Implement file system API and add shutdown functionality for desktop builds

simulator/Program.cs

@@ -1,12 +1,77 @@
 using System;
+using System.IO;
 using System.Runtime.InteropServices;
 using System.Threading;
+using Zio;
+using Zio.FileSystems;
 
 internal static class Program
 {
+    private static readonly IFileSystem SdFileSystem = new PhysicalFileSystem();
+    private static readonly UPath SdRoot = new UPath(Path.Combine(AppContext.BaseDirectory, "sd").Replace('\\', '/').Replace("C:", "/mnt/c"));
+
+    private static UPath GetSlotFilePath(uint slotIdx, string filePath)
+    {
+        var normalizedPath = (filePath ?? string.Empty).Replace('\\', '/').TrimStart('/');
+        return SdRoot / $"slot{slotIdx}" / normalizedPath;
+    }
+
     private static readonly Nova64Core.DisplayFlushDelegate DisplayFlush = (buffer, width, height) => { };
     private static readonly Nova64Core.AudioOutputDelegate AudioOutput = (samples, count) => { };
-    private static readonly Nova64Core.SdReadSectorDelegate SdReadSector = (sectorIdx, destinationBuffer, sectorCount) => false;
+    private static readonly Nova64Core.SdReadFileDelegate SdReadFile = (slotIdx, filePath, destinationBuffer, destinationLength) =>
+    {
+        var path = GetSlotFilePath(slotIdx, filePath);
+        Console.WriteLine($"[Core] SD read request: slot {slotIdx}, file '{filePath}', resolved path '{path}' destination length {destinationLength}");
+
+        if (destinationBuffer == IntPtr.Zero)
+        {
+            Console.WriteLine("[Core] SD read request failed: destination buffer is null.");
+            return -1;
+        }
+
+        if (!SdFileSystem.FileExists(path))
+        {
+            Console.WriteLine($"[Core] SD read request failed: file not found '{path}'");
+            return -1;
+        }
+
+        try
+        {
+            using var stream = SdFileSystem.OpenFile(path, FileMode.Open, FileAccess.Read, FileShare.Read);
+            var bytesToRead = (int)Math.Min(destinationLength, stream.Length);
+            var buffer = new byte[bytesToRead];
+            var bytesRead = stream.Read(buffer, 0, bytesToRead);
+            Marshal.Copy(buffer, 0, destinationBuffer, bytesRead);
+            return bytesRead;
+        }
+        catch (Exception ex)
+        {
+            Console.WriteLine($"[Core] SD read request failed: {ex.Message}");
+            return -1;
+        }
+    };
+    private static readonly Nova64Core.SdGetFileSizeDelegate SdGetFileSize = (slotIdx, filePath) =>
+    {
+        var path = GetSlotFilePath(slotIdx, filePath);
+        Console.WriteLine($"[Core] SD get file size request: slot {slotIdx}, file '{filePath}', resolved path '{path}'");
+
+        if (!SdFileSystem.FileExists(path))
+        {
+            Console.WriteLine($"[Core] SD get file size failed: file not found '{path}'");
+            return -1;
+        }
+
+        try
+        {
+            var length = SdFileSystem.GetFileLength(path);
+            return length > int.MaxValue ? -1 : (int)length;
+        }
+        catch (Exception ex)
+        {
+            Console.WriteLine($"[Core] SD get file size failed: {ex.Message}");
+            return -1;
+        }
+    };
     private static readonly Nova64Core.CartridgeStatusDelegate CartridgeStatus = (slotIdx, isInserted) => { };
     private static readonly Nova64Core.LogMessageDelegate LogMessage = (message) =>
     {
@@ -51,7 +116,8 @@ internal static class Program
             {
                 display_flush = Marshal.GetFunctionPointerForDelegate(DisplayFlush),
                 audio_output = Marshal.GetFunctionPointerForDelegate(AudioOutput),
-                sd_read_sector = Marshal.GetFunctionPointerForDelegate(SdReadSector),
+                sd_read_file = Marshal.GetFunctionPointerForDelegate(SdReadFile),
+                sd_get_file_size = Marshal.GetFunctionPointerForDelegate(SdGetFileSize),
                 cartridge_status = Marshal.GetFunctionPointerForDelegate(CartridgeStatus),
                 log_message = Marshal.GetFunctionPointerForDelegate(LogMessage)
             };