException;
+	Ack readAck() throws IOException;
+
+	boolean hasBatch() throws IOException;
+	Batch readBatch() throws IOException;
+
+	boolean hasOffer() throws IOException;
+	Offer readOffer() throws IOException;
+
+	boolean hasRequest() throws IOException;
+	Request readRequest() throws IOException;
+
+	boolean hasSubscriptionUpdate() throws IOException;
+	SubscriptionUpdate readSubscriptionUpdate() throws IOException;
+
+	boolean hasTransportUpdate() throws IOException;
+	TransportUpdate readTransportUpdate() throws IOException;
+}

api/net/sf/briar/api/transport/PacketWriter.java

@@ -0,0 +1,24 @@
+package net.sf.briar.api.transport;
+
+import java.io.IOException;
+import java.io.OutputStream;
+
+/**
+ * A filter that adds tags and MACs to outgoing packets. Encryption is handled
+ * by the underlying output stream.
+ */
+public interface PacketWriter {
+
+	/**
+	 * Returns the output stream to which packets should be written. (Note that
+	 * this is not the underlying output stream.)
+	 */
+	OutputStream getOutputStream();
+
+	/**
+	 * Finishes writing the current packet (if any) and prepares to write the
+	 * next packet. If this method is called twice in succession without any
+	 * intervening writes, the underlying output stream will be unaffected.
+	 */
+	void nextPacket() throws IOException;
+}