made i/o and memory intensive operations execute in serial order

1 files changed, 34 insertions, 0 deletions

diff --git a/src/main/java/eu/siacs/conversations/utils/SerialSingleThreadExecutor.java b/src/main/java/eu/siacs/conversations/utils/SerialSingleThreadExecutor.java
new file mode 100644
index 00000000..bfb4668d
--- /dev/null
+++ b/src/main/java/eu/siacs/conversations/utils/SerialSingleThreadExecutor.java
@@ -0,0 +1,34 @@
+package eu.siacs.conversations.utils;
+
+import java.util.ArrayDeque;
+import java.util.Queue;
+import java.util.concurrent.Executor;
+import java.util.concurrent.Executors;
+
+public class SerialSingleThreadExecutor implements Executor {
+
+	final Executor executor = Executors.newSingleThreadExecutor();
+	final Queue<Runnable> tasks = new ArrayDeque();
+	Runnable active;
+
+	public synchronized void execute(final Runnable r) {
+		tasks.offer(new Runnable() {
+			public void run() {
+				try {
+					r.run();
+				} finally {
+					scheduleNext();
+				}
+			}
+		});
+		if (active == null) {
+			scheduleNext();
+		}
+	}
+
+	protected synchronized void scheduleNext() {
+		if ((active =  tasks.poll()) != null) {
+			executor.execute(active);
+		}
+	}
+}
\ No newline at end of file