如果不使用“fixed”,如何访问结构体中数组的值?
本文关键字:结构体 访问 数组 fixed 何访问 如果不 | 更新日期: 2023-09-27 17:50:12
我正在做c++ -> c#互操作的东西,我有一堆结构体彼此包含像俄罗斯套娃。问题是其中一个"嵌套"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;
遵循Eric Gunnerson的神圣教诲,我在c#中做了以下工作:
[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,我如何访问BIRDREADINGa
和BIRDFRAME
中包含的BIRDREADING
的127个实例中的每个实例?还是我犯了大错?
我想你只是想要这个:
[StructLayout(LayoutKind.Sequential)]
public struct BIRDFRAME
{
public uint dwTime;
[MarshalAs(UnmanagedType.ByValArray, SizeConst=127)]
public BIRDREADING[] readings;
}
要在不使用数组的情况下访问所有这些实例,您需要使用一个不安全块来获取您设置的"假数组"的地址,然后使用指针算术。这会很难看的:
public struct BIRDREADINGa
{
public BIRDREADING reading;
public BIRDREADING GetReading(int index)
{
unsafe
{
fixed(BIRDREADING* r = &reading)
{
return *(r + index);
}
}
}
}