/*
* 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.annotation.IntDef;
import android.annotation.NonNull;
import android.annotation.TestApi;
import android.annotation.UnsupportedAppUsage;
import android.os.MessageQueueProto;
import android.util.Log;
import android.util.Printer;
import android.util.SparseArray;
import android.util.proto.ProtoOutputStream;
import java.io.FileDescriptor;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
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 {
private static final String TAG = "MessageQueue";
private static final boolean DEBUG = false;
// True if the message queue can be quit.
@UnsupportedAppUsage
private final boolean mQuitAllowed;
@UnsupportedAppUsage
@SuppressWarnings("unused")
private long mPtr; // used by native code
@UnsupportedAppUsage
Message mMessages;
@UnsupportedAppUsage
private final ArrayList<IdleHandler> mIdleHandlers = new ArrayList<IdleHandler>();
private SparseArray<FileDescriptorRecord> mFileDescriptorRecords;
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.
@UnsupportedAppUsage
private int mNextBarrierToken;
private native static long nativeInit();
private native static void nativeDestroy(long ptr);
@UnsupportedAppUsage
private native void nativePollOnce(long ptr, int timeoutMillis); /*non-static for callbacks*/
private native static void nativeWake(long ptr);
private native static boolean nativeIsPolling(long ptr);
private native static void nativeSetFileDescriptorEvents(long ptr, int fd, int events);
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;
}
}
/**
* Returns true if the looper has no pending messages which are due to be processed.
*
* <p>This method is safe to call from any thread.
*
* @return True if the looper is idle.
*/
public boolean isIdle() {
synchronized (this) {
final long now = SystemClock.uptimeMillis();
return mMessages == null || now < mMessages.when;
}
}
/**
* 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(@NonNull 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.
*
* <p>This method is safe to call from any thread.
*
* @param handler The IdleHandler to be removed.
*/
public void removeIdleHandler(@NonNull IdleHandler handler) {
synchronized (this) {
mIdleHandlers.remove(handler);
}
}
/**
* Returns whether this looper's thread is currently polling for more work to do.
* This is a good signal that the loop is still alive rather than being stuck
* handling a callback. Note that this method is intrinsically racy, since the
* state of the loop can change before you get the result back.
*
* <p>This method is safe to call from any thread.
*
* @return True if the looper is currently polling for events.
* @hide
*/
public boolean isPolling() {
synchronized (this) {
return isPollingLocked();
}
}
private boolean isPollingLocked() {
// If the loop is quitting then it must not be idling.
// We can assume mPtr != 0 when mQuitting is false.
return !mQuitting && nativeIsPolling(mPtr);
}
/**
* Adds a file descriptor listener to receive notification when file descriptor
* related events occur.
* <p>
* If the file descriptor has already been registered, the specified events
* and listener will replace any that were previously associated with it.
* It is not possible to set more than one listener per file descriptor.
* </p><p>
* It is important to always unregister the listener when the file descriptor
* is no longer of use.
* </p>
*
* @param fd The file descriptor for which a listener will be registered.
* @param events The set of events to receive: a combination of the
* {@link OnFileDescriptorEventListener#EVENT_INPUT},
* {@link OnFileDescriptorEventListener#EVENT_OUTPUT}, and
* {@link OnFileDescriptorEventListener#EVENT_ERROR} event masks. If the requested
* set of events is zero, then the listener is unregistered.
* @param listener The listener to invoke when file descriptor events occur.
*
* @see OnFileDescriptorEventListener
* @see #removeOnFileDescriptorEventListener
*/
public void addOnFileDescriptorEventListener(@NonNull FileDescriptor fd,
@OnFileDescriptorEventListener.Events int events,
@NonNull OnFileDescriptorEventListener listener) {
if (fd == null) {
throw new IllegalArgumentException("fd must not be null");
}
if (listener == null) {
throw new IllegalArgumentException("listener must not be null");
}
synchronized (this) {
updateOnFileDescriptorEventListenerLocked(fd, events, listener);
}
}
/**
* Removes a file descriptor listener.
* <p>
* This method does nothing if no listener has been registered for the
* specified file descriptor.
* </p>
*
* @param fd The file descriptor whose listener will be unregistered.
*
* @see OnFileDescriptorEventListener
* @see #addOnFileDescriptorEventListener
*/
public void removeOnFileDescriptorEventListener(@NonNull FileDescriptor fd) {
if (fd == null) {
throw new IllegalArgumentException("fd must not be null");
}
synchronized (this) {
updateOnFileDescriptorEventListenerLocked(fd, 0, null);
}
}
private void updateOnFileDescriptorEventListenerLocked(FileDescriptor fd, int events,
OnFileDescriptorEventListener listener) {
final int fdNum = fd.getInt$();
int index = -1;
FileDescriptorRecord record = null;
if (mFileDescriptorRecords != null) {
index = mFileDescriptorRecords.indexOfKey(fdNum);
if (index >= 0) {
record = mFileDescriptorRecords.valueAt(index);
if (record != null && record.mEvents == events) {
return;
}
}
}
if (events != 0) {
events |= OnFileDescriptorEventListener.EVENT_ERROR;
if (record == null) {
if (mFileDescriptorRecords == null) {
mFileDescriptorRecords = new SparseArray<FileDescriptorRecord>();
}
record = new FileDescriptorRecord(fd, events, listener);
mFileDescriptorRecords.put(fdNum, record);
} else {
record.mListener = listener;
record.mEvents = events;
record.mSeq += 1;
}
nativeSetFileDescriptorEvents(mPtr, fdNum, events);
} else if (record != null) {
record.mEvents = 0;
mFileDescriptorRecords.removeAt(index);
nativeSetFileDescriptorEvents(mPtr, fdNum, 0);
}
}
// Called from native code.
@UnsupportedAppUsage
private int dispatchEvents(int fd, int events) {
// Get the file descriptor record and any state that might change.
final FileDescriptorRecord record;
final int oldWatchedEvents;
final OnFileDescriptorEventListener listener;
final int seq;
synchronized (this) {
record = mFileDescriptorRecords.get(fd);
if (record == null) {
return 0; // spurious, no listener registered
}
oldWatchedEvents = record.mEvents;
events &= oldWatchedEvents; // filter events based on current watched set
if (events == 0) {
return oldWatchedEvents; // spurious, watched events changed
}
listener = record.mListener;
seq = record.mSeq;
}
// Invoke the listener outside of the lock.
int newWatchedEvents = listener.onFileDescriptorEvents(
record.mDescriptor, events);
if (newWatchedEvents != 0) {
newWatchedEvents |= OnFileDescriptorEventListener.EVENT_ERROR;
}
// Update the file descriptor record if the listener changed the set of
// events to watch and the listener itself hasn't been updated since.
if (newWatchedEvents != oldWatchedEvents) {
synchronized (this) {
int index = mFileDescriptorRecords.indexOfKey(fd);
if (index >= 0 && mFileDescriptorRecords.valueAt(index) == record
&& record.mSeq == seq) {
record.mEvents = newWatchedEvents;
if (newWatchedEvents == 0) {
mFileDescriptorRecords.removeAt(index);
}
}
}
}
// Return the new set of events to watch for native code to take care of.
return newWatchedEvents;
}
@UnsupportedAppUsage
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 (DEBUG) Log.v(TAG, "Returning message: " + msg);
msg.markInUse();
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(TAG, "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);
}
}
/**
* Posts a synchronization barrier to the Looper's message queue.
*
* Message processing occurs as usual until the message queue encounters the
* synchronization barrier that has been posted. When the barrier is encountered,
* later synchronous messages in the queue are stalled (prevented from being executed)
* until the barrier is released by calling {@link #removeSyncBarrier} and specifying
* the token that identifies the synchronization barrier.
*
* This method is used to immediately postpone execution of all subsequently posted
* synchronous messages until a condition is met that releases the barrier.
* Asynchronous messages (see {@link Message#isAsynchronous} are exempt from the barrier
* and continue to be processed as usual.
*
* This call must be always matched by a call to {@link #removeSyncBarrier} with
* the same token to ensure that the message queue resumes normal operation.
* Otherwise the application will probably hang!
*
* @return A token that uniquely identifies the barrier. This token must be
* passed to {@link #removeSyncBarrier} to release the barrier.
*
* @hide
*/
@TestApi
public int postSyncBarrier() {
return postSyncBarrier(SystemClock.uptimeMillis());
}
private int postSyncBarrier(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;
}
}
/**
* Removes a synchronization barrier.
*
* @param token The synchronization barrier token that was returned by
* {@link #postSyncBarrier}.
*
* @throws IllegalStateException if the barrier was not found.
*
* @hide
*/
@TestApi
public 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(TAG, 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;
}
}
@UnsupportedAppUsage
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 hasMessages(Handler h) {
if (h == null) {
return false;
}
synchronized (this) {
Message p = mMessages;
while (p != null) {
if (p.target == h) {
return true;
}
p = p.next;
}
return false;
}
}
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, Handler h) {
synchronized (this) {
long now = SystemClock.uptimeMillis();
int n = 0;
for (Message msg = mMessages; msg != null; msg = msg.next) {
if (h == null || h == msg.target) {
pw.println(prefix + "Message " + n + ": " + msg.toString(now));
}
n++;
}
pw.println(prefix + "(Total messages: " + n + ", polling=" + isPollingLocked()
+ ", quitting=" + mQuitting + ")");
}
}
void writeToProto(ProtoOutputStream proto, long fieldId) {
final long messageQueueToken = proto.start(fieldId);
synchronized (this) {
for (Message msg = mMessages; msg != null; msg = msg.next) {
msg.writeToProto(proto, MessageQueueProto.MESSAGES);
}
proto.write(MessageQueueProto.IS_POLLING_LOCKED, isPollingLocked());
proto.write(MessageQueueProto.IS_QUITTING, mQuitting);
}
proto.end(messageQueueToken);
}
/**
* 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();
}
/**
* A listener which is invoked when file descriptor related events occur.
*/
public interface OnFileDescriptorEventListener {
/**
* File descriptor event: Indicates that the file descriptor is ready for input
* operations, such as reading.
* <p>
* The listener should read all available data from the file descriptor
* then return <code>true</code> to keep the listener active or <code>false</code>
* to remove the listener.
* </p><p>
* In the case of a socket, this event may be generated to indicate
* that there is at least one incoming connection that the listener
* should accept.
* </p><p>
* This event will only be generated if the {@link #EVENT_INPUT} event mask was
* specified when the listener was added.
* </p>
*/
public static final int EVENT_INPUT = 1 << 0;
/**
* File descriptor event: Indicates that the file descriptor is ready for output
* operations, such as writing.
* <p>
* The listener should write as much data as it needs. If it could not
* write everything at once, then it should return <code>true</code> to
* keep the listener active. Otherwise, it should return <code>false</code>
* to remove the listener then re-register it later when it needs to write
* something else.
* </p><p>
* This event will only be generated if the {@link #EVENT_OUTPUT} event mask was
* specified when the listener was added.
* </p>
*/
public static final int EVENT_OUTPUT = 1 << 1;
/**
* File descriptor event: Indicates that the file descriptor encountered a
* fatal error.
* <p>
* File descriptor errors can occur for various reasons. One common error
* is when the remote peer of a socket or pipe closes its end of the connection.
* </p><p>
* This event may be generated at any time regardless of whether the
* {@link #EVENT_ERROR} event mask was specified when the listener was added.
* </p>
*/
public static final int EVENT_ERROR = 1 << 2;
/** @hide */
@Retention(RetentionPolicy.SOURCE)
@IntDef(flag = true, prefix = { "EVENT_" }, value = {
EVENT_INPUT,
EVENT_OUTPUT,
EVENT_ERROR
})
public @interface Events {}
/**
* Called when a file descriptor receives events.
*
* @param fd The file descriptor.
* @param events The set of events that occurred: a combination of the
* {@link #EVENT_INPUT}, {@link #EVENT_OUTPUT}, and {@link #EVENT_ERROR} event masks.
* @return The new set of events to watch, or 0 to unregister the listener.
*
* @see #EVENT_INPUT
* @see #EVENT_OUTPUT
* @see #EVENT_ERROR
*/
@Events int onFileDescriptorEvents(@NonNull FileDescriptor fd, @Events int events);
}
private static final class FileDescriptorRecord {
public final FileDescriptor mDescriptor;
public int mEvents;
public OnFileDescriptorEventListener mListener;
public int mSeq;
public FileDescriptorRecord(FileDescriptor descriptor,
int events, OnFileDescriptorEventListener listener) {
mDescriptor = descriptor;
mEvents = events;
mListener = listener;
}
}
}