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Merge #4129 Option to clone smaller instances with junction points (W…
…indows) or symbolic links (Unix)
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,167 @@ | ||
| using System; | ||
| using System.IO; | ||
| using System.Runtime.InteropServices; | ||
| using System.Text; | ||
| using Microsoft.Win32.SafeHandles; | ||
|
|
||
| using ChinhDo.Transactions.FileManager; | ||
|
|
||
| namespace CKAN | ||
| { | ||
| /// <summary> | ||
| /// Junctions on Windows, symbolic links on Unix | ||
| /// </summary> | ||
| public static class DirectoryLink | ||
| { | ||
| public static void Create(string target, string link, TxFileManager txMgr) | ||
| { | ||
| if (!CreateImpl(target, link, txMgr)) | ||
| { | ||
| throw new Kraken(Platform.IsWindows | ||
| ? $"Failed to create junction at {link}: {Marshal.GetLastWin32Error()}" | ||
| : $"Failed to create symbolic link at {link}"); | ||
| } | ||
| } | ||
|
|
||
| private static bool CreateImpl(string target, string link, TxFileManager txMgr) | ||
| => Platform.IsWindows ? CreateJunction(link, target, txMgr) | ||
| : symlink(target, link) == 0; | ||
|
|
||
| [DllImport("libc")] | ||
| private static extern int symlink(string target, string link); | ||
|
|
||
| private static bool CreateJunction(string link, string target, TxFileManager txMgr) | ||
| { | ||
| // A junction is a directory with some extra magic attached | ||
| if (!txMgr.DirectoryExists(link)) | ||
| { | ||
| txMgr.CreateDirectory(link); | ||
| } | ||
| using (var h = CreateFile(link, GenericWrite, FileShare.Read | FileShare.Write, IntPtr.Zero, | ||
| FileMode.Open, BackupSemantics | OpenReparsePoint, IntPtr.Zero)) | ||
| { | ||
| if (!h.IsInvalid) | ||
| { | ||
| var junctionInfo = ReparseDataBuffer.FromPath(target, out int byteCount); | ||
| return DeviceIoControl(h, FSCTL_SET_REPARSE_POINT, | ||
| ref junctionInfo, byteCount + 20, | ||
| null, 0, | ||
| out _, IntPtr.Zero); | ||
| } | ||
| } | ||
| return false; | ||
| } | ||
|
|
||
| public static bool TryGetTarget(string link, out string target) | ||
| { | ||
| target = null; | ||
| var fi = new DirectoryInfo(link); | ||
| if (fi.Attributes.HasFlag(FileAttributes.ReparsePoint)) | ||
| { | ||
| if (Platform.IsWindows) | ||
| { | ||
| var h = CreateFile(link, 0, FileShare.Read, IntPtr.Zero, | ||
| FileMode.Open, BackupSemantics | OpenReparsePoint, IntPtr.Zero); | ||
| if (!h.IsInvalid) | ||
| { | ||
| if (DeviceIoControl(h, FSCTL_GET_REPARSE_POINT, | ||
| null, 0, | ||
| out ReparseDataBuffer junctionInfo, Marshal.SizeOf(typeof(ReparseDataBuffer)), | ||
| out _, IntPtr.Zero)) | ||
| { | ||
| if (junctionInfo.ReparseTag == IO_REPARSE_TAG_MOUNT_POINT) | ||
| { | ||
| target = junctionInfo.PathBuffer.TrimStart("\\\\?\\"); | ||
| } | ||
| } | ||
| h.Close(); | ||
| } | ||
| } | ||
| else | ||
| { | ||
| var bytes = new byte[1024]; | ||
| var result = readlink(link, bytes, bytes.Length); | ||
| if (result > 0) | ||
| { | ||
| target = Encoding.UTF8.GetString(bytes); | ||
| } | ||
| } | ||
| } | ||
| return !string.IsNullOrEmpty(target); | ||
| } | ||
|
|
||
| private const uint GenericWrite = 0x40000000u; | ||
| private const uint BackupSemantics = 0x02000000u; | ||
| private const uint OpenReparsePoint = 0x00200000u; | ||
| private const uint FSCTL_SET_REPARSE_POINT = 0x000900A4u; | ||
| private const uint IO_REPARSE_TAG_MOUNT_POINT = 0xA0000003u; | ||
| private const uint FSCTL_GET_REPARSE_POINT = 0x000900A8u; | ||
|
|
||
| [DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Auto)] | ||
| private static extern bool DeviceIoControl(SafeFileHandle hDevice, | ||
| uint IoControlCode, | ||
| ref ReparseDataBuffer InBuffer, | ||
| int nInBufferSize, | ||
| byte[] OutBuffer, | ||
| int nOutBufferSize, | ||
| out int pBytesReturned, | ||
| IntPtr Overlapped); | ||
|
|
||
| [DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Auto)] | ||
| private static extern bool DeviceIoControl(SafeFileHandle hDevice, | ||
| uint IoControlCode, | ||
| byte[] InBuffer, | ||
| int nInBufferSize, | ||
| out ReparseDataBuffer OutBuffer, | ||
| int nOutBufferSize, | ||
| out int pBytesReturned, | ||
| IntPtr Overlapped); | ||
|
|
||
| [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)] | ||
| private struct ReparseDataBuffer | ||
| { | ||
| public uint ReparseTag; | ||
| public ushort ReparseDataLength; | ||
| private readonly ushort Reserved; | ||
| public ushort SubstituteNameOffset; | ||
| public ushort SubstituteNameLength; | ||
| public ushort PrintNameOffset; | ||
| public ushort PrintNameLength; | ||
| [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 8184)] | ||
| public string PathBuffer; | ||
|
|
||
| public static ReparseDataBuffer FromPath(string target, out int byteCount) | ||
| { | ||
| var fullTarget = $@"\??\{Path.GetFullPath(target)}"; | ||
| byteCount = Encoding.Unicode.GetByteCount(fullTarget); | ||
| return new ReparseDataBuffer | ||
| { | ||
| ReparseTag = IO_REPARSE_TAG_MOUNT_POINT, | ||
| ReparseDataLength = (ushort)(byteCount + 12), | ||
| SubstituteNameOffset = 0, | ||
| SubstituteNameLength = (ushort)byteCount, | ||
| PrintNameOffset = (ushort)(byteCount + 2), | ||
| PrintNameLength = 0, | ||
| PathBuffer = fullTarget, | ||
| }; | ||
| } | ||
| } | ||
|
|
||
| [DllImport("libc")] | ||
| private static extern int readlink(string link, byte[] buf, int bufsize); | ||
|
|
||
| [DllImport("kernel32.dll", CharSet = CharSet.Auto, SetLastError = true)] | ||
| private static extern SafeFileHandle CreateFile([MarshalAs(UnmanagedType.LPTStr)] string filename, | ||
| [MarshalAs(UnmanagedType.U4)] uint access, | ||
| [MarshalAs(UnmanagedType.U4)] FileShare share, | ||
| IntPtr securityAttributes, | ||
| [MarshalAs(UnmanagedType.U4)] FileMode creationDisposition, | ||
| [MarshalAs(UnmanagedType.U4)] uint flagsAndAttributes, | ||
| IntPtr templateFile); | ||
|
|
||
| private static string TrimStart(this string orig, string toRemove) | ||
| => orig.StartsWith(toRemove) ? orig.Remove(0, toRemove.Length) | ||
| : orig; | ||
|
|
||
| } | ||
| } |
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