Jan 25

C#读取大容量文本文件的另一方法,仅作参考用 不指定

kcao , 13:18 , 技术 , 评论(0) , 引用(0) , 阅读(4067) , Via 本站原创

PRO文件大多比较臃肿,想找一个能快速读取大容量文本文件的方法,在网上找到了如下的代码,但是实际运行下来的结果并不比filestream有什么优势,因此就把这段代码帖在这里,以作参考用.

用于试验的PRO文件为1.9M左右,73917行,用以下方法和filestream读取全部并AppendText到文本框中,大约都是7秒钟.但是这种方法就烦杂了很多.

HiddenC# Code Copy Code To Clipboard
  1. public const uint CREATE_NEW = 1;
  2. public const uint CREATE_ALWAYS = 2;
  3. public const uint OPEN_EXISTING = 3;
  4. public const uint FILE_BEGIN = 0;
  5. public const uint FILE_CURRENT = 1;
  6. public const uint FILE_END = 2;
  7. public const int GENERIC_READ = -2147483648; //0x80000000
  8. public const int GENERIC_WRITE = 0x40000000;
  9. public const int GENERIC_EXECUTE = 0x20000000;
  10. public const int GENERIC_ALL = 0x10000000;
  11. public const int FILE_ATTRIBUTE_NORMAL = 0x80;
  12. public const int FILE_FLAG_SEQUENTIAL_SCAN = 0x8000000;
  13. public const int INVALID_HANDLE_VALUE = -1;
  14.  
  15. public const int PAGE_NOACCESS = 1;
  16. public const int PAGE_READONLY = 2;
  17. public const int PAGE_READWRITE = 4;
  18.  
  19. public const int FILE_MAP_COPY = 1;
  20. public const int FILE_MAP_WRITE = 2;
  21. public const int FILE_MAP_READ = 4;
  22.  
  23.  
  24. [DllImport("kernel32.dll")]
  25. public static extern IntPtr CreateFileMapping(IntPtr hFile,
  26. IntPtr lpFileMappingAttributes, uint flProtect,
  27. uint dwMaximumSizeHigh,
  28. uint dwMaximumSizeLow, string lpName);
  29.  
  30. [DllImport("kernel32.dll")]
  31. public static extern IntPtr MapViewOfFile(IntPtr hFileMappingObject, uint
  32. dwDesiredAccess, uint dwFileOffsetHigh, uint dwFileOffsetLow,
  33. IntPtr dwNumberOfBytesToMap);
  34.  
  35. [DllImport("kernel32.dll")]
  36. public static extern bool UnmapViewOfFile(IntPtr lpBaseAddress);
  37.  
  38. [DllImport("kernel32.dll")]
  39. public static extern bool CloseHandle(IntPtr hObject);
  40.  
  41. [DllImport("kernel32.dll")]
  42. public static extern IntPtr CreateFile(string lpFileName,
  43. int dwDesiredAccess, FileShare dwShareMode, IntPtr securityAttrs,
  44. FileMode dwCreationDisposition, int dwFlagsAndAttributes, IntPtr hTemplateFile);
  45.  
  46. [DllImport("kernel32.dll")]
  47. public static extern uint GetFileSize(IntPtr hFile, IntPtr lpFileSizeHigh);
  48.  
  49. public string returnback(string path)
  50. {
  51. string str = "";
  52. /*IntPtr vFileHandle = CreateFile(path,
  53. GENERIC_READ | GENERIC_WRITE, FileShare.Read | FileShare.Write,
  54. IntPtr.Zero, FileMode.Open,
  55. FILE_ATTRIBUTE_NORMAL | FILE_FLAG_SEQUENTIAL_SCAN, IntPtr.Zero);*/
  56. IntPtr vFileHandle = CreateFile(path,
  57. GENERIC_READ, FileShare.Read,IntPtr.Zero,
  58. FileMode.Open,
  59. FILE_ATTRIBUTE_NORMAL,IntPtr.Zero);
  60.  
  61.  
  62. if (INVALID_HANDLE_VALUE != (int)vFileHandle)
  63. {
  64. IntPtr vMappingHandle = CreateFileMapping(
  65. vFileHandle, IntPtr.Zero, PAGE_READONLY, 0, 0, "");
  66. if (vMappingHandle != IntPtr.Zero)
  67. {
  68. IntPtr vHead = MapViewOfFile(vMappingHandle,
  69. FILE_MAP_READ, 0, 0, IntPtr.Zero);
  70. if (vHead != IntPtr.Zero)
  71. {
  72. uint vSize = GetFileSize(vFileHandle, IntPtr.Zero);
  73. byte[] temp = new byte[vSize];
  74. for (int i = 0; i < vSize; i++)
  75. {
  76. byte vTemp = Marshal.ReadByte((IntPtr)((int)vHead + i));
  77. temp[i] = vTemp;
  78. }
  79. ASCIIEncoding encoding = new ASCIIEncoding();
  80. str = encoding.GetString(temp).Replace("rn", "rn");
  81. UnmapViewOfFile(vHead);
  82. }
  83. CloseHandle(vMappingHandle);
  84. CloseHandle(vHead);
  85. }
  86. CloseHandle(vFileHandle);
  87.  
  88. }
  89. return str;
  90. }

 

 

以下是第二种方法的代码:

C# Code Copy Code To Clipboard
  1. private string ReadSource(string filename)
  2. {
  3. if (!File.Exists(filename)) return filename + " is invalid.";
  4.  
  5. FileStream fs = new FileStream(@filename, FileMode.Open, FileAccess.Read, FileShare.Read);
  6. byte[] bt = new byte[fs.Length];
  7. int i = 1;
  8.  
  9. i = fs.Read(bt, 0, bt.Length);
  10. string str = System.Text.Encoding.ASCII.GetString(bt);
  11.  
  12. return str;

 

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