Improvements to DosDriveManager (#2161)

* Move CurrentDosDirectory property from VirtualDrive to DosDriveBase and make it optional.

* Added drive letter/index conversion methods to DosDriveManager.

* Replaced internal DosDriveManager.DriveLetters dictionary with new drive letter/index methods.

* Complete rewrite of DosDriveManager internal storage to use a single generic array for all drives instead of a dictionary for each drive type.

Changed dictionary interface of DosDriveManager to use DosDriveBase instead of VirtualDrive.

Added a number of generic methods for mounting, unmounting, and retrieving drives of different types.

Added capability to retrieve drives by drive index as well as by drive letter.

* Added DosDriveManager.TryGetDriveLetterIndex helper method. Changed internal HasDriveAtIndex to use int instead of ushort.

* Fixed problematic use of ElementAtOrDefault when used with DosDriveManager. Applied a few optimizations relating to use of DosDriveManager.

* Renamed some drive letter/index helper methods and parameters.

* Change drive letter in test to unassigned letter Q: because drive letter Z: is assigned by default as a memory drive (it's just not a virtual drive).

* Remove problematic assertions in DosDriveManager (CopyTo methods).

* Fixed DOS FCB manager test ParseFilename_InvalidDrive_ContinuesParsing.

* Fixed drive count in DosDriveManager. Also removed unnecessary DosDriveManager.NumberOfPotentiallyValidDriveLetters property. The drive manager now knows exactly how many drives are mounted.

* Added more documentation to DosDriveManager.

* Removed generic exception handler from DosDriveManager.Clear methods.

* Fixed DOS IOCTL function for IsDeviceRemovable.

AX = media type (0000h removable, 0001h fixed)

* [DOS] Fixed DosDriveManager CopyTo() methods.

DriveLetterCollection and DriveCollection both had a bug which prevented them from enumerating all drive slots. This had resulted in array elements not set when using CopyTo.

* [DOS] Added some DosDriveManager unit tests.

* chore: Removed `#region` directives from DosDriveManager.

Per project maintainer's request.

Author: assumenothing

src/Spice86.Core/Emulator/InterruptHandlers/Dos/DosDiskInt25Handler.cs

@@ -25,7 +25,7 @@ public override void Run() {
         ushort startingLogicalSector = State.DX;
         SegmentedAddress bufferForData = new(State.DS, State.BX);
 
-        if (driveNumber >= DosDriveManager.MaxDriveCount || !_dosDriveManager.HasDriveAtIndex(State.AL)) {
+        if (!_dosDriveManager.HasDriveAtIndex(State.AL)) {
             State.AX = 0x8002;
             SetCarryFlag(true, true);
         } else {

src/Spice86.Core/Emulator/InterruptHandlers/Dos/DosDiskInt26Handler.cs

@@ -21,7 +21,7 @@ public override void Run() {
         if (LoggerService.IsEnabled(Serilog.Events.LogEventLevel.Warning)) {
             LoggerService.Warning("DOS INT26H was called, hope for the best!");
         }
-        if (State.AL >= DosDriveManager.MaxDriveCount || !_dosDriveManager.HasDriveAtIndex(State.AL)) {
+        if (!_dosDriveManager.HasDriveAtIndex(State.AL)) {
             State.AX = 0x8002;
             SetCarryFlag(true, true);
         } else {

src/Spice86.Core/Emulator/InterruptHandlers/Dos/DosInt21Handler.cs

@@ -662,12 +662,7 @@ private bool TryGetAllocationInfoDrive(byte driveRequest, out byte driveIndex, o
             driveIndex = (byte)(driveRequest - 1);
         }
 
-        if (driveIndex >= DosDriveManager.MaxDriveCount) {
-            return false;
-        }
-
-        char driveLetter = (char)('A' + driveIndex);
-        if (!_dosDriveManager.TryGetValue(driveLetter, out VirtualDrive? resolvedDrive) || resolvedDrive == null) {
+        if (!_dosDriveManager.TryGetDriveAtIndex(driveIndex, out VirtualDrive? resolvedDrive)) {
             return false;
         }
 
@@ -1781,8 +1776,7 @@ public override void Run() {
     public void SelectDefaultDrive() {
         byte driveIndex = State.DL;
         if (driveIndex < DosDriveManager.MaxDriveCount) {
-            char driveLetter = (char)('A' + driveIndex);
-            if (_dosDriveManager.TryGetValue(driveLetter, out VirtualDrive? mountedDrive)) {
+            if (_dosDriveManager.TryGetDriveAtIndex(driveIndex, out VirtualDrive? mountedDrive)) {
                 _dosDriveManager.CurrentDrive = mountedDrive;
             }
         } else if (LoggerService.IsEnabled(LogEventLevel.Error)) {

src/Spice86.Core/Emulator/Mcp/EmulatorMcpTools.cs

@@ -1154,6 +1154,8 @@ public CallToolResult QueryDosState() {
             lock (_services.ToolsLock) {
                 Dos dos = GetDos();
                 List<DosDriveResponse> drives = dos.DosDriveManager.Values
+                    .Where(static drive => drive is VirtualDrive)
+                    .Cast<VirtualDrive>()
                     .Select(static drive => new DosDriveResponse {
                         Drive = drive.DosVolume,
                         CurrentDosDirectory = drive.CurrentDosDirectory,
@@ -1164,7 +1166,7 @@ public CallToolResult QueryDosState() {
                 return new DosStateResponse {
                     CurrentDrive = dos.DosDriveManager.CurrentDrive.DosVolume,
                     CurrentDriveIndex = dos.DosDriveManager.CurrentDriveIndex,
-                    PotentialDriveLetters = dos.DosDriveManager.NumberOfPotentiallyValidDriveLetters,
+                    PotentialDriveLetters = dos.DosDriveManager.Count,
                     CurrentProgramSegmentPrefix = dos.DosSwappableDataArea.CurrentProgramSegmentPrefix,
                     DeviceCount = dos.Devices.Count,
                     HasEms = dos.Ems != null,
@@ -1238,7 +1240,7 @@ public CallToolResult DosSetDefaultDrive(string driveLetter) {
                 }
 
                 char normalizedDriveLetter = char.ToUpperInvariant(driveLetter[0]);
-                if (!dos.DosDriveManager.TryGetValue(normalizedDriveLetter, out VirtualDrive? mountedDrive) || mountedDrive == null) {
+                if (!dos.DosDriveManager.TryGetDrive(normalizedDriveLetter, out VirtualDrive? mountedDrive) || mountedDrive == null) {
                     throw new InvalidOperationException($"Drive '{normalizedDriveLetter}' is not mounted");
                 }
 
@@ -1524,12 +1526,10 @@ private static byte ResolveDosDriveNumber(Dos dos, string driveLetter, out strin
             throw new ArgumentException("Drive letter must be empty or a single character between A and Z");
         }
 
-        char normalizedDriveLetter = char.ToUpperInvariant(driveLetter[0]);
-        if (!DosDriveManager.DriveLetters.TryGetValue(normalizedDriveLetter, out byte driveIndex)) {
-            throw new ArgumentException($"Drive letter '{normalizedDriveLetter}' is invalid");
-        }
-        if (!dos.DosDriveManager.TryGetValue(normalizedDriveLetter, out VirtualDrive? virtualDrive) || virtualDrive == null) {
-            throw new InvalidOperationException($"Drive '{normalizedDriveLetter}' is not mounted");
+        char driveLetterChar = driveLetter[0];
+        int driveIndex = DosDriveManager.GetDriveIndexOrThrow(driveLetterChar, nameof(driveLetter));
+        if (!dos.DosDriveManager.TryGetDrive(driveLetterChar, out VirtualDrive? virtualDrive) || virtualDrive == null) {
+            throw new InvalidOperationException($"Drive '{driveLetterChar}' is not mounted");
         }
 
         resolvedDrive = virtualDrive.DosVolume;