library/cpp/threading/equeue/equeue.cpp


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#include "equeue.h"

TElasticQueue::TElasticQueue(THolder<IThreadPool> slaveQueue)
    : SlaveQueue_(std::move(slaveQueue))
{
}

size_t TElasticQueue::ObjectCount() const {
    return (size_t)AtomicGet(ObjectCount_);
}

bool TElasticQueue::TryIncCounter() {
    if ((size_t)AtomicIncrement(GuardCount_) > MaxQueueSize_) {
        AtomicDecrement(GuardCount_);
        return false;
    }

    return true;
}


class TElasticQueue::TDecrementingWrapper: TNonCopyable, public IObjectInQueue {
public:
    TDecrementingWrapper(IObjectInQueue* realObject, TElasticQueue* queue)
        : RealObject_(realObject)
        , Queue_(queue)
    {
        AtomicIncrement(Queue_->ObjectCount_);
    }

    ~TDecrementingWrapper() override {
        AtomicDecrement(Queue_->ObjectCount_);
        AtomicDecrement(Queue_->GuardCount_);
    }
private:
    void Process(void *tsr) override {
        THolder<TDecrementingWrapper> self(this);
        RealObject_->Process(tsr);
    }
private:
    IObjectInQueue* const RealObject_;
    TElasticQueue* const Queue_;
};


bool TElasticQueue::Add(IObjectInQueue* obj) {
    if (!TryIncCounter()) {
        return false;
    }

    THolder<TDecrementingWrapper> wrapper;
    try {
        wrapper.Reset(new TDecrementingWrapper(obj, this));
    } catch (...) {
        AtomicDecrement(GuardCount_);
        throw;
    }

    if (SlaveQueue_->Add(wrapper.Get())) {
        Y_UNUSED(wrapper.Release());
        return true;
    } else {
        return false;
    }
}

void TElasticQueue::Start(size_t threadCount, size_t maxQueueSize) {
    MaxQueueSize_ = maxQueueSize;
    SlaveQueue_->Start(threadCount, maxQueueSize);
}

void TElasticQueue::Stop() noexcept {
    return SlaveQueue_->Stop();
}

size_t TElasticQueue::Size() const noexcept {
    return SlaveQueue_->Size();
}