Acquire wakelock when alarm goes off

briar-android/src/main/java/org/briarproject/briar/android/SleepMonitor.java

@@ -0,0 +1,67 @@
+package org.briarproject.briar.android;
+
+import android.os.SystemClock;
+import android.util.Log;
+
+import java.text.DateFormat;
+import java.text.SimpleDateFormat;
+import java.util.Date;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledExecutorService;
+
+import static java.util.Locale.US;
+import static java.util.concurrent.TimeUnit.MILLISECONDS;
+
+public class SleepMonitor implements Runnable {
+
+	/**
+	 * How often to check the uptime and real time.
+	 */
+	private static final int INTERVAL_MS = 5000;
+
+	/**
+	 * If the difference between uptime and real time changes by more than this amount, assume deep
+	 * sleep has occurred.
+	 */
+	private static final int MIN_SLEEP_DURATION_MS = 1000;
+
+	private final ScheduledExecutorService executorService;
+
+	private volatile long uptime, realtime, diff;
+
+	SleepMonitor() {
+		uptime = SystemClock.uptimeMillis();
+		realtime = SystemClock.elapsedRealtime();
+		diff = realtime - uptime;
+		executorService = Executors.newSingleThreadScheduledExecutor();
+	}
+
+	void start() {
+		executorService.scheduleAtFixedRate(this, 0, INTERVAL_MS, MILLISECONDS);
+	}
+
+	@Override
+	public void run() {
+		long sleepDuration = getSleepDuration();
+		if (sleepDuration > MIN_SLEEP_DURATION_MS) {
+			String start = getTime(System.currentTimeMillis() - sleepDuration);
+			Log.i("SLEEP_INFO", "System slept for " + sleepDuration + " ms (since " + start + ")");
+		}
+	}
+
+	/**
+	 * Returns the amount of time spent in deep sleep since the last check.
+	 */
+	private long getSleepDuration() {
+		uptime = SystemClock.uptimeMillis();
+		realtime = SystemClock.elapsedRealtime();
+		long lastDiff = diff;
+		diff = realtime - uptime;
+		return diff - lastDiff;
+	}
+
+	private String getTime(long time) {
+		DateFormat sdf = new SimpleDateFormat("HH:mm:ss", US);
+		return sdf.format(new Date(time));
+	}
+}