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QuestionHow to call a .dll written in unmanaged C++ from C# and pass structs to and from? [Solved] Pin
CircuitDoc27-Oct-09 8:05
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AnswerRe: How to call a .dll written in unmanaged C++ from C# and pass structs to and from? Pin
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GeneralRe: How to call a .dll written in unmanaged C++ from C# and pass structs to and from? Pin
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GeneralRe: How to call a .dll written in unmanaged C++ from C# and pass structs to and from? Pin
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AnswerRe: How to call a .dll written in unmanaged C++ from C# and pass structs to and from? [Solved] Pin
CircuitDoc29-Oct-09 7:48
CircuitDoc29-Oct-09 7:48 
Thanks to Luc Pattyn and a little more reasearch on the Web, I solved this using the GCHandle Class.

Here is the updated working code:

public struct MY_Input_Type
       {
           public UInt32 iSignalCount;
           public IntPtr dSignal;
           public UInt32 iFilterCount;
           public IntPtr dFilterKernel;
       }

       public struct MY_Return_Type
       {
           public UInt32 iDftCount;
           public IntPtr dDft;
           public IntPtr dFilteredSignal;
       }
       [DllImport(@"MY_DLL.dll")]
       public static extern uint PowerOfTwo(uint b);
       [DllImport(@"MY_DLL.dll")]
       public static extern void FFT_Convolution(MY_Input_Type input, MY_Return_Type rtrn);

       public void Start(string rawFile, string filterFile, string outFile)
       {
           //Instantiate the input and return structs
           MY_Input_Type input;
           MY_Return_Type rtrn;

           //Create arrays to hold the data while in the C# program
           double[] filterData;
           double[] rawData;
           double[] returnData;
           double[] returnFilter;

           //Fill the input arrays with data from files.
           filterData = ReadFile(rawFile);
           rawData = ReadFile(filterFile);

           //Create handles for input arrays so they do not get Garbage collected
           GCHandle rawHandle = GCHandle.Alloc(rawData, GCHandleType.Pinned);
           GCHandle filterHandle = GCHandle.Alloc(filterData, GCHandleType.Pinned);

           //Set the pointers in the input struct equal to the address of the handles for the arrays
           input.dSignal = rawHandle.AddrOfPinnedObject();
           input.dFilterKernel = filterHandle.AddrOfPinnedObject();

           //Initialize input integers to the sizes of the arrays
           input.iFilterCount = Convert.ToUInt32(filterData.Length);
           input.iSignalCount = Convert.ToUInt32(rawData.Length);

           //Set counter in return struct to the size of the return arrays (input size rounded up to power of two)
           rtrn.iDftCount = PowerOfTwo(Convert.ToUInt32(rawData.Length));

           //Initialize the return arrays to the size needed for the return data
           returnData = new double[Convert.ToInt32(rtrn.iDftCount)];
           returnFilter = new double[Convert.ToInt32(rtrn.iDftCount)];

           //Create handles for output arrays so they do not get Garbage collected
           GCHandle rtrnData = GCHandle.Alloc(returnData, GCHandleType.Pinned);
           GCHandle rtrnFilter = GCHandle.Alloc(returnFilter, GCHandleType.Pinned);

           //Set the pointers in the output struct equal to the address of the handles for the arrays
           rtrn.dDft = rtrnData.AddrOfPinnedObject();
           rtrn.dFilteredSignal = rtrnFilter.AddrOfPinnedObject();

           //Call the function, feeding in the structs for the input and return
           FFT_Convolution(input, rtrn);

           //Write the data to a file
           WriteOutput(returnFilter, returnData, outFile);

           //Release Handles to free up the unmanaged memory
           rawHandle.Free();
           filterHandle.Free();
           rtrnData.Free();
           rtrnFilter.Free();
       }


If anyone sees a way to optimize this code, please let me know. Thanks...
QuestionPass string " Hello {0}" though MessageBox Pin
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