Class ConcurrentPool

core/src/main/java/io/questdb/mp/ConcurrentPool.java:30–74

import java.util.concurrent.atomic.AtomicInteger;

public class ConcurrentPool<T> {
    @SuppressWarnings("rawtypes")
    public static final ConcurrentSegmentManipulator POOL_MANIPULATOR = new ConcurrentSegmentManipulator() {

        @Override
        public Object dequeue(ConcurrentQueueSegment.Slot[] slots, int slotsIndex, Object unused) {
            var val = slots[slotsIndex].item;
            slots[slotsIndex].item = null;
            return val;
        }

        @Override
        public void enqueue(Object item, ConcurrentQueueSegment.Slot[] slots, int slotsIndex) {
            slots[slotsIndex].item = item;
        }
    };
    private final AtomicInteger count = new AtomicInteger(0);
    private final ConcurrentQueue<T> queue;

    public ConcurrentPool() {
        //noinspection unchecked
        this.queue = new ConcurrentQueue<T>(() -> null, POOL_MANIPULATOR);
    }

    public int capacity() {
        return queue.capacity();
    }

    public int count() {
        return count.get();
    }

    public T pop() {
        T val = queue.tryDequeueValue(null);
        if (val != null) {
            count.decrementAndGet();
        }
        return val;
    }

    public void push(T item) {
        queue.enqueue(item);
        count.incrementAndGet();
    }
}