Port FluidSim core and scenarios to C++20

include/FluidSim/SimulationRingBuffer.hpp

@@ -0,0 +1,35 @@
+#pragma once
+
+#include <atomic>
+#include <condition_variable>
+#include <cstddef>
+#include <cstdint>
+#include <mutex>
+#include <span>
+#include <stop_token>
+#include <vector>
+
+namespace fluidsim::port {
+
+class SimulationRingBuffer {
+public:
+    explicit SimulationRingBuffer(std::size_t capacity);
+    std::size_t available_samples() const;
+    std::size_t free_space() const;
+    bool write(float left, float right, std::stop_token stop = {});
+    bool wait_for_space(std::size_t target_fill, std::stop_token stop);
+    void reset_consumer();
+    std::size_t read_interpolated(std::span<float> left, std::span<float> right, double speed);
+
+private:
+    std::vector<float> left_, right_;
+    std::size_t mask_{};
+    std::atomic<std::uint64_t> write_head_{};
+    std::atomic<std::uint64_t> read_head_{};
+    double read_position_{};
+    bool consumer_initialized_{};
+    mutable std::mutex wait_mutex_;
+    std::condition_variable space_available_;
+};
+
+} // namespace fluidsim::port