C#指针复习示例zz

*内容和&地址。&获取一个十进制的uint地址，而*获得地址的内容。

 

/// <summary>
/// 指针，存储的是一个地址的整数。
/// </summary>
class Program
{
    delegate void Methods();

    static void Main(string[] args)
    {
        Demo6();
        Console.ReadKey();
    }

    static void S(object o)
    {
        Console.WriteLine(o.ToString());
    }

    static void S(params object[] o)
    {
        foreach (object obj in o)
            S(obj);
    }

    #region 指针简单示例
    unsafe static void Demo1()
    {
        int x = 10;//整数类型
        int* pX, pY;//指针坐标X、Y
        pX = &x;//取pX地址
        pY = pX;//将pX赋值给pY

        x = 15;
        *pX = 16;
        *pY = 17;

        S(x);
        S(*pX);//取得地址的内容
        S(*pY);
    }
    #endregion

    #region 指针的类型转换
    unsafe static void Demo2()
    {
        //NOTE:类型转换后，uint获得的是地址的十进制格式，并非获取地址的内容。

        int x = 10;//整数类型
        int* pX, pY;//指针坐标X、Y
        pX = &x;//取pX地址
        pY = pX;//将pX的地址赋值给pY
        uint ux = (uint) pX;//类型转换，获取地址的十进制
        int* pZ = (int*) ux;//类型转换，将地址赋值给pZ

        S(x);
        S(((uint) pX).ToString("x"));//十六进制内存地址
        S((uint) pY);//十进制内存地址
        S(ux);
        S((uint) pZ);//十进制内存地址
        S(*pZ);//输出地址的内容
    }
    #endregion

    #region DWORD内存块
    unsafe static void Demo3()
    {
        decimal m2 = 4.00m;
        byte b = 100;
        short s = 200;
        int i = 300;
        long l = 400;

        float f = 1.00f;
        double d = 2.00;
        decimal m = 3.00m;


        S(string.Format("byte:{0}", sizeof(byte)));
        S(string.Format("short:{0}", sizeof(short)));
        S(string.Format("int:{0}", sizeof(int)));
        S(string.Format("long:{0}", sizeof(long)));
        S(string.Format("float:{0}", sizeof(float)));
        S(string.Format("double:{0}", sizeof(double)));
        S(string.Format("decimal:{0}", sizeof(decimal)));
        S("");
        S("从高到矮……");
        S(string.Format("decimal:{0} +16  ↑", (uint) &m2));
        S(string.Format("byte:{0} +1  ↑", (uint) &b));
        S(string.Format("short:{0}  +2  ↑", (uint) &s));
        S(string.Format("int:{0}  +4  ↑", (uint) &i));
        S(string.Format("long:{0}  +8  ↑", (uint) &l));
        S(string.Format("float:{0}  +4  ↑", (uint) &f));
        S(string.Format("double:{0}  +8  ↑", (uint) &d));
        S(string.Format("decimal:{0}  +16  ↑", (uint) &m));
        S("有没有发现byte和short也是4个字节的内存块？因为.NET约定，最少要占用4个字节。");
    }
    #endregion

    #region 指针的运算
    unsafe static void Demo4()
    {

        byte b = 8;
        uint u = 3;
        double d = 10.0;

        byte* pByte = &b;
        uint* pUint = &u;
        double* pDouble = &d;
        S(string.Format("byte:{0}", (uint) pByte));
        S(string.Format("uint:{0}", (uint) pUint));
        S(string.Format("double:{0}", (uint) pDouble));
        pByte -= 3;
        ++pUint;
        S("\n");
        double* pDouble2 = pDouble + 4;
        S(string.Format("byte:{0}。old - 3 * 1", (uint) pByte));
        S(string.Format("uint:{0}。old + 4 * 1", (uint) pUint));
        S(string.Format("double2:{0}。pDouble + 4 * 8", (uint) pDouble2));

    }
    #endregion

    #region 结构指针
    unsafe static void Demo5()
    {

        MyStruct ms = new MyStruct();
        MyStruct* pms = &ms;
        (*pms).X = 5;//传统方式
        pms->Y = 10;//与C++雷同方式

        S(ms.X);
        S(ms.Y);

        int* X = &(pms->X);
        S(*X);
        *X = 15;
        S(*X);
        S(ms.X);
    }

    struct MyStruct
    {
        public int X;
        public int Y;
    }
    #endregion

    #region 类指针
    unsafe static void Demo6()
    {
        MyClass mc = new MyClass();
        //MyClass* pmc = &mc;//error,无法获取托管类型，因为它们嵌入一个对象。（结构是值类型）
        fixed (int* X = &(mc.X))
        fixed (int* Y = &(mc.Y))//*X和*Y固定或者fixed (int* X = &(mc.X), Q = &(mc.Y))。唯一限制，数据类型必须都是int*。
        {
            *X = 5;
            *Y = 6;
            S(mc.X + "<-X  Y-> " + mc.Y);
            fixed (int* Z = &(mc.Z))//*Z固定在X中。生命周期在于X、Y之间。
            {
                *Z = 7;
                *X = 8;
                *Y = 9;
                S(mc.X + "<-X  Y-> " + mc.Y + "  Z->" + mc.Z);
            }
            *X = 10;
            *Y = 11;
            S(mc.X + "<-X  Y-> " + mc.Y);
        }

    }
    class MyClass
    {
        public int X;
        public int Y;
        public int Z;
    }
    #endregion

}

实现字符串倒置：

public static string RevertString2(string src)
        {
            char tmp;
            unsafe
            {
                fixed (char* ps = src)
                {
                    for (int i = 0; i < src.Length / 2; i++)
                    {
                        tmp = ps[i];
                        ps[i] = ps[src.Length - i - 1];
                        ps[src.Length - i - 1] = tmp;
                    }
                }
            }
            return src;
        }