1package eu.siacs.conversations.utils;
 2
 3import android.os.Looper;
 4
 5import java.util.ArrayDeque;
 6import java.util.Queue;
 7import java.util.concurrent.Executor;
 8import java.util.concurrent.Executors;
 9
10import eu.siacs.conversations.services.AttachFileToConversationRunnable;
11
12public class SerialSingleThreadExecutor implements Executor {
13
14	final Executor executor = Executors.newSingleThreadExecutor();
15	protected final ArrayDeque<Runnable> tasks = new ArrayDeque<>();
16	private Runnable active;
17
18	public SerialSingleThreadExecutor() {
19		this(false);
20	}
21
22	public SerialSingleThreadExecutor(boolean prepareLooper) {
23		if (prepareLooper) {
24			execute(new Runnable() {
25				@Override
26				public void run() {
27					Looper.prepare();
28				}
29			});
30		}
31	}
32
33	public synchronized void execute(final Runnable r) {
34		tasks.offer(new Runnable() {
35			public void run() {
36				try {
37					r.run();
38				} finally {
39					scheduleNext();
40				}
41			}
42		});
43		if (active == null) {
44			scheduleNext();
45		}
46	}
47
48	protected synchronized void scheduleNext() {
49		if ((active =  tasks.poll()) != null) {
50			executor.execute(active);
51		}
52	}
53}