From b2aa2e16029d984109049fce98c58466be867709 Mon Sep 17 00:00:00 2001
From: BlauFx <clanpower15@gmail.com>
Date: Wed, 28 Dec 2022 13:23:07 +0100
Subject: [PATCH] Add hardlink support for Linux

---
 osu.Game/Database/RealmFileStore.cs           | 16 +++++++++++----
 osu.Game/IO/HardLinkHelper.cs                 | 20 ++++++++++++++-----
 .../FirstRunSetup/ScreenImportFromStable.cs   |  2 +-
 3 files changed, 28 insertions(+), 10 deletions(-)

diff --git a/osu.Game/Database/RealmFileStore.cs b/osu.Game/Database/RealmFileStore.cs
index 04b503b808..49102d81e5 100644
--- a/osu.Game/Database/RealmFileStore.cs
+++ b/osu.Game/Database/RealmFileStore.cs
@@ -63,11 +63,19 @@ namespace osu.Game.Database
 
         private void copyToStore(RealmFile file, Stream data, bool preferHardLinks)
         {
-            if (RuntimeInfo.OS == RuntimeInfo.Platform.Windows && data is FileStream fs && preferHardLinks)
+            // attempt to do a fast hard link rather than copy.
+            if (data is FileStream fs && preferHardLinks)
             {
-                // attempt to do a fast hard link rather than copy.
-                if (HardLinkHelper.CreateHardLink(Storage.GetFullPath(file.GetStoragePath(), true), fs.Name, IntPtr.Zero))
-                    return;
+                if (RuntimeInfo.OS == RuntimeInfo.Platform.Windows)
+                {
+                    if (HardLinkHelper.CreateHardLink(Storage.GetFullPath(file.GetStoragePath(), true), fs.Name, IntPtr.Zero))
+                        return;
+                }
+                else if (RuntimeInfo.OS == RuntimeInfo.Platform.Linux)
+                {
+                    if (HardLinkHelper.link(fs.Name, Storage.GetFullPath(file.GetStoragePath(), true)) == 0)
+                        return;
+                }
             }
 
             data.Seek(0, SeekOrigin.Begin);
diff --git a/osu.Game/IO/HardLinkHelper.cs b/osu.Game/IO/HardLinkHelper.cs
index 1393bf26fd..8d521bab9f 100644
--- a/osu.Game/IO/HardLinkHelper.cs
+++ b/osu.Game/IO/HardLinkHelper.cs
@@ -14,9 +14,8 @@ namespace osu.Game.IO
     {
         public static bool CheckAvailability(string testDestinationPath, string testSourcePath)
         {
-            // We can support other operating systems quite easily in the future.
-            // Let's handle the most common one for now, though.
-            if (RuntimeInfo.OS != RuntimeInfo.Platform.Windows)
+            // TODO: Add macOS support for hardlinks.
+            if (RuntimeInfo.OS != RuntimeInfo.Platform.Windows || RuntimeInfo.OS != RuntimeInfo.Platform.Linux)
                 return false;
 
             const string test_filename = "_hard_link_test";
@@ -26,12 +25,20 @@ namespace osu.Game.IO
 
             cleanupFiles();
 
+
             try
             {
                 File.WriteAllText(testSourcePath, string.Empty);
-
                 // Test availability by creating an arbitrary hard link between the source and destination paths.
-                return CreateHardLink(testDestinationPath, testSourcePath, IntPtr.Zero);
+
+                bool isHardLinkAvailable = false;
+
+                if (RuntimeInfo.OS == RuntimeInfo.Platform.Windows)
+                    isHardLinkAvailable = CreateHardLink(testDestinationPath, testSourcePath, IntPtr.Zero);
+                else if (RuntimeInfo.OS == RuntimeInfo.Platform.Linux)
+                    isHardLinkAvailable = link(testSourcePath, testDestinationPath) == 0;
+
+                return isHardLinkAvailable;
             }
             catch
             {
@@ -70,6 +77,9 @@ namespace osu.Game.IO
             return result;
         }
 
+        [DllImport("libc",  SetLastError = true)]
+        public static extern int link(string oldpath, string newpath);
+
         [DllImport("Kernel32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
         public static extern bool CreateHardLink(string lpFileName, string lpExistingFileName, IntPtr lpSecurityAttributes);
 
diff --git a/osu.Game/Overlays/FirstRunSetup/ScreenImportFromStable.cs b/osu.Game/Overlays/FirstRunSetup/ScreenImportFromStable.cs
index 0f8a78453d..2603a6c6c4 100644
--- a/osu.Game/Overlays/FirstRunSetup/ScreenImportFromStable.cs
+++ b/osu.Game/Overlays/FirstRunSetup/ScreenImportFromStable.cs
@@ -132,7 +132,7 @@ namespace osu.Game.Overlays.FirstRunSetup
 
                 copyInformation.AddLink("Learn more about how \"hard links\" work", LinkAction.OpenWiki, @"Client/Release_stream/Lazer/File_storage#via-hard-links");
             }
-            else if (RuntimeInfo.OS != RuntimeInfo.Platform.Windows)
+            else if (RuntimeInfo.OS != RuntimeInfo.Platform.Windows || RuntimeInfo.OS != RuntimeInfo.Platform.Linux)
                 copyInformation.Text = "Lightweight linking of files is not supported on your operating system yet, so a copy of all files will be made during import.";
             else
             {