C#中结构和类成员指针的内存分配

时间：2010-09-23 来源：关羽

C#中结构和类成员指针的内存分配

http://mgc.name/article.asp?id=600

作者:Magci 日期:2009-01-08 02:29

字体大小: 小中大通过结构和类成员指针的操作，观察内存分配情况：
1.结构、类成员是按顺序排列在内存中的；
2.通过指针操作可以方便的指向任意变量。

TestPointerExampleTwo.cs:
view source print? 01.using System; 02. 03.namespace Magci.Test.Pointers 04.{ 05. //结构 06. internal struct CurrencyStruct 07. { 08. public long Dollars; 09. public byte Cents; 10. 11. public override string ToString() 12. { 13. return "$" + Dollars + "." + Cents; 14. } 15. } 16. 17. //类 18. internal class CurrencyClass 19. { 20. public long Dollars; 21. public byte Cents; 22. 23. public override string ToString() 24. { 25. return "$" + Dollars + "." + Cents; 26. } 27. } 28. 29. public class TestPointerExampleTwo 30. { 31. public static unsafe void Main() 32. { 33. Console.WriteLine("Size of CurrencyStruct struct is " + sizeof(CurrencyStruct)); 34. CurrencyStruct amount1, amount2; 35. CurrencyStruct* pAmount = &amount1; 36. long* pDollars = & (pAmount->Dollars); 37. byte* pCents = & (pAmount->Cents); 38. 39. Console.WriteLine("Address of amount1 is [0x{0:X}]", (uint)&amount1); 40. Console.WriteLine("Address of amount2 is [0x{0:X}]", (uint)&amount2); 41. Console.WriteLine("Address of pAmount is [0x{0:X}]", (uint)&pAmount); 42. Console.WriteLine("Address of pDollars is [0x{0:X}]", (uint)&pDollars); 43. Console.WriteLine("Address of pCents is [0x{0:X}]", (uint)&pCents); 44. 45. pAmount->Dollars = 20; 46. *pCents = 50; 47. 48. Console.WriteLine("amount1 contains [{0}]", amount1); 49. //amount2存储在amount1后面的地址上，pAmount开始指向amount1，递减后就指向了amount2 50. --pAmount; 51. //amount2没有进行初始化，值是随机的；使用指针时会绕过很多通常的编译检查，因此指针算法是不安全的 52. Console.WriteLine("amount2 has address [0x{0:X}] and contains [{1}]", (uint)pAmount, *pAmount); 53. 54. //将pCents指向amount2.Cents 55. CurrencyStruct* pTempCurrency = (CurrencyStruct*)pCents; 56. pCents = (byte*)(--pTempCurrency); 57. Console.WriteLine("Address of pCents is now [0x{0:X}]", (uint)&pCents); 58. 59. Console.WriteLine("\nNow with classes"); 60. CurrencyClass amount3 = new CurrencyClass(); 61. 62. fixed (long* pDollars2 = &(amount3.Dollars)) 63. fixed (byte* pCents2 = &(amount3.Cents)) 64. { 65. Console.WriteLine("amount3.Dollars has address [0x{0:X}]", (uint)pDollars2); 66. Console.WriteLine("amount3.Cents has address [0x{0:X}]", (uint)pCents2); 67. *pDollars2 = -100; 68. Console.WriteLine("amount3 contains [{0}]", amount3); 69. } 70. } 71. } 72.}