CPowerRequest.h

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#ifdef _WIN32

typedef HANDLE (WINAPI * pPowerCreateRequest_t) (
    __in void* Context
    );

typedef BOOL (WINAPI * pPowerSetRequest_t) (
    __in HANDLE PowerRequest,
    __in POWER_REQUEST_TYPE RequestType
    );

typedef BOOL (WINAPI * pPowerClearRequest_t) (
    __in HANDLE PowerRequest,
    __in POWER_REQUEST_TYPE RequestType
    );

class CPowerRequestAPI {
public:
    CPowerRequestAPI() : PowerCreateRequest(), PowerSetRequest(), PowerClearRequest()  {
        Bind();
    }
    bool Bind() {
        HMODULE kernel32 = GetModuleHandle(_T("kernel32.dll"));
        return Bind(PowerCreateRequest, kernel32, "PowerCreateRequest")
            && Bind(PowerSetRequest, kernel32, "PowerSetRequest") 
            && Bind(PowerClearRequest, kernel32, "PowerClearRequest") ;
    }
    bool IsValid() {return PowerCreateRequest != NULL;}

    void ToggleSystem(HANDLE hRequest, bool bSystem) {
        Toggle(hRequest, bSystem, PowerRequestSystemRequired);
    }

    void ToggleExecution(HANDLE hRequest, bool bSystem) {
        const POWER_REQUEST_TYPE _PowerRequestExecutionRequired = (POWER_REQUEST_TYPE)3;
        const POWER_REQUEST_TYPE RequestType = IsWin8() ? _PowerRequestExecutionRequired : PowerRequestSystemRequired;
        Toggle(hRequest, bSystem, RequestType);
    }

    void ToggleDisplay(HANDLE hRequest, bool bDisplay) {
        Toggle(hRequest, bDisplay, PowerRequestDisplayRequired);
    }

    void Toggle(HANDLE hRequest, bool bToggle, POWER_REQUEST_TYPE what) {
        if (bToggle) {
            PowerSetRequest(hRequest, what);
        } else {
            PowerClearRequest(hRequest, what);
        }

    }
    HANDLE PowerCreateRequestNamed( const wchar_t * str );

    static bool IsWin8() {
        auto ver = myGetOSVersion();
        return ver >= 0x602;
    }
    static WORD myGetOSVersion() {
        const DWORD ver = GetVersion();
        return (WORD)HIBYTE(LOWORD(ver)) | ((WORD)LOBYTE(LOWORD(ver)) << 8);
    }

    pPowerCreateRequest_t PowerCreateRequest;
    pPowerSetRequest_t PowerSetRequest;
    pPowerClearRequest_t PowerClearRequest;
private:
    template<typename func_t> static bool Bind(func_t & f, HMODULE dll, const char * name) {
        f = reinterpret_cast<func_t>(GetProcAddress(dll, name));
        return f != NULL;
    }
};

class CPowerRequest {
public:
    CPowerRequest(const wchar_t * Reason);
    void SetSystem(bool bSystem);
    void SetExecution(bool bExecution);
    void SetDisplay(bool bDisplay);
    ~CPowerRequest();
private:
    void _UpdateTES();
    HANDLE m_Request;
    bool m_bSystem, m_bDisplay;
    CPowerRequestAPI m_API;
    CPowerRequest(const CPowerRequest&);
    void operator=(const CPowerRequest&);
};
#else

class CPowerRequest {
public:
    CPowerRequest(const wchar_t * Reason) {}
    void SetSystem(bool bSystem) {}
    void SetExecution(bool bExecution) {}
    void SetDisplay(bool bDisplay) {}
private:
    CPowerRequest(const CPowerRequest&);
    void operator=(const CPowerRequest&);
};

#endif