ardupilot/libraries/AP_HAL_Empty/Semaphores.h

#pragma once

#include "AP_HAL_Empty.h"

class Empty::Semaphore : public AP_HAL::Semaphore {
public:

    bool give() override;
    bool take(uint32_t timeout_ms) override;
    bool take_nonblocking() override;
private:
    bool _taken;
};