在C ++ / CLI中将HANDLE变量传递到非托管.dll [英] passing a HANDLE variable to an unmanaged .dll in C++/CLI

问题描述

我试图包装一个非托管的c ++ dll，谈到c ++ / CLI中的视频捕获卡，所以我可以引用我有一个c＃项目的功能。我有麻烦得到第一次包装调用工作，因为我是新的到c ++ / cli语法。这是我有的。

这里是我想要换行的函数declataion。

  __ declspec（dllimport）BOOL AZ_DeviceCreate（HANDLE& hLiveEvent，DWORD * hEncoderEvent，DWORD * pdwEncoderAddress，HANDLE& hAudioEvent，DWORD& dwAudioAddress） 
  

这里是我的c ++ / cli .h文件

 命名空间CaptureLibrary 
 {
 public ref class CaptureCard 
 {
 public：
 HANDLE m_hLiveEvent; 
 DWORD * m_hEncoderEvent; 
 HANDLE m_hAudioEvent; 
 
 public：
 CaptureCard（）; 
 bool CreateDevice（）; 
 void DisposeDevice（）; 
}; 
} 
  

和我的.cpp

 命名空间CaptureLibrary 
 {
 CaptureCard :: CaptureCard（）
 {
 m_hLiveEvent = INVALID_HANDLE_VALUE; 
 
 m_hEncoderEvent = new DWORD [MAX_VIDEO_CHANNEL]; 
 for（BYTE i = 0; i  {
 m_hEncoderEvent [i] =（DWORD）INVALID_HANDLE_VALUE; 
} 
 
 m_hAudioEvent = INVALID_HANDLE_VALUE; 
} 
 
 bool CaptureCard :: CreateDevice（）
 {
 DWORD dwEncoderBuff [MAX_VIDEO_CHANNEL]; 
 DWORD dwACaptureBuffer = 0; 
 
 if（AZ_DeviceCreate（m_hLiveEvent，m_hEncoderEvent，dwEncoderBuff，m_hAudioEvent，dwACaptureBuffer）== FALSE）
 {
 return false; 
} 
 
 return true; 
} 
 
 void CaptureCard :: DisposeDevice（）
 {
 AZ_DeviceClose（）; 
} 
} 
  

此错误：

错误C2664：'AZ_DeviceCreate'：无法将参数1 'HANDLE'至'HANDLE&'

任何人都可以帮助我，因为我知道这是一个愚蠢的语法，我做错了。

提前感谢。

解决方案

我的意思是建设性的：你走错了脚。 C ++ / CLI的目标是以非托管库的方式包装非托管库，但是你的 CaptureCard 类不会这样做。 / p>

• 不要公开字段，公开属性（我认为它们应该是 CaptureCard 的成员）


• 不要暴露原始指针类型（例如 HANDLE ），暴露 IntPtr


• 不要暴露原始C数组（例如 DWORD * ）， $ c> array< T> ^ ， ReadOnlyCollection< T> ^ 或 IEnumerable< T& c $ c>（但是不要通过属性暴露数组< T> ^ ：Copy ）


• 不仅公开一个 DisposeDevice 方法， code> IDisposable ，因此可以用使用语句关闭设备，而不是强制使用 try ..最后


• 由于类控制非托管资源，需要终结符

.h ：

 命名空间CaptureLibrary 
 {
 public ref class CaptureCard sealed 
 {
 public：
 CaptureCard（）; 
〜CaptureCard（）; 
！CaptureCard（）; 
 
属性IntPtr LiveEvent {IntPtr get（）; } 
 property IEnumerable< DWORD> ^ EncoderEvent {IEnumerable< DWORD> ^ get（）; } 
 property IntPtr AudioEvent {IntPtr get（）; } 
 
 bool CreateDevice（）; 
 void DisposeDevice（）; 
 
 private：
 bool m_bOpened; 
 IntPtr m_hLiveEvent; 
 array< DWORD> ^ m_hEncoderEvent; 
 IntPtr m_hAudioEvent; 
}; 
} 
  

.cpp ：

 命名空间CaptureLibrary 
 {
 CaptureCard :: CaptureCard（）
：m_hLiveEvent（INVALID_HANDLE_VALUE ），
 m_hEncoderEvent（gcnew array< DWORD>（MAX_VIDEO_CHANNEL）），
 m_hAudioEvent（INVALID_HANDLE_VALUE）
 {
 for（int i = 0，i_max = m_hEncoderEvent-> Length; i！= i_max; ++ i）
 m_hEncoderEvent [i] = reinterpret_cast< DWORD>（INVALID_HANDLE_VALUE）; 
} 
 
 CaptureCard ::〜CaptureCard（）
 {
 this->！CaptureCard 
} 
 
 CaptureCard ::！CaptureCard（）
 {
 DisposeDevice（）; 
} 
 
 IntPtr CaptureCard :: LiveEvent :: get（）
 {
 return m_hLiveEvent; 
} 
 
 IEnumerable< DWORD> ^ CaptureCard :: EncoderEvent :: get（）
 {
 return m_hEncoderEvent; 
} 
 
 IntPtr CaptureCard :: AudioEvent :: get（）
 {
 return m_hAudioEvent; 
} 
 
 bool CaptureCard :: CreateDevice（）
 {
 DisposeDevice（）; 
 
 DWORD dwAudioAddress = 0u; 
 DWORD dwEncoderAddress [MAX_VIDEO_CHANNEL]; 
 
 HANDLE hLiveEvent = m_hLiveEvent.ToPointer（）; 
 HANDLE hAudioEvent = m_hAudioEvent.ToPointer（）; 
 {
 pin_ptr< DWORD> hEncoderEvent =& m_hEncoderEvent [0]; 
 m_bOpened = AZ_DeviceCreate（hLiveEvent，hEncoderEvent，dwEncoderAddress，hAudioEvent，dwAudioAddress）== TRUE; 
} 
 m_hLiveEvent = IntPtr（hLiveEvent）; 
 m_hAudioEvent = IntPtr（hAudioEvent）; 
 
 return m_bOpened; 
} 
 
 void CaptureCard :: DisposeDevice（）
 {
 if（m_bOpened）
 {
 AZ_DeviceClose 
 m_bOpened = false; 
} 
} 
} 
  

---

进一步改进的建议：

• 移除 CreateDevice DisposeDevice 。这个代码有一个非常C-ish的心态; .NET用户期望构造的对象具有有意义的值，而不调用单独的初始化函数，因此假设 AZ_DeviceCreate 不会定期失败，然后 CreateDevice 的逻辑应该直接在类的构造函数中，并且在失败时抛出异常


• 如果调用 AZ_DeviceClose 多次是无害的，然后摆脱 m_bOpened 完全

I am trying to wrap an unmanaged c++ dll that talks to a video capture card in c++/CLI so i can reference the functions from a c# project that i have. I am having trouble getting the 1st wrapped call to work as I am new to c++/cli syntax. here is what i have.

here is the function declataion i am trying to wrap.

__declspec(dllimport) BOOL AZ_DeviceCreate(HANDLE& hLiveEvent, DWORD* hEncoderEvent, DWORD* pdwEncoderAddress, HANDLE& hAudioEvent, DWORD& dwAudioAddress);

here is my c++/cli .h file

namespace CaptureLibrary 
{
    public ref class CaptureCard
    {
    public:
        HANDLE m_hLiveEvent;
        DWORD *m_hEncoderEvent;
        HANDLE m_hAudioEvent;

    public:
        CaptureCard();
        bool CreateDevice();
        void DisposeDevice();
    };
}

and my .cpp

namespace CaptureLibrary
{
    CaptureCard::CaptureCard()
    {
        m_hLiveEvent = INVALID_HANDLE_VALUE;

        m_hEncoderEvent = new DWORD[MAX_VIDEO_CHANNEL];
        for (BYTE i=0;i<MAX_VIDEO_CHANNEL;i++)
        {
            m_hEncoderEvent[i] = (DWORD)INVALID_HANDLE_VALUE;
        }

        m_hAudioEvent = INVALID_HANDLE_VALUE;
    }

    bool CaptureCard::CreateDevice()
    {
        DWORD dwEncoderBuff[MAX_VIDEO_CHANNEL];
        DWORD dwACaptureBuffer = 0;

        if(AZ_DeviceCreate(m_hLiveEvent, m_hEncoderEvent, dwEncoderBuff, m_hAudioEvent, dwACaptureBuffer)==FALSE)
        {
            return false;
        }

        return true;
    }

    void CaptureCard::DisposeDevice()
    {
        AZ_DeviceClose();
    }
}

when i compile this with the required headers, i get this error:

error C2664: 'AZ_DeviceCreate' : cannot convert parameter 1 from 'HANDLE' to 'HANDLE &'

Can anyone help me as I know this is a stupid syntax thing that I am doing wrong.

Thanks in advance.

解决方案

I mean this constructively: you're off on the wrong foot. Your goal with C++/CLI here is to wrap the unmanaged library in a manner that won't seem foreign in .NET, but your CaptureCard class doesn't do that.

• Don't expose fields, expose properties (I assume they should be get-only for CaptureCard's members)
• Don't expose raw pointer types (e.g. HANDLE), expose IntPtr
• Don't expose raw C-arrays (e.g. DWORD*), expose array<T>^, ReadOnlyCollection<T>^, or IEnumerable<T>^ (but don't expose array<T>^s intended to be read-only via properties, only via methods + Array::Copy)
• Don't only expose a DisposeDevice method, also make the class actually implement IDisposable so the device can be closed with a using statement rather than forcing use of try..finally
• As the class controls unmanaged resources, it needs a finalizer

.h:

namespace CaptureLibrary 
{
    public ref class CaptureCard sealed
    {
    public:
        CaptureCard();
        ~CaptureCard();
        !CaptureCard();

        property IntPtr LiveEvent { IntPtr get(); }
        property IEnumerable<DWORD>^ EncoderEvent { IEnumerable<DWORD>^ get(); }
        property IntPtr AudioEvent { IntPtr get(); }

        bool CreateDevice();
        void DisposeDevice();

    private:
        bool m_bOpened;
        IntPtr m_hLiveEvent;
        array<DWORD>^ m_hEncoderEvent;
        IntPtr m_hAudioEvent;
    };
}

.cpp:

namespace CaptureLibrary
{
    CaptureCard::CaptureCard()
      : m_hLiveEvent(INVALID_HANDLE_VALUE),
        m_hEncoderEvent(gcnew array<DWORD>(MAX_VIDEO_CHANNEL)),
        m_hAudioEvent(INVALID_HANDLE_VALUE)
    {
        for (int i = 0, i_max = m_hEncoderEvent->Length; i != i_max; ++i)
            m_hEncoderEvent[i] = reinterpret_cast<DWORD>(INVALID_HANDLE_VALUE);
    }

    CaptureCard::~CaptureCard()
    {
        this->!CaptureCard();
    }

    CaptureCard::!CaptureCard()
    {
        DisposeDevice();
    }

    IntPtr CaptureCard::LiveEvent::get()
    {
        return m_hLiveEvent;
    }

    IEnumerable<DWORD>^ CaptureCard::EncoderEvent::get()
    {
        return m_hEncoderEvent;
    }

    IntPtr CaptureCard::AudioEvent::get()
    {
        return m_hAudioEvent;
    }

    bool CaptureCard::CreateDevice()
    {
        DisposeDevice();

        DWORD dwAudioAddress = 0u;
        DWORD dwEncoderAddress[MAX_VIDEO_CHANNEL];

        HANDLE hLiveEvent = m_hLiveEvent.ToPointer();
        HANDLE hAudioEvent = m_hAudioEvent.ToPointer();
        {
            pin_ptr<DWORD> hEncoderEvent = &m_hEncoderEvent[0];
            m_bOpened = AZ_DeviceCreate(hLiveEvent, hEncoderEvent, dwEncoderAddress, hAudioEvent, dwAudioAddress) == TRUE;
        }
        m_hLiveEvent = IntPtr(hLiveEvent);
        m_hAudioEvent = IntPtr(hAudioEvent);

        return m_bOpened;
    }

    void CaptureCard::DisposeDevice()
    {
        if (m_bOpened)
        {
            AZ_DeviceClose();
            m_bOpened = false;
        }
    }
}

---

Suggestions for further improvement:

• Get rid of CreateDevice and DisposeDevice altogether. This code has a very C-ish mentality; .NET users would expect a constructed object to have a meaningful value without calling a separate initialization function, so assuming AZ_DeviceCreate is not expected to fail regularly then CreateDevice's logic should go straight in the class' constructor and an exception should be thrown upon failure
• If calling AZ_DeviceClose multiple times is harmless then get rid of m_bOpened altogether

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