1 files changed, 126 insertions, 0 deletions
diff --git a/java/src/com/android/inputmethod/latin/utils/PrioritizedSerialExecutor.java b/java/src/com/android/inputmethod/latin/utils/PrioritizedSerialExecutor.java
new file mode 100644
index 000000000..3c1db6529
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+++ b/java/src/com/android/inputmethod/latin/utils/PrioritizedSerialExecutor.java
@@ -0,0 +1,126 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.inputmethod.latin.utils;
+
+import java.util.ArrayDeque;
+import java.util.Queue;
+
+/**
+ * An object that executes submitted tasks using a thread.
+ */
+public class PrioritizedSerialExecutor {
+    public static final String TAG = PrioritizedSerialExecutor.class.getSimpleName();
+
+    private final Object mLock = new Object();
+
+    // The default value of capacities of task queues.
+    private static final int TASK_QUEUE_CAPACITY = 1000;
+    private final Queue<Runnable> mTasks;
+    private final Queue<Runnable> mPrioritizedTasks;
+
+    // The task which is running now.
+    private Runnable mActive;
+
+    public PrioritizedSerialExecutor() {
+        mTasks = new ArrayDeque<Runnable>(TASK_QUEUE_CAPACITY);
+        mPrioritizedTasks = new ArrayDeque<Runnable>(TASK_QUEUE_CAPACITY);
+    }
+
+    /**
+     * Clears all queued tasks.
+     */
+    public void clearAllTasks() {
+        synchronized(mLock) {
+            mTasks.clear();
+            mPrioritizedTasks.clear();
+        }
+    }
+
+    /**
+     * Enqueues the given task into the task queue.
+     * @param r the enqueued task
+     */
+    public void execute(final Runnable r) {
+        synchronized(mLock) {
+            mTasks.offer(r);
+            if (mActive == null) {
+                scheduleNext();
+            }
+        }
+    }
+
+    /**
+     * Enqueues the given task into the prioritized task queue.
+     * @param r the enqueued task
+     */
+    public void executePrioritized(final Runnable r) {
+        synchronized(mLock) {
+            mPrioritizedTasks.offer(r);
+            if (mActive ==  null) {
+                scheduleNext();
+            }
+        }
+    }
+
+    private boolean fetchNextTasks() {
+        synchronized(mLock) {
+            mActive = mPrioritizedTasks.poll();
+            if (mActive == null) {
+                mActive = mTasks.poll();
+            }
+            return mActive != null;
+        }
+    }
+
+    private void scheduleNext() {
+        synchronized(mLock) {
+            if (!fetchNextTasks()) {
+                return;
+            }
+            new Thread(new Runnable() {
+                @Override
+                public void run() {
+                    try {
+                        do {
+                            synchronized(mLock) {
+                                if (mActive != null) {
+                                    mActive.run();
+                                }
+                            }
+                        } while (fetchNextTasks());
+                    } finally {
+                        scheduleNext();
+                    }
+                }
+            }).start();
+        }
+    }
+
+    public void remove(final Runnable r) {
+        synchronized(mLock) {
+            mTasks.remove(r);
+            mPrioritizedTasks.remove(r);
+        }
+    }
+
+    public void replaceAndExecute(final Runnable oldTask, final Runnable newTask) {
+        synchronized(mLock) {
+            if (oldTask != null) remove(oldTask);
+            execute(newTask);
+        }
+    }
+}