implement remove and rename feature for fat32 (#233)

* feat: implement remove for fat32, rename in same dir feature for fat32, add new unit-tests

filesystem/fat32/directory.go

@@ -1,6 +1,7 @@
 package fat32
 
 import (
+	"fmt"
 	"time"
 )
 
@@ -41,7 +42,7 @@ func (d *Directory) entriesToBytes(bytesPerCluster int) ([]byte, error) {
 func (d *Directory) createEntry(name string, cluster uint32, dir bool) (*directoryEntry, error) {
 	// is it a long filename or a short filename?
 	var isLFN bool
-	// TODO: convertLfnSfn does not calculate if the short name conflicts and thus shoukld increment the last character
+	// TODO: convertLfnSfn does not calculate if the short name conflicts and thus should increment the last character
 	//       that should happen here, once we can look in the directory entry
 	shortName, extension, isLFN, _ := convertLfnSfn(name)
 	lfn := ""
@@ -70,6 +71,60 @@ func (d *Directory) createEntry(name string, cluster uint32, dir bool) (*directo
 	return &entry, nil
 }
 
+// removeEntry removes an entry in the given directory
+func (d *Directory) removeEntry(name string) error {
+	// TODO implement check for long/short filename after increment of sfn is correctly implemented
+
+	removeEntryIndex := -1
+	for i, entry := range d.entries {
+		if entry.filenameLong == name { // || entry.filenameShort == shortName  do not compare SFN, since it is not incremented correctly
+			removeEntryIndex = i
+		}
+	}
+
+	if removeEntryIndex == -1 {
+		return fmt.Errorf("cannot find entry for name %s", name)
+	}
+
+	// remove the entry from the list
+	d.entries = append(d.entries[:removeEntryIndex], d.entries[removeEntryIndex+1:]...)
+
+	return nil
+}
+
+// renameEntry renames an entry in the given directory, and returns the handle to it
+func (d *Directory) renameEntry(oldFileName, newFileName string) error {
+	// TODO implement check for long/short filename after increment of sfn is correctly implemented
+
+	newEntries := make([]*directoryEntry, 0, len(d.entries))
+	var isReplaced = false
+	for _, entry := range d.entries {
+		if entry.filenameLong == newFileName {
+			continue // skip adding already existing file, will be overwritten
+		}
+		if entry.filenameLong == oldFileName { //  || entry.filenameShort == shortName  do not compare SFN, since it is not incremented correctly
+			var lfn string
+			shortName, extension, isLFN, _ := convertLfnSfn(newFileName)
+			if isLFN {
+				lfn = newFileName
+			}
+			entry.filenameLong = lfn
+			entry.filenameShort = shortName
+			entry.fileExtension = extension
+			entry.modifyTime = time.Now()
+			isReplaced = true
+		}
+		newEntries = append(newEntries, entry)
+	}
+	if !isReplaced {
+		return fmt.Errorf("cannot find file entry for %s", oldFileName)
+	}
+
+	d.entries = newEntries
+
+	return nil
+}
+
 // createVolumeLabel create a volume label entry in the given directory, and return the handle to it
 func (d *Directory) createVolumeLabel(name string) (*directoryEntry, error) {
 	// allocate a slot for the new filename in the existing directory

filesystem/fat32/fat32.go

@@ -637,18 +637,128 @@ func (fs *FileSystem) OpenFile(p string, flag int) (filesystem.File, error) {
 	}, nil
 }
 
+// removes the named file or (empty) directory.
+func (fs *FileSystem) Remove(pathname string) error {
+	// get the path
+	dir := path.Dir(pathname)
+	filename := path.Base(pathname)
+	// if the dir == filename, then it is just /
+	if dir == filename {
+		return fmt.Errorf("cannot remove directory %s as file", pathname)
+	}
+	// get the directory entries
+	parentDir, entries, err := fs.readDirWithMkdir(dir, false)
+	if err != nil {
+		return fmt.Errorf("could not read directory entries for %s", dir)
+	}
+	// we now know that the directory exists, see if the file exists
+	var targetEntry *directoryEntry
+	for _, e := range entries {
+		shortName := e.filenameShort
+		if e.fileExtension != "" {
+			shortName += "." + e.fileExtension
+		}
+		if e.filenameLong != filename && shortName != filename {
+			continue
+		}
+		// cannot do anything with directories
+		if e.isSubdirectory {
+			content, err := fs.ReadDir(pathname)
+			if err != nil {
+				return fmt.Errorf("error while checking if file to delete is empty: %+v", err)
+			}
+			// '.' & '..' are always present in directory
+			if len(content) > 2 {
+				return fmt.Errorf("cannot remove non-empty directory %s", pathname)
+			}
+		}
+		// if we got this far, we have found the file
+		targetEntry = e
+	}
+
+	// see if the file exists
+	// if the file does not exist, and is not opened for os.O_CREATE, return an error
+	if targetEntry == nil {
+		return fmt.Errorf("target file %s does not exist", pathname)
+	}
+	err = parentDir.removeEntry(filename)
+	if err != nil {
+		return fmt.Errorf("failed to remove file %s: %v", pathname, err)
+	}
+
+	// we need to make sure that clusters are removed which may not be used anymore
+	_, err = fs.allocateSpace(uint64(parentDir.fileSize), parentDir.clusterLocation)
+	if err != nil {
+		return fmt.Errorf("failed to allocate clusters: %v", err)
+	}
+
+	// write the directory entries to disk
+	err = fs.writeDirectoryEntries(parentDir)
+	if err != nil {
+		return fmt.Errorf("error writing directory file %s to disk: %v", pathname, err)
+	}
+
+	return nil
+}
+
 // Rename renames (moves) oldpath to newpath. If newpath already exists and is not a directory, Rename replaces it.
-//
-//nolint:revive // parameters will be used eventually
 func (fs *FileSystem) Rename(oldpath, newpath string) error {
-	return filesystem.ErrNotImplemented
-}
+	// get the path
+	dir := path.Dir(oldpath)
+	filename := path.Base(oldpath)
 
-// removes the named file or (empty) directory.
-//
-//nolint:revive // parameters will be used eventually
-func (fs *FileSystem) Remove(pathname string) error {
-	return filesystem.ErrNotImplemented
+	newDir := path.Dir(newpath)
+	newname := path.Base(newpath)
+	if dir != newDir {
+		return errors.New("can only rename files within the same directory")
+	}
+
+	// if the dir == filename, then it is just /
+	if dir == filename {
+		return fmt.Errorf("cannot rename directory %s as file", oldpath)
+	}
+	// get the directory entries
+	parentDir, entries, err := fs.readDirWithMkdir(dir, false)
+	if err != nil {
+		return fmt.Errorf("could not read directory entries for %s", dir)
+	}
+	// we now know that the directory exists, see if the file exists
+	var targetEntry *directoryEntry
+	for _, e := range entries {
+		shortName := e.filenameShort
+		if e.fileExtension != "" {
+			shortName += "." + e.fileExtension
+		}
+		if e.filenameLong != filename && shortName != filename {
+			continue
+		}
+		// if we got this far, we have found the file
+		targetEntry = e
+	}
+
+	// see if the file exists
+	// if the file does not exist, and is not opened for os.O_CREATE, return an error
+	if targetEntry == nil {
+		return fmt.Errorf("target file %s does not exist", oldpath)
+	}
+	err = parentDir.renameEntry(filename, newname)
+	if err != nil {
+		return fmt.Errorf("failed to rename file %s: %v", oldpath, err)
+	}
+
+	// we need to make sure that clusters are removed which may not be used anymore
+	_, err = fs.allocateSpace(uint64(parentDir.fileSize), parentDir.clusterLocation)
+	if err != nil {
+		return fmt.Errorf("failed to allocate clusters: %v", err)
+	}
+
+	// write the directory entries to disk
+	err = fs.writeDirectoryEntries(parentDir)
+	if err != nil {
+		return fmt.Errorf("error writing directory file %s to disk: %v", oldpath, err)
+	}
+
+	return nil
 }
 
 // Label get the label of the filesystem from the secial file in the root directory.
@@ -801,7 +911,7 @@ func (fs *FileSystem) mkSubdir(parent *Directory, name string) (*directoryEntry,
 }
 
 func (fs *FileSystem) writeDirectoryEntries(dir *Directory) error {
-	// we need to save the entries of theparent
+	// we need to save the entries of the parent
 	b, err := dir.entriesToBytes(fs.bytesPerCluster)
 	if err != nil {
 		return fmt.Errorf("could not create a valid byte stream for a FAT32 Entries: %w", err)