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osu-lazer/osu.Game/IO/HardLinkHelper.cs

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// Copyright (c) ppy Pty Ltd <contact@ppy.sh>. Licensed under the MIT Licence.
// See the LICENCE file in the repository root for full licence text.
using System;
using System.IO;
using System.Runtime.InteropServices;
using System.Runtime.InteropServices.ComTypes;
using Microsoft.Win32.SafeHandles;
using osu.Framework;
namespace osu.Game.IO
{
internal static class HardLinkHelper
{
public static bool CheckAvailability(string testDestinationPath, string testSourcePath)
{
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// For simplicity, only support desktop operating systems for now.
if (!RuntimeInfo.IsDesktop)
return false;
const string test_filename = "_hard_link_test";
testDestinationPath = Path.Combine(testDestinationPath, test_filename);
testSourcePath = Path.Combine(testSourcePath, test_filename);
cleanupFiles();
try
{
File.WriteAllText(testSourcePath, string.Empty);
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// Test availability by creating an arbitrary hard link between the source and destination paths.
return TryCreateHardLink(testDestinationPath, testSourcePath);
}
catch
{
return false;
}
finally
{
cleanupFiles();
}
void cleanupFiles()
{
try
{
File.Delete(testDestinationPath);
File.Delete(testSourcePath);
}
catch
{
}
}
}
/// <summary>
/// Attempts to create a hard link from <paramref name="sourcePath"/> to <paramref name="destinationPath"/>,
/// using platform-specific native methods.
/// </summary>
/// <remarks>
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/// Hard links are only available on desktop platforms.
/// </remarks>
/// <returns>Whether the hard link was successfully created.</returns>
public static bool TryCreateHardLink(string destinationPath, string sourcePath)
{
switch (RuntimeInfo.OS)
{
case RuntimeInfo.Platform.Windows:
return CreateHardLink(destinationPath, sourcePath, IntPtr.Zero);
case RuntimeInfo.Platform.Linux:
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case RuntimeInfo.Platform.macOS:
return link(sourcePath, destinationPath) == 0;
default:
return false;
}
}
// For future use (to detect if a file is a hard link with other references existing on disk).
public static int GetFileLinkCount(string filePath)
{
int result = 0;
switch (RuntimeInfo.OS)
{
case RuntimeInfo.Platform.Windows:
SafeFileHandle handle = CreateFile(filePath, FileAccess.Read, FileShare.Read, IntPtr.Zero, FileMode.Open, FileAttributes.Archive, IntPtr.Zero);
ByHandleFileInformation fileInfo;
if (GetFileInformationByHandle(handle, out fileInfo))
result = (int)fileInfo.NumberOfLinks;
CloseHandle(handle);
break;
case RuntimeInfo.Platform.Linux:
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case RuntimeInfo.Platform.macOS:
if (stat(filePath, out var statbuf) == 0)
result = (int)statbuf.st_nlink;
break;
}
return result;
}
#region Windows native methods
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[DllImport("Kernel32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
public static extern bool CreateHardLink(string lpFileName, string lpExistingFileName, IntPtr lpSecurityAttributes);
[DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Auto)]
private static extern SafeFileHandle CreateFile(
string lpFileName,
[MarshalAs(UnmanagedType.U4)] FileAccess dwDesiredAccess,
[MarshalAs(UnmanagedType.U4)] FileShare dwShareMode,
IntPtr lpSecurityAttributes,
[MarshalAs(UnmanagedType.U4)] FileMode dwCreationDisposition,
[MarshalAs(UnmanagedType.U4)] FileAttributes dwFlagsAndAttributes,
IntPtr hTemplateFile);
[DllImport("kernel32.dll", SetLastError = true)]
private static extern bool GetFileInformationByHandle(SafeFileHandle handle, out ByHandleFileInformation lpFileInformation);
[DllImport("kernel32.dll", SetLastError = true)]
[return: MarshalAs(UnmanagedType.Bool)]
private static extern bool CloseHandle(SafeHandle hObject);
[StructLayout(LayoutKind.Sequential)]
private struct ByHandleFileInformation
{
public readonly uint FileAttributes;
public readonly FILETIME CreationTime;
public readonly FILETIME LastAccessTime;
public readonly FILETIME LastWriteTime;
public readonly uint VolumeSerialNumber;
public readonly uint FileSizeHigh;
public readonly uint FileSizeLow;
public readonly uint NumberOfLinks;
public readonly uint FileIndexHigh;
public readonly uint FileIndexLow;
}
#endregion
#region Linux native methods
#pragma warning disable IDE1006 // Naming rule violation
[DllImport("libc", SetLastError = true)]
public static extern int link(string oldpath, string newpath);
[DllImport("libc", SetLastError = true)]
private static extern int stat(string pathname, out struct_stat statbuf);
// ReSharper disable once InconsistentNaming
// Struct layout is likely non-portable across unices. Tread with caution.
[StructLayout(LayoutKind.Sequential)]
private struct struct_stat
{
public readonly long st_dev;
public readonly long st_ino;
public readonly long st_nlink;
public readonly int st_mode;
public readonly int st_uid;
public readonly int st_gid;
public readonly long st_rdev;
public readonly long st_size;
public readonly long st_blksize;
public readonly long st_blocks;
public readonly timespec st_atim;
public readonly timespec st_mtim;
public readonly timespec st_ctim;
}
// ReSharper disable once InconsistentNaming
[StructLayout(LayoutKind.Sequential)]
private struct timespec
{
public readonly long tv_sec;
public readonly long tv_nsec;
}
#pragma warning restore IDE1006
#endregion
}
}