No .NET, como faço para criar uma junção no NTFS, em oposição a um symblink?

Question

Estou tentando criar uma junção NTFS. Da linha CMD, posso fazer isso usando o Ferramenta Junction.exe da SysInternals. A saída de um DIR CMD para uma junção é assim:

 Volume in drive C has no label.
 Volume Serial Number is C8BC-2EBD

 Directory of c:\users\cheeso\Documents

03/22/2009  09:45 PM    <JUNCTION>     My Music [\??\c:\users\cheeso\Music]
05/11/2007  05:42 PM    <DIR>          My Received Files
03/22/2009  09:46 PM    <JUNCTION>     my videos [\??\c:\users\cheeso\Videos]

Eu li em algum lugar que as junções são um subconjunto de links simbólicos.

Então eu tentei usar CreateSymbolicLink para criar uma junção. Quando faço isso, na verdade eu recebo um link simbólico, não uma junção.

09/09/2009  11:50 AM    <SYMLINKD>     newLink [.\]

Há também CreateHardLink. O documento diz que os cruzamentos (também conhecidos como "Pontos REPARSE") são um subconjunto de links hardings. Mas não consigo fazer esse chamado para funcionar. Ele completa, mas não há hardlink ou junção criada.

Estou usando .NET/C# e as importações são assim:

    [Interop.DllImport("kernel32.dll", EntryPoint="CreateSymbolicLinkW", CharSet=Interop.CharSet.Unicode)]
    public static extern int CreateSymbolicLink(string lpSymlinkFileName, string lpTargetFileName, int dwFlags);

    [Interop.DllImport("kernel32.dll", EntryPoint="CreateHardLinkW", CharSet=Interop.CharSet.Unicode)]
    public static extern bool CreateHardLink(string lpFileName,
                                             string lpExistingFileName,
                                             IntPtr mustBeNull);

O que estou fazendo errado?
Como posso criar uma junção de dentro de C#?

Answer 1

Parece que você pode, e alguém criou uma biblioteca no CodeProject que possui várias funções que construíram em C# para trabalhar com pontos de junção.

http://www.codeproject.com/kb/files/junctionPointsnet.aspx

Parece que ele está realmente usando o seguinte dllimport para realizá -lo:

    [DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
    private static extern bool DeviceIoControl(IntPtr hDevice, uint dwIoControlCode,
        IntPtr InBuffer, int nInBufferSize,
        IntPtr OutBuffer, int nOutBufferSize,
        out int pBytesReturned, IntPtr lpOverlapped);

Answer 2

O código é de http://www.codeproject.com/kb/files/junctionPointsnet.aspx Como atalho para aqueles que não conseguem alcançar esse link ou um backup, caso a página original esteja inativa.

Não vote com essa resposta, já que não sou autor deste código.

Obrigado ao autor original Jeff.brown@CodeProject.

using System;
using System.IO;
using System.Runtime.InteropServices;
using System.Text;
using Microsoft.Win32.SafeHandles;

namespace Monitor.Core.Utilities
{
    /// <summary>
    /// Provides access to NTFS junction points in .Net.
    /// </summary>
    public static class JunctionPoint
    {
        /// <summary>
        /// The file or directory is not a reparse point.
        /// </summary>
        private const int ERROR_NOT_A_REPARSE_POINT = 4390;

        /// <summary>
        /// The reparse point attribute cannot be set because it conflicts with an existing attribute.
        /// </summary>
        private const int ERROR_REPARSE_ATTRIBUTE_CONFLICT = 4391;

        /// <summary>
        /// The data present in the reparse point buffer is invalid.
        /// </summary>
        private const int ERROR_INVALID_REPARSE_DATA = 4392;

        /// <summary>
        /// The tag present in the reparse point buffer is invalid.
        /// </summary>
        private const int ERROR_REPARSE_TAG_INVALID = 4393;

        /// <summary>
        /// There is a mismatch between the tag specified in the request and the tag present in the reparse point.
        /// </summary>
        private const int ERROR_REPARSE_TAG_MISMATCH = 4394;

        /// <summary>
        /// Command to set the reparse point data block.
        /// </summary>
        private const int FSCTL_SET_REPARSE_POINT = 0x000900A4;

        /// <summary>
        /// Command to get the reparse point data block.
        /// </summary>
        private const int FSCTL_GET_REPARSE_POINT = 0x000900A8;

        /// <summary>
        /// Command to delete the reparse point data base.
        /// </summary>
        private const int FSCTL_DELETE_REPARSE_POINT = 0x000900AC;

        /// <summary>
        /// Reparse point tag used to identify mount points and junction points.
        /// </summary>
        private const uint IO_REPARSE_TAG_MOUNT_POINT = 0xA0000003;

        /// <summary>
        /// This prefix indicates to NTFS that the path is to be treated as a non-interpreted
        /// path in the virtual file system.
        /// </summary>
        private const string NonInterpretedPathPrefix = @"\??\";

        [Flags]
        private enum EFileAccess : uint
        {
            GenericRead = 0x80000000,
            GenericWrite = 0x40000000,
            GenericExecute = 0x20000000,
            GenericAll = 0x10000000,
        }

        [Flags]
        private enum EFileShare : uint
        {
            None = 0x00000000,
            Read = 0x00000001,
            Write = 0x00000002,
            Delete = 0x00000004,
        }

        private enum ECreationDisposition : uint
        {
            New = 1,
            CreateAlways = 2,
            OpenExisting = 3,
            OpenAlways = 4,
            TruncateExisting = 5,
        }

        [Flags]
        private enum EFileAttributes : uint
        {
            Readonly = 0x00000001,
            Hidden = 0x00000002,
            System = 0x00000004,
            Directory = 0x00000010,
            Archive = 0x00000020,
            Device = 0x00000040,
            Normal = 0x00000080,
            Temporary = 0x00000100,
            SparseFile = 0x00000200,
            ReparsePoint = 0x00000400,
            Compressed = 0x00000800,
            Offline = 0x00001000,
            NotContentIndexed = 0x00002000,
            Encrypted = 0x00004000,
            Write_Through = 0x80000000,
            Overlapped = 0x40000000,
            NoBuffering = 0x20000000,
            RandomAccess = 0x10000000,
            SequentialScan = 0x08000000,
            DeleteOnClose = 0x04000000,
            BackupSemantics = 0x02000000,
            PosixSemantics = 0x01000000,
            OpenReparsePoint = 0x00200000,
            OpenNoRecall = 0x00100000,
            FirstPipeInstance = 0x00080000
        }

        [StructLayout(LayoutKind.Sequential)]
        private struct REPARSE_DATA_BUFFER
        {
            /// <summary>
            /// Reparse point tag. Must be a Microsoft reparse point tag.
            /// </summary>
            public uint ReparseTag;

            /// <summary>
            /// Size, in bytes, of the data after the Reserved member. This can be calculated by:
            /// (4 * sizeof(ushort)) + SubstituteNameLength + PrintNameLength + 
            /// (namesAreNullTerminated ? 2 * sizeof(char) : 0);
            /// </summary>
            public ushort ReparseDataLength;

            /// <summary>
            /// Reserved; do not use. 
            /// </summary>
            public ushort Reserved;

            /// <summary>
            /// Offset, in bytes, of the substitute name string in the PathBuffer array.
            /// </summary>
            public ushort SubstituteNameOffset;

            /// <summary>
            /// Length, in bytes, of the substitute name string. If this string is null-terminated,
            /// SubstituteNameLength does not include space for the null character.
            /// </summary>
            public ushort SubstituteNameLength;

            /// <summary>
            /// Offset, in bytes, of the print name string in the PathBuffer array.
            /// </summary>
            public ushort PrintNameOffset;

            /// <summary>
            /// Length, in bytes, of the print name string. If this string is null-terminated,
            /// PrintNameLength does not include space for the null character. 
            /// </summary>
            public ushort PrintNameLength;

            /// <summary>
            /// A buffer containing the unicode-encoded path string. The path string contains
            /// the substitute name string and print name string.
            /// </summary>
            [MarshalAs(UnmanagedType.ByValArray, SizeConst = 0x3FF0)]
            public byte[] PathBuffer;
        }

        [DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)]
        private static extern bool DeviceIoControl(IntPtr hDevice, uint dwIoControlCode,
            IntPtr InBuffer, int nInBufferSize,
            IntPtr OutBuffer, int nOutBufferSize,
            out int pBytesReturned, IntPtr lpOverlapped);

        [DllImport("kernel32.dll", SetLastError = true)]
        private static extern IntPtr CreateFile(
            string lpFileName,
            EFileAccess dwDesiredAccess,
            EFileShare dwShareMode,
            IntPtr lpSecurityAttributes,
            ECreationDisposition dwCreationDisposition,
            EFileAttributes dwFlagsAndAttributes,
            IntPtr hTemplateFile);

        /// <summary>
        /// Creates a junction point from the specified directory to the specified target directory.
        /// </summary>
        /// <remarks>
        /// Only works on NTFS.
        /// </remarks>
        /// <param name="junctionPoint">The junction point path</param>
        /// <param name="targetDir">The target directory</param>
        /// <param name="overwrite">If true overwrites an existing reparse point or empty directory</param>
        /// <exception cref="IOException">Thrown when the junction point could not be created or when
        /// an existing directory was found and <paramref name="overwrite" /> if false</exception>
        public static void Create(string junctionPoint, string targetDir, bool overwrite)
        {
            targetDir = Path.GetFullPath(targetDir);

            if (!Directory.Exists(targetDir))
                throw new IOException("Target path does not exist or is not a directory.");

            if (Directory.Exists(junctionPoint))
            {
                if (!overwrite)
                    throw new IOException("Directory already exists and overwrite parameter is false.");
            }
            else
            {
                Directory.CreateDirectory(junctionPoint);
            }

            using (SafeFileHandle handle = OpenReparsePoint(junctionPoint, EFileAccess.GenericWrite))
            {
                byte[] targetDirBytes = Encoding.Unicode.GetBytes(NonInterpretedPathPrefix + Path.GetFullPath(targetDir));

                REPARSE_DATA_BUFFER reparseDataBuffer = new REPARSE_DATA_BUFFER();

                reparseDataBuffer.ReparseTag = IO_REPARSE_TAG_MOUNT_POINT;
                reparseDataBuffer.ReparseDataLength = (ushort)(targetDirBytes.Length + 12);
                reparseDataBuffer.SubstituteNameOffset = 0;
                reparseDataBuffer.SubstituteNameLength = (ushort)targetDirBytes.Length;
                reparseDataBuffer.PrintNameOffset = (ushort)(targetDirBytes.Length + 2);
                reparseDataBuffer.PrintNameLength = 0;
                reparseDataBuffer.PathBuffer = new byte[0x3ff0];
                Array.Copy(targetDirBytes, reparseDataBuffer.PathBuffer, targetDirBytes.Length);

                int inBufferSize = Marshal.SizeOf(reparseDataBuffer);
                IntPtr inBuffer = Marshal.AllocHGlobal(inBufferSize);

                try
                {
                    Marshal.StructureToPtr(reparseDataBuffer, inBuffer, false);

                    int bytesReturned;
                    bool result = DeviceIoControl(handle.DangerousGetHandle(), FSCTL_SET_REPARSE_POINT,
                        inBuffer, targetDirBytes.Length + 20, IntPtr.Zero, 0, out bytesReturned, IntPtr.Zero);

                    if (!result)
                        ThrowLastWin32Error("Unable to create junction point.");
                }
                finally
                {
                    Marshal.FreeHGlobal(inBuffer);
                }
            }
        }

        /// <summary>
        /// Deletes a junction point at the specified source directory along with the directory itself.
        /// Does nothing if the junction point does not exist.
        /// </summary>
        /// <remarks>
        /// Only works on NTFS.
        /// </remarks>
        /// <param name="junctionPoint">The junction point path</param>
        public static void Delete(string junctionPoint)
        {
            if (!Directory.Exists(junctionPoint))
            {
                if (File.Exists(junctionPoint))
                    throw new IOException("Path is not a junction point.");

                return;
            }

            using (SafeFileHandle handle = OpenReparsePoint(junctionPoint, EFileAccess.GenericWrite))
            {
                REPARSE_DATA_BUFFER reparseDataBuffer = new REPARSE_DATA_BUFFER();

                reparseDataBuffer.ReparseTag = IO_REPARSE_TAG_MOUNT_POINT;
                reparseDataBuffer.ReparseDataLength = 0;
                reparseDataBuffer.PathBuffer = new byte[0x3ff0];

                int inBufferSize = Marshal.SizeOf(reparseDataBuffer);
                IntPtr inBuffer = Marshal.AllocHGlobal(inBufferSize);
                try
                {
                    Marshal.StructureToPtr(reparseDataBuffer, inBuffer, false);

                    int bytesReturned;
                    bool result = DeviceIoControl(handle.DangerousGetHandle(), FSCTL_DELETE_REPARSE_POINT,
                        inBuffer, 8, IntPtr.Zero, 0, out bytesReturned, IntPtr.Zero);

                    if (!result)
                        ThrowLastWin32Error("Unable to delete junction point.");
                }
                finally
                {
                    Marshal.FreeHGlobal(inBuffer);
                }

                try
                {
                    Directory.Delete(junctionPoint);
                }
                catch (IOException ex)
                {
                    throw new IOException("Unable to delete junction point.", ex);
                }
            }
        }

        /// <summary>
        /// Determines whether the specified path exists and refers to a junction point.
        /// </summary>
        /// <param name="path">The junction point path</param>
        /// <returns>True if the specified path represents a junction point</returns>
        /// <exception cref="IOException">Thrown if the specified path is invalid
        /// or some other error occurs</exception>
        public static bool Exists(string path)
        {
            if (! Directory.Exists(path))
                return false;

            using (SafeFileHandle handle = OpenReparsePoint(path, EFileAccess.GenericRead))
            {
                string target = InternalGetTarget(handle);
                return target != null;
            }
        }

        /// <summary>
        /// Gets the target of the specified junction point.
        /// </summary>
        /// <remarks>
        /// Only works on NTFS.
        /// </remarks>
        /// <param name="junctionPoint">The junction point path</param>
        /// <returns>The target of the junction point</returns>
        /// <exception cref="IOException">Thrown when the specified path does not
        /// exist, is invalid, is not a junction point, or some other error occurs</exception>
        public static string GetTarget(string junctionPoint)
        {
            using (SafeFileHandle handle = OpenReparsePoint(junctionPoint, EFileAccess.GenericRead))
            {
                string target = InternalGetTarget(handle);
                if (target == null)
                    throw new IOException("Path is not a junction point.");

                return target;
            }
        }

        private static string InternalGetTarget(SafeFileHandle handle)
        {
            int outBufferSize = Marshal.SizeOf(typeof(REPARSE_DATA_BUFFER));
            IntPtr outBuffer = Marshal.AllocHGlobal(outBufferSize);

            try
            {
                int bytesReturned;
                bool result = DeviceIoControl(handle.DangerousGetHandle(), FSCTL_GET_REPARSE_POINT,
                    IntPtr.Zero, 0, outBuffer, outBufferSize, out bytesReturned, IntPtr.Zero);

                if (!result)
                {
                    int error = Marshal.GetLastWin32Error();
                    if (error == ERROR_NOT_A_REPARSE_POINT)
                        return null;

                    ThrowLastWin32Error("Unable to get information about junction point.");
                }

                REPARSE_DATA_BUFFER reparseDataBuffer = (REPARSE_DATA_BUFFER)
                    Marshal.PtrToStructure(outBuffer, typeof(REPARSE_DATA_BUFFER));

                if (reparseDataBuffer.ReparseTag != IO_REPARSE_TAG_MOUNT_POINT)
                    return null;

                string targetDir = Encoding.Unicode.GetString(reparseDataBuffer.PathBuffer,
                    reparseDataBuffer.SubstituteNameOffset, reparseDataBuffer.SubstituteNameLength);

                if (targetDir.StartsWith(NonInterpretedPathPrefix))
                    targetDir = targetDir.Substring(NonInterpretedPathPrefix.Length);

                return targetDir;
            }
            finally
            {
                Marshal.FreeHGlobal(outBuffer);
            }
        }

        private static SafeFileHandle OpenReparsePoint(string reparsePoint, EFileAccess accessMode)
        {
            SafeFileHandle reparsePointHandle = new SafeFileHandle(CreateFile(reparsePoint, accessMode,
                EFileShare.Read | EFileShare.Write | EFileShare.Delete,
                IntPtr.Zero, ECreationDisposition.OpenExisting,
                EFileAttributes.BackupSemantics | EFileAttributes.OpenReparsePoint, IntPtr.Zero), true);

            if (Marshal.GetLastWin32Error() != 0)
                ThrowLastWin32Error("Unable to open reparse point.");

            return reparsePointHandle;
        }

        private static void ThrowLastWin32Error(string message)
        {
            throw new IOException(message, Marshal.GetExceptionForHR(Marshal.GetHRForLastWin32Error()));
        }
    }
}