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	/*
	* Copyright (c) 1998, 2017, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	package com.sun.tools.jdi;

	import com.sun.jdi.*;
	import com.sun.jdi.request.BreakpointRequest;
	import java.util.*;
	import java.lang.ref.WeakReference;

	public class ThreadReferenceImpl extends ObjectReferenceImpl
	implements ThreadReference, VMListener {
	static final int SUSPEND_STATUS_SUSPENDED = 0x1;
	static final int SUSPEND_STATUS_BREAK = 0x2;

	private int suspendedZombieCount = 0;

	/*
	* Some objects can only be created while a thread is suspended and are valid
	* only while the thread remains suspended. Examples are StackFrameImpl
	* and MonitorInfoImpl. When the thread resumes, these objects have to be
	* marked as invalid so that their methods can throw
	* InvalidStackFrameException if they are called. To do this, such objects
	* register themselves as listeners of the associated thread. When the
	* thread is resumed, its listeners are notified and mark themselves
	* invalid.
	* Also, note that ThreadReferenceImpl itself caches some info that
	* is valid only as long as the thread is suspended. When the thread
	* is resumed, that cache must be purged.
	* Lastly, note that ThreadReferenceImpl and its super, ObjectReferenceImpl
	* cache some info that is only valid as long as the entire VM is suspended.
	* If _any_ thread is resumed, this cache must be purged. To handle this,
	* both ThreadReferenceImpl and ObjectReferenceImpl register themselves as
	* VMListeners so that they get notified when all threads are suspended and
	* when any thread is resumed.
	*/

	// This is cached for the life of the thread
	private ThreadGroupReference threadGroup;

	// This is cached only while this one thread is suspended. Each time
	// the thread is resumed, we abandon the current cache object and
	// create a new initialized one.
	private static class LocalCache {
	JDWP.ThreadReference.Status status = null;
	List<StackFrame> frames = null;
	int framesStart = -1;
	int framesLength = 0;
	int frameCount = -1;
	List<ObjectReference> ownedMonitors = null;
	List<MonitorInfo> ownedMonitorsInfo = null;
	ObjectReference contendedMonitor = null;
	boolean triedCurrentContended = false;
	}

	/*
	* The localCache instance var is set by resetLocalCache to an initialized
	* object as shown above. This occurs when the ThreadReference
	* object is created, and when the mirrored thread is resumed.
	* The fields are then filled in by the relevant methods as they
	* are called. A problem can occur if resetLocalCache is called
	* (ie, a resume() is executed) at certain points in the execution
	* of some of these methods - see 6751643. To avoid this, each
	* method that wants to use this cache must make a local copy of
	* this variable and use that. This means that each invocation of
	* these methods will use a copy of the cache object that was in
	* effect at the point that the copy was made; if a racy resume
	* occurs, it won't affect the method's local copy. This means that
	* the values returned by these calls may not match the state of
	* the debuggee at the time the caller gets the values. EG,
	* frameCount() is called and comes up with 5 frames. But before
	* it returns this, a resume of the debuggee thread is executed in a
	* different debugger thread. The thread is resumed and running at
	* the time that the value 5 is returned. Or even worse, the thread
	* could be suspended again and have a different number of frames, eg, 24,
	* but this call will still return 5.
	*/
	private LocalCache localCache;

	private void resetLocalCache() {
	localCache = new LocalCache();
	}

	// This is cached only while all threads in the VM are suspended
	// Yes, someone could change the name of a thread while it is suspended.
	private static class Cache extends ObjectReferenceImpl.Cache {
	String name = null;
	}
	protected ObjectReferenceImpl.Cache newCache() {
	return new Cache();
	}

	// Listeners - synchronized on vm.state()
	private List<WeakReference<ThreadListener>> listeners = new ArrayList<WeakReference<ThreadListener>>();


	ThreadReferenceImpl(VirtualMachine aVm, long aRef) {
	super(aVm,aRef);
	resetLocalCache();
	vm.state().addListener(this);
	}

	protected String description() {
	return "ThreadReference " + uniqueID();
	}

	/*
	* VMListener implementation
	*/
	public boolean vmNotSuspended(VMAction action) {
	if (action.resumingThread() == null) {
	// all threads are being resumed
	synchronized (vm.state()) {
	processThreadAction(new ThreadAction(this,
	ThreadAction.THREAD_RESUMABLE));
	}

	}

	/*
	* Othewise, only one thread is being resumed:
	* if it is us,
	* we have already done our processThreadAction to notify our
	* listeners when we processed the resume.
	* if it is not us,
	* we don't want to notify our listeners
	* because we are not being resumed.
	*/
	return super.vmNotSuspended(action);
	}

	/**
	* Note that we only cache the name string while the entire VM is suspended
	* because the name can change via Thread.setName arbitrarily while this
	* thread is running.
	*/
	public String name() {
	String name = null;
	try {
	Cache local = (Cache)getCache();

	if (local != null) {
	name = local.name;
	}
	if (name == null) {
	name = JDWP.ThreadReference.Name.process(vm, this)
	.threadName;
	if (local != null) {
	local.name = name;
	}
	}
	} catch (JDWPException exc) {
	throw exc.toJDIException();
	}
	return name;
	}

	/*
	* Sends a command to the back end which is defined to do an
	* implicit vm-wide resume.
	*/
	PacketStream sendResumingCommand(CommandSender sender) {
	synchronized (vm.state()) {
	processThreadAction(new ThreadAction(this,
	ThreadAction.THREAD_RESUMABLE));
	return sender.send();
	}
	}

	public void suspend() {
	try {
	JDWP.ThreadReference.Suspend.process(vm, this);
	} catch (JDWPException exc) {
	throw exc.toJDIException();
	}
	// Don't consider the thread suspended yet. On reply, notifySuspend()
	// will be called.
	}

	public void resume() {
	/*
	* If it's a zombie, we can just update internal state without
	* going to back end.
	*/
	if (suspendedZombieCount > 0) {
	suspendedZombieCount--;
	return;
	}

	PacketStream stream;
	synchronized (vm.state()) {
	processThreadAction(new ThreadAction(this,
	ThreadAction.THREAD_RESUMABLE));
	stream = JDWP.ThreadReference.Resume.enqueueCommand(vm, this);
	}
	try {
	JDWP.ThreadReference.Resume.waitForReply(vm, stream);
	} catch (JDWPException exc) {
	throw exc.toJDIException();
	}
	}

	public int suspendCount() {
	/*
	* If it's a zombie, we maintain the count in the front end.
	*/
	if (suspendedZombieCount > 0) {
	return suspendedZombieCount;
	}

	try {
	return JDWP.ThreadReference.SuspendCount.process(vm, this).suspendCount;
	} catch (JDWPException exc) {
	throw exc.toJDIException();
	}
	}

	public void stop(ObjectReference throwable) throws InvalidTypeException {
	validateMirrorOrNull(throwable);
	// Verify that the given object is a Throwable instance
	List<ReferenceType> list = vm.classesByName("java.lang.Throwable");
	ClassTypeImpl throwableClass = (ClassTypeImpl)list.get(0);
	if ((throwable == null) \|\|
	!throwableClass.isAssignableFrom(throwable)) {
	throw new InvalidTypeException("Not an instance of Throwable");
	}

	try {
	JDWP.ThreadReference.Stop.process(vm, this,
	(ObjectReferenceImpl)throwable);
	} catch (JDWPException exc) {
	throw exc.toJDIException();
	}
	}

	public void interrupt() {
	try {
	JDWP.ThreadReference.Interrupt.process(vm, this);
	} catch (JDWPException exc) {
	throw exc.toJDIException();
	}
	}

	private JDWP.ThreadReference.Status jdwpStatus() {
	LocalCache snapshot = localCache;
	JDWP.ThreadReference.Status myStatus = snapshot.status;
	try {
	if (myStatus == null) {
	myStatus = JDWP.ThreadReference.Status.process(vm, this);
	if ((myStatus.suspendStatus & SUSPEND_STATUS_SUSPENDED) != 0) {
	// thread is suspended, we can cache the status.
	snapshot.status = myStatus;
	}
	}
	} catch (JDWPException exc) {
	throw exc.toJDIException();
	}
	return myStatus;
	}

	public int status() {
	return jdwpStatus().threadStatus;
	}

	public boolean isSuspended() {
	return ((suspendedZombieCount > 0) \|\|
	((jdwpStatus().suspendStatus & SUSPEND_STATUS_SUSPENDED) != 0));
	}

	public boolean isAtBreakpoint() {
	/*
	* TO DO: This fails to take filters into account.
	*/
	try {
	StackFrame frame = frame(0);
	Location location = frame.location();
	List<BreakpointRequest> requests = vm.eventRequestManager().breakpointRequests();
	Iterator<BreakpointRequest> iter = requests.iterator();
	while (iter.hasNext()) {
	BreakpointRequest request = iter.next();
	if (location.equals(request.location())) {
	return true;
	}
	}
	return false;
	} catch (IndexOutOfBoundsException iobe) {
	return false; // no frames on stack => not at breakpoint
	} catch (IncompatibleThreadStateException itse) {
	// Per the javadoc, not suspended => return false
	return false;
	}
	}

	public ThreadGroupReference threadGroup() {
	/*
	* Thread group can't change, so it's cached once and for all.
	*/
	if (threadGroup == null) {
	try {
	threadGroup = JDWP.ThreadReference.ThreadGroup.
	process(vm, this).group;
	} catch (JDWPException exc) {
	throw exc.toJDIException();
	}
	}
	return threadGroup;
	}

	public int frameCount() throws IncompatibleThreadStateException {
	LocalCache snapshot = localCache;
	try {
	if (snapshot.frameCount == -1) {
	snapshot.frameCount = JDWP.ThreadReference.FrameCount
	.process(vm, this).frameCount;
	}
	} catch (JDWPException exc) {
	switch (exc.errorCode()) {
	case JDWP.Error.THREAD_NOT_SUSPENDED:
	case JDWP.Error.INVALID_THREAD: /* zombie */
	throw new IncompatibleThreadStateException();
	default:
	throw exc.toJDIException();
	}
	}
	return snapshot.frameCount;
	}

	public List<StackFrame> frames() throws IncompatibleThreadStateException {
	return privateFrames(0, -1);
	}

	public StackFrame frame(int index) throws IncompatibleThreadStateException {
	List<StackFrame> list = privateFrames(index, 1);
	return list.get(0);
	}

	/**
	* Is the requested subrange within what has been retrieved?
	* local is known to be non-null. Should only be called from
	* a sync method.
	*/
	private boolean isSubrange(LocalCache snapshot,
	int start, int length) {
	if (start < snapshot.framesStart) {
	return false;
	}
	if (length == -1) {
	return (snapshot.framesLength == -1);
	}
	if (snapshot.framesLength == -1) {
	if ((start + length) > (snapshot.framesStart +
	snapshot.frames.size())) {
	throw new IndexOutOfBoundsException();
	}
	return true;
	}
	return ((start + length) <= (snapshot.framesStart + snapshot.framesLength));
	}

	public List<StackFrame> frames(int start, int length)
	throws IncompatibleThreadStateException {
	if (length < 0) {
	throw new IndexOutOfBoundsException(
	"length must be greater than or equal to zero");
	}
	return privateFrames(start, length);
	}

	/**
	* Private version of frames() allows "-1" to specify all
	* remaining frames.
	*/
	synchronized private List<StackFrame> privateFrames(int start, int length)
	throws IncompatibleThreadStateException {

	// Lock must be held while creating stack frames so if that two threads
	// do this at the same time, one won't clobber the subset created by the other.
	LocalCache snapshot = localCache;
	try {
	if (snapshot.frames == null \|\| !isSubrange(snapshot, start, length)) {
	JDWP.ThreadReference.Frames.Frame[] jdwpFrames
	= JDWP.ThreadReference.Frames.
	process(vm, this, start, length).frames;
	int count = jdwpFrames.length;
	snapshot.frames = new ArrayList<StackFrame>(count);

	for (int i = 0; i<count; i++) {
	if (jdwpFrames[i].location == null) {
	throw new InternalException("Invalid frame location");
	}
	StackFrame frame = new StackFrameImpl(vm, this,
	jdwpFrames[i].frameID,
	jdwpFrames[i].location);
	// Add to the frame list
	snapshot.frames.add(frame);
	}
	snapshot.framesStart = start;
	snapshot.framesLength = length;
	return Collections.unmodifiableList(snapshot.frames);
	} else {
	int fromIndex = start - snapshot.framesStart;
	int toIndex;
	if (length == -1) {
	toIndex = snapshot.frames.size() - fromIndex;
	} else {
	toIndex = fromIndex + length;
	}
	return Collections.unmodifiableList(snapshot.frames.subList(fromIndex, toIndex));
	}
	} catch (JDWPException exc) {
	switch (exc.errorCode()) {
	case JDWP.Error.THREAD_NOT_SUSPENDED:
	case JDWP.Error.INVALID_THREAD: /* zombie */
	throw new IncompatibleThreadStateException();
	default:
	throw exc.toJDIException();
	}
	}
	}

	public List<ObjectReference> ownedMonitors() throws IncompatibleThreadStateException {
	LocalCache snapshot = localCache;
	try {
	if (snapshot.ownedMonitors == null) {
	snapshot.ownedMonitors = Arrays.asList(
	(ObjectReference[])JDWP.ThreadReference.OwnedMonitors.
	process(vm, this).owned);
	if ((vm.traceFlags & VirtualMachine.TRACE_OBJREFS) != 0) {
	vm.printTrace(description() +
	" temporarily caching owned monitors"+
	" (count = " + snapshot.ownedMonitors.size() + ")");
	}
	}
	} catch (JDWPException exc) {
	switch (exc.errorCode()) {
	case JDWP.Error.THREAD_NOT_SUSPENDED:
	case JDWP.Error.INVALID_THREAD: /* zombie */
	throw new IncompatibleThreadStateException();
	default:
	throw exc.toJDIException();
	}
	}
	return snapshot.ownedMonitors;
	}

	public ObjectReference currentContendedMonitor()
	throws IncompatibleThreadStateException {
	LocalCache snapshot = localCache;
	try {
	if (snapshot.contendedMonitor == null &&
	!snapshot.triedCurrentContended) {
	snapshot.contendedMonitor = JDWP.ThreadReference.CurrentContendedMonitor.
	process(vm, this).monitor;
	snapshot.triedCurrentContended = true;
	if ((snapshot.contendedMonitor != null) &&
	((vm.traceFlags & VirtualMachine.TRACE_OBJREFS) != 0)) {
	vm.printTrace(description() +
	" temporarily caching contended monitor"+
	" (id = " + snapshot.contendedMonitor.uniqueID() + ")");
	}
	}
	} catch (JDWPException exc) {
	switch (exc.errorCode()) {
	case JDWP.Error.THREAD_NOT_SUSPENDED:
	case JDWP.Error.INVALID_THREAD: /* zombie */
	throw new IncompatibleThreadStateException();
	default:
	throw exc.toJDIException();
	}
	}
	return snapshot.contendedMonitor;
	}

	public List<MonitorInfo> ownedMonitorsAndFrames() throws IncompatibleThreadStateException {
	LocalCache snapshot = localCache;
	try {
	if (snapshot.ownedMonitorsInfo == null) {
	JDWP.ThreadReference.OwnedMonitorsStackDepthInfo.monitor[] minfo;
	minfo = JDWP.ThreadReference.OwnedMonitorsStackDepthInfo.process(vm, this).owned;

	snapshot.ownedMonitorsInfo = new ArrayList<MonitorInfo>(minfo.length);

	for (int i=0; i < minfo.length; i++) {
	JDWP.ThreadReference.OwnedMonitorsStackDepthInfo.monitor mi =
	minfo[i];
	MonitorInfo mon = new MonitorInfoImpl(vm, minfo[i].monitor, this, minfo[i].stack_depth);
	snapshot.ownedMonitorsInfo.add(mon);
	}

	if ((vm.traceFlags & VirtualMachine.TRACE_OBJREFS) != 0) {
	vm.printTrace(description() +
	" temporarily caching owned monitors"+
	" (count = " + snapshot.ownedMonitorsInfo.size() + ")");
	}
	}

	} catch (JDWPException exc) {
	switch (exc.errorCode()) {
	case JDWP.Error.THREAD_NOT_SUSPENDED:
	case JDWP.Error.INVALID_THREAD: /* zombie */
	throw new IncompatibleThreadStateException();
	default:
	throw exc.toJDIException();
	}
	}
	return snapshot.ownedMonitorsInfo;
	}

	public void popFrames(StackFrame frame) throws IncompatibleThreadStateException {
	// Note that interface-wise this functionality belongs
	// here in ThreadReference, but implementation-wise it
	// belongs in StackFrame, so we just forward it.
	if (!frame.thread().equals(this)) {
	throw new IllegalArgumentException("frame does not belong to this thread");
	}
	if (!vm.canPopFrames()) {
	throw new UnsupportedOperationException(
	"target does not support popping frames");
	}
	((StackFrameImpl)frame).pop();
	}

	public void forceEarlyReturn(Value returnValue) throws InvalidTypeException,
	ClassNotLoadedException,
	IncompatibleThreadStateException {
	if (!vm.canForceEarlyReturn()) {
	throw new UnsupportedOperationException(
	"target does not support the forcing of a method to return early");
	}

	validateMirrorOrNull(returnValue);

	StackFrameImpl sf;
	try {
	sf = (StackFrameImpl)frame(0);
	} catch (IndexOutOfBoundsException exc) {
	throw new InvalidStackFrameException("No more frames on the stack");
	}
	sf.validateStackFrame();
	MethodImpl meth = (MethodImpl)sf.location().method();
	ValueImpl convertedValue = ValueImpl.prepareForAssignment(returnValue,
	meth.getReturnValueContainer());

	try {
	JDWP.ThreadReference.ForceEarlyReturn.process(vm, this, convertedValue);
	} catch (JDWPException exc) {
	switch (exc.errorCode()) {
	case JDWP.Error.OPAQUE_FRAME:
	throw new NativeMethodException();
	case JDWP.Error.THREAD_NOT_SUSPENDED:
	throw new IncompatibleThreadStateException(
	"Thread not suspended");
	case JDWP.Error.THREAD_NOT_ALIVE:
	throw new IncompatibleThreadStateException(
	"Thread has not started or has finished");
	case JDWP.Error.NO_MORE_FRAMES:
	throw new InvalidStackFrameException(
	"No more frames on the stack");
	default:
	throw exc.toJDIException();
	}
	}
	}

	public String toString() {
	return "instance of " + referenceType().name() +
	"(name='" + name() + "', " + "id=" + uniqueID() + ")";
	}

	byte typeValueKey() {
	return JDWP.Tag.THREAD;
	}

	void addListener(ThreadListener listener) {
	synchronized (vm.state()) {
	listeners.add(new WeakReference<ThreadListener>(listener));
	}
	}

	void removeListener(ThreadListener listener) {
	synchronized (vm.state()) {
	Iterator<WeakReference<ThreadListener>> iter = listeners.iterator();
	while (iter.hasNext()) {
	WeakReference<ThreadListener> ref = iter.next();
	if (listener.equals(ref.get())) {
	iter.remove();
	break;
	}
	}
	}
	}

	/**
	* Propagate the the thread state change information
	* to registered listeners.
	* Must be entered while synchronized on vm.state()
	*/
	private void processThreadAction(ThreadAction action) {
	synchronized (vm.state()) {
	Iterator<WeakReference<ThreadListener>> iter = listeners.iterator();
	while (iter.hasNext()) {
	WeakReference<ThreadListener> ref = iter.next();
	ThreadListener listener = ref.get();
	if (listener != null) {
	switch (action.id()) {
	case ThreadAction.THREAD_RESUMABLE:
	if (!listener.threadResumable(action)) {
	iter.remove();
	}
	break;
	}
	} else {
	// Listener is unreachable; clean up
	iter.remove();
	}
	}

	// Discard our local cache
	resetLocalCache();
	}
	}
	}

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