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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();    }}