Always use drive-remapping (internally)

Rather than conditionally using subdirectories as drives, we now
just do that always.  If drives are in use then we have amapping:

* A: -> A/
* B: -> B/
etc

If they are not?

*A: -> .
*B: -> .

That means we can always use our lookup table (i.e. map) to know
where to look for things and don't need to have special cases.

This closes #101.

Author: skx

cpm/cpm.go

@@ -147,9 +147,8 @@ type CPM struct {
 	// be able to emulate that.
 	CPU z80.CPU
 
-	// Drives specifies whether we use sub-directories for the
-	// CP/M drives we emulate, instead of the current working directory.
-	Drives bool
+	// Drives specifies the local paths for each directory.
+	drives map[string]string
 
 	// currentDrive contains the currently selected drive.
 	// Valid values are 0-15, where they work in the obvious way:
@@ -420,6 +419,7 @@ func New(logger *slog.Logger, prn string, condriver string, ccp string) (*CPM, e
 		Logger:       logger,
 		ccp:          ccp,
 		dma:          0x0080,
+		drives:       make(map[string]string),
 		files:        make(map[uint16]FileCache),
 		input:        consolein.New(),
 		output:       driver,
@@ -823,12 +823,11 @@ func (cpm *CPM) RunAutoExec() {
 	// without doing anything.
 	for _, name := range files {
 
-		path := "."
-		if cpm.Drives {
-			path = string(cpm.currentDrive + 'A')
-		}
+		// Get the local prefix.
+		prefix := cpm.drives[string(cpm.currentDrive+'A')]
 
-		dst := filepath.Join(path, name)
+		// Add the name
+		dst := filepath.Join(prefix, name)
 
 		handle, err := os.OpenFile(dst, os.O_RDONLY, 0644)
 		if err != nil {
@@ -843,9 +842,19 @@ func (cpm *CPM) RunAutoExec() {
 }
 
 // SetDrives enables/disables the use of subdirectories upon the host system
-// to represent CP/M drives
+// to represent CP/M drives.
+//
+// We use a map to handle the drive->path mappings, and if directories are
+// not used we just store "." in the appropriate entry.
 func (cpm *CPM) SetDrives(enabled bool) {
-	cpm.Drives = true
+
+	for _, c := range []string{"A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P"} {
+		if enabled {
+			cpm.drives[c] = c
+		} else {
+			cpm.drives[c] = "."
+		}
+	}
 }
 
 // In is called to handle the I/O reading of a Z80 port.

cpm/cpm_bdos.go

@@ -267,13 +267,10 @@ func SysCallDriveAllReset(cpm *CPM) error {
 	var ret uint8 = 0
 
 	// drive will default to our current drive, if the FCB drive field is 0
-	drive := cpm.currentDrive + 'A'
+	drive := string(cpm.currentDrive + 'A')
 
-	// Should we remap drives?
-	path := "."
-	if cpm.Drives {
-		path = string(drive)
-	}
+	// Remap to the place we're supposed to use.
+	path := cpm.drives[drive]
 
 	// Look for a file with $ in its name
 	files, err := os.ReadDir(path)
@@ -354,11 +351,8 @@ func SysCallFileOpen(cpm *CPM) error {
 		drive = fcbPtr.Drive + 'A' - 1
 	}
 
-	// Should we remap drives?
-	path := "."
-	if cpm.Drives {
-		path = string(drive)
-	}
+	// Remap to the place we're supposed to use.
+	path := cpm.drives[string(drive)]
 
 	//
 	// Ok we have a filename, but we probably have an upper-case
@@ -384,16 +378,8 @@ func SysCallFileOpen(cpm *CPM) error {
 		slog.String("drive", string(cpm.currentDrive+'A')),
 		slog.String("result", fileName))
 
-	// Should we remap drives?
-	if cpm.Drives {
-		before := fileName
-
-		fileName = filepath.Join(string(drive), fileName)
-
-		l.Debug("SysCallFileOpen remapped path",
-			slog.String("before", before),
-			slog.String("after", fileName))
-	}
+	// Ensure the filename is qualified
+	fileName = filepath.Join(path, fileName)
 
 	// Now we open..
 	file, err := os.OpenFile(fileName, os.O_RDWR, 0644)
@@ -531,10 +517,8 @@ func SysCallFindFirst(cpm *CPM) error {
 	// Create a structure with the contents
 	fcbPtr := fcb.FromBytes(xxx)
 
-	dir := "."
-	if cpm.Drives {
-		dir = string(cpm.currentDrive + 'A')
-	}
+	// Look in the correct location.
+	dir := cpm.drives[string(cpm.currentDrive+'A')]
 
 	// Find files in the FCB.
 	res, err := fcbPtr.GetMatches(dir)
@@ -651,10 +635,8 @@ func SysCallDeleteFile(cpm *CPM) error {
 		drive = fcbPtr.Drive + 'A' - 1
 	}
 
-	path := "."
-	if cpm.Drives {
-		path = string(drive)
-	}
+	// Remap to the place we're supposed to use.
+	path := cpm.drives[string(drive)]
 
 	// Find files in the FCB.
 	res, err := fcbPtr.GetMatches(path)
@@ -857,11 +839,8 @@ func SysCallMakeFile(cpm *CPM) error {
 		drive = fcbPtr.Drive + 'A' - 1
 	}
 
-	// Should we remap drives?
-	path := "."
-	if cpm.Drives {
-		path = string(drive)
-	}
+	// Remap to the place we're supposed to use.
+	path := cpm.drives[string(drive)]
 
 	//
 	// Ok we have a filename, but we probably have an upper-case
@@ -887,16 +866,8 @@ func SysCallMakeFile(cpm *CPM) error {
 		slog.String("drive", string(cpm.currentDrive+'A')),
 		slog.String("result", fileName))
 
-	// Should we remap drives?
-	if cpm.Drives {
-		before := fileName
-
-		fileName = filepath.Join(string(drive), fileName)
-
-		l.Debug("SysCallMakeFile remapped path",
-			slog.String("before", before),
-			slog.String("after", fileName))
-	}
+	// Qualify the path
+	fileName = filepath.Join(path, fileName)
 
 	// Create the file
 	file, err := os.OpenFile(fileName, os.O_CREATE|os.O_RDWR, 0644)
@@ -967,11 +938,8 @@ func SysCallRenameFile(cpm *CPM) error {
 		fileName += ext
 	}
 
-	// Should we remap drives?
-	path := "."
-	if cpm.Drives {
-		path = string(cpm.currentDrive + 'A')
-	}
+	// Point to the directory
+	path := cpm.drives[string(cpm.currentDrive+'A')]
 
 	//
 	// Ok we have a filename, but we probably have an upper-case
@@ -989,10 +957,8 @@ func SysCallRenameFile(cpm *CPM) error {
 		}
 	}
 
-	// Should we remap drives?
-	if cpm.Drives {
-		fileName = filepath.Join(string(cpm.currentDrive+'A'), fileName)
-	}
+	// Ensure the filename is qualified
+	fileName = filepath.Join(path, fileName)
 
 	// 2. DEST
 	// The pointer to the FCB
@@ -1011,10 +977,8 @@ func SysCallRenameFile(cpm *CPM) error {
 		dstName += dExt
 	}
 
-	// Should we remap drives?
-	if cpm.Drives {
-		dstName = filepath.Join(string(cpm.currentDrive+'A'), dstName)
-	}
+	// ensure the name is qualified
+	dstName = filepath.Join(path, dstName)
 
 	cpm.Logger.Debug("Renaming file",
 		slog.String("src", fileName),
@@ -1287,10 +1251,7 @@ func SysCallFileSize(cpm *CPM) error {
 	}
 
 	// Should we remap drives?
-	path := "."
-	if cpm.Drives {
-		path = string(cpm.currentDrive + 'A')
-	}
+	path := cpm.drives[string(cpm.currentDrive+'A')]
 
 	//
 	// Ok we have a filename, but we probably have an upper-case
@@ -1308,10 +1269,8 @@ func SysCallFileSize(cpm *CPM) error {
 		}
 	}
 
-	// Should we remap drives?
-	if cpm.Drives {
-		fileName = filepath.Join(string(cpm.currentDrive+'A'), fileName)
-	}
+	// esnure the path is qualified
+	fileName = filepath.Join(path, fileName)
 
 	file, err := os.OpenFile(fileName, os.O_RDONLY, 0644)
 	if err != nil {

cpm/cpm_bios.go

@@ -199,11 +199,11 @@ func BiosSysCallReserved1(cpm *CPM) error {
 	//
 	getStringFromMemory := func(addr uint16) string {
 		str := ""
-		c := cpm.Memory.Get(addr)
-		for c != ' ' && c != 0x00 {
-			str += string(c)
+		x := cpm.Memory.Get(addr)
+		for x != ' ' && x != 0x00 {
+			str += string(x)
 			addr++
-			c = cpm.Memory.Get(addr)
+			x = cpm.Memory.Get(addr)
 		}
 
 		// Useful when the CCP has passed a string, because

main.go

@@ -173,10 +173,13 @@ func main() {
 		}
 	}
 
+	// Default to not using subdirectories for drives
+	obj.SetDrives(false)
+
 	// Are we using drives?
 	if *useDirectories {
 
-		// Enable drives
+		// Enable the use of directories.
 		obj.SetDrives(true)
 
 		// Count how many drives exist - if zero show a warning