WaitFreeRingBuffer.h

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#ifndef IMT_BASE_CORE_UTIL_WAITFREERINGBUFFER_H
#define IMT_BASE_CORE_UTIL_WAITFREERINGBUFFER_H
 
// Platform include.
#include <Imt.Base.Core.Platform/Platform.h>
 
// Standard includes.
#include <array>
#include <atomic>
#include <cstring>
 
namespace imt {
namespace base {
namespace core {
namespace util {
 
template<typename ElementType, uint16_t MaxSize>
class WaitFreeRingBuffer final {
 
    // At least one element required.
    static_assert(MaxSize > 0U);
 
    // Lock-Free assurance, see https://en.cppreference.com/w/cpp/atomic/atomic_is_lock_free
    static_assert(ATOMIC_SHORT_LOCK_FREE == 2);
 
public:
 
    /*
     * Default constructor.
     */
    WaitFreeRingBuffer() = default;
 
    /*
     * Destructor.
     */
    ~WaitFreeRingBuffer() noexcept = default;
 
    bool push(ElementType const& value) {
        uint16_t const inPos {m_inPos.load(std::memory_order_relaxed)};
        uint16_t const nextPos {next(inPos)};
        if (nextPos == m_outPos.load(std::memory_order_acquire)) {
            return false;
        }
        m_buf[inPos] = value;
        m_inPos.store(nextPos, std::memory_order_release);
        return true;
    }
 
    // AXIVION Next Routine AutosarC++19_03-A8.4.4: Use output parameter instead of return value for better usage.
    // AXIVION Next Routine AutosarC++19_03-A8.4.8: Use output parameter instead of return value for better usage.
    // AXIVION Next Routine AutosarC++19_03-A8.4.9: Intended that output parameter is replaced, not modified.
    bool pop(ElementType& value) {
        uint16_t const outPos {m_outPos.load(std::memory_order_relaxed)};
        if (outPos == m_inPos.load(std::memory_order_acquire)) {
            return false;
        }
        value = m_buf[outPos];
        m_outPos.store(next(outPos), std::memory_order_release);
        return true;
    }
 
    uint16_t getReadAvailable() const {
        uint16_t const inPos {m_inPos.load(std::memory_order_acquire)};
        uint16_t const outPos {m_outPos.load(std::memory_order_relaxed)};
        return getSizeUsed(inPos, outPos);
    }
 
    uint16_t getWriteAvailable() const {
        uint16_t const inPos {m_inPos.load(std::memory_order_relaxed)};
        uint16_t const outPos {m_outPos.load(std::memory_order_acquire)};
        uint16_t const sizeUsed {getSizeUsed(inPos, outPos)};
        return BUFFER_SIZE - sizeUsed - 1U;
    }
 
    static uint16_t getMaxSize() {
        return MAX_SIZE;
    }
 
private:
 
    // Constants.
    static constexpr uint16_t MAX_SIZE {MaxSize};
    static constexpr uint16_t BUFFER_SIZE {MAX_SIZE + 1U};
 
    // Deleted constructors/assigners.
    WaitFreeRingBuffer(WaitFreeRingBuffer const&) = delete;
    WaitFreeRingBuffer(WaitFreeRingBuffer&& other) = delete;
    WaitFreeRingBuffer& operator=(WaitFreeRingBuffer const&) = delete;
    WaitFreeRingBuffer& operator=(WaitFreeRingBuffer&& other) = delete;
 
    // Helpers.
    static uint16_t next(uint16_t const current) {
        return (current + 1U) % BUFFER_SIZE;
    }
 
    static uint16_t getSizeUsed(uint16_t const inPos, uint16_t const outPos) {
        return (inPos >= outPos) ? (inPos - outPos) : (BUFFER_SIZE - (outPos - inPos));
    }
 
    // Members.
    std::atomic<uint16_t> m_inPos {0U};
    std::atomic<uint16_t> m_outPos {0U};
    std::array<ElementType, BUFFER_SIZE> m_buf {};
};
 
} // namespace util
} // namespace core
} // namespace base
} // namespace imt
 
#endif // IMT_BASE_CORE_UTIL_WAITFREERINGBUFFER_H