ring_queue.h

#pragma once
 
namespace resumef
{
    //使用自旋锁完成的线程安全的环形队列。
    //支持多个线程同时push和pop。
    //_Option : 如果队列保存的数据不支持拷贝只支持移动，则需要设置为true；或者数据希望pop后销毁，都需要设置为true。
    //_Sty : 内存保持数量和索引的整数类型。用于外部控制队列的结构体大小。
    template<class _Ty, bool _Option = false, class _Sty = uint32_t>
    struct ring_queue
    {
        using value_type = _Ty;
        using size_type = _Sty;
 
        static constexpr bool use_option = _Option;
        using optional_type = std::conditional_t<use_option, std::optional<value_type>, value_type>;
    public:
        ring_queue(size_t sz);
 
        ring_queue(const ring_queue&) = delete;
        ring_queue(ring_queue&&) = default;
        ring_queue& operator =(const ring_queue&) = delete;
        ring_queue& operator =(ring_queue&&) = default;
 
        auto size() const noexcept->size_type;
        auto capacity() const noexcept->size_type;
        bool empty() const noexcept;
        bool full() const noexcept;
        template<class U>
        bool try_push(U&& value) noexcept(std::is_nothrow_move_assignable_v<U>);
        template<class U>
        bool try_pop(U& value) noexcept(std::is_nothrow_move_assignable_v<value_type>);
    private:
        using container_type = std::unique_ptr<optional_type[]>;
        container_type m_bufferPtr;
        size_type m_bufferSize;
 
        size_type m_writeIndex;
        size_type m_readIndex;
    #ifdef _WITH_LOCK_FREE_Q_KEEP_REAL_SIZE
        std::atomic<size_type> m_count;
    #endif
 
        auto nextIndex(size_type a_count) const noexcept->size_type;
    };
 
    template<class _Ty, bool _Option, class _Sty>
    ring_queue<_Ty, _Option, _Sty>::ring_queue(size_t sz)
        : m_bufferPtr(new optional_type[sz + 1])
        , m_bufferSize(static_cast<size_type>(sz + 1))
        , m_writeIndex(0)
        , m_readIndex(0)
    #ifdef _WITH_LOCK_FREE_Q_KEEP_REAL_SIZE
        , m_count(0)
    #endif
    {
        assert(sz < (std::numeric_limits<size_type>::max)());
    }
 
    template<class _Ty, bool _Option, class _Sty>
    auto ring_queue<_Ty, _Option, _Sty>::nextIndex(size_type a_count) const noexcept->size_type
    {
        return static_cast<size_type>((a_count + 1) % m_bufferSize);
    }
 
    template<class _Ty, bool _Option, class _Sty>
    auto ring_queue<_Ty, _Option, _Sty>::size() const noexcept->size_type
    {
    #ifdef _WITH_LOCK_FREE_Q_KEEP_REAL_SIZE
        return m_count.load(std::memory_order_acquire);
    #else
        if (m_writeIndex >= m_readIndex)
            return (m_writeIndex - m_readIndex);
        else
            return (m_bufferSize + m_writeIndex - m_readIndex);
    #endif // _WITH_LOCK_FREE_Q_KEEP_REAL_SIZE
    }
 
    template<class _Ty, bool _Option, class _Sty>
    auto ring_queue<_Ty, _Option, _Sty>::capacity() const noexcept->size_type
    {
        return m_bufferSize - 1;
    }
 
    template<class _Ty, bool _Option, class _Sty>
    bool ring_queue<_Ty, _Option, _Sty>::empty() const noexcept
    {
    #ifdef _WITH_LOCK_FREE_Q_KEEP_REAL_SIZE
        return m_count.load(std::memory_order_acquire) == 0;
    #else
        return m_writeIndex == m_readIndex;
    #endif // _WITH_LOCK_FREE_Q_KEEP_REAL_SIZE
    }
 
    template<class _Ty, bool _Option, class _Sty>
    bool ring_queue<_Ty, _Option, _Sty>::full() const noexcept
    {
    #ifdef _WITH_LOCK_FREE_Q_KEEP_REAL_SIZE
        return (m_count.load(std::memory_order_acquire) == (m_bufferSize - 1));
    #else
        return nextIndex(m_writeIndex) == m_readIndex;
    #endif // _WITH_LOCK_FREE_Q_KEEP_REAL_SIZE
    }
 
    template<class _Ty, bool _Option, class _Sty>
    template<class U>
    bool ring_queue<_Ty, _Option, _Sty>::try_push(U&& value) noexcept(std::is_nothrow_move_assignable_v<U>)
    {
        auto nextWriteIndex = nextIndex(m_writeIndex);
        if (nextWriteIndex == m_readIndex)
            return false;
 
        assert(m_writeIndex < m_bufferSize);
 
        m_bufferPtr[m_writeIndex] = std::move(value);
        m_writeIndex = nextWriteIndex;
 
    #ifdef _WITH_LOCK_FREE_Q_KEEP_REAL_SIZE
        m_count.fetch_add(1, std::memory_order_acq_rel);
    #endif
        return true;
    }
 
    template<class _Ty, bool _Option, class _Sty>
    template<class U>
    bool ring_queue<_Ty, _Option, _Sty>::try_pop(U& value) noexcept(std::is_nothrow_move_assignable_v<value_type>)
    {
        if (m_readIndex == m_writeIndex)
            return false;
 
        optional_type& ov = m_bufferPtr[m_readIndex];
        if constexpr (use_option)
        {
            value = std::move(ov).value();
            ov = std::nullopt;
        }
        else
        {
            value = std::move(ov);
        }
 
        m_readIndex = nextIndex(m_readIndex);
 
    #ifdef _WITH_LOCK_FREE_Q_KEEP_REAL_SIZE
        m_count.fetch_sub(1, std::memory_order_acq_rel);
    #endif
        return true;
    }
}