我該如何聲明一個指向P/Invoke結構的指針？

Question

我正在嘗試使用P/Invoke Interop Assistant在C＃中調用C++ Dll。大多數頭的轉換很好，但我有這個麻煩：

#define FULLOCTAVE_BINS    12 
#define THIRDOCTAVE_BINS    36 

typedef struct tagTimeHistory 
{ 
    UINT m_nAction; 
    int m_nFlag; 
    int m_nRecordNum; 
    int m_nTimeStamp; 
    int m_nMiscStartIndex; 
    float m_pfTHFloatVals[256]; // Number of valid values given by m_nNumFloatVals in Settings. 
    float m_pfTH11OBAVals[4][FULLOCTAVE_BINS]; // 0-4 spectra given by m_nNumOBA11Vals in Settings 
    float m_pfTH13OBAVals[4][THIRDOCTAVE_BINS]; // 0-4 spectra given by m_nNumOBA13Vals in Settings 
    float m_fDuration; 
} stTimeHistory_t; 

typedef struct tagSlmBulkRecords 
{ 
    int nRecType; 
    union 
    { 
     stTimeHistory_t *m_ThRecs; 
     stInterval_t *m_Interval; 
     stExceedence_t *m_Exceedences; 
     stRunRecord_t *m_RunRecord; 
     stSpeechData_t *m_VoiceRecord; 
     stSpeechData_t *m_AudioRecord; 
    }; 
} stSlmBulkRecord_t; 

這被轉換爲：

[System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Explicit)] 
public struct Anonymous_d2bf9406_c664_4664_9196_800cc23f445a { 

    /// stTimeHistory_t* 
    [System.Runtime.InteropServices.FieldOffsetAttribute(0)] 
    public System.IntPtr m_ThRecs; 

    /// stInterval_t* 
    [System.Runtime.InteropServices.FieldOffsetAttribute(0)] 
    public System.IntPtr m_Interval; 

    /// stExceedence_t* 
    [System.Runtime.InteropServices.FieldOffsetAttribute(0)] 
    public System.IntPtr m_Exceedences; 

    /// stRunRecord_t* 
    [System.Runtime.InteropServices.FieldOffsetAttribute(0)] 
    public System.IntPtr m_RunRecord; 

    /// stSpeechData_t* 
    [System.Runtime.InteropServices.FieldOffsetAttribute(0)] 
    public System.IntPtr m_VoiceRecord; 

    /// stSpeechData_t* 
    [System.Runtime.InteropServices.FieldOffsetAttribute(0)] 
    public System.IntPtr m_AudioRecord; 
} 

[System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)] 
public struct tagSlmBulkRecords { 

    /// int 
    public int nRecType; 

    /// Anonymous_d2bf9406_c664_4664_9196_800cc23f445a 
    public Anonymous_d2bf9406_c664_4664_9196_800cc23f445a Union1; 
} 

但我怎麼使用m_ThRecs時，它只是一個System.IntPtr？有什麼方法顯式聲明它是stTimeHistory_t的指針嗎？我移植到C＃的C++代碼使用這樣的：

stSlmBulkRecord_t bulkRecord; 
bulkRecord.m_ThRecs = new stTimeHistory_t[dataCounts.m_nNumTH]; 

但如果我嘗試在C＃：

tagSlmBulkRecords bulkRecord; 
bulkRecord.Union1.m_ThRecs = new tagTimeHistory[dataCounts.m_nNumTH]; 

我得到：

錯誤1無法隱式轉換鍵入'SlmTest.Program.tagTimeHistory []'到'SlmTest.Program.tagTimeHistory'「

如果我嘗試unsaf Ë定義：

[System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Sequential)] 
public struct tagTimeHistory 
{ 
    /// UINT->unsigned int 
    public uint m_nAction; 

    /// int 
    public int m_nFlag; 

    /// int 
    public int m_nRecordNum; 

    /// int 
    public int m_nTimeStamp; 

    /// int 
    public int m_nMiscStartIndex; 

    /// float[256] 
    [System.Runtime.InteropServices.MarshalAsAttribute(System.Runtime.InteropServices.UnmanagedType.ByValArray, SizeConst = 256, ArraySubType = System.Runtime.InteropServices.UnmanagedType.R4)] 
    public float[] m_pfTHFloatVals; 

    /// float[48] 
    [System.Runtime.InteropServices.MarshalAsAttribute(System.Runtime.InteropServices.UnmanagedType.ByValArray, SizeConst = 48, ArraySubType = System.Runtime.InteropServices.UnmanagedType.R4)] 
    public float[] m_pfTH11OBAVals; 

    /// float[144] 
    [System.Runtime.InteropServices.MarshalAsAttribute(System.Runtime.InteropServices.UnmanagedType.ByValArray, SizeConst = 144, ArraySubType = System.Runtime.InteropServices.UnmanagedType.R4)] 
    public float[] m_pfTH13OBAVals; 

    /// float 
    public float m_fDuration; 
} 

[System.Runtime.InteropServices.StructLayoutAttribute(System.Runtime.InteropServices.LayoutKind.Explicit)] 
public unsafe struct Anonymous_d2bf9406_c664_4664_9196_800cc23f445a 
{ 
    /// stTimeHistory_t* 
    [System.Runtime.InteropServices.FieldOffsetAttribute(0)] 
    public tagTimeHistory *m_ThRecs; 
    /// stInterval_t* 
    [System.Runtime.InteropServices.FieldOffsetAttribute(0)] 
    public System.IntPtr *m_Interval; 
    /// stExceedence_t* 
    [System.Runtime.InteropServices.FieldOffsetAttribute(0)] 
    public System.IntPtr m_Exceedences; 
    /// stRunRecord_t* 
    [System.Runtime.InteropServices.FieldOffsetAttribute(0)] 
    public System.IntPtr m_RunRecord; 
    /// stSpeechData_t* 
    [System.Runtime.InteropServices.FieldOffsetAttribute(0)] 
    public System.IntPtr m_VoiceRecord; 
    /// stSpeechData_t* 
    [System.Runtime.InteropServices.FieldOffsetAttribute(0)] 
    public System.IntPtr m_AudioRecord; 
} 

我得到：

錯誤CS0208：不能取的地址，獲取的大小，或宣佈一個指向託管類型

Answer 1

如果真想想與本機代碼互操作，可以用fixed運營商：

var array = new tagTimeHistory[dataCounts.m_nNumTH]; 
fixed (tagTimeHistory* ptr = array) 
{ 
    // do anything with the raw pointer 
} 

請注意，fixed運算符和C＃中的指針類型需要unsafe的能力。而且您可能需要使用正確的指針類型替換IntPtr以獲得更多的類型安全性（雖然有一種將指針轉換爲IntPtr的方法）。

另一種方法是通過Marshal class的方法。

編輯。下面是修改後的不安全定義你的搞笑命名的工會結構的一個樣本：

[StructLayout(LayoutKind.Explicit)] 
public unsafe struct Anonymous_d2bf9406_c664_4664_9196_800cc23f445a 
{ 
    [FieldOffset(0)] 
    public stTimeHistory_t* m_ThRecs; 

    [FieldOffset(0)] 
    public stInterval_t* m_Interval; 

    [FieldOffset(0)] 
    public stExceedence_t* m_Exceedences; 

    [FieldOffset(0)] 
    public stRunRecord_t* m_RunRecord; 

    [FieldOffset(0)] 
    public stSpeechData_t* m_VoiceRecord; 

    [FieldOffset(0)] 
    public stSpeechData_t* m_AudioRecord; 
} 

你應該定義所有的結構，如在你的代碼stTimeHistory_t（或更換您不一般的IntPtr關心的人S）。

關於用Marshal創建結構數組：原生內存池沒有structure array這樣的概念;它所關心的只是字節。所以，你可以，例如，使用Marshal.AllocHGlobal method：

IntPtr myPtr = Marshal.AllocHGlobal(Marshal.SizeOf<tagTimeHistory>() * dataCounts.m_nNumTH); 
// ... write something to an array, use it 
// And don't forget to free it to prevent memory leaks! 
Marshal.FreeHGlobal(myPtr); 

EDIT 2。關於「無法獲取地址，獲取大小或聲明託管類型的指針」錯誤 - 您的定義不完全不受管理。不安全的定義和使用編組邏輯的定義並不總是相同的;在這裏它認爲你的類是「管理」的，因爲它的數組引用。嘗試使用固定陣列：

[StructLayout(LayoutKind.Sequential)] 
public unsafe struct tagTimeHistory 
{ 
    public uint m_nAction; 
    public int m_nFlag; 
    public int m_nRecordNum; 
    public int m_nTimeStamp; 
    public int m_nMiscStartIndex; 
    public fixed float m_pfTHFloatVals[256]; 
    public fixed float m_pfTH11OBAVals[48]; 
    public fixed float m_pfTH13OBAVals[144]; 
    public float m_fDuration; 
}