C#如何实现快速查询文件

今天小编给大家分享一下C#如何实现快速查询文件的相关知识点，内容详细，逻辑清晰，相信大部分人都还太了解这方面的知识，所以分享这篇文章给大家参考一下，希望大家阅读完这篇文章后有所收获，下面我们一起来了解一下吧。

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。

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。

    public class MFTScanner    {        private static IntPtr INVALID_HANDLE_VALUE = new IntPtr(-1);        private const uint GENERIC_READ = 0x80000000;        private const int FILE_SHARE_READ = 0x1;        private const int FILE_SHARE_WRITE = 0x2;        private const int OPEN_EXISTING = 3;        private const int FILE_READ_ATTRIBUTES = 0x80;        private const int FILE_NAME_IINFORMATION = 9;        private const int FILE_FLAG_BACKUP_SEMANTICS = 0x2000000;        private const int FILE_OPEN_FOR_BACKUP_INTENT = 0x4000;        private const int FILE_OPEN_BY_FILE_ID = 0x2000;        private const int FILE_OPEN = 0x1;        private const int OBJ_CASE_INSENSITIVE = 0x40;        private const int FSCTL_ENUM_USN_DATA = 0x900b3;        [StructLayout(LayoutKind.Sequential)]        private struct MFT_ENUM_DATA        {            public long StartFileReferenceNumber;            public long LowUsn;            public long HighUsn;        }        [StructLayout(LayoutKind.Sequential)]        private struct USN_RECORD        {            public int RecordLength;            public short MajorVersion;            public short MinorVersion;            public long FileReferenceNumber;            public long ParentFileReferenceNumber;            public long Usn;            public long TimeStamp;            public int Reason;            public int SourceInfo;            public int SecurityId;            public FileAttributes FileAttributes;            public short FileNameLength;            public short FileNameOffset;        }        [StructLayout(LayoutKind.Sequential)]        private struct IO_STATUS_BLOCK        {            public int Status;            public int Information;        }        [StructLayout(LayoutKind.Sequential)]        private struct UNICODE_STRING        {            public short Length;            public short MaximumLength;            public IntPtr Buffer;        }        [StructLayout(LayoutKind.Sequential)]        private struct OBJECT_ATTRIBUTES        {            public int Length;            public IntPtr RootDirectory;            public IntPtr ObjectName;            public int Attributes;            public int SecurityDescriptor;            public int SecurityQualityOfService;        }        //// MFT_ENUM_DATA        [DllImport("kernel32.dll", ExactSpelling = true, SetLastError = true, CharSet = CharSet.Auto)]        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);        [DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Auto)]        private static extern IntPtr CreateFile(string lpFileName, uint dwDesiredAccess, int dwShareMode, IntPtr lpSecurityAttributes, int dwCreationDisposition, int dwFlagsAndAttributes, IntPtr hTemplateFile);        [DllImport("kernel32.dll", ExactSpelling = true, SetLastError = true, CharSet = CharSet.Auto)]        private static extern Int32 CloseHandle(IntPtr lpObject);        [DllImport("ntdll.dll", ExactSpelling = true, SetLastError = true, CharSet = CharSet.Auto)]        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,        int EaLength);        [DllImport("ntdll.dll", ExactSpelling = true, SetLastError = true, CharSet = CharSet.Auto)]        private static extern int NtQueryInformationFile(IntPtr FileHandle, ref IO_STATUS_BLOCK IoStatusBlock, IntPtr FileInformation, int Length, int FileInformationClass);        private IntPtr m_hCJ;        private IntPtr m_Buffer;        private int m_BufferSize;        private string m_DriveLetter;        private class FSNode        {            public long FRN;            public long ParentFRN;            public string FileName;            public bool IsFile;            public FSNode(long lFRN, long lParentFSN, string sFileName, bool bIsFile)            {                FRN = lFRN;                ParentFRN = lParentFSN;                FileName = sFileName;                IsFile = bIsFile;            }        }        private IntPtr OpenVolume(string szDriveLetter)        {            IntPtr hCJ = default(IntPtr);            //// volume handle            m_DriveLetter = szDriveLetter;            hCJ = CreateFile(@"\\.\" + szDriveLetter, GENERIC_READ, FILE_SHARE_READ | FILE_SHARE_WRITE, IntPtr.Zero, OPEN_EXISTING, 0, IntPtr.Zero);            return hCJ;        }        private void Cleanup()        {            if (m_hCJ != IntPtr.Zero)            {                // Close the volume handle.                CloseHandle(m_hCJ);                m_hCJ = INVALID_HANDLE_VALUE;            }            if (m_Buffer != IntPtr.Zero)            {                // Free the allocated memory                Marshal.FreeHGlobal(m_Buffer);                m_Buffer = IntPtr.Zero;            }        }        public IEnumerable<String> EnumerateFiles(string szDriveLetter)        {            try            {                var usnRecord = default(USN_RECORD);                var mft = default(MFT_ENUM_DATA);                var dwRetBytes = 0;                var cb = 0;                var dicFRNLookup = new Dictionary<long, FSNode>();                var bIsFile = false;                // This shouldn't be called more than once.                if (m_Buffer.ToInt32() != 0)                {                    throw new Exception("invalid buffer");                }                // Assign buffer size                m_BufferSize = 65536;                //64KB                // Allocate a buffer to use for reading records.                m_Buffer = Marshal.AllocHGlobal(m_BufferSize);                // correct path                szDriveLetter = szDriveLetter.TrimEnd('\\');                // Open the volume handle                m_hCJ = OpenVolume(szDriveLetter);                // Check if the volume handle is valid.                if (m_hCJ == INVALID_HANDLE_VALUE)                {                    string errorMsg = "Couldn't open handle to the volume.";                    if (!IsAdministrator())                        errorMsg += "Current user is not administrator";                    throw new Exception(errorMsg);                }                mft.StartFileReferenceNumber = 0;                mft.LowUsn = 0;                mft.HighUsn = long.MaxValue;                do                {                    if (DeviceIoControl(m_hCJ, FSCTL_ENUM_USN_DATA, ref mft, Marshal.SizeOf(mft), m_Buffer, m_BufferSize, ref dwRetBytes, IntPtr.Zero))                    {                        cb = dwRetBytes;                        // Pointer to the first record                        IntPtr pUsnRecord = new IntPtr(m_Buffer.ToInt32() + 8);                        while ((dwRetBytes > 8))                        {                            // Copy pointer to USN_RECORD structure.                            usnRecord = (USN_RECORD)Marshal.PtrToStructure(pUsnRecord, usnRecord.GetType());                            // The filename within the USN_RECORD.                            string FileName = Marshal.PtrToStringUni(new IntPtr(pUsnRecord.ToInt32() + usnRecord.FileNameOffset), usnRecord.FileNameLength / 2);                            bIsFile = !usnRecord.FileAttributes.HasFlag(FileAttributes.Directory);                            dicFRNLookup.Add(usnRecord.FileReferenceNumber, new FSNode(usnRecord.FileReferenceNumber, usnRecord.ParentFileReferenceNumber, FileName, bIsFile));                            // Pointer to the next record in the buffer.                            pUsnRecord = new IntPtr(pUsnRecord.ToInt32() + usnRecord.RecordLength);                            dwRetBytes -= usnRecord.RecordLength;                        }                        // The first 8 bytes is always the start of the next USN.                        mft.StartFileReferenceNumber = Marshal.ReadInt64(m_Buffer, 0);                    }                    else                    {                        break; // TODO: might not be correct. Was : Exit Do                    }                } while (!(cb <= 8));                // Resolve all paths for Files                foreach (FSNode oFSNode in dicFRNLookup.Values.Where(o => o.IsFile))                {                    string sFullPath = oFSNode.FileName;                    FSNode oParentFSNode = oFSNode;                    while (dicFRNLookup.TryGetValue(oParentFSNode.ParentFRN, out oParentFSNode))                    {                        sFullPath = string.Concat(oParentFSNode.FileName, @"\", sFullPath);                    }                    sFullPath = string.Concat(szDriveLetter, @"\", sFullPath);                    yield return sFullPath;                }            }            finally            {                //// cleanup                Cleanup();            }        }        public static bool IsAdministrator()        {            WindowsIdentity identity = WindowsIdentity.GetCurrent();            WindowsPrincipal principal = new WindowsPrincipal(identity);            return principal.IsInRole(WindowsBuiltInRole.Administrator);        }    }

本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。 

    public static class DriveInfoExtension    {        public static IEnumerable<String> EnumerateFiles(this DriveInfo drive)        {            return (new MFTScanner()).EnumerateFiles(drive.Name);        }    }

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。

以上就是“C#如何实现快速查询文件”这篇文章的所有内容，感谢各位的阅读！相信大家阅读完这篇文章都有很大的收获，小编每天都会为大家更新不同的知识，如果还想学习更多的知识，请关注编程网行业资讯频道。