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[ASP.net教程]C#各种数组直接的数据复制/转换


        之前做Opengl程序,用的的C#的SharpGL这个库,里面有各种奇怪绑定的函数,比如原型为:

void glInterleavedArrays(uint format, int stride, void * pointer);

的函数被他绑定成:

private static extern void glInterleavedArrays(uint format, int stride, int[] pointer);

然后我就被逼着学习了各种float[] 转 int[] 的方法,比较他们的效率(其实我还是感觉c++比较快,一个指针类型转换,欧啦)

        下面是我写的各种数组赋值转换的方法和结果对比。

1.Marshal.Copy,存在数组到IntPtr,IntPtr到数组的2次拷贝【当T2不是Copy支持的类型会出错,之所以引入dynamic dTo 是因为使用T2[] dTo 无法编译通过】,处理2000000*100字节1120.0018ms

public static T2[] Arr2Arr<T1, T2>(T1[] from)  where T1: struct   where T2 :struct{  int byteNum = from.Length * from[0].Sizeof();  T2 testByte = new T2();  dynamic dFrom = from;  dynamic dTo = new T2[byteNum / testByte.Sizeof()];  IntPtr ptr = Marshal.AllocHGlobal(byteNum);  Marshal.Copy(dFrom, 0, ptr, from.Length);  Marshal.Copy(ptr, dTo, 0, dTo.Length);  return dTo;}

2.unsafe的方法,通过指针获得IntPtr,减少了一次复制,速度变快【当T2不是Copy支持的类型会出错,之所以引入pFrom是因为无法fixed泛型T1[]】,处理2000000*100字节695.9993ms

public unsafe static T2[] Arr2Arr<T1, T2>(T1[] from, void * pFrom)  where T1 : struct  where T2 : struct{  int byteNum = from.Length * from[0].Sizeof();  T2 testByte = new T2();  dynamic dTo = new T2[byteNum / testByte.Sizeof()];  IntPtr ptr = new IntPtr(pFrom);  Marshal.Copy(ptr, dTo, 0, dTo.Length);  return dTo;}

3.通过GCHandle获得IntPtr,然后复制【当T2不是Copy支持的类型会出错】,处理2000000*100字节930.0481ms

public static T2[] Arr2Arr2<T1, T2>(T1[] from)  where T1 : struct  where T2 : struct{  var gch = GCHandle.Alloc(from,GCHandleType.Pinned);  IntPtr ptr = gch.AddrOfPinnedObject();  int byteNum = from.Length * from[0].Sizeof();  T2 testByte = new T2();  dynamic dTo = new T2[byteNum / testByte.Sizeof()];  Marshal.Copy(ptr, dTo, 0, dTo.Length);  gch.Free();  return dTo;}

4.Array.Copy的方法,原生的数组复制方法【没有了Copy,可以处理任意值类型】,处理2000000*100字节620.042ms

public static T2[] Arr2Arr3<T1, T2>(T1[] from)  where T1 : struct  where T2 : struct{  int byteNum = from.Length * from[0].Sizeof();  T2 testByte = new T2();  T2[] dTo = new T2[byteNum / testByte.Sizeof()];  Array.Copy(from, dTo, dTo.Length);  return dTo;}

5.通过Buffer.BlockCopy拷贝数组,速度最快,感觉类似于c++的memcpy【没有了Copy,可以处理任意值类型】,处理2000000*100字节300.0329ms

public static T2[] Arr2Arr4<T1, T2>(T1[] from)  where T1 : struct  where T2 : struct{  int byteNum = from.Length * from[0].Sizeof();  T2 testByte = new T2();  T2[] dTo = new T2[byteNum / testByte.Sizeof()];  Buffer.BlockCopy(from, 0, dTo, 0, byteNum);  return dTo;}

测试部分代码:

byte[] from = new byte[100];from[0] = 1;from[1] = 1;var last = DateTime.Now;for (int i = 0; i < 2000000; i++){  。。。}Console.WriteLine((DateTime.Now- last).TotalMilliseconds);

//sizeof扩展方法
internal static class ExFunc{  public static int Sizeof(this ValueType t)  {    return Marshal.SizeOf(t);  }}

综上所述,Buffer.BlockCopy 适用场合最广泛,效率最高。

例子下载地址:http://files.cnblogs.com/files/chihirosan/Convert.zip