1 using System;
2 using System.Collections.Generic;
3 using System.Linq;
4 using System.Text;
5 using System.Threading.Tasks;
6
7 namespace UnsafeCode
8 {
9 struct Point
10 {
11 public int x;
12 public int y;
13
14 public override string ToString()
15 {
16 return string.Format("({0}, {1})", x, y);
17 }
18 }
19
20 class PointRef
21 {
22 public int x;
23 public int y;
24 public override string ToString()
25 {
26 return string.Format("({0}, {1})", x, y);
27 }
28 }
29
30 class Program
31 {
32 static void Main( string[] args )
33 {
34 Console.WriteLine("***** Calling method with unsafe code *****");
35
36 int i = 10, j = 20;
37
38 // 安全交换
39 Console.WriteLine("\n***** Safe swap *****");
40 Console.WriteLine("Values before safe swap: i = {0}, j = {1}", i, j);
41 SafeSwap(ref i, ref j);
42 Console.WriteLine("Values after safe swap: i = {0}, j = {1}", i, j);
43
44 // 不安全交换
45 Console.WriteLine("\n***** Unsafe swap *****");
46 Console.WriteLine("Values before unsafe swap: i = {0}, j = {1}", i, j);
47 unsafe { UnsafeSwap(&i, &j); }
48 Console.WriteLine("Values after unsafe swap: i = {0}, j = {1}", i, j);
49
50 UsePointerToPoint();
51 PrintValueAndAddress();
52 UseAndPinPoint();
53 UseSizeOfOperator();
54
55 Console.ReadLine();
56 }
57
58 unsafe static void UsePointerToPoint()
59 {
60 // 指针访问成员
61 Point point;
62 Point* p = &point;
63 p->x = 100;
64 p->y = 200;
65 Console.WriteLine(p->ToString());
66
67 // 指针间接寻址访问成员
68 Point point2;
69 Point* p2 = &point2;
70 (*p2).x = 100;
71 (*p2).y = 200;
72 Console.WriteLine((*p2).ToString());
73 }
74
75 unsafe static void UnsafeStackAlloc()
76 {
77 char* p = stackalloc char[256];
78 for (int k = 0; k < 256; k++)
79 p[k] = (char)k;
80 }
81
82 // 静态方法或实例方法均可被标记为不安全
83 unsafe static void SquareIntPointer( int* myIntPointer )
84 {
85 *myIntPointer *= *myIntPointer;
86 }
87
88 unsafe static void PrintValueAndAddress()
89 {
90 int myInt;
91 int* ptrToMyInt = &myInt;
92
93 // 指针间接寻址为myInt赋值
94 *ptrToMyInt = 123;
95
96 Console.WriteLine("Value of myInt {0}", myInt);
97 Console.WriteLine("Address of myInt {0:X}", (int)&ptrToMyInt);
98 }
99
100 unsafe public static void UnsafeSwap( int* i, int* j )
101 {
102 int temp = *i;
103 *i = *j;
104 *j = temp;
105 }
106
107 unsafe public static void UseAndPinPoint()
108 {
109 PointRef pt = new PointRef();
110 pt.x = 5;
111 pt.y = 6;
112
113 // fixed 语句设置指向托管类型的指针并在代码执行过程中固定该变量
114 // 固定pt
115 fixed (int* p = &pt.x)
116 {
117 // 此处可使用 int* 变量
118 }
119
120 // pt未固定，该方法完成后可被GC清除
121 Console.WriteLine("Point is: {0}", pt);
122 }
123
124 unsafe static void UseSizeOfOperator()
125 {// 不安全关键字 sizeof
126 Console.WriteLine("The size of short is {0}.", sizeof(short));
127 Console.WriteLine("The size of int is {0}.", sizeof(int));
128 Console.WriteLine("The size of long is {0}.", sizeof(long));
129 Console.WriteLine("The size of Point is {0}.", sizeof(Point));
130 }
131
132 public static void SafeSwap( ref int i, ref int j )
133 {
134 int temp = i;
135 i = j;
136 j = temp;
137 }
138 }
139 }
