Question

我正在做C ++ - ＆gt; C＃interop stuff和我有一堆结构，像Matryoshka娃娃一样互相包含。问题是这些“嵌套”中的一个采用固定长度数组的形式：

typedef struct tagBIRDREADING
{
    BIRDPOSITION    position;
    BIRDANGLES      angles;
    BIRDMATRIX      matrix;
    BIRDQUATERNION  quaternion;
    WORD            wButtons;
}
BIRDREADING;

typedef struct tagBIRDFRAME
{
    DWORD           dwTime;
    BIRDREADING     reading[BIRD_MAX_DEVICE_NUM + 1];
}
BIRDFRAME;

在hallowed teachings of Eric Gunnerson之后，我在C＃中执行了以下操作：

[StructLayout(LayoutKind.Sequential, Pack = 0)]
public struct BIRDREADING
{
    public BIRDPOSITION position;
    public BIRDANGLES angles;
    public BIRDMATRIX matrix;
    public BIRDQUATERNION quaternion;
    public ushort wButtons;
}

[StructLayout(LayoutKind.Sequential, Size = 127)]
public struct BIRDREADINGa
{
    public BIRDREADING reading;
}

public struct BIRDFRAME
{
    public uint dwTime;
    public BIRDREADINGa readings; 
}

我的问题是，如何访问BIRDREADING中包含的BIRDREADINGa的127个实例中的每一个，因此BIRDFRAME？或者我出错了？

Answer 1

我想你只想要这个：

[StructLayout(LayoutKind.Sequential)]
public struct BIRDFRAME
{
    public uint dwTime;
    [MarshalAs(UnmanagedType.ByValArray, SizeConst=127)] 
    public BIRDREADING[] readings; 
}

Answer 2

要在不使用数组的情况下访问所有这些实例，您需要使用不安全的块来获取您设置的“假数组”的地址，然后使用指针算法。它会变丑：

public struct BIRDREADINGa
{
    public BIRDREADING reading;

    public BIRDREADING GetReading(int index)
    {
        unsafe
        {
            fixed(BIRDREADING* r = &reading)
            {
                return *(r + index);
            }
        }
    }
}

不使用“fixed”，如何在结构中访问数组的值？

2 个答案: