java的AtomicBitSet实现 [英] AtomicBitSet implementation for java

问题描述

标准api不包括AtomicBitSet实现。我可以在AtomicIntegerArray之上滚动我自己，但也不喜欢。

The standard api does not include an AtomicBitSet implementation. I could roll my own on top of AtomicIntegerArray, but would prefer not too.

有没有人知道与Apache 2兼容的许可证下发布的现有实现？我只需要基本操作来设置和检查位。

Is anyone aware of an existing implementation released under a licence compatible with Apache 2? I require only basic operations to set and check bits.

编辑：

代码是性能和内存如果可能，我想避免同步或每个标志的整数。

The code is both performance and memory critical so I'd like to avoid synchronization or an integer per flag if possible.

推荐答案

我会使用AtomicIntegerArray，每个整数使用32个标志，这将给你与BitSet相同的密度，但不需要锁线程安全。

I would use an AtomicIntegerArray and I would use 32 flags per integer which would give you the same density as BitSet but without needing locks for thread safety.

public class AtomicBitSet {
    private final AtomicIntegerArray array;

    public AtomicBitSet(int length) {
        int intLength = (length + 31) / 32;
        array = new AtomicIntegerArray(intLength);
    }

    public void set(long n) {
        int bit = 1 << n;
        int idx = (int) (n >>> 5);
        while (true) {
            int num = array.get(idx);
            int num2 = num | bit;
            if (num == num2 || array.compareAndSet(idx, num, num2))
                return;
        }
    }

    public boolean get(long n) {
        int bit = 1 << n;
        int idx = (int) (n >>> 5);
        int num = array.get(idx);
        return (num & bit) != 0;
    }
}

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