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在C#中快速查询文件

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2024年07月01日

相信使用过Everything的人都对其超快的搜索速度印象非常深刻,它的主要原理是通过扫描NTFS磁盘的USN Journal读取的文件列表,而不是磁盘目录,由于USN Journal非常小,因此能实现快速搜索。在CodePlex上也有人对这个功能进行了.Net的封装:MFT Scanner in VB.NET

由于.Net程序的Dll基本上是通用的,在C#中也可以直接使用它。今天发现了有人将其翻译成了C#的版本《使用MFT Scanner遍巡USN Journal,快速找出磁碟內的所有檔案》,使用起来更为方便了。不过,原文貌似有点Bug,编译不过去,这里我改了一下,附录如下: 

  1     public class MFTScanner
  2     {
  3         private static IntPtr INVALID_HANDLE_VALUE = new IntPtr(-1);
  4         private const uint GENERIC_READ = 0x80000000;
  5         private const int FILE_SHARE_READ = 0x1;
  6         private const int FILE_SHARE_WRITE = 0x2;
  7         private const int OPEN_EXISTING = 3;
  8         private const int FILE_READ_ATTRIBUTES = 0x80;
  9         private const int FILE_NAME_IINFORMATION = 9;
 10         private const int FILE_FLAG_BACKUP_SEMANTICS = 0x2000000;
 11         private const int FILE_OPEN_FOR_BACKUP_INTENT = 0x4000;
 12         private const int FILE_OPEN_BY_FILE_ID = 0x2000;
 13         private const int FILE_OPEN = 0x1;
 14         private const int OBJ_CASE_INSENSITIVE = 0x40;
 15         private const int FSCTL_ENUM_USN_DATA = 0x900b3;
 16 
 17         [StructLayout(LayoutKind.Sequential)]
 18         private struct MFT_ENUM_DATA
 19         {
 20             public long StartFileReferenceNumber;
 21             public long LowUsn;
 22             public long HighUsn;
 23         }
 24 
 25         [StructLayout(LayoutKind.Sequential)]
 26         private struct USN_RECORD
 27         {
 28             public int RecordLength;
 29             public short MajorVersion;
 30             public short MinorVersion;
 31             public long FileReferenceNumber;
 32             public long ParentFileReferenceNumber;
 33             public long Usn;
 34             public long TimeStamp;
 35             public int Reason;
 36             public int SourceInfo;
 37             public int SecurityId;
 38             public FileAttributes FileAttributes;
 39             public short FileNameLength;
 40             public short FileNameOffset;
 41         }
 42 
 43         [StructLayout(LayoutKind.Sequential)]
 44         private struct IO_STATUS_BLOCK
 45         {
 46             public int Status;
 47             public int Information;
 48         }
 49 
 50         [StructLayout(LayoutKind.Sequential)]
 51         private struct UNICODE_STRING
 52         {
 53             public short Length;
 54             public short MaximumLength;
 55             public IntPtr Buffer;
 56         }
 57 
 58         [StructLayout(LayoutKind.Sequential)]
 59         private struct OBJECT_ATTRIBUTES
 60         {
 61             public int Length;
 62             public IntPtr RootDirectory;
 63             public IntPtr ObjectName;
 64             public int Attributes;
 65             public int SecurityDescriptor;
 66             public int SecurityQualityOfService;
 67         }
 68 
 69         //// MFT_ENUM_DATA
 70         [DllImport("kernel32.dll", ExactSpelling = true, SetLastError = true, CharSet = CharSet.Auto)]
 71         private static extern bool DeviceIoControl(IntPtr hDevice, int dwIoControlCode, ref MFT_ENUM_DATA lpInBuffer, int nInBufferSize, IntPtr lpOutBuffer, int nOutBufferSize, ref int lpBytesReturned, IntPtr lpOverlapped);
 72 
 73         [DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Auto)]
 74         private static extern IntPtr CreateFile(string lpFileName, uint dwDesiredAccess, int dwShareMode, IntPtr lpSecurityAttributes, int dwCreationDisposition, int dwFlagsAndAttributes, IntPtr hTemplateFile);
 75 
 76         [DllImport("kernel32.dll", ExactSpelling = true, SetLastError = true, CharSet = CharSet.Auto)]
 77         private static extern Int32 CloseHandle(IntPtr lpObject);
 78 
 79         [DllImport("ntdll.dll", ExactSpelling = true, SetLastError = true, CharSet = CharSet.Auto)]
 80         private static extern int NtCreateFile(ref IntPtr FileHandle, int DesiredAccess, ref OBJECT_ATTRIBUTES ObjectAttributes, ref IO_STATUS_BLOCK IoStatusBlock, int AllocationSize, int FileAttribs, int SharedAccess, int CreationDisposition, int CreateOptions, int EaBuffer,
 81         int EaLength);
 82 
 83         [DllImport("ntdll.dll", ExactSpelling = true, SetLastError = true, CharSet = CharSet.Auto)]
 84         private static extern int NtQueryInformationFile(IntPtr FileHandle, ref IO_STATUS_BLOCK IoStatusBlock, IntPtr FileInformation, int Length, int FileInformationClass);
 85 
 86         private IntPtr m_hCJ;
 87         private IntPtr m_Buffer;
 88         private int m_BufferSize;
 89 
 90         private string m_DriveLetter;
 91 
 92         private class FSNode
 93         {
 94             public long FRN;
 95             public long ParentFRN;
 96             public string FileName;
 97 
 98             public bool IsFile;
 99             public FSNode(long lFRN, long lParentFSN, string sFileName, bool bIsFile)
100             {
101                 FRN = lFRN;
102                 ParentFRN = lParentFSN;
103                 FileName = sFileName;
104                 IsFile = bIsFile;
105             }
106         }
107 
108         private IntPtr OpenVolume(string szDriveLetter)
109         {
110 
111             IntPtr hCJ = default(IntPtr);
112             //// volume handle
113 
114             m_DriveLetter = szDriveLetter;
115             hCJ = CreateFile(@"\\.\" + szDriveLetter, GENERIC_READ, FILE_SHARE_READ | FILE_SHARE_WRITE, IntPtr.Zero, OPEN_EXISTING, 0, IntPtr.Zero);
116 
117             return hCJ;
118 
119         }
120 
121 
122         private void Cleanup()
123         {
124             if (m_hCJ != IntPtr.Zero)
125             {
126                 // Close the volume handle.
127                 CloseHandle(m_hCJ);
128                 m_hCJ = INVALID_HANDLE_VALUE;
129             }
130 
131             if (m_Buffer != IntPtr.Zero)
132             {
133                 // Free the allocated memory
134                 Marshal.FreeHGlobal(m_Buffer);
135                 m_Buffer = IntPtr.Zero;
136             }
137 
138         }
139 
140 
141         public IEnumerable<String> EnumerateFiles(string szDriveLetter)
142         {
143             try
144             {
145                 var usnRecord = default(USN_RECORD);
146                 var mft = default(MFT_ENUM_DATA);
147                 var dwRetBytes = 0;
148                 var cb = 0;
149                 var dicFRNLookup = new Dictionary<long, FSNode>();
150                 var bIsFile = false;
151 
152                 // This shouldn't be called more than once.
153                 if (m_Buffer.ToInt32() != 0)
154                 {
155                     throw new Exception("invalid buffer");
156                 }
157 
158                 // Assign buffer size
159                 m_BufferSize = 65536;
160                 //64KB
161 
162                 // Allocate a buffer to use for reading records.
163                 m_Buffer = Marshal.AllocHGlobal(m_BufferSize);
164 
165                 // correct path
166                 szDriveLetter = szDriveLetter.TrimEnd('\\');
167 
168                 // Open the volume handle 
169                 m_hCJ = OpenVolume(szDriveLetter);
170 
171                 // Check if the volume handle is valid.
172                 if (m_hCJ == INVALID_HANDLE_VALUE)
173                 {
174                     string errorMsg = "Couldn't open handle to the volume.";
175                     if (!IsAdministrator())
176                         errorMsg += "Current user is not administrator";
177 
178                     throw new Exception(errorMsg);
179                 }
180 
181                 mft.StartFileReferenceNumber = 0;
182                 mft.LowUsn = 0;
183                 mft.HighUsn = long.MaxValue;
184 
185                 do
186                 {
187                     if (DeviceIoControl(m_hCJ, FSCTL_ENUM_USN_DATA, ref mft, Marshal.SizeOf(mft), m_Buffer, m_BufferSize, ref dwRetBytes, IntPtr.Zero))
188                     {
189                         cb = dwRetBytes;
190                         // Pointer to the first record
191                         IntPtr pUsnRecord = new IntPtr(m_Buffer.ToInt32() + 8);
192 
193                         while ((dwRetBytes > 8))
194                         {
195                             // Copy pointer to USN_RECORD structure.
196                             usnRecord = (USN_RECORD)Marshal.PtrToStructure(pUsnRecord, usnRecord.GetType());
197 
198                             // The filename within the USN_RECORD.
199                             string FileName = Marshal.PtrToStringUni(new IntPtr(pUsnRecord.ToInt32() + usnRecord.FileNameOffset), usnRecord.FileNameLength / 2);
200 
201                             bIsFile = !usnRecord.FileAttributes.HasFlag(FileAttributes.Directory);
202                             dicFRNLookup.Add(usnRecord.FileReferenceNumber, new FSNode(usnRecord.FileReferenceNumber, usnRecord.ParentFileReferenceNumber, FileName, bIsFile));
203 
204                             // Pointer to the next record in the buffer.
205                             pUsnRecord = new IntPtr(pUsnRecord.ToInt32() + usnRecord.RecordLength);
206 
207                             dwRetBytes -= usnRecord.RecordLength;
208                         }
209 
210                         // The first 8 bytes is always the start of the next USN.
211                         mft.StartFileReferenceNumber = Marshal.ReadInt64(m_Buffer, 0);
212 
213 
214                     }
215                     else
216                     {
217                         break; // TODO: might not be correct. Was : Exit Do
218 
219                     }
220 
221                 } while (!(cb <= 8));
222 
223                 // Resolve all paths for Files
224                 foreach (FSNode oFSNode in dicFRNLookup.Values.Where(o => o.IsFile))
225                 {
226                     string sFullPath = oFSNode.FileName;
227                     FSNode oParentFSNode = oFSNode;
228 
229                     while (dicFRNLookup.TryGetValue(oParentFSNode.ParentFRN, out oParentFSNode))
230                     {
231                         sFullPath = string.Concat(oParentFSNode.FileName, @"\", sFullPath);
232                     }
233                     sFullPath = string.Concat(szDriveLetter, @"\", sFullPath);
234 
235                     yield return sFullPath;
236                 }
237             }
238             finally
239             {
240                 //// cleanup
241                 Cleanup();
242             }
243         }
244 
245         public static bool IsAdministrator()
246         {
247             WindowsIdentity identity = WindowsIdentity.GetCurrent();
248             WindowsPrincipal principal = new WindowsPrincipal(identity);
249             return principal.IsInRole(WindowsBuiltInRole.Administrator);
250         }
251     }

View Code

原文还提供了一个扩展方法,方便我们获取某个磁盘下的所有的文件名。 

1     public static class DriveInfoExtension
2     {
3         public static IEnumerable<String> EnumerateFiles(this DriveInfo drive)
4         {
5             return (new MFTScanner()).EnumerateFiles(drive.Name);
6         }
7     }

需要注意的是,读取USN Journal是需要管理员权限的,因此使用这个类需要管理员权限才能正常运行。

另外,这个类封装的也略为简单,只读取了文件名,实际上还可以读取文件大小,属性等常用信息,修改一下代码非常容易获取这些属性。通过它们可以非常方便写出一些分析磁盘空间占用的程序,这里就不举例了。

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