core/java/android/os/MessageQueue.java - platform/frameworks/base - Git at Google

 /*
  * Copyright (C) 2006 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 android.os;

 import android.util.Log;
 import android.util.Printer;

 import java.util.ArrayList;

 /**
  * Low-level class holding the list of messages to be dispatched by a
  * {@link Looper}.  Messages are not added directly to a MessageQueue,
  * but rather through {@link Handler} objects associated with the Looper.
  *
  * <p>You can retrieve the MessageQueue for the current thread with
  * {@link Looper#myQueue() Looper.myQueue()}.
  */
 public final class MessageQueue {
     // True if the message queue can be quit.
     private final boolean mQuitAllowed;

     @SuppressWarnings("unused")
     private long mPtr; // used by native code

     Message mMessages;
     private final ArrayList<IdleHandler> mIdleHandlers = new ArrayList<IdleHandler>();
     private IdleHandler[] mPendingIdleHandlers;
     private boolean mQuitting;

     // Indicates whether next() is blocked waiting in pollOnce() with a non-zero timeout.
     private boolean mBlocked;

     // The next barrier token.
     // Barriers are indicated by messages with a null target whose arg1 field carries the token.
     private int mNextBarrierToken;

     private native static long nativeInit();
     private native static void nativeDestroy(long ptr);
     private native static void nativePollOnce(long ptr, int timeoutMillis);
     private native static void nativeWake(long ptr);
     private native static boolean nativeIsIdling(long ptr);

     /**
      * Callback interface for discovering when a thread is going to block
      * waiting for more messages.
      */
     public static interface IdleHandler {
         /**
          * Called when the message queue has run out of messages and will now
          * wait for more.  Return true to keep your idle handler active, false
          * to have it removed.  This may be called if there are still messages
          * pending in the queue, but they are all scheduled to be dispatched
          * after the current time.
          */
         boolean queueIdle();
     }

     /**
      * Add a new {@link IdleHandler} to this message queue.  This may be
      * removed automatically for you by returning false from
      * {@link IdleHandler#queueIdle IdleHandler.queueIdle()} when it is
      * invoked, or explicitly removing it with {@link #removeIdleHandler}.
      *
      * <p>This method is safe to call from any thread.
      *
      * @param handler The IdleHandler to be added.
      */
     public void addIdleHandler(IdleHandler handler) {
         if (handler == null) {
             throw new NullPointerException("Can't add a null IdleHandler");
         }
         synchronized (this) {
             mIdleHandlers.add(handler);
         }
     }

     /**
      * Remove an {@link IdleHandler} from the queue that was previously added
      * with {@link #addIdleHandler}.  If the given object is not currently
      * in the idle list, nothing is done.
      *
      * @param handler The IdleHandler to be removed.
      */
     public void removeIdleHandler(IdleHandler handler) {
         synchronized (this) {
             mIdleHandlers.remove(handler);
         }
     }

     MessageQueue(boolean quitAllowed) {
         mQuitAllowed = quitAllowed;
         mPtr = nativeInit();
     }

     @Override
     protected void finalize() throws Throwable {
         try {
             dispose();
         } finally {
             super.finalize();
         }
     }

     // Disposes of the underlying message queue.
     // Must only be called on the looper thread or the finalizer.
     private void dispose() {
         if (mPtr != 0) {
             nativeDestroy(mPtr);
             mPtr = 0;
         }
     }

     Message next() {
         // Return here if the message loop has already quit and been disposed.
         // This can happen if the application tries to restart a looper after quit
         // which is not supported.
         final long ptr = mPtr;
         if (ptr == 0) {
             return null;
         }

         int pendingIdleHandlerCount = -1; // -1 only during first iteration
         int nextPollTimeoutMillis = 0;
         for (;;) {
             if (nextPollTimeoutMillis != 0) {
                 Binder.flushPendingCommands();
             }

             nativePollOnce(ptr, nextPollTimeoutMillis);

             synchronized (this) {
                 // Try to retrieve the next message.  Return if found.
                 final long now = SystemClock.uptimeMillis();
                 Message prevMsg = null;
                 Message msg = mMessages;
                 if (msg != null && msg.target == null) {
                     // Stalled by a barrier.  Find the next asynchronous message in the queue.
                     do {
                         prevMsg = msg;
                         msg = msg.next;
                     } while (msg != null && !msg.isAsynchronous());
                 }
                 if (msg != null) {
                     if (now < msg.when) {
                         // Next message is not ready.  Set a timeout to wake up when it is ready.
                         nextPollTimeoutMillis = (int) Math.min(msg.when - now, Integer.MAX_VALUE);
                     } else {
                         // Got a message.
                         mBlocked = false;
                         if (prevMsg != null) {
                             prevMsg.next = msg.next;
                         } else {
                             mMessages = msg.next;
                         }
                         msg.next = null;
                         if (false) Log.v("MessageQueue", "Returning message: " + msg);
                         return msg;
                     }
                 } else {
                     // No more messages.
                     nextPollTimeoutMillis = -1;
                 }

                 // Process the quit message now that all pending messages have been handled.
                 if (mQuitting) {
                     dispose();
                     return null;
                 }

                 // If first time idle, then get the number of idlers to run.
                 // Idle handles only run if the queue is empty or if the first message
                 // in the queue (possibly a barrier) is due to be handled in the future.
                 if (pendingIdleHandlerCount < 0
                         && (mMessages == null || now < mMessages.when)) {
                     pendingIdleHandlerCount = mIdleHandlers.size();
                 }
                 if (pendingIdleHandlerCount <= 0) {
                     // No idle handlers to run.  Loop and wait some more.
                     mBlocked = true;
                     continue;
                 }

                 if (mPendingIdleHandlers == null) {
                     mPendingIdleHandlers = new IdleHandler[Math.max(pendingIdleHandlerCount, 4)];
                 }
                 mPendingIdleHandlers = mIdleHandlers.toArray(mPendingIdleHandlers);
             }

             // Run the idle handlers.
             // We only ever reach this code block during the first iteration.
             for (int i = 0; i < pendingIdleHandlerCount; i++) {
                 final IdleHandler idler = mPendingIdleHandlers[i];
                 mPendingIdleHandlers[i] = null; // release the reference to the handler

                 boolean keep = false;
                 try {
                     keep = idler.queueIdle();
                 } catch (Throwable t) {
                     Log.wtf("MessageQueue", "IdleHandler threw exception", t);
                 }

                 if (!keep) {
                     synchronized (this) {
                         mIdleHandlers.remove(idler);
                     }
                 }
             }

             // Reset the idle handler count to 0 so we do not run them again.
             pendingIdleHandlerCount = 0;

             // While calling an idle handler, a new message could have been delivered
             // so go back and look again for a pending message without waiting.
             nextPollTimeoutMillis = 0;
         }
     }

     void quit(boolean safe) {
         if (!mQuitAllowed) {
             throw new IllegalStateException("Main thread not allowed to quit.");
         }

         synchronized (this) {
             if (mQuitting) {
                 return;
             }
             mQuitting = true;

             if (safe) {
                 removeAllFutureMessagesLocked();
             } else {
                 removeAllMessagesLocked();
             }

             // We can assume mPtr != 0 because mQuitting was previously false.
             nativeWake(mPtr);
         }
     }

     int enqueueSyncBarrier(long when) {
         // Enqueue a new sync barrier token.
         // We don't need to wake the queue because the purpose of a barrier is to stall it.
         synchronized (this) {
             final int token = mNextBarrierToken++;
             final Message msg = Message.obtain();
             msg.markInUse();
             msg.when = when;
             msg.arg1 = token;

             Message prev = null;
             Message p = mMessages;
             if (when != 0) {
                 while (p != null && p.when <= when) {
                     prev = p;
                     p = p.next;
                 }
             }
             if (prev != null) { // invariant: p == prev.next
                 msg.next = p;
                 prev.next = msg;
             } else {
                 msg.next = p;
                 mMessages = msg;
             }
             return token;
         }
     }

     void removeSyncBarrier(int token) {
         // Remove a sync barrier token from the queue.
         // If the queue is no longer stalled by a barrier then wake it.
         synchronized (this) {
             Message prev = null;
             Message p = mMessages;
             while (p != null && (p.target != null || p.arg1 != token)) {
                 prev = p;
                 p = p.next;
             }
             if (p == null) {
                 throw new IllegalStateException("The specified message queue synchronization "
                         + " barrier token has not been posted or has already been removed.");
             }
             final boolean needWake;
             if (prev != null) {
                 prev.next = p.next;
                 needWake = false;
             } else {
                 mMessages = p.next;
                 needWake = mMessages == null || mMessages.target != null;
             }
             p.recycleUnchecked();

             // If the loop is quitting then it is already awake.
             // We can assume mPtr != 0 when mQuitting is false.
             if (needWake && !mQuitting) {
                 nativeWake(mPtr);
             }
         }
     }

     boolean enqueueMessage(Message msg, long when) {
         if (msg.target == null) {
             throw new IllegalArgumentException("Message must have a target.");
         }
         if (msg.isInUse()) {
             throw new IllegalStateException(msg + " This message is already in use.");
         }

         synchronized (this) {
             if (mQuitting) {
                 IllegalStateException e = new IllegalStateException(
                         msg.target + " sending message to a Handler on a dead thread");
                 Log.w("MessageQueue", e.getMessage(), e);
                 msg.recycle();
                 return false;
             }

             msg.markInUse();
             msg.when = when;
             Message p = mMessages;
             boolean needWake;
             if (p == null || when == 0 || when < p.when) {
                 // New head, wake up the event queue if blocked.
                 msg.next = p;
                 mMessages = msg;
                 needWake = mBlocked;
             } else {
                 // Inserted within the middle of the queue.  Usually we don't have to wake
                 // up the event queue unless there is a barrier at the head of the queue
                 // and the message is the earliest asynchronous message in the queue.
                 needWake = mBlocked && p.target == null && msg.isAsynchronous();
                 Message prev;
                 for (;;) {
                     prev = p;
                     p = p.next;
                     if (p == null || when < p.when) {
                         break;
                     }
                     if (needWake && p.isAsynchronous()) {
                         needWake = false;
                     }
                 }
                 msg.next = p; // invariant: p == prev.next
                 prev.next = msg;
             }

             // We can assume mPtr != 0 because mQuitting is false.
             if (needWake) {
                 nativeWake(mPtr);
             }
         }
         return true;
     }

     boolean hasMessages(Handler h, int what, Object object) {
         if (h == null) {
             return false;
         }

         synchronized (this) {
             Message p = mMessages;
             while (p != null) {
                 if (p.target == h && p.what == what && (object == null || p.obj == object)) {
                     return true;
                 }
                 p = p.next;
             }
             return false;
         }
     }

     boolean hasMessages(Handler h, Runnable r, Object object) {
         if (h == null) {
             return false;
         }

         synchronized (this) {
             Message p = mMessages;
             while (p != null) {
                 if (p.target == h && p.callback == r && (object == null || p.obj == object)) {
                     return true;
                 }
                 p = p.next;
             }
             return false;
         }
     }

     boolean isIdling() {
         synchronized (this) {
             return isIdlingLocked();
         }
     }

     private boolean isIdlingLocked() {
         // If the loop is quitting then it must not be idling.
         // We can assume mPtr != 0 when mQuitting is false.
         return !mQuitting && nativeIsIdling(mPtr);
      }

     void removeMessages(Handler h, int what, Object object) {
         if (h == null) {
             return;
         }

         synchronized (this) {
             Message p = mMessages;

             // Remove all messages at front.
             while (p != null && p.target == h && p.what == what
                    && (object == null || p.obj == object)) {
                 Message n = p.next;
                 mMessages = n;
                 p.recycleUnchecked();
                 p = n;
             }

             // Remove all messages after front.
             while (p != null) {
                 Message n = p.next;
                 if (n != null) {
                     if (n.target == h && n.what == what
                         && (object == null || n.obj == object)) {
                         Message nn = n.next;
                         n.recycleUnchecked();
                         p.next = nn;
                         continue;
                     }
                 }
                 p = n;
             }
         }
     }

     void removeMessages(Handler h, Runnable r, Object object) {
         if (h == null || r == null) {
             return;
         }

         synchronized (this) {
             Message p = mMessages;

             // Remove all messages at front.
             while (p != null && p.target == h && p.callback == r
                    && (object == null || p.obj == object)) {
                 Message n = p.next;
                 mMessages = n;
                 p.recycleUnchecked();
                 p = n;
             }

             // Remove all messages after front.
             while (p != null) {
                 Message n = p.next;
                 if (n != null) {
                     if (n.target == h && n.callback == r
                         && (object == null || n.obj == object)) {
                         Message nn = n.next;
                         n.recycleUnchecked();
                         p.next = nn;
                         continue;
                     }
                 }
                 p = n;
             }
         }
     }

     void removeCallbacksAndMessages(Handler h, Object object) {
         if (h == null) {
             return;
         }

         synchronized (this) {
             Message p = mMessages;

             // Remove all messages at front.
             while (p != null && p.target == h
                     && (object == null || p.obj == object)) {
                 Message n = p.next;
                 mMessages = n;
                 p.recycleUnchecked();
                 p = n;
             }

             // Remove all messages after front.
             while (p != null) {
                 Message n = p.next;
                 if (n != null) {
                     if (n.target == h && (object == null || n.obj == object)) {
                         Message nn = n.next;
                         n.recycleUnchecked();
                         p.next = nn;
                         continue;
                     }
                 }
                 p = n;
             }
         }
     }

     private void removeAllMessagesLocked() {
         Message p = mMessages;
         while (p != null) {
             Message n = p.next;
             p.recycleUnchecked();
             p = n;
         }
         mMessages = null;
     }

     private void removeAllFutureMessagesLocked() {
         final long now = SystemClock.uptimeMillis();
         Message p = mMessages;
         if (p != null) {
             if (p.when > now) {
                 removeAllMessagesLocked();
             } else {
                 Message n;
                 for (;;) {
                     n = p.next;
                     if (n == null) {
                         return;
                     }
                     if (n.when > now) {
                         break;
                     }
                     p = n;
                 }
                 p.next = null;
                 do {
                     p = n;
                     n = p.next;
                     p.recycleUnchecked();
                 } while (n != null);
             }
         }
     }

     void dump(Printer pw, String prefix) {
         synchronized (this) {
             long now = SystemClock.uptimeMillis();
             int n = 0;
             for (Message msg = mMessages; msg != null; msg = msg.next) {
                 pw.println(prefix + "Message " + n + ": " + msg.toString(now));
                 n++;
             }
             pw.println(prefix + "(Total messages: " + n + ", idling=" + isIdlingLocked()
                     + ", quitting=" + mQuitting + ")");
         }
     }
 }
	/*
	* Copyright (C) 2006 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 android.os;

	import android.util.Log;
	import android.util.Printer;

	import java.util.ArrayList;

	/**
	* Low-level class holding the list of messages to be dispatched by a
	* {@link Looper}. Messages are not added directly to a MessageQueue,
	* but rather through {@link Handler} objects associated with the Looper.
	*
	* <p>You can retrieve the MessageQueue for the current thread with
	* {@link Looper#myQueue() Looper.myQueue()}.
	*/
	public final class MessageQueue {
	// True if the message queue can be quit.
	private final boolean mQuitAllowed;

	@SuppressWarnings("unused")
	private long mPtr; // used by native code

	Message mMessages;
	private final ArrayList<IdleHandler> mIdleHandlers = new ArrayList<IdleHandler>();
	private IdleHandler[] mPendingIdleHandlers;
	private boolean mQuitting;

	// Indicates whether next() is blocked waiting in pollOnce() with a non-zero timeout.
	private boolean mBlocked;

	// The next barrier token.
	// Barriers are indicated by messages with a null target whose arg1 field carries the token.
	private int mNextBarrierToken;

	private native static long nativeInit();
	private native static void nativeDestroy(long ptr);
	private native static void nativePollOnce(long ptr, int timeoutMillis);
	private native static void nativeWake(long ptr);
	private native static boolean nativeIsIdling(long ptr);

	/**
	* Callback interface for discovering when a thread is going to block
	* waiting for more messages.
	*/
	public static interface IdleHandler {
	/**
	* Called when the message queue has run out of messages and will now
	* wait for more. Return true to keep your idle handler active, false
	* to have it removed. This may be called if there are still messages
	* pending in the queue, but they are all scheduled to be dispatched
	* after the current time.
	*/
	boolean queueIdle();
	}

	/**
	* Add a new {@link IdleHandler} to this message queue. This may be
	* removed automatically for you by returning false from
	* {@link IdleHandler#queueIdle IdleHandler.queueIdle()} when it is
	* invoked, or explicitly removing it with {@link #removeIdleHandler}.
	*
	* <p>This method is safe to call from any thread.
	*
	* @param handler The IdleHandler to be added.
	*/
	public void addIdleHandler(IdleHandler handler) {
	if (handler == null) {
	throw new NullPointerException("Can't add a null IdleHandler");
	}
	synchronized (this) {
	mIdleHandlers.add(handler);
	}
	}

	/**
	* Remove an {@link IdleHandler} from the queue that was previously added
	* with {@link #addIdleHandler}. If the given object is not currently
	* in the idle list, nothing is done.
	*
	* @param handler The IdleHandler to be removed.
	*/
	public void removeIdleHandler(IdleHandler handler) {
	synchronized (this) {
	mIdleHandlers.remove(handler);
	}
	}

	MessageQueue(boolean quitAllowed) {
	mQuitAllowed = quitAllowed;
	mPtr = nativeInit();
	}

	@Override
	protected void finalize() throws Throwable {
	try {
	dispose();
	} finally {
	super.finalize();
	}
	}

	// Disposes of the underlying message queue.
	// Must only be called on the looper thread or the finalizer.
	private void dispose() {
	if (mPtr != 0) {
	nativeDestroy(mPtr);
	mPtr = 0;
	}
	}

	Message next() {
	// Return here if the message loop has already quit and been disposed.
	// This can happen if the application tries to restart a looper after quit
	// which is not supported.
	final long ptr = mPtr;
	if (ptr == 0) {
	return null;
	}

	int pendingIdleHandlerCount = -1; // -1 only during first iteration
	int nextPollTimeoutMillis = 0;
	for (;;) {
	if (nextPollTimeoutMillis != 0) {
	Binder.flushPendingCommands();
	}

	nativePollOnce(ptr, nextPollTimeoutMillis);

	synchronized (this) {
	// Try to retrieve the next message. Return if found.
	final long now = SystemClock.uptimeMillis();
	Message prevMsg = null;
	Message msg = mMessages;
	if (msg != null && msg.target == null) {
	// Stalled by a barrier. Find the next asynchronous message in the queue.
	do {
	prevMsg = msg;
	msg = msg.next;
	} while (msg != null && !msg.isAsynchronous());
	}
	if (msg != null) {
	if (now < msg.when) {
	// Next message is not ready. Set a timeout to wake up when it is ready.
	nextPollTimeoutMillis = (int) Math.min(msg.when - now, Integer.MAX_VALUE);
	} else {
	// Got a message.
	mBlocked = false;
	if (prevMsg != null) {
	prevMsg.next = msg.next;
	} else {
	mMessages = msg.next;
	}
	msg.next = null;
	if (false) Log.v("MessageQueue", "Returning message: " + msg);
	return msg;
	}
	} else {
	// No more messages.
	nextPollTimeoutMillis = -1;
	}

	// Process the quit message now that all pending messages have been handled.
	if (mQuitting) {
	dispose();
	return null;
	}

	// If first time idle, then get the number of idlers to run.
	// Idle handles only run if the queue is empty or if the first message
	// in the queue (possibly a barrier) is due to be handled in the future.
	if (pendingIdleHandlerCount < 0
	&& (mMessages == null \|\| now < mMessages.when)) {
	pendingIdleHandlerCount = mIdleHandlers.size();
	}
	if (pendingIdleHandlerCount <= 0) {
	// No idle handlers to run. Loop and wait some more.
	mBlocked = true;
	continue;
	}

	if (mPendingIdleHandlers == null) {
	mPendingIdleHandlers = new IdleHandler[Math.max(pendingIdleHandlerCount, 4)];
	}
	mPendingIdleHandlers = mIdleHandlers.toArray(mPendingIdleHandlers);
	}

	// Run the idle handlers.
	// We only ever reach this code block during the first iteration.
	for (int i = 0; i < pendingIdleHandlerCount; i++) {
	final IdleHandler idler = mPendingIdleHandlers[i];
	mPendingIdleHandlers[i] = null; // release the reference to the handler

	boolean keep = false;
	try {
	keep = idler.queueIdle();
	} catch (Throwable t) {
	Log.wtf("MessageQueue", "IdleHandler threw exception", t);
	}

	if (!keep) {
	synchronized (this) {
	mIdleHandlers.remove(idler);
	}
	}
	}

	// Reset the idle handler count to 0 so we do not run them again.
	pendingIdleHandlerCount = 0;

	// While calling an idle handler, a new message could have been delivered
	// so go back and look again for a pending message without waiting.
	nextPollTimeoutMillis = 0;
	}
	}

	void quit(boolean safe) {
	if (!mQuitAllowed) {
	throw new IllegalStateException("Main thread not allowed to quit.");
	}

	synchronized (this) {
	if (mQuitting) {
	return;
	}
	mQuitting = true;

	if (safe) {
	removeAllFutureMessagesLocked();
	} else {
	removeAllMessagesLocked();
	}

	// We can assume mPtr != 0 because mQuitting was previously false.
	nativeWake(mPtr);
	}
	}

	int enqueueSyncBarrier(long when) {
	// Enqueue a new sync barrier token.
	// We don't need to wake the queue because the purpose of a barrier is to stall it.
	synchronized (this) {
	final int token = mNextBarrierToken++;
	final Message msg = Message.obtain();
	msg.markInUse();
	msg.when = when;
	msg.arg1 = token;

	Message prev = null;
	Message p = mMessages;
	if (when != 0) {
	while (p != null && p.when <= when) {
	prev = p;
	p = p.next;
	}
	}
	if (prev != null) { // invariant: p == prev.next
	msg.next = p;
	prev.next = msg;
	} else {
	msg.next = p;
	mMessages = msg;
	}
	return token;
	}
	}

	void removeSyncBarrier(int token) {
	// Remove a sync barrier token from the queue.
	// If the queue is no longer stalled by a barrier then wake it.
	synchronized (this) {
	Message prev = null;
	Message p = mMessages;
	while (p != null && (p.target != null \|\| p.arg1 != token)) {
	prev = p;
	p = p.next;
	}
	if (p == null) {
	throw new IllegalStateException("The specified message queue synchronization "
	+ " barrier token has not been posted or has already been removed.");
	}
	final boolean needWake;
	if (prev != null) {
	prev.next = p.next;
	needWake = false;
	} else {
	mMessages = p.next;
	needWake = mMessages == null \|\| mMessages.target != null;
	}
	p.recycleUnchecked();

	// If the loop is quitting then it is already awake.
	// We can assume mPtr != 0 when mQuitting is false.
	if (needWake && !mQuitting) {
	nativeWake(mPtr);
	}
	}
	}

	boolean enqueueMessage(Message msg, long when) {
	if (msg.target == null) {
	throw new IllegalArgumentException("Message must have a target.");
	}
	if (msg.isInUse()) {
	throw new IllegalStateException(msg + " This message is already in use.");
	}

	synchronized (this) {
	if (mQuitting) {
	IllegalStateException e = new IllegalStateException(
	msg.target + " sending message to a Handler on a dead thread");
	Log.w("MessageQueue", e.getMessage(), e);
	msg.recycle();
	return false;
	}

	msg.markInUse();
	msg.when = when;
	Message p = mMessages;
	boolean needWake;
	if (p == null \|\| when == 0 \|\| when < p.when) {
	// New head, wake up the event queue if blocked.
	msg.next = p;
	mMessages = msg;
	needWake = mBlocked;
	} else {
	// Inserted within the middle of the queue. Usually we don't have to wake
	// up the event queue unless there is a barrier at the head of the queue
	// and the message is the earliest asynchronous message in the queue.
	needWake = mBlocked && p.target == null && msg.isAsynchronous();
	Message prev;
	for (;;) {
	prev = p;
	p = p.next;
	if (p == null \|\| when < p.when) {
	break;
	}
	if (needWake && p.isAsynchronous()) {
	needWake = false;
	}
	}
	msg.next = p; // invariant: p == prev.next
	prev.next = msg;
	}

	// We can assume mPtr != 0 because mQuitting is false.
	if (needWake) {
	nativeWake(mPtr);
	}
	}
	return true;
	}

	boolean hasMessages(Handler h, int what, Object object) {
	if (h == null) {
	return false;
	}

	synchronized (this) {
	Message p = mMessages;
	while (p != null) {
	if (p.target == h && p.what == what && (object == null \|\| p.obj == object)) {
	return true;
	}
	p = p.next;
	}
	return false;
	}
	}

	boolean hasMessages(Handler h, Runnable r, Object object) {
	if (h == null) {
	return false;
	}

	synchronized (this) {
	Message p = mMessages;
	while (p != null) {
	if (p.target == h && p.callback == r && (object == null \|\| p.obj == object)) {
	return true;
	}
	p = p.next;
	}
	return false;
	}
	}

	boolean isIdling() {
	synchronized (this) {
	return isIdlingLocked();
	}
	}

	private boolean isIdlingLocked() {
	// If the loop is quitting then it must not be idling.
	// We can assume mPtr != 0 when mQuitting is false.
	return !mQuitting && nativeIsIdling(mPtr);
	}

	void removeMessages(Handler h, int what, Object object) {
	if (h == null) {
	return;
	}

	synchronized (this) {
	Message p = mMessages;

	// Remove all messages at front.
	while (p != null && p.target == h && p.what == what
	&& (object == null \|\| p.obj == object)) {
	Message n = p.next;
	mMessages = n;
	p.recycleUnchecked();
	p = n;
	}

	// Remove all messages after front.
	while (p != null) {
	Message n = p.next;
	if (n != null) {
	if (n.target == h && n.what == what
	&& (object == null \|\| n.obj == object)) {
	Message nn = n.next;
	n.recycleUnchecked();
	p.next = nn;
	continue;
	}
	}
	p = n;
	}
	}
	}

	void removeMessages(Handler h, Runnable r, Object object) {
	if (h == null \|\| r == null) {
	return;
	}

	synchronized (this) {
	Message p = mMessages;

	// Remove all messages at front.
	while (p != null && p.target == h && p.callback == r
	&& (object == null \|\| p.obj == object)) {
	Message n = p.next;
	mMessages = n;
	p.recycleUnchecked();
	p = n;
	}

	// Remove all messages after front.
	while (p != null) {
	Message n = p.next;
	if (n != null) {
	if (n.target == h && n.callback == r
	&& (object == null \|\| n.obj == object)) {
	Message nn = n.next;
	n.recycleUnchecked();
	p.next = nn;
	continue;
	}
	}
	p = n;
	}
	}
	}

	void removeCallbacksAndMessages(Handler h, Object object) {
	if (h == null) {
	return;
	}

	synchronized (this) {
	Message p = mMessages;

	// Remove all messages at front.
	while (p != null && p.target == h
	&& (object == null \|\| p.obj == object)) {
	Message n = p.next;
	mMessages = n;
	p.recycleUnchecked();
	p = n;
	}

	// Remove all messages after front.
	while (p != null) {
	Message n = p.next;
	if (n != null) {
	if (n.target == h && (object == null \|\| n.obj == object)) {
	Message nn = n.next;
	n.recycleUnchecked();
	p.next = nn;
	continue;
	}
	}
	p = n;
	}
	}
	}

	private void removeAllMessagesLocked() {
	Message p = mMessages;
	while (p != null) {
	Message n = p.next;
	p.recycleUnchecked();
	p = n;
	}
	mMessages = null;
	}

	private void removeAllFutureMessagesLocked() {
	final long now = SystemClock.uptimeMillis();
	Message p = mMessages;
	if (p != null) {
	if (p.when > now) {
	removeAllMessagesLocked();
	} else {
	Message n;
	for (;;) {
	n = p.next;
	if (n == null) {
	return;
	}
	if (n.when > now) {
	break;
	}
	p = n;
	}
	p.next = null;
	do {
	p = n;
	n = p.next;
	p.recycleUnchecked();
	} while (n != null);
	}
	}
	}

	void dump(Printer pw, String prefix) {
	synchronized (this) {
	long now = SystemClock.uptimeMillis();
	int n = 0;
	for (Message msg = mMessages; msg != null; msg = msg.next) {
	pw.println(prefix + "Message " + n + ": " + msg.toString(now));
	n++;
	}
	pw.println(prefix + "(Total messages: " + n + ", idling=" + isIdlingLocked()
	+ ", quitting=" + mQuitting + ")");
	}
	}
	}