Add more fs methods to Filesystem interface

Interface is extended as a part of ext4 improvements effort
#9 (comment)

New methods introduced:

* Mknod
* Link
* Symlink
* Chmod
* Chown
* Rename
* Remove

filesystem.ErrNotSupported is returned if FS does not support a method.

Methods lacking implementation return filesystem.ErrNotImplemented.

disk/disk.go

@@ -189,7 +189,7 @@ func (d *Disk) CreateFilesystem(spec FilesystemSpec) (filesystem.FileSystem, err
 	case filesystem.TypeExt4:
 		return ext4.Create(d.File, size, start, d.LogicalBlocksize, nil)
 	case filesystem.TypeSquashfs:
-		return nil, errors.New("squashfs is a read-only filesystem")
+		return nil, filesystem.ErrReadonlyFilesystem
 	default:
 		return nil, errors.New("unknown filesystem type requested")
 	}

filesystem/ext4/ext4.go

@@ -684,6 +684,9 @@ func Read(file util.File, size, start, sectorsize int64) (*FileSystem, error) {
 	}, nil
 }
 
+// interface guard
+var _ filesystem.FileSystem = (*FileSystem)(nil)
+
 // Type returns the type code for the filesystem. Always returns filesystem.TypeExt4
 func (fs *FileSystem) Type() filesystem.Type {
 	return filesystem.TypeExt4
@@ -699,6 +702,34 @@ func (fs *FileSystem) Mkdir(p string) error {
 	return err
 }
 
+// creates a filesystem node (file, device special file, or named pipe) named pathname,
+// with attributes specified by mode and dev
+func (fs *FileSystem) Mknod(_ /*pathname*/ string, _ /*mode*/ uint32, _ /*dev*/ int) error {
+	return filesystem.ErrNotImplemented
+}
+
+// creates a new link (also known as a hard link) to an existing file.
+func (fs *FileSystem) Link(_ /*oldpath*/, _ /*newpath*/ string) error {
+	return filesystem.ErrNotImplemented
+}
+
+// creates a symbolic link named linkpath which contains the string target.
+func (fs *FileSystem) Symlink(_ /*oldpath*/, _ /*newpath*/ string) error {
+	return filesystem.ErrNotImplemented
+}
+
+// Chmod changes the mode of the named file to mode. If the file is a symbolic link,
+// it changes the mode of the link's target.
+func (fs *FileSystem) Chmod(_ /*name*/ string, _ /*mode*/ os.FileMode) error {
+	return filesystem.ErrNotImplemented
+}
+
+// Chown changes the numeric uid and gid of the named file. If the file is a symbolic link,
+// it changes the uid and gid of the link's target. A uid or gid of -1 means to not change that value
+func (fs *FileSystem) Chown(_ /*name*/ string, _ /*uid*/, _ /*gid*/ int) error {
+	return filesystem.ErrNotImplemented
+}
+
 // ReadDir return the contents of a given directory in a given filesystem.
 //
 // Returns a slice of os.FileInfo with all of the entries in the directory.
@@ -808,12 +839,22 @@ func (fs *FileSystem) Label() string {
 	return fs.superblock.volumeLabel
 }
 
-// Rm remove file or directory at path.
+// Rename renames (moves) oldpath to newpath. If newpath already exists and is not a directory, Rename replaces it.
+func (fs *FileSystem) Rename(_ /*oldpath*/, _ /*newpath*/ string) error {
+	return filesystem.ErrNotImplemented
+}
+
+// Deprecated: use filesystem.Remove(p string) instead
+func (fs *FileSystem) Rm(p string) error {
+	return fs.Remove(p)
+}
+
+// Removes file or directory at path.
 // If path is directory, it only will remove if it is empty.
 // If path is a file, it will remove the file.
 // Will not remove any parents.
 // Error if the file does not exist or is not an empty directory
-func (fs *FileSystem) Rm(p string) error {
+func (fs *FileSystem) Remove(p string) error {
 	parentDir, entry, err := fs.getEntryAndParent(p)
 	if err != nil {
 		return err

filesystem/fat32/fat32.go

@@ -470,6 +470,9 @@ func (fs *FileSystem) writeFat() error {
 	return nil
 }
 
+// interface guard
+var _ filesystem.FileSystem = (*FileSystem)(nil)
+
 // Type returns the type code for the filesystem. Always returns filesystem.TypeFat32
 func (fs *FileSystem) Type() filesystem.Type {
 	return filesystem.TypeFat32
@@ -485,6 +488,34 @@ func (fs *FileSystem) Mkdir(p string) error {
 	return err
 }
 
+// creates a filesystem node (file, device special file, or named pipe) named pathname,
+// with attributes specified by mode and dev
+func (fs *FileSystem) Mknod(_ string, _ uint32, _ int) error {
+	return filesystem.ErrNotSupported
+}
+
+// creates a new link (also known as a hard link) to an existing file.
+func (fs *FileSystem) Link(_, _ string) error {
+	return filesystem.ErrNotSupported
+}
+
+// creates a symbolic link named linkpath which contains the string target.
+func (fs *FileSystem) Symlink(_, _ string) error {
+	return filesystem.ErrNotSupported
+}
+
+// Chmod changes the mode of the named file to mode. If the file is a symbolic link,
+// it changes the mode of the link's target.
+func (fs *FileSystem) Chmod(_ string, _ os.FileMode) error {
+	return filesystem.ErrNotSupported
+}
+
+// Chown changes the numeric uid and gid of the named file. If the file is a symbolic link,
+// it changes the uid and gid of the link's target. A uid or gid of -1 means to not change that value
+func (fs *FileSystem) Chown(_ string, _, _ int) error {
+	return filesystem.ErrNotSupported
+}
+
 // ReadDir return the contents of a given directory in a given filesystem.
 //
 // Returns a slice of os.FileInfo with all of the entries in the directory.
@@ -606,6 +637,15 @@ func (fs *FileSystem) OpenFile(p string, flag int) (filesystem.File, error) {
 	}, nil
 }
 
+// Rename renames (moves) oldpath to newpath. If newpath already exists and is not a directory, Rename replaces it.
+func (fs *FileSystem) Rename(_ /*oldpath*/, _ /*newpath*/ string) error {
+	return filesystem.ErrNotImplemented
+}
+
+func (fs *FileSystem) Remove(_ /*pathname*/ string) error {
+	return filesystem.ErrNotImplemented
+}
+
 // Label get the label of the filesystem from the secial file in the root directory.
 // The label stored in the boot sector is ignored to mimic Windows behavior which
 // only stores and reads the label from the special file in the root directory.

filesystem/fat32/fat32_test.go

@@ -455,9 +455,9 @@ func TestFat32OpenFile(t *testing.T) {
 				{"/CORTO1.TXT", os.O_RDWR, false, "This is a very long replacement string", "Tenemos un archivo corto\nThis is a very long replacement string", nil},
 				{"/CORTO1.TXT", os.O_RDWR, false, "Two", "Tenemos un archivo corto\nTwo", nil},
 				//  - open for append file that does exist (write contents, check that appended)
-				{"/CORTO1.TXT", os.O_APPEND, false, "More", "", fmt.Errorf("cannot write to file opened read-only")},
+				{"/CORTO1.TXT", os.O_APPEND, false, "More", "", filesystem.ErrReadonlyFilesystem},
 				{"/CORTO1.TXT", os.O_APPEND | os.O_RDWR, false, "More", "Tenemos un archivo corto\nMore", nil},
-				{"/CORTO1.TXT", os.O_APPEND, true, "More", "", fmt.Errorf("cannot write to file opened read-only")},
+				{"/CORTO1.TXT", os.O_APPEND, true, "More", "", filesystem.ErrReadonlyFilesystem},
 				{"/CORTO1.TXT", os.O_APPEND | os.O_RDWR, true, "More", "Moremos un archivo corto\n", nil},
 			}
 			for _, t2 := range tests {

filesystem/fat32/file.go

@@ -4,6 +4,8 @@ import (
 	"fmt"
 	"io"
 	"os"
+
+	"github.com/diskfs/go-diskfs/filesystem"
 )
 
 // File represents a single file in a FAT32 filesystem
@@ -108,7 +110,7 @@ func (fl *File) Write(p []byte) (int, error) {
 	fs := fl.filesystem
 	// if the file was not opened RDWR, nothing we can do
 	if !fl.isReadWrite {
-		return totalWritten, fmt.Errorf("cannot write to file opened read-only")
+		return totalWritten, filesystem.ErrReadonlyFilesystem
 	}
 	// what is the new file size?
 	writeSize := len(p)

filesystem/filesystem.go

@@ -3,25 +3,49 @@
 package filesystem
 
 import (
+	"errors"
 	"os"
 )
 
+var (
+	ErrNotSupported       = errors.New("method not supported by this filesystem")
+	ErrNotImplemented     = errors.New("method not implemented (patches are welcome)")
+	ErrReadonlyFilesystem = errors.New("read-only filesystem")
+)
+
 // FileSystem is a reference to a single filesystem on a disk
 type FileSystem interface {
 	// Type return the type of filesystem
 	Type() Type
 	// Mkdir make a directory
-	Mkdir(string) error
+	Mkdir(pathname string) error
+	// creates a filesystem node (file, device special file, or named pipe) named pathname,
+	// with attributes specified by mode and dev
+	Mknod(pathname string, mode uint32, dev int) error
+	// creates a new link (also known as a hard link) to an existing file.
+	Link(oldpath, newpath string) error
+	// creates a symbolic link named linkpath which contains the string target.
+	Symlink(oldpath, newpath string) error
+	// Chmod changes the mode of the named file to mode. If the file is a symbolic link,
+	// it changes the mode of the link's target.
+	Chmod(name string, mode os.FileMode) error
+	// Chown changes the numeric uid and gid of the named file. If the file is a symbolic link,
+	// it changes the uid and gid of the link's target. A uid or gid of -1 means to not change that value
+	Chown(name string, uid, gid int) error
 	// ReadDir read the contents of a directory
-	ReadDir(string) ([]os.FileInfo, error)
+	ReadDir(pathname string) ([]os.FileInfo, error)
 	// OpenFile open a handle to read or write to a file
-	OpenFile(string, int) (File, error)
+	OpenFile(pathname string, flag int) (File, error)
+	// Rename renames (moves) oldpath to newpath. If newpath already exists and is not a directory, Rename replaces it.
+	Rename(oldpath, newpath string) error
+	// removes the named file or (empty) directory.
+	Remove(pathname string) error
 	// Label get the label for the filesystem, or "" if none. Be careful to trim it, as it may contain
 	// leading or following whitespace. The label is passed as-is and not cleaned up at all.
 	Label() string
 	// SetLabel changes the label on the writable filesystem. Different file system may hav different
 	// length constraints.
-	SetLabel(string) error
+	SetLabel(label string) error
 }
 
 // Type represents the type of disk this is

filesystem/iso9660/file.go

@@ -4,6 +4,8 @@ import (
 	"fmt"
 	"io"
 	"os"
+
+	"github.com/diskfs/go-diskfs/filesystem"
 )
 
 // File represents a single file in an iso9660 filesystem
@@ -65,7 +67,7 @@ func (fl *File) Read(b []byte) (int, error) {
 //
 //	you cannot write to an iso, so this returns an error
 func (fl *File) Write(_ []byte) (int, error) {
-	return 0, fmt.Errorf("cannot write to a read-only iso filesystem")
+	return 0, filesystem.ErrReadonlyFilesystem
 }
 
 // Seek set the offset to a particular point in the file

filesystem/iso9660/iso9660.go

@@ -282,6 +282,9 @@ func Read(file util.File, size, start, blocksize int64) (*FileSystem, error) {
 	return fs, nil
 }
 
+// interface guard
+var _ filesystem.FileSystem = (*FileSystem)(nil)
+
 // Type returns the type code for the filesystem. Always returns filesystem.TypeFat32
 func (fsm *FileSystem) Type() filesystem.Type {
 	return filesystem.TypeISO9660
@@ -295,7 +298,7 @@ func (fsm *FileSystem) Type() filesystem.Type {
 // if readonly and not in workspace, will return an error
 func (fsm *FileSystem) Mkdir(p string) error {
 	if fsm.workspace == "" {
-		return fmt.Errorf("cannot write to read-only filesystem")
+		return filesystem.ErrReadonlyFilesystem
 	}
 	err := os.MkdirAll(path.Join(fsm.workspace, p), 0o755)
 	if err != nil {
@@ -305,6 +308,42 @@ func (fsm *FileSystem) Mkdir(p string) error {
 	return err
 }
 
+// creates a filesystem node (file, device special file, or named pipe) named pathname,
+// with attributes specified by mode and dev
+func (fsm *FileSystem) Mknod(_ /*pathname*/ string, _ /*mode*/ uint32, _ /*dev*/ int) error {
+	// Rock Ridge has device files support
+	// https://en.wikipedia.org/wiki/ISO_9660#Rock_Ridge
+	return filesystem.ErrNotImplemented
+}
+
+// creates a new link (also known as a hard link) to an existing file.
+func (fsm *FileSystem) Link(_, _ string) error {
+	return filesystem.ErrNotSupported
+}
+
+// creates a symbolic link named linkpath which contains the string target.
+func (fsm *FileSystem) Symlink(_ /*oldpath*/, _ /*newpath*/ string) error {
+	// Rock Ridge has symlink support
+	// https://en.wikipedia.org/wiki/ISO_9660#Rock_Ridge
+	return filesystem.ErrNotImplemented
+}
+
+// Chmod changes the mode of the named file to mode. If the file is a symbolic link,
+// it changes the mode of the link's target.
+func (fsm *FileSystem) Chmod(_ /*name*/ string, _ /*mode*/ os.FileMode) error {
+	// Rock Ridge has UNIX-style file modes support
+	// https://en.wikipedia.org/wiki/ISO_9660#Rock_Ridge
+	return filesystem.ErrNotImplemented
+}
+
+// Chown changes the numeric uid and gid of the named file. If the file is a symbolic link,
+// it changes the uid and gid of the link's target. A uid or gid of -1 means to not change that value
+func (fsm *FileSystem) Chown(_ /*name*/ string, _ /*uid*/, _ /*gid*/ int) error {
+	// Rock Ridge has user ids and group ids support
+	// https://en.wikipedia.org/wiki/ISO_9660#Rock_Ridge
+	return filesystem.ErrNotImplemented
+}
+
 // ReadDir return the contents of a given directory in a given filesystem.
 //
 // Returns a slice of os.FileInfo with all of the entries in the directory.
@@ -368,7 +407,7 @@ func (fsm *FileSystem) OpenFile(p string, flag int) (filesystem.File, error) {
 	writeMode := flag&os.O_WRONLY != 0 || flag&os.O_RDWR != 0 || flag&os.O_APPEND != 0 || flag&os.O_CREATE != 0 || flag&os.O_TRUNC != 0 || flag&os.O_EXCL != 0
 	if fsm.workspace == "" {
 		if writeMode {
-			return nil, fmt.Errorf("cannot write to read-only filesystem")
+			return nil, filesystem.ErrReadonlyFilesystem
 		}
 
 		// get the directory entries
@@ -414,6 +453,21 @@ func (fsm *FileSystem) OpenFile(p string, flag int) (filesystem.File, error) {
 	return f, nil
 }
 
+// Rename renames (moves) oldpath to newpath. If newpath already exists and is not a directory, Rename replaces it.
+func (fsm *FileSystem) Rename(oldpath, newpath string) error {
+	if fsm.workspace == "" {
+		return filesystem.ErrReadonlyFilesystem
+	}
+	return os.Rename(path.Join(fsm.workspace, oldpath), path.Join(fsm.workspace, newpath))
+}
+
+func (fsm *FileSystem) Remove(p string) error {
+	if fsm.workspace == "" {
+		return filesystem.ErrReadonlyFilesystem
+	}
+	return os.Remove(path.Join(fsm.workspace, p))
+}
+
 // readDirectory - read directory entry on iso only (not workspace)
 func (fsm *FileSystem) readDirectory(p string) ([]*directoryEntry, error) {
 	var (

filesystem/squashfs/file.go

@@ -4,6 +4,8 @@ import (
 	"fmt"
 	"io"
 	"os"
+
+	"github.com/diskfs/go-diskfs/filesystem"
 )
 
 // File represents a single file in a squashfs filesystem
@@ -148,7 +150,7 @@ func (fl *File) Read(b []byte) (int, error) {
 //
 //nolint:unused,revive // but it is important to implement the interface
 func (fl *File) Write(p []byte) (int, error) {
-	return 0, fmt.Errorf("cannot write to a read-only squashfs filesystem")
+	return 0, filesystem.ErrReadonlyFilesystem
 }
 
 // Seek set the offset to a particular point in the file