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 * 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
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package sun.java2d.pipe;

import sun.misc.Unsafe;


The RenderBuffer class is a simplified, high-performance, Unsafe wrapper
used for buffering rendering operations in a single-threaded rendering
environment.  It's functionality is similar to the ByteBuffer and related
NIO classes.  However, the methods in this class perform little to no
alignment or bounds checks for performance reasons.  Therefore, it is
the caller's responsibility to ensure that all put() calls are properly
aligned and within bounds:
  - int and float values must be aligned on 4-byte boundaries
  - long and double values must be aligned on 8-byte boundaries
This class only includes the bare minimum of methods to support
single-threaded rendering.  For example, there is no put(double[]) method
because we currently have no need for such a method in the STR classes.
/**
 * The RenderBuffer class is a simplified, high-performance, Unsafe wrapper
 * used for buffering rendering operations in a single-threaded rendering
 * environment.  It's functionality is similar to the ByteBuffer and related
 * NIO classes.  However, the methods in this class perform little to no
 * alignment or bounds checks for performance reasons.  Therefore, it is
 * the caller's responsibility to ensure that all put() calls are properly
 * aligned and within bounds:
 *   - int and float values must be aligned on 4-byte boundaries
 *   - long and double values must be aligned on 8-byte boundaries
 *
 * This class only includes the bare minimum of methods to support
 * single-threaded rendering.  For example, there is no put(double[]) method
 * because we currently have no need for such a method in the STR classes.
 */
public class RenderBuffer {

    
These constants represent the size of various data types (in bytes).
/**
     * These constants represent the size of various data types (in bytes).
     */
    protected static final long SIZEOF_BYTE   = 1L;
    protected static final long SIZEOF_SHORT  = 2L;
    protected static final long SIZEOF_INT    = 4L;
    protected static final long SIZEOF_FLOAT  = 4L;
    protected static final long SIZEOF_LONG   = 8L;
    protected static final long SIZEOF_DOUBLE = 8L;

    
Represents the number of elements at which we have empirically
determined that the average cost of a JNI call exceeds the expense
of an element by element copy.  In other words, if the number of
elements in an array to be copied exceeds this value, then we should
use the copyFromArray() method to complete the bulk put operation.
(This value can be adjusted if the cost of JNI downcalls is reduced
in a future release.)
/**
     * Represents the number of elements at which we have empirically
     * determined that the average cost of a JNI call exceeds the expense
     * of an element by element copy.  In other words, if the number of
     * elements in an array to be copied exceeds this value, then we should
     * use the copyFromArray() method to complete the bulk put operation.
     * (This value can be adjusted if the cost of JNI downcalls is reduced
     * in a future release.)
     */
    private static final int COPY_FROM_ARRAY_THRESHOLD = 6;

    protected final Unsafe unsafe;
    protected final long baseAddress;
    protected final long endAddress;
    protected long curAddress;
    protected final int capacity;

    protected RenderBuffer(int numBytes) {
        unsafe = Unsafe.getUnsafe();
        curAddress = baseAddress = unsafe.allocateMemory(numBytes);
        endAddress = baseAddress + numBytes;
        capacity = numBytes;
    }

    
Allocates a fresh buffer using the machine endianness.
/**
     * Allocates a fresh buffer using the machine endianness.
     */
    public static RenderBuffer allocate(int numBytes) {
        return new RenderBuffer(numBytes);
    }

    
Returns the base address of the underlying memory buffer.
/**
     * Returns the base address of the underlying memory buffer.
     */
    public final long getAddress() {
        return baseAddress;
    }

    
The behavior (and names) of the following methods are nearly
identical to their counterparts in the various NIO Buffer classes.
/**
     * The behavior (and names) of the following methods are nearly
     * identical to their counterparts in the various NIO Buffer classes.
     */

    public final int capacity() {
        return capacity;
    }

    public final int remaining() {
        return (int)(endAddress - curAddress);
    }

    public final int position() {
        return (int)(curAddress - baseAddress);
    }

    public final void position(long numBytes) {
        curAddress = baseAddress + numBytes;
    }

    public final void clear() {
        curAddress = baseAddress;
    }

    public final RenderBuffer skip(long numBytes) {
        curAddress += numBytes;
        return this;
    }

    
putByte() methods...
/**
     * putByte() methods...
     */

    public final RenderBuffer putByte(byte x) {
        unsafe.putByte(curAddress, x);
        curAddress += SIZEOF_BYTE;
        return this;
    }

    public RenderBuffer put(byte[] x) {
        return put(x, 0, x.length);
    }

    public RenderBuffer put(byte[] x, int offset, int length) {
        if (length > COPY_FROM_ARRAY_THRESHOLD) {
            long offsetInBytes = offset * SIZEOF_BYTE + Unsafe.ARRAY_BYTE_BASE_OFFSET;
            long lengthInBytes = length * SIZEOF_BYTE;
            unsafe.copyMemory(x, offsetInBytes, null, curAddress, lengthInBytes);
            position(position() + lengthInBytes);
        } else {
            int end = offset + length;
            for (int i = offset; i < end; i++) {
                putByte(x[i]);
            }
        }
        return this;
    }

    
putShort() methods...
/**
     * putShort() methods...
     */

    public final RenderBuffer putShort(short x) {
        // assert (position() % SIZEOF_SHORT == 0);
        unsafe.putShort(curAddress, x);
        curAddress += SIZEOF_SHORT;
        return this;
    }

    public RenderBuffer put(short[] x) {
        return put(x, 0, x.length);
    }

    public RenderBuffer put(short[] x, int offset, int length) {
        // assert (position() % SIZEOF_SHORT == 0);
        if (length > COPY_FROM_ARRAY_THRESHOLD) {
            long offsetInBytes = offset * SIZEOF_SHORT + Unsafe.ARRAY_SHORT_BASE_OFFSET;
            long lengthInBytes = length * SIZEOF_SHORT;
            unsafe.copyMemory(x, offsetInBytes, null, curAddress, lengthInBytes);
            position(position() + lengthInBytes);
        } else {
            int end = offset + length;
            for (int i = offset; i < end; i++) {
                putShort(x[i]);
            }
        }
        return this;
    }

    
putInt() methods...
/**
     * putInt() methods...
     */

    public final RenderBuffer putInt(int pos, int x) {
        // assert (baseAddress + pos % SIZEOF_INT == 0);
        unsafe.putInt(baseAddress + pos, x);
        return this;
    }

    public final RenderBuffer putInt(int x) {
        // assert (position() % SIZEOF_INT == 0);
        unsafe.putInt(curAddress, x);
        curAddress += SIZEOF_INT;
        return this;
    }

    public RenderBuffer put(int[] x) {
        return put(x, 0, x.length);
    }

    public RenderBuffer put(int[] x, int offset, int length) {
        // assert (position() % SIZEOF_INT == 0);
        if (length > COPY_FROM_ARRAY_THRESHOLD) {
            long offsetInBytes = offset * SIZEOF_INT + Unsafe.ARRAY_INT_BASE_OFFSET;
            long lengthInBytes = length * SIZEOF_INT;
            unsafe.copyMemory(x, offsetInBytes, null, curAddress, lengthInBytes);
            position(position() + lengthInBytes);
        } else {
            int end = offset + length;
            for (int i = offset; i < end; i++) {
                putInt(x[i]);
            }
        }
        return this;
    }

    
putFloat() methods...
/**
     * putFloat() methods...
     */

    public final RenderBuffer putFloat(float x) {
        // assert (position() % SIZEOF_FLOAT == 0);
        unsafe.putFloat(curAddress, x);
        curAddress += SIZEOF_FLOAT;
        return this;
    }

    public RenderBuffer put(float[] x) {
        return put(x, 0, x.length);
    }

    public RenderBuffer put(float[] x, int offset, int length) {
        // assert (position() % SIZEOF_FLOAT == 0);
        if (length > COPY_FROM_ARRAY_THRESHOLD) {
            long offsetInBytes = offset * SIZEOF_FLOAT + Unsafe.ARRAY_FLOAT_BASE_OFFSET;
            long lengthInBytes = length * SIZEOF_FLOAT;
            unsafe.copyMemory(x, offsetInBytes, null, curAddress, lengthInBytes);
            position(position() + lengthInBytes);
        } else {
            int end = offset + length;
            for (int i = offset; i < end; i++) {
                putFloat(x[i]);
            }
        }
        return this;
    }

    
putLong() methods...
/**
     * putLong() methods...
     */

    public final RenderBuffer putLong(long x) {
        // assert (position() % SIZEOF_LONG == 0);
        unsafe.putLong(curAddress, x);
        curAddress += SIZEOF_LONG;
        return this;
    }

    public RenderBuffer put(long[] x) {
        return put(x, 0, x.length);
    }

    public RenderBuffer put(long[] x, int offset, int length) {
        // assert (position() % SIZEOF_LONG == 0);
        if (length > COPY_FROM_ARRAY_THRESHOLD) {
            long offsetInBytes = offset * SIZEOF_LONG + Unsafe.ARRAY_LONG_BASE_OFFSET;
            long lengthInBytes = length * SIZEOF_LONG;
            unsafe.copyMemory(x, offsetInBytes, null, curAddress, lengthInBytes);
            position(position() + lengthInBytes);
        } else {
            int end = offset + length;
            for (int i = offset; i < end; i++) {
                putLong(x[i]);
            }
        }
        return this;
    }

    
putDouble() method(s)...
/**
     * putDouble() method(s)...
     */

    public final RenderBuffer putDouble(double x) {
        // assert (position() % SIZEOF_DOUBLE == 0);
        unsafe.putDouble(curAddress, x);
        curAddress += SIZEOF_DOUBLE;
        return this;
    }
}