从C＃调用非托管C ++库（dll）：如何在托管代码和非托管代码之间正确传递数据

Question

我一直在使用从传感器读取测量数据并使用C ++编写的库来分析该数据的接口。

该功能大致如下：

1. 在C ++库上设置测量参数
2. 从传感器获取数据（总共进行了1200次测量）
3. 将数据写入C ++库
4. 在C ++库中处理所有1200次测量
5. 从C ++库读取结果

从C＃代码调用此C ++库以前已解决以下问题：从C＃ 调用非托管C ++库（dll）会产生访问冲突错误（0xc0000005）。

现在看来，C ++库要么

• 无法正确获取数据
• 无法保存数据
• 无法将结果正确返回到我的C＃代码。

不好的是，我无法调试此C ++库。

我的代码有什么问题？

1）设置测量参数

namespace PdWaveApi
{
[StructLayout(LayoutKind.Sequential)]
public struct PDDataInfo

{                   
   public int   nPings;              
   public int   nDataRate;          
   public int   nSamples;            
   public float fFrequency;          
   public float fBeamAngle;          
   public int   nInstrument;         
   public int   nCoordSystem;        
   [MarshalAs(UnmanagedType.ByValArray, SizeConst = 9)]
   public short[] hBeamToXYZ;       
   public short hWaveT1;

    // Constructor
   public static PDDataInfo Create()
   {
       PDDataInfo DataStruct = new PDDataInfo();
       DataStruct.hBeamToXYZ = new short[9];
       return DataStruct;
   }
   }
}

public class PdWaveBaseLWrapper
{
   [DllImport("PdWaveBase.dll", EntryPoint = "PDSetInstrumentConfig")]
   public static extern int PDSetInstrumentConfig(ref PDDataInfo pDataInfo);
}

public void SetInstrumentConfiguration()
{
    PdWaveApi.PDDataInfo InstrumentConfiguration = new PdWaveApi.PDDataInfo();
    .................
    Initializing the InstrumentConfiguration structure
    ...............
    PdWaveBaseLWrapper.PDSetInstrumentConfig(ref InstrumentConfiguration);
}

3）从传感器读取数据并将数据写入C ++库

namespace PdWaveApi
{
    [StructLayout(LayoutKind.Sequential)]
    public struct PDWaveSample
    {   
        [MarshalAs(UnmanagedType.I1)]
        public bool Valid;
        public float fPressure;
        public float fDistance;
        [MarshalAs(UnmanagedType.ByValArray, SizeConst = Constants.PD_MAX_WAVEBEAMS)]
        public float[] fVel;
        [MarshalAs(UnmanagedType.ByValArray, SizeConst = Constants.PD_MAX_WAVEBEAMS)]
        public ushort[] nAmp;

        // Constructor

        public static PDWaveSample Create()
        {
            PDWaveSample DataStruct = new PDWaveSample();
            DataStruct.fVel = new float[Constants.PD_MAX_WAVEBEAMS];
            DataStruct.nAmp = new ushort[Constants.PD_MAX_WAVEBEAMS];
            return DataStruct;
        }
    }
}

public class PdWaveBaseLWrapper
{
    [DllImport("PdWaveBase.dll", EntryPoint = "PDSetWaveSample")]
    public static extern int PDSetWaveSample(ref PDWaveSample pWaveSample);
}

namespace SensorInterface
{
    public partial class frmSensorInterface : Form
    {
        public PdWaveApi.PDWaveSample WaveSampleData = PdWaveApi.PDWaveSample.Create();

        private void OnNewData(object sender, OnNewDataEvent e)
        {
            ReadWaveSample(ref WaveSampleData);
            SetWaveSample(ref WaveSampleData);
        }

        public void ReadWaveSample(ref PdWaveApi.PDWaveSample WaveSampleData)
        {
            DateTime MeasurementTimeStamp;
            float[] dVel = new float[4];
            float dTemperature = new float();
            float dPitch = new float();
            float dRoll = new float();
            float dHeading = new float();
            float dPressure = new float();
            short[] sAmp = new short[4];

            //  Read some of the latest data from the control
            GetVelocity(ref dVel[0], ref dVel[1], ref dVel[2], ref dVel[3]);
            GetAmplitude(ref sAmp[0], ref sAmp[1], ref sAmp[2], ref sAmp[2]);

            ..............
            // Set other data to the structure

        }

        public void SetWaveSample(ref PdWaveApi.PDWaveSample WaveSampleData)
        {
            PdWaveBaseLWrapper.PDSetWaveSample(ref WaveSampleData);
        }
    }
}

4）在C ++库中处理所有1200次测量

[StructLayout(LayoutKind.Sequential)]
public struct PDWaveBurst
{
    [MarshalAs(UnmanagedType.ByValArray , SizeConst = Constants.PD_MAX_WAVEMEAS_AST)]    
    public float[] fST; 
    public float fWinFloor;
    public float fWinCeil;
    [MarshalAs(UnmanagedType.I1)]
    public bool bUseWindow;
    [MarshalAs(UnmanagedType.I1)]
    public bool bSTOk;
    [MarshalAs(UnmanagedType.I1)]
    public bool bGetRawAST;
    [MarshalAs(UnmanagedType.I1)]
    public bool bValidBurst;

    public static PDWaveBurst Create()
    {
        PDWaveBurst DataStruct = new PDWaveBurst();
        DataStruct.fST = new float[Constants.PD_MAX_WAVEMEAS_AST];
        return DataStruct;
    }
}

[DllImport("PdWaveBase.dll", EntryPoint = "PDPreProcess")]
public static extern int PDPreProcess(int nSample, ref PDWaveBurst pWaveBurst);

[DllImport("PdWaveBase.dll", EntryPoint = "PDProcessReturnInt")]
public static extern int PDProcessReturnInt();

public void PreprocessBurstData(int nSamples)
{
    PdWaveApi.PDWaveBurst WaveBurstData = PdWaveApi.PDWaveBurst.Create();

    WaveBurstData.fST = new float[4096];
    WaveBurstData.fWinFloor = (float)1.25;
    WaveBurstData.fWinCeil = 2;
    WaveBurstData.bUseWindow = false;
    WaveBurstData.bSTOk = false;
    WaveBurstData.bGetRawAST = false;
    WaveBurstData.bValidBurst = false;

    PdWaveBaseLWrapper.PDPreProcess(nSamples, ref WaveBurstData);
}

public void ProcessData()
{
    int ProcessError = PdWaveBaseLWrapper.PDProcessReturnInt();
}

5）从C ++库读取结果

[StructLayout(LayoutKind.Sequential)]
public struct PDWavePar {
   public float fTm02;  
   public float fTp;     
   public float fDirTp;  
   public float fSprTp;  
   public float fMainDir;
   public float fUI;     
   public float fHm0;   
   public float fH3;
   public float fT3;    
   public float fH10; 
   public float fT10;
   public float fHmax;
   public float fTmax;
   public float fTz;
   public float fMeanPres;
   public int   nNumNoDet;
   public int   nNumBadDet;
   public int   nErrCode;  
   public int   nSpectrum; 
   public float fMeanAST;
}


[DllImport("PdWaveBase.dll", EntryPoint = "PDGetWavePar")]
public static extern int PDGetWavePar(ref PDWavePar pwWavePar);

public void GetOutput()
{
    PdWaveApi.PDWavePar WaveParameters = new PdWaveApi.PDWavePar();
    PdWaveBaseLWrapper.PDGetWavePar(ref WaveParameters);
}

因此，作为结论：

我应该在代码中进行哪些更改-正确地将数据传递给非托管dll-使dll保留并处理其内部结构中的数据-从非托管代码正确读取结果到C＃程序？

（很抱歉，我的提问时间太长了。）

Answer 1

我的问题的最终解决方案是将对齐方式更改为1个字节，如下所示：

C＃结构定义：来自：

    [StructLayout(LayoutKind.Sequential)]

至

    [StructLayout(LayoutKind.Sequential, Pack=1)]

至少在这里已对此进行了讨论： 从c＃Metro应用程序调用C ++ Metro dll并返回填充的结构