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P/Invoke函数调用问题

pinvoke struct function c#

Johnny Egeland · 技术社区 · 16 年前

C头文件定义了如下结构和功能:

#pragma pack(1)
typedef struct {
   DWORD JobId; 
   DWORD CardNum;
   HANDLE hPrinter;
} CARDIDTYPE, FAR *LPCARDIDTYPE;
#pragma pack()

typedef struct {
   BOOL        bActive;
   BOOL        bSuccess;
} CARD_INFO_1, *PCARD_INFO_1, FAR *LPCARD_INFO_1;

typedef struct {
   DWORD       dwCopiesPrinted;
   DWORD       dwRemakeAttempts;
   SYSTEMTIME  TimeCompleted;
} CARD_INFO_2, *PCARD_INFO_2, FAR *LPCARD_INFO_2;

BOOL ICEAPI GetCardId(HDC hdc, LPCARDIDTYPE pCardId);
BOOL ICEAPI GetCardStatus(CARDIDTYPE CardId, DWORD level, LPBYTE pData, DWORD cbBuf, LPDWORD pcbNeeded );

我曾尝试实现P/Invoke包装器,如下所示:

[StructLayout(LayoutKind.Sequential, Pack=1)]
public class CARDIDTYPE {
    public UInt32 JobId;
    public UInt32 CardNum;
    public IntPtr hPrinter;
}

[StructLayout(LayoutKind.Sequential)]
public class CARD_INFO_1 {
    public bool bActive;
    public bool bSuccess;
}

[StructLayout(LayoutKind.Sequential)]
public class CARD_INFO_2 {
    public UInt32 dwCopiesPrinted;
    public UInt32 dwRemakeAttempts;
    public Win32Util.SYSTEMTIME TimeCompleted;
}
[DllImport("ICE_API.DLL", CharSet = CharSet.Auto, CallingConvention = CallingConvention.Winapi, SetLastError = true)]
public static extern bool GetCardId(HandleRef hDC, [Out]CARDIDTYPE pCardId);

[DllImport("ICE_API.DLL", CharSet = CharSet.Auto, CallingConvention = CallingConvention.Winapi, SetLastError = true)]
public static extern bool GetCardStatus(CARDIDTYPE CardId, UInt32 level, [Out] byte[] pData, UInt32 cbBuf, out UInt32 pcbNeeded);

打电话给“GetCardd”似乎效果不错。调用CardType实例后,我在该实例中获得了合理的数据。然而,当我调用“GetCardStatus”时,问题就开始了。应返回的结构类型由“level”参数定义,值为1将导致在“pData”中返回一个CARD_INFO_1结构。

文档包含以下C示例:

CARD_INFO_1 ci1;
DWORD cbNeeded;
ci1.bActive = TRUE;
if (GetCardStatus(*lpCardID, 1, (LPBYTE)&ci1, sizeof(ci1), &cbNeeded )) { /* success */ }

我的等效C#实现如下所示:

uint needed;
byte[] byteArray = new byte[Marshal.SizeOf(typeof(CARD_INFO_1))];
if (GetCardStatus(cardId, 1, byteArray, (uint)byteArray.Length, out needed)) { /* success */ }

当我执行这个C#代码时,该方法返回false和Marshal.GetLastWin32Error()返回-1073741737(这对我来说没有多大意义)。我看不出这个调用失败的原因,而且肯定不是因为这个错误代码。因此,我怀疑我的P/Invoke包装中有什么错误。

我知道使用“byte[]”作为pData类型可能是不正确的,但根据一些谷歌搜索,“LPBYTE”会转换为“[Out]byte[]”。我想正确的方法是将pData作为IntPtr,并使用Marshal.PtrToStructure(…)创建结构。我试过这个,但结果是一样的。以下是此场景的代码:

[DllImport(@"ICE_API.DLL", CharSet = CharSet.Auto, EntryPoint = "_GetCardStatus@28", CallingConvention = CallingConvention.Winapi, SetLastError = true)]
public static extern bool GetCardStatus(CARDIDTYPE CardId, UInt32 level, IntPtr pData, UInt32 cbBuf, out UInt32 pcbNeeded);

uint needed;
int memSize = Marshal.SizeOf(typeof(CARD_INFO_1));
IntPtr memPtr = Marshal.AllocHGlobal(memSize);
if (!GetCardStatus(cardId, 1, memPtr, (uint)memSize, out needed)) {
    int lastError = Marshal.GetLastWin32Error();
    // error code is -1073741737
}
CARD_INFO_1 info = (CARD_INFO_1)Marshal.PtrToStructure(memPtr, typeof(CARD_INFO_1));
Marshal.FreeHGlobal(memPtr);

编辑: 我忘记提到的一件事是,由于某种原因,如果我没有指定EntryPoint=,GetCardStatus调用将失败,并出现未知的入口点异常_GetCardStatus@28". 我包装的任何其他函数都没有出现这种情况,所以我有点疑惑。

3 回复 | 直到 16 年前

Anton Tykhyy 16 年前

_GetCardStatus@28 GetCardStatus 会是 _GetCardStatus@20 ,因为它有5个32位参数。你的C声明 GetCardStatus 似乎接受了这个事实 cardId CARDIDTYPE 是12字节长,这将给出参数列表的正确长度(28)。此外,这将解释您收到的错误代码为-1073741737(C0000057, STATUS_INVALID_PARAMETER 卡迪德 GetCardStatus 试图写信给 pcbNeeded ,这是垃圾,因为元帅还没推它!

[DllImport("ICE_API.DLL", CharSet = CharSet.Auto, 
     CallingConvention = CallingConvention.Winapi, SetLastError = true)]
 public static extern bool GetCardStatus (
     IntPtr hPrinter, UInt32 cardNum, UInt32 jobId, UInt32 level, 
    [In, Out] CARD_INFO_1 data, UInt32 cbBuf, out UInt32 pcbNeeded) ;
[DllImport("ICE_API.DLL", CharSet = CharSet.Auto, 
     CallingConvention = CallingConvention.Winapi, SetLastError = true)]
 public static extern bool GetCardStatus (
     IntPtr hPrinter, UInt32 cardNum, UInt32 jobId, UInt32 level, 
    [In, Out] CARD_INFO_2 data, UInt32 cbBuf, out UInt32 pcbNeeded) ;

注意三者的相反顺序 梳棉机 stdcall struct

CloseHandle ,我建议你把把手收起来进入一个适当的阶段 SafeHandle ,而不是光秃秃的 IntPtr ,并宣布接受安全手柄。

Johnny Egeland 16 年前

正如Anton所说,问题在于传递给函数的参数。我昨天没有注意到这一点,但是CardType结构在GetCardID函数中通过指针传递,在GetCardStatus函数中通过值传递。在调用中,我还通过指向GetCardStatus的指针传递了CardType,通过指定Dependecy Walker中的确切函数名,强制P/Invoke框架定位正确的函数。

我通过将CardType定义为结构而不是类来解决这个问题,并通过引用将其传递给GetCardId函数。此外,CardType在传递给GetCardStatus函数时被封送为结构。除了Anton使用两种不同pData类型(CARD_INFO_1和CARD_INFO_2)的函数定义的技术之外,这项技术现在可以正常工作。以下是最终定义:

[StructLayout(LayoutKind.Sequential, Pack = 1)]
public struct CARDIDTYPE {
    public UInt32 JobId;
    public UInt32 CardNum;
    public IntPtr hPrinter;
}

[StructLayout(LayoutKind.Sequential)]
public class CARD_INFO_1 {
    public bool bActive;
    public bool bSuccess;
}

[StructLayout(LayoutKind.Sequential)]
public class CARD_INFO_2 {
    public UInt32 dwCopiesPrinted;
    public UInt32 dwRemakeAttempts;
    public Win32Util.SYSTEMTIME TimeCompleted;
}

[DllImport("ICE_API.DLL", CharSet = CharSet.Auto, CallingConvention = CallingConvention.Winapi, SetLastError = true)]
public static extern bool GetCardId(HandleRef hDC, ref CARDIDTYPE pCardId);

[DllImport(@"ICE_API.DLL", EntryPoint = "GetCardStatus", CallingConvention = CallingConvention.Winapi, SetLastError = true)]
public static extern bool GetCardStatus([MarshalAs(UnmanagedType.Struct)]CARDIDTYPE CardId, UInt32 level,
    [In, Out] CARD_INFO_1 pData, UInt32 cbBuf, out UInt32 pcbNeeded);

[DllImport(@"ICE_API.DLL", EntryPoint = "GetCardStatus", CallingConvention = CallingConvention.Winapi, SetLastError = true)]
public static extern bool GetCardStatus([MarshalAs(UnmanagedType.Struct)]CARDIDTYPE CardId, UInt32 level,
    [In, Out] CARD_INFO_2 pData, UInt32 cbBuf, out UInt32 pcbNeeded);

感谢你们为解决这个问题所做的贡献:-)

JaredPar 16 年前

问题是你在使用[Out],而你不应该使用任何东西

[DllImport("ICE_API.DLL", CharSet = CharSet.Auto, CallingConvention = CallingConvention.Winapi, SetLastError = true)]
public static extern bool GetCardStatus(CARDIDTYPE CardId, UInt32 level, byte[] pData, UInt32 cbBuf, out UInt32 pcbNeeded);

Out/In属性告诉CLR封送拆收器 立即的 变量将被封送。在字节[]的情况下,参数实际上什么也不做。它的一个子元素正在移动。

[DllImport("ICE_API.DLL", CharSet = CharSet.Auto, CallingConvention = CallingConvention.Winapi, SetLastError = true)]
public static extern bool GetCardStatus(CARDIDTYPE CardId, UInt32 level, IntPtr pData, UInt32 cbBuf, out UInt32 pcbNeeded);

public void Example(uint size) {
  // Get other params
  var ptr = Marshal.AllocHGlobal(size);
  GetCardStatus(cardId, level, ptr, size, out needed);
  // Marshal back the byte array here
  Marshal.FreeHGlobal(ptr);
}