Preserve the order of descriptors in QR code payloads.

briar-api/src/org/briarproject/api/keyagreement/Payload.java

@@ -1,11 +1,9 @@
 package org.briarproject.api.keyagreement;
 
 import org.briarproject.api.Bytes;
-import org.briarproject.api.TransportId;
-import org.briarproject.api.data.BdfList;
 import org.briarproject.api.nullsafety.NotNullByDefault;
 
-import java.util.Map;
+import java.util.List;
 
 import javax.annotation.concurrent.Immutable;
 
@@ -17,9 +15,9 @@ import javax.annotation.concurrent.Immutable;
 public class Payload implements Comparable<Payload> {
 
 	private final Bytes commitment;
-	private final Map<TransportId, BdfList> descriptors;
+	private final List<TransportDescriptor> descriptors;
 
-	public Payload(byte[] commitment, Map<TransportId, BdfList> descriptors) {
+	public Payload(byte[] commitment, List<TransportDescriptor> descriptors) {
 		this.commitment = new Bytes(commitment);
 		this.descriptors = descriptors;
 	}
@@ -34,7 +32,7 @@ public class Payload implements Comparable<Payload> {
 	/**
 	 * Returns the transport descriptors contained in this payload.
 	 */
-	public Map<TransportId, BdfList> getTransportDescriptors() {
+	public List<TransportDescriptor> getTransportDescriptors() {
 		return descriptors;
 	}
 

briar-api/src/org/briarproject/api/keyagreement/TransportDescriptor.java

@@ -0,0 +1,28 @@
+package org.briarproject.api.keyagreement;
+
+import org.briarproject.api.TransportId;
+import org.briarproject.api.data.BdfList;
+import org.briarproject.api.nullsafety.NotNullByDefault;
+
+import javax.annotation.concurrent.Immutable;
+
+@Immutable
+@NotNullByDefault
+public class TransportDescriptor {
+
+	private final TransportId id;
+	private final BdfList descriptor;
+
+	public TransportDescriptor(TransportId id, BdfList descriptor) {
+		this.id = id;
+		this.descriptor = descriptor;
+	}
+
+	public TransportId getId() {
+		return id;
+	}
+
+	public BdfList getDescriptor() {
+		return descriptor;
+	}
+}