Add more fs methods to Filesystem interface

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

Also, Remove method is introduced for all supported filesystems.

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 +702,22 @@ 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(path 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 string, newpath string) error {
+	return filesystem.ErrNotImplemented
+}
+
+// creates a symbolic link named linkpath which contains the string target.
+func (fs *FileSystem) Symlink(oldpath string, newpath string) 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 +827,17 @@ func (fs *FileSystem) Label() string {
 	return fs.superblock.volumeLabel
 }
 
-// Rm remove file or directory at path.
+// FIXME: API backwards compatibility
+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 +488,22 @@ 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(path string, mode uint32, dev int) error {
+	return filesystem.ErrNotSupported
+}
+
+// creates a new link (also known as a hard link) to an existing file.
+func (fs *FileSystem) Link(oldpath string, newpath string) error {
+	return filesystem.ErrNotSupported
+}
+
+// creates a symbolic link named linkpath which contains the string target.
+func (fs *FileSystem) Symlink(oldpath string, newpath string) 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 +625,10 @@ func (fs *FileSystem) OpenFile(p string, flag int) (filesystem.File, error) {
 	}, nil
 }
 
+func (fs *FileSystem) Remove(p 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/filesystem.go

@@ -3,25 +3,40 @@
 package filesystem
 
 import (
+	"errors"
 	"os"
 )
 
+var (
+	ErrNotSupported   = errors.New("method not supported by this filesystem")
+	ErrNotImplemented = errors.New("method not implemented (patches are welcome)")
+)
+
 // 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(path string) error
+	// creates a filesystem node (file, device special file, or named pipe) named pathname,
+	// with attributes specified by mode and dev
+	Mknod(path string, mode uint32, dev int) error
+	// creates a new link (also known as a hard link) to an existing file.
+	Link(oldpath string, newpath string) error
+	// creates a symbolic link named linkpath which contains the string target.
+	Symlink(oldpath string, newpath string) error
 	// ReadDir read the contents of a directory
-	ReadDir(string) ([]os.FileInfo, error)
+	ReadDir(path string) ([]os.FileInfo, error)
 	// OpenFile open a handle to read or write to a file
-	OpenFile(string, int) (File, error)
+	OpenFile(path string, flag int) (File, error)
+	// removes the named file or (empty) directory.
+	Remove(path 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/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
@@ -305,6 +308,22 @@ 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 (fs *FileSystem) Mknod(path string, mode uint32, dev int) error {
+	return filesystem.ErrNotSupported
+}
+
+// creates a new link (also known as a hard link) to an existing file.
+func (fs *FileSystem) Link(oldpath string, newpath string) error {
+	return filesystem.ErrNotSupported
+}
+
+// creates a symbolic link named linkpath which contains the string target.
+func (fs *FileSystem) Symlink(oldpath string, newpath string) 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.
@@ -414,6 +433,13 @@ func (fsm *FileSystem) OpenFile(p string, flag int) (filesystem.File, error) {
 	return f, nil
 }
 
+func (fsm *FileSystem) Remove(p string) error {
+	if fsm.workspace == "" {
+		return filesystem.ErrNotSupported
+	}
+	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/squashfs.go

@@ -229,6 +229,9 @@ 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 (fs *FileSystem) Type() filesystem.Type {
 	return filesystem.TypeSquashfs
@@ -276,6 +279,22 @@ 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(path string, mode uint32, dev int) error {
+	return filesystem.ErrNotSupported
+}
+
+// creates a new link (also known as a hard link) to an existing file.
+func (fs *FileSystem) Link(oldpath string, newpath string) error {
+	return filesystem.ErrNotSupported
+}
+
+// creates a symbolic link named linkpath which contains the string target.
+func (fs *FileSystem) Symlink(oldpath string, newpath string) 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.
@@ -379,6 +398,13 @@ func (fs *FileSystem) OpenFile(p string, flag int) (filesystem.File, error) {
 	return f, nil
 }
 
+func (fs *FileSystem) Remove(p string) error {
+	if fs.workspace == "" {
+		return filesystem.ErrNotSupported
+	}
+	return os.Remove(path.Join(fs.workspace, p))
+}
+
 // readDirectory - read directory entry on squashfs only (not workspace)
 func (fs *FileSystem) readDirectory(p string) ([]*directoryEntry, error) {
 	// use the root inode to find the location of the root direectory in the table