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Launcher/WiiCompiled.Setup/WorkspaceTimestamps.cs

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+namespace WiiCompiled.Setup;
+
+
+internal static class WorkspaceTimestamps
+{
+    public static void MarkChangedFiles(string installedWorkspace, string stagedWorkspace,
+        Action<string> diagnostic, CancellationToken cancellationToken = default)
+    {
+        if (!Directory.Exists(installedWorkspace) || !Directory.Exists(stagedWorkspace)) return;
+        installedWorkspace = Path.GetFullPath(installedWorkspace);
+        stagedWorkspace = Path.GetFullPath(stagedWorkspace);
+
+        var stampUtc = DateTime.UtcNow;
+        var changed = 0;
+        var unchanged = 0;
+        foreach (var stagedFile in Directory.EnumerateFiles(stagedWorkspace, "*",
+                     SearchOption.AllDirectories))
+        {
+            cancellationToken.ThrowIfCancellationRequested();
+            var relative = Path.GetRelativePath(stagedWorkspace, stagedFile);
+            if (FileUnchanged(Path.Combine(installedWorkspace, relative), stagedFile))
+            {
+                unchanged++;
+                continue;
+            }
+            File.SetLastWriteTimeUtc(stagedFile, stampUtc);
+            changed++;
+        }
+        diagnostic($"Marked {changed} changed workspace file(s) for recompilation; " +
+                   $"{unchanged} unchanged file(s) keep the incremental build cache valid.");
+    }
+
+    private static bool FileUnchanged(string installedFile, string stagedFile)
+    {
+        try
+        {
+            if (!File.Exists(installedFile)) return false;
+            using var installed = File.OpenRead(installedFile);
+            using var staged = File.OpenRead(stagedFile);
+            if (installed.Length != staged.Length) return false;
+            var installedBuffer = new byte[81920];
+            var stagedBuffer = new byte[81920];
+            while (true)
+            {
+                var installedRead = installed.ReadAtLeast(installedBuffer, installedBuffer.Length,
+                    throwOnEndOfStream: false);
+                var stagedRead = staged.ReadAtLeast(stagedBuffer, stagedBuffer.Length,
+                    throwOnEndOfStream: false);
+                if (installedRead != stagedRead) return false;
+                if (installedRead == 0) return true;
+                if (!installedBuffer.AsSpan(0, installedRead)
+                        .SequenceEqual(stagedBuffer.AsSpan(0, stagedRead)))
+                    return false;
+            }
+        }
+        catch (Exception ex) when (ex is IOException or UnauthorizedAccessException)
+        {
+            return false;
+        }
+    }
+}