中山网站外包,长沙seo男团,用wordpress做个,做海外生意的网站通过预留字段来补齐内存分配。在实际项目中采用这种方法较多#xff0c;即保证了长度一致#xff0c;也为以后的扩展提供了容错的可能性。
unsafe struct StructSequential{public fixed float x[8];public fixed float y[8];public fixed float z[8];public fixed float ti…通过预留字段来补齐内存分配。在实际项目中采用这种方法较多即保证了长度一致也为以后的扩展提供了容错的可能性。
unsafe struct StructSequential{public fixed float x[8];public fixed float y[8];public fixed float z[8];public fixed float time[8];public fixed float radius[8];[MarshalAs(UnmanagedType.ByValArray, SizeConst 8)]public float[] reserved;}或者
public unsafe struct RTCPointQuery8{public fixed float x[8];public fixed float y[8];public fixed float z[8];public fixed float time[8];public fixed float radius[8];}
Spanbyte stack stackalloc byte[sizeof(RTCPointQuery8) 32];
ref var test ref StackAllocAlignedRTCPointQuery8(stack, 32);static unsafe ref T StackAllocAlignedT(Spanbyte stack, nuint alignment) where T : unmanaged{return ref Unsafe.AsRefT((void*)(((nint)Unsafe.AsPointer(ref MemoryMarshal.GetReference(stack)) ((nint)alignment - 1)) ~(nint)(alignment - 1)));}C#内存对齐有三种方式分别是LayoutKind.Sequential、LayoutKind.Explicit、LayoutKind.Auto。
LayoutKind.Sequential
顺序对齐这是默认的内存对齐方式。会按照定义的struct中最大成员的长度进行内存对齐使用这种对齐方式容易造成内存空间浪费。这种方式常用于和非托管代码交互的情形CLR对struct的Layout处理方法与C/C中默认的处理方式相同都是按照结构体中占用空间最大的成员进行内存对齐。
[StructLayout(LayoutKind.Sequential)]struct StructSequential{public int A;public char B;}public static void Start(){StructSequential structSequential new StructSequential();Debug.WriteLine(A的长度为{0}, Marshal.SizeOf(structSequential.A));Debug.WriteLine(B的长度为{0}, Marshal.SizeOf(structSequential.B));Debug.WriteLine(structSequential的长度为{0}, Marshal.SizeOf(structSequential));}
//A的长度为4
//B的长度为1
//structSequential的长度为8如果我们正在创建一个与非托管代码没有任何交互的struct类型我们也希望改变C#编译器的这种默认规则因此除了Sequential外还有Explicit和Auto。
除此之外你还可以通过设置StructLayout.Pack的值来达到内存大小分配一致但这种方法可能会因硬件性能约束或者其他的问题。
[StructLayout(LayoutKind.Sequential, Pack 32)]unsafe struct StructSequential{public fixed float x[8];public fixed float y[8];public fixed float z[8];public fixed float time[8];public fixed float radius[8];}LayoutKind.Explicit
精确对齐CLR会按照程序的设置对内存进行精确对齐。传入LayoutKind.Explicit可以使字段按照我们设定的FieldOffset设置字段排序方式CLR不对结构体进行内存对齐但是这种方式也是有缺陷的如果设置错误后果将比较严重。
[StructLayout(LayoutKind.Explicit)]struct StructSequential{[FieldOffset(0)]public int A;[FieldOffset(0)]public char B;}public static void Start(){StructSequential structSequential new StructSequential();Debug.WriteLine(A的长度为{0}, Marshal.SizeOf(structSequential.A));Debug.WriteLine(B的长度为{0}, Marshal.SizeOf(structSequential.B));Debug.WriteLine(structSequential的长度为{0}, Marshal.SizeOf(structSequential));structSequential.A 0;structSequential.B 0;Debug.WriteLine(structSequential.A: {0}, structSequential.A);Debug.WriteLine(structSequential.B: {0}, structSequential.B);}
//A的长度为4
//B的长度为1
//structSequential的长度为4
//structSequential.A: 48
//structSequential.B: 0[FieldOffset(0)]表示内存不会有任何偏移这种情形下同一字节中存储了两条数据当其中一条改变时另一条也随之而改变。
LayoutKind.Auto
自动对齐。CLR会调整struct中成员的顺序来自动对齐使实例仅可能占用更少的内存同时会进行一定字节的内存对齐。 按照自己选择的最优方式对实例中的字段进行排列。
[StructLayout(LayoutKind.Auto)]struct StructSequential{public int A;public char B;}public static void Start(){StructSequential structSequential new StructSequential();Debug.WriteLine(A的长度为{0}, Marshal.SizeOf(structSequential.A));Debug.WriteLine(B的长度为{0}, Marshal.SizeOf(structSequential.B));//Debug.WriteLine(structSequential的长度为{0}, Marshal.SizeOf(structSequential));unsafe{Debug.WriteLine(structSequential的长度为{0}, sizeof(StructSequential));}structSequential.A 0;structSequential.B a;Debug.WriteLine(structSequential.A: {0}, structSequential.A);Debug.WriteLine(structSequential.B: {0}, structSequential.B);}
