Question

对于某些方法，我们有一个带有以下简化IDL的遗留COM DLL：

AllocateMemory( [in] LONG lSize, [out] LONG *pAddr );

此方法的实现包含以下内容：

BYTE *pArr = (BYTE*)CoTaskMemAlloc( lSize );  
*pAddr = &pArr;

新分配的内存的地址作为long值返回给调用者。

使用此COM对象的C ++客户端可以调用该方法，然后按如下方式访问内存：

//---- C++ ----------------   
long lSize = 10;  
long lAddr;  
pCOMObj->AllocateMemory( lSize, &lAddr );  
byte **bArray = (byte**)lAddr;  
for (int i = 0; i < iSize; i++)  
{  
    printf( "array[%d] = %d\n", i, (*bArray)[i] );  
}  
// Now deallocate memory.  
CoTaskMemFree( *bArray ); 
//--------------------

一切都适用于C ++ COM客户端。

添加了相同的COM DLL作为Visual Studio 2010项目的引用我们的目标是能够使用Interop从C＃客户端执行相同的操作：

//---- C# ----------------  
int iSize = 10;  
int iAddr = 0;  
objCOM.AllocateMemory( iSize, ref iAddr );  
...    

// ??? *UNKNOWN*  
// At this point we need to be able to access allocated memory pointed to by iAddr.  


// The following does NOT work, i.e., no errors occur but array contents are totally
// different from what has been initialized inside AllocateMemory() method, implying 
// that totally different memory is being accessed/copied:    
byte [] bArray = new byte [iSize];  
IntPtr rAddr = new IntPtr( iAddr );  

// Marshal the array from an unmanaged to a managed heap.  
Marshal.Copy( rAddr, bArray, 0, iSize );  
for (int i=0; i < iSize; i++)  
   Console.WriteLine( bArray[i] );  

// Release the unmanaged array.  
Marshal.FreeCoTaskMem( rAddr );  
//--------------------

有没有人知道潜在的解决方案？

Answer 1

首先，您必须只构建x86-代码将在64位上失败。其次，您必须使用unsafe代码在C＃中执行此类转换。

Answer 2

IntPtr bAddr = new IntPtr( iAddr );  // bAddr = (byte**)iAddr
IntPtr rAddr = new IntPtr(Marshal.ReadInt32(bAddr)); //rAddr = (*bAddr);

byte [] bArray = new byte [iSize];   
// Marshal the array from an unmanaged to a managed heap.   
Marshal.Copy( rAddr, bArray, 0, iSize );   
for (int i=0; i < iSize; i++)   
   Console.WriteLine( bArray[i] );   

// Release the unmanaged array.   
Marshal.FreeCoTaskMem( rAddr );

Answer 3

有一个ReadIntPtr方法可从地址读取本机宽度指针。与ReadInt32不同，它将在两种体系结构上都能工作

通过Interop从C＃在COM / C ++中分配的地址访问非托管内存

3 个答案: