New polling logic for Bluetooth. #251

The polling interval increases exponentially each time polling is unsuccessful, up to a maximum of 60 minutes. The interval is reset to 2 minutes whenever a connection is made and whenever Bluetooth is re-enabled.

briar-api/src/org/briarproject/api/plugins/Backoff.java

@@ -0,0 +1,22 @@
+package org.briarproject.api.plugins;
+
+/**
+ * Calculates polling intervals for transport plugins that use backoff.
+ */
+public interface Backoff {
+
+	/**
+	 * Returns the current polling interval.
+	 */
+	int getPollingInterval();
+
+	/**
+	 * Increments the backoff counter.
+	 */
+	void increment();
+
+	/**
+	 * Resets the backoff counter.
+	 */
+	void reset();
+}

briar-api/src/org/briarproject/api/plugins/BackoffFactory.java

@@ -0,0 +1,7 @@
+package org.briarproject.api.plugins;
+
+public interface BackoffFactory {
+
+	Backoff createBackoff(int minInterval, int maxInterval,
+			double base);
+}