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	/*
	* Copyright (c) 2005, 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 sun.java2d.pipe;

	import java.util.HashSet;
	import java.util.Set;
	import sun.awt.SunToolkit;

	/**
	* The RenderQueue class encapsulates a RenderBuffer on which rendering
	* operations are enqueued. Note that the RenderQueue lock must be acquired
	* before performing any operations on the queue (e.g. enqueuing an operation
	* or flushing the queue). A sample usage scenario follows:
	*
	* public void drawSomething(...) {
	* rq.lock();
	* try {
	* ctx.validate(...);
	* rq.ensureCapacity(4);
	* rq.getBuffer().putInt(DRAW_SOMETHING);
	* ...
	* } finally {
	* rq.unlock();
	* }
	* }
	*
	* If you are enqueuing an operation that involves 8-byte parameters (i.e.
	* long or double values), it is imperative that you ensure proper
	* alignment of the underlying RenderBuffer. This can be accomplished
	* simply by providing an offset to the first 8-byte parameter in your
	* operation to the ensureCapacityAndAlignment() method. For example:
	*
	* public void drawStuff(...) {
	* rq.lock();
	* try {
	* RenderBuffer buf = rq.getBuffer();
	* ctx.validate(...);
	* // 28 total bytes in the operation, 12 bytes to the first long
	* rq.ensureCapacityAndAlignment(28, 12);
	* buf.putInt(DRAW_STUFF);
	* buf.putInt(x).putInt(y);
	* buf.putLong(addr1);
	* buf.putLong(addr2);
	* } finally {
	* rq.unlock();
	* }
	* }
	*/
	public abstract class RenderQueue {

	/** The size of the underlying buffer, in bytes. */
	private static final int BUFFER_SIZE = 32000;

	/** The underlying buffer for this queue. */
	protected RenderBuffer buf;

	/**
	* A Set containing hard references to Objects that must stay alive until
	* the queue has been completely flushed.
	*/
	protected Set refSet;

	protected RenderQueue() {
	refSet = new HashSet();
	buf = RenderBuffer.allocate(BUFFER_SIZE);
	}

	/**
	* Locks the queue for read/write access.
	*/
	public final void lock() {
	/*
	* Implementation note: In theory we should have two separate locks:
	* one lock to synchronize access to the RenderQueue, and then a
	* separate lock (the AWT lock) that only needs to be acquired when
	* we are about to flush the queue (using native windowing system
	* operations). In practice it has been difficult to enforce the
	* correct lock ordering; sometimes AWT will have already acquired
	* the AWT lock before grabbing the RQ lock (see 6253009), while the
	* expected order should be RQ lock and then AWT lock. Due to this
	* issue, using two separate locks is prone to deadlocks. Therefore,
	* to solve this issue we have decided to eliminate the separate RQ
	* lock and instead just acquire the AWT lock here. (Someday it might
	* be nice to go back to the old two-lock system, but that would
	* require potentially risky changes to AWT to ensure that it never
	* acquires the AWT lock before calling into 2D code that wants to
	* acquire the RQ lock.)
	*/
	SunToolkit.awtLock();
	}

	/**
	* Attempts to lock the queue. If successful, this method returns true,
	* indicating that the caller is responsible for calling
	* <code>unlock</code>; otherwise this method returns false.
	*/
	public final boolean tryLock() {
	return SunToolkit.awtTryLock();
	}

	/**
	* Unlocks the queue.
	*/
	public final void unlock() {
	SunToolkit.awtUnlock();
	}

	/**
	* Adds the given Object to the set of hard references, which will
	* prevent that Object from being disposed until the queue has been
	* flushed completely. This is useful in cases where some enqueued
	* data could become invalid if the reference Object were garbage
	* collected before the queue could be processed. (For example, keeping
	* a hard reference to a FontStrike will prevent any enqueued glyph
	* images associated with that strike from becoming invalid before the
	* queue is flushed.) The reference set will be cleared immediately
	* after the queue is flushed each time.
	*/
	public final void addReference(Object ref) {
	refSet.add(ref);
	}

	/**
	* Returns the encapsulated RenderBuffer object.
	*/
	public final RenderBuffer getBuffer() {
	return buf;
	}

	/**
	* Ensures that there will be enough room on the underlying buffer
	* for the following operation. If the operation will not fit given
	* the remaining space, the buffer will be flushed immediately, leaving
	* an empty buffer for the impending operation.
	*
	* @param opsize size (in bytes) of the following operation
	*/
	public final void ensureCapacity(int opsize) {
	if (buf.remaining() < opsize) {
	flushNow();
	}
	}

	/**
	* Convenience method that is equivalent to calling ensureCapacity()
	* followed by ensureAlignment(). The ensureCapacity() call allows for an
	* extra 4 bytes of space in case the ensureAlignment() method needs to
	* insert a NOOP token on the buffer.
	*
	* @param opsize size (in bytes) of the following operation
	* @param first8ByteValueOffset offset (in bytes) from the current
	* position to the first 8-byte value used in the following operation
	*/
	public final void ensureCapacityAndAlignment(int opsize,
	int first8ByteValueOffset)
	{
	ensureCapacity(opsize + 4);
	ensureAlignment(first8ByteValueOffset);
	}

	/**
	* Inserts a 4-byte NOOP token when necessary to ensure that all 8-byte
	* parameters for the following operation are added to the underlying
	* buffer with an 8-byte memory alignment.
	*
	* @param first8ByteValueOffset offset (in bytes) from the current
	* position to the first 8-byte value used in the following operation
	*/
	public final void ensureAlignment(int first8ByteValueOffset) {
	int first8ByteValuePosition = buf.position() + first8ByteValueOffset;
	if ((first8ByteValuePosition & 7) != 0) {
	buf.putInt(BufferedOpCodes.NOOP);
	}
	}

	/**
	* Immediately processes each operation currently pending on the buffer.
	* This method will block until the entire buffer has been flushed. The
	* queue lock must be acquired before calling this method.
	*/
	public abstract void flushNow();

	/**
	* Immediately processes each operation currently pending on the buffer,
	* and then invokes the provided task. This method will block until the
	* entire buffer has been flushed and the provided task has been executed.
	* The queue lock must be acquired before calling this method.
	*/
	public abstract void flushAndInvokeNow(Runnable task);

	/**
	* Updates the current position of the underlying buffer, and then
	* flushes the queue immediately. This method is useful when native code
	* has added data to the queue and needs to flush immediately.
	*/
	public void flushNow(int position) {
	buf.position(position);
	flushNow();
	}
	}

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