Java多线程深入学习-atomic原子类实现-AtomicIntegerArray源码分析

/**
 * AtomicIntegerArray 原子操作IntegerArray的类
 */
public class AtomicIntegerArray implements java.io.Serializable {
    private static final long serialVersionUID = 2862133569453604235L;

    /** 引入Unsafe类 */
    private static final Unsafe unsafe = Unsafe.getUnsafe();
    private static final int base = unsafe.arrayBaseOffset(int[].class);	//数组类型的第一个元素的偏移地址
    private static final int shift; //偏移地址的增量 的二进制有效位数
    /** 存放数据的数组 */
    private final int[] array;

    static {
        int scale = unsafe.arrayIndexScale(int[].class);	//数组中元素与元素之间的偏移地址的增量 
        if ((scale & (scale - 1)) != 0) //scale不是2的n次方
            throw new Error("data type scale not a power of two");
        /*
         * Integer.numberOfLeadingZeros(scale) 获取scale转换成二进制后 前面有多少位是0
         */
        shift = 31 - Integer.numberOfLeadingZeros(scale);	//二进制有效数据位数
    }
    /** 获取下标位i的数据的偏移地址 */
    private long checkedByteOffset(int i) {
        if (i < 0 || i >= array.length)
            throw new IndexOutOfBoundsException("index " + i);
        return byteOffset(i);
    }
    private static long byteOffset(int i) {
        return ((long) i << shift) + base;
    }

    /**
     * 构造
     */
    public AtomicIntegerArray(int length) {
        array = new int[length];
    }
    public AtomicIntegerArray(int[] array) {
        this.array = array.clone();
    }
    /** 返回数组大小 */
    public final int length() {
        return array.length;
    }
    /** 获取指定下标数据 */
    public final int get(int i) {
        return getRaw(checkedByteOffset(i));
    }
    private int getRaw(long offset) {
        return unsafe.getIntVolatile(array, offset);	//unsafe操作直接获取对应地址的数据
    }

    /**
     * 指定下标赋值
     */
    public final void set(int i, int newValue) {
        unsafe.putIntVolatile(array, checkedByteOffset(i), newValue);//unsafe操作直接赋值对应地址的数据
    }
    public final void lazySet(int i, int newValue) {
        unsafe.putOrderedInt(array, checkedByteOffset(i), newValue);
    }

    /**
     * 获取并修改值
     */
    public final int getAndSet(int i, int newValue) {
        return unsafe.getAndSetInt(array, checkedByteOffset(i), newValue);
    }

    /**
     * 比较并修改
     */
    public final boolean compareAndSet(int i, int expect, int update) {
        return compareAndSetRaw(checkedByteOffset(i), expect, update);
    }
    private boolean compareAndSetRaw(long offset, int expect, int update) {
        return unsafe.compareAndSwapInt(array, offset, expect, update);
    }
    public final boolean weakCompareAndSet(int i, int expect, int update) {
        return compareAndSet(i, expect, update);
    }

    /**
     * 对应下标数据+1和-1操作
     */
    public final int getAndIncrement(int i) {
        return getAndAdd(i, 1);
    }
    public final int getAndDecrement(int i) {
        return getAndAdd(i, -1);
    }

    /**
     * 对应下标数据加操作  返回操作前的值
     */
    public final int getAndAdd(int i, int delta) {
        return unsafe.getAndAddInt(array, checkedByteOffset(i), delta);
    }

    /**
     * 对应下标数据加减操作  返回操作后的值
     */
    public final int incrementAndGet(int i) {
        return getAndAdd(i, 1) + 1;
    }
    public final int decrementAndGet(int i) {
        return getAndAdd(i, -1) - 1;
    }
    public final int addAndGet(int i, int delta) {
        return getAndAdd(i, delta) + delta;
    }


    /**
     * 获取并修改
     */
    public final int getAndUpdate(int i, IntUnaryOperator updateFunction) {
        long offset = checkedByteOffset(i);
        int prev, next;
        do {
            prev = getRaw(offset);
            next = updateFunction.applyAsInt(prev);
        } while (!compareAndSetRaw(offset, prev, next));	//循环操作直到操作成功
        return prev;
    }

    /**
     * 修改并获取
     */
    public final int updateAndGet(int i, IntUnaryOperator updateFunction) {
        long offset = checkedByteOffset(i);
        int prev, next;
        do {
            prev = getRaw(offset);
            next = updateFunction.applyAsInt(prev);
        } while (!compareAndSetRaw(offset, prev, next));	//循环操作直到操作成功
        return next;
    }

    /**
     * 根据传入函数式接口对指定下标数据进行操作
     */
    public final int getAndAccumulate(int i, int x,
                                      IntBinaryOperator accumulatorFunction) {
        long offset = checkedByteOffset(i);
        int prev, next;
        do {
            prev = getRaw(offset);
            next = accumulatorFunction.applyAsInt(prev, x);
        } while (!compareAndSetRaw(offset, prev, next));
        return prev;
    }
    public final int accumulateAndGet(int i, int x,
                                      IntBinaryOperator accumulatorFunction) {
        long offset = checkedByteOffset(i);
        int prev, next;
        do {
            prev = getRaw(offset);
            next = accumulatorFunction.applyAsInt(prev, x);
        } while (!compareAndSetRaw(offset, prev, next));
        return next;
    }

    public String toString() {
        int iMax = array.length - 1;
        if (iMax == -1)
            return "[]";

        StringBuilder b = new StringBuilder();
        b.append('[');
        for (int i = 0; ; i++) {
            b.append(getRaw(byteOffset(i)));
            if (i == iMax)
                return b.append(']').toString();
            b.append(',').append(' ');
        }
    }

}