HeapDoubleBufferR.java

/*
 * Copyright (c) 2000, 2016, 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 java.nio;

/**
 * A read-only HeapDoubleBuffer.  This class extends the corresponding
 * read/write class, overriding the mutation methods to throw a {@link
 * ReadOnlyBufferException} and overriding the view-buffer methods to return an
 * instance of this class rather than of the superclass.
 */

// 只读、非直接缓冲区，是HeapDoubleBuffer的只读版本，禁止写入操作，内部存储结构实现为double[]
class HeapDoubleBufferR extends HeapDoubleBuffer {
    
    // Cached array base offset
    private static final long ARRAY_BASE_OFFSET = UNSAFE.arrayBaseOffset(double[].class);
    // Cached array base offset
    private static final long ARRAY_INDEX_SCALE = UNSAFE.arrayIndexScale(double[].class);
    
    
    /*▼ 构造方法 ████████████████████████████████████████████████████████████████████████████████┓ */
    
    protected HeapDoubleBufferR(double[] buf, int mark, int pos, int lim, int cap, int off) {
        super(buf, mark, pos, lim, cap, off);
        this.isReadOnly = true;
    }
    
    HeapDoubleBufferR(int cap, int lim) {            // package-private
        super(cap, lim);
        this.isReadOnly = true;
    }
    
    HeapDoubleBufferR(double[] buf, int off, int len) { // package-private
        super(buf, off, len);
        this.isReadOnly = true;
    }
    
    /*▲ 构造方法 ████████████████████████████████████████████████████████████████████████████████┛ */
    
    
    
    /*▼ 只读/非直接 ████████████████████████████████████████████████████████████████████████████████┓ */
    
    public boolean isReadOnly() {
        return true;
    }
    
    /*▲ 只读/非直接 ████████████████████████████████████████████████████████████████████████████████┛ */
    
    
    /*▼ 创建新缓冲区，新旧缓冲区共享内部的存储容器 ████████████████████████████████████████████████████████████████████████████████┓ */
    
    public DoubleBuffer slice() {
        return new HeapDoubleBufferR(hb, -1, 0, this.remaining(), this.remaining(), this.position() + offset);
    }
    
    public DoubleBuffer duplicate() {
        return new HeapDoubleBufferR(hb, this.markValue(), this.position(), this.limit(), this.capacity(), offset);
    }
    
    public DoubleBuffer asReadOnlyBuffer() {
        return duplicate();
    }
    
    /*▲ 创建新缓冲区，新旧缓冲区共享内部的存储容器 ████████████████████████████████████████████████████████████████████████████████┛ */
    
    
    
    /*▼ 只读缓冲区，禁止写入操作 ████████████████████████████████████████████████████████████████████████████████┓ */
    
    public DoubleBuffer put(double x) {
        throw new ReadOnlyBufferException();
    }
    
    public DoubleBuffer put(int i, double x) {
        throw new ReadOnlyBufferException();
    }
    
    public DoubleBuffer put(double[] src, int offset, int length) {
        throw new ReadOnlyBufferException();
    }
    
    public DoubleBuffer put(DoubleBuffer src) {
        throw new ReadOnlyBufferException();
    }
    
    /*▲ 只读缓冲区，禁止写入操作 ████████████████████████████████████████████████████████████████████████████████┛ */
    
    
    
    /*▼ 禁止压缩，因为禁止写入，压缩没意义 ████████████████████████████████████████████████████████████████████████████████┓ */
    
    public DoubleBuffer compact() {
        throw new ReadOnlyBufferException();
    }
    
    /*▲ 禁止压缩，因为禁止写入，压缩没意义 ████████████████████████████████████████████████████████████████████████████████┛ */
    
    
    
    /*▼ 字节顺序 ████████████████████████████████████████████████████████████████████████████████┓ */
    
    public ByteOrder order() {
        return ByteOrder.nativeOrder();
    }
    
    /*▲ 字节顺序 ████████████████████████████████████████████████████████████████████████████████┛ */
}