engine_noise.hpp

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#pragma once
 
#include <cstdint>
 
namespace ts {

class EngineNoise {
public:
    [[nodiscard]] std::uint16_t next() noexcept
    {
        auto step = static_cast<std::uint16_t>(shift_ >> 1);
        if (((shift_ & 0x20) != 0) != ((shift_ & 0x8000) != 0)) {
            step = static_cast<std::uint16_t>(step | 0x8000);
        }
        shift_ = step;
 
        const bool insert_one = (walk_ & 4) != 0 ? (walk_ & 0x2000) == 0 : (walk_ & 0x200) != 0;
        walk_ = static_cast<std::uint16_t>((walk_ << 1) | (insert_one ? 1 : 0));
 
        return static_cast<std::uint16_t>(walk_ ^ shift_);
    }

    [[nodiscard]] int next_pan() noexcept { return next() >> 9; }

    void reset() noexcept
    {
        shift_ = 0xEFA6;
        walk_ = 0x9C23;
    }
 
private:
    std::uint16_t shift_ = 0xEFA6;
    std::uint16_t walk_ = 0x9C23;
};
 
} // namespace ts