是否有更快/更清晰的方法将结构复制到C#中的数组？

Question

我有一个float4x4结构,它只包含16个浮点数:

struct float4x4
{
        public float M11; public float M12; public float M13; public float M14;
        public float M21; public float M22; public float M23; public float M24;
        public float M31; public float M32; public float M33; public float M34;
        public float M41; public float M42; public float M43; public float M44;
}

我想将这些结构的数组复制到一大堆浮点数中.据我所知,这是一块内存的1:1副本

我所知道的是相当丑陋,而不是那么快:

        int n = 0;
        for (int i = 0; i < Length; i++)
        {
            array[n++] = value[i].M11;
            array[n++] = value[i].M12;
            array[n++] = value[i].M13;
            array[n++] = value[i].M14;

            array[n++] = value[i].M21;
            array[n++] = value[i].M22;
            array[n++] = value[i].M23;
            array[n++] = value[i].M24;

            array[n++] = value[i].M31;
            array[n++] = value[i].M32;
            array[n++] = value[i].M33;
            array[n++] = value[i].M34;

            array[n++] = value[i].M41;
            array[n++] = value[i].M42;
            array[n++] = value[i].M43;
            array[n++] = value[i].M44;
        }

如果我使用的是较低级别的语言,我只想使用memcpy,我可以在C#中使用什么作为等效语言？

Answer 1

这也许同样丑陋，但速度非常快。

using System.Runtime.InteropServices;

namespace ConsoleApplication23 {
  public class Program {
    public static void Main() {
      var values=new[] {
        new float4x4(1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16),
        new float4x4(-1, -2, -3, -4, -5, -6, -7, -8, -9, -10, -11, -12, -13, -14, -15, -16)
      };
      var result=Transform(values);
    }

    public static unsafe float[] Transform(float4x4[] values) {
      var array=new float[values.Length*16];
      fixed(float* arrayStart=array) {
        var destp=arrayStart;
        fixed(float4x4* valuesStart=values) {
          int count=values.Length;
          for(var valuesp=valuesStart; count>0; ++valuesp, --count) {
            var sourcep=valuesp->data;
            for(var i=0; i<16/4; ++i) {
              *destp++=*sourcep++;
              *destp++=*sourcep++;
              *destp++=*sourcep++;
              *destp++=*sourcep++;
            }
          }
        }
        return array;
      }
    }

    [StructLayout(LayoutKind.Explicit)]
    public unsafe struct float4x4 {
      [FieldOffset(0)] public float M11;
      [FieldOffset(4)] public float M12;
      [FieldOffset(8)] public float M13;
      [FieldOffset(12)] public float M14;
      [FieldOffset(16)] public float M21;
      [FieldOffset(20)] public float M22;
      [FieldOffset(24)] public float M23;
      [FieldOffset(28)] public float M24;
      [FieldOffset(32)] public float M31;
      [FieldOffset(36)] public float M32;
      [FieldOffset(40)] public float M33;
      [FieldOffset(44)] public float M34;
      [FieldOffset(48)] public float M41;
      [FieldOffset(52)] public float M42;
      [FieldOffset(56)] public float M43;
      [FieldOffset(60)] public float M44;

      //notice the use of "fixed" keyword to make the array inline
      //and the use of the FieldOffset attribute to overlay that inline array on top of the other fields
      [FieldOffset(0)] public fixed float data[16];

      public float4x4(float m11, float m12, float m13, float m14,
        float m21, float m22, float m23, float m24,
        float m31, float m32, float m33, float m34,
        float m41, float m42, float m43, float m44) {
        M11=m11; M12=m12; M13=m13; M14=m14;
        M21=m21; M22=m22; M23=m23; M24=m24;
        M31=m31; M32=m32; M33=m33; M34=m34;
        M41=m41; M42=m42; M43=m43; M44=m44;
      }
    }
  }
}