c# - 使用 StructureToPtr 将 C# 结构编码为 C++

Question

我有 C# 类:

namespace Models
{
    [StructLayout(LayoutKind.Explicit, Size = 120, CharSet = CharSet.Unicode)]
    public struct DynamicState
    {
        [FieldOffset(0)]
        public double[] Position;

        [FieldOffset(24)]
        public double[] Velocity;

        [FieldOffset(48)]
        public double[] Acceleration;

        [FieldOffset(72)]
        public double[] Attitude;

        [FieldOffset(96)]
        public double[] AngularVelocity;
    }
}

和 C++/CLI 方法:

Models::DynamicState SomeClassClr::DoSomething(Models::DynamicState ds)
{
    int struct_size = Marshal::SizeOf(ds);
    System::IntPtr ptr = Marshal::AllocHGlobal(struct_size);
    DynamicStateStruct ds_struct;
    struct_size = sizeof(ds_struct);

    Marshal::StructureToPtr(ds, ptr, false);
    ds_struct = *(DynamicStateStruct*)ptr.ToPointer();

    Models::DynamicState returnVal;
    mpSomeClass->doSomething(ds_struct);

    return returnVal;
}

其中 DynamicStateStruct 是原生 C++ 类:

struct DynamicStateStruct
{
    double mPosition[3];
    double mVelocity[3];
    double mAcceleration[3];
    double mAttitude[3];
    double mAngularVelocity[3];
};

当我在 native C++ 中恢复结构 (ds_struct) 时，我没有得到正确的值，对我缺少的有什么想法吗？

Answer 1

尝试以下变体:

public struct DynamicState
{
    [MarshalAs (UnmanagedType.ByValArray, SizeConst=3)]
    public double[] Position;

    [MarshalAs (UnmanagedType.ByValArray, SizeConst=3)]
    public double[] Velocity;

    [MarshalAs (UnmanagedType.ByValArray, SizeConst=3)]
    public double[] Acceleration;

    [MarshalAs (UnmanagedType.ByValArray, SizeConst=3)]
    public double[] Attitude;

    [MarshalAs (UnmanagedType.ByValArray, SizeConst=3)]
    public double[] AngularVelocity;
}

另一种选择是使用不安全代码中可用的固定数组:

public unsafe struct DynamicState
{
    public fixed double Position[3];

    public fixed double Velocity[3];

    public fixed double Acceleration[3];

    public fixed double Attitude[3];

    public fixed double AngularVelocity[3];
}

附言可以在此处找到有关 .Net 互操作的良好指南:http://www.mono-project.com/Interop_with_Native_Libraries