Fixing hard landing on failure to load SRAM. This is needed to prevent crashes in dosbox when preserving hard disk contents

src/BizHawk.Emulation.Cores/Computers/DOS/DOSBox.ISettable.cs

@@ -234,6 +234,11 @@ namespace BizHawk.Emulation.Cores.Computers.DOS
 			[TypeConverter(typeof(DescribableEnumConverter))]
 			public WriteableHardDiskOptions WriteableHardDisk { get; set; }
 
+			[DisplayName("Preserve Hard Disk Contents")]
+			[Description("Determines whether to store the contents of the writeable hard disk as SaveRAM to be reloaded on the next start. Enabling this option may cause the core to take some seconds to store and load the SRAM upon restart.")]
+			[DefaultValue(false)]
+			public bool PreserveHardDiskContents { get; set; }
+
 			[DisplayName("FPS Numerator")]
 			[Description("Numerator for FPS: how many Bizhawk frames to run per second of emulation. Default represents the numerator for the typical video frames per second in DOS (70.086303). We recommend leaving this value unmodified. You can set it higher if you need finer subframe inputs, and; lower, in case your game runs in lower FPS and it feels more natural.")]
 			[DefaultValue(LibDOSBox.VIDEO_NUMERATOR_DOS)]

src/BizHawk.Emulation.Cores/Computers/DOS/DOSBox.cs

@@ -250,13 +250,13 @@ namespace BizHawk.Emulation.Cores.Computers.DOS
 			Console.WriteLine("Configuration: {0}", System.Text.Encoding.Default.GetString(configData.ToArray()));
 
 			////////////// Initializing Core
-			if (!_libDOSBox.Init(
-				joystick1Enabled: _syncSettings.EnableJoystick1,
-				joystick2Enabled: _syncSettings.EnableJoystick2,
-				mouseEnabled: _syncSettings.EnableMouse,
-				hardDiskDriveSize: writableHDDImageFileSize,
-				fpsNumerator: _syncSettings.FPSNumerator,
-				fpsDenominator: _syncSettings.FPSDenominator))
+			if (!_libDOSBox.Init(new LibDOSBox.InitSettings() {
+				joystick1Enabled = _syncSettings.EnableJoystick1 ? 1 : 0,
+				joystick2Enabled = _syncSettings.EnableJoystick2 ? 1 : 0,
+				hardDiskDriveSize = writableHDDImageFileSize,
+				preserveHardDiskContents = _syncSettings.PreserveHardDiskContents ? 1 : 0,
+				fpsNumerator = _syncSettings.FPSNumerator,
+				fpsDenominator = _syncSettings.FPSDenominator }))
 			{
 				throw new InvalidOperationException("Core rejected the rom!");
 			}

src/BizHawk.Emulation.Cores/Computers/DOS/LibDOSBox.cs

@@ -58,10 +58,21 @@ namespace BizHawk.Emulation.Cores.Computers.DOS
 		[BizImport(CC)]
 		public abstract void pushTrackData(int cdIdx, int trackId, CDTrack data);
 
+		[StructLayout(LayoutKind.Sequential)]
+		public class InitSettings
+		{
+			public int joystick1Enabled;
+			public int joystick2Enabled;
+			public ulong hardDiskDriveSize;
+			public int preserveHardDiskContents;
+			public ulong fpsNumerator;
+			public ulong fpsDenominator;
+		}
+
 		// CD Management Logic END
 
 		[BizImport(CC, Compatibility = true)]
-		public abstract bool Init(bool joystick1Enabled, bool joystick2Enabled, bool mouseEnabled, ulong hardDiskDriveSize, ulong fpsNumerator, ulong fpsDenominator);
+		public abstract bool Init(InitSettings settings);
 
 		[BizImport(CC, Compatibility = true)]
 		public abstract bool getDriveActivityFlag();

src/BizHawk.Emulation.Cores/Waterbox/WaterboxCore.cs

@@ -176,20 +176,25 @@ namespace BizHawk.Emulation.Cores.Waterbox
 
 		public virtual void StoreSaveRam(byte[] data)
 		{
+			// Checking if the size of the SaveRAM provided coincides with that expected. This is important for cores whose SaveRAM size can vary depending on their configuration.
+			if (data.Length != _saveramSize)
+			{
+				Console.WriteLine($"Could not push SaveRam into the core: the length of the data provided ({data.Length}) is different than expected ({_saveramSize})");
+				
+				// Here, the exception was too traumatic. The emulator shuts down when in debug mode, and is left in an unstable state on release.
+				// Using a softer landing here, although returning true/false plus a string explanation would be more adequate.
+				return;
+			}
+
 			using (_exe.EnterExit())
 			{
-				if (data.Length != _saveramSize)
-					throw new InvalidOperationException("Saveram size mismatch");
-				using (_exe.EnterExit())
+				var source = new MemoryStream(data, false);
+				foreach (var area in _saveramAreas)
 				{
-					var source = new MemoryStream(data, false);
-					foreach (var area in _saveramAreas)
-					{
-						MemoryBlockUtils.CopySome(source, new MemoryDomainStream(area), area.Size);
-					}
+					MemoryBlockUtils.CopySome(source, new MemoryDomainStream(area), area.Size);
 				}
 			}
-		}
+        }
 
 		protected abstract LibWaterboxCore.FrameInfo FrameAdvancePrep(IController controller, bool render, bool rendersound);
 		protected virtual void FrameAdvancePost()

waterbox/dosbox/dosbox-x

@@ -1 +1 @@
-Subproject commit e2b4045639cd51efea595513eaae1fcb6d680855
+Subproject commit 116c7bcf65fe640ac6efc9accc727553830a9f5a