new Filesystem interfaces

Author: mcuadros

fs.go

@@ -4,54 +4,123 @@ import (
 	"errors"
 	"io"
 	"os"
+	"time"
 )
 
 var (
-	ErrClosed       = errors.New("file: Writing on closed file.")
-	ErrReadOnly     = errors.New("this is a read-only filesystem")
+	ErrClosed       = errors.New("writing on closed file")
+	ErrReadOnly     = errors.New("read-only filesystem")
 	ErrNotSupported = errors.New("feature not supported")
 )
 
 // Filesystem abstract the operations in a storage-agnostic interface.
-// It allows you to:
-// * Create files.
-// * Open existing files.
-// * Get info about files.
-// * List files in a directory.
-// * Get a temporal file.
-// * Rename files.
-// * Remove files.
-// * Create directories.
-// * Join parts of path.
-// * Obtain a filesystem starting on a subdirectory in the current filesystem.
-// * Get the base path for the filesystem.
-// Each method implementation varies from implementation to implementation. Refer to
-// the specific documentation for more info.
+// Each method implementation mimics the behavior of the equivalent functions
+// at the os package from the standard library.
 type Filesystem interface {
+	Basic
+	Dir
+	Symlink
+	TempFile
+
+	// Dir returns a new Filesystem from the same type of fs using as baseDir the
+	// given path
+	Dir(path string) Filesystem
+	// Base returns the base path of the filesystem
+	Base() string
+}
+
+// Basic abstract the basic operations in a storage-agnostic interface as
+// an extension to the Basic interface
+type Basic interface {
+	// Create creates the named file with mode 0666 (before umask), truncating
+	// it if it already exists. If successful, methods on the returned File can
+	// be used for I/O; the associated file descriptor has mode O_RDWR. If there
+	// is an error, it will be of type *PathError.
 	Create(filename string) (File, error)
+	// Open opens the named file for reading. If successful, methods on the
+	// returned file can be used for reading; the associated file descriptor has
+	// mode O_RDONLY. If there is an error, it will be of type *PathError.
 	Open(filename string) (File, error)
+	// OpenFile is the generalized open call; most users will use Open or Create
+	// instead. It opens the named file with specified flag (O_RDONLY etc.) and
+	// perm, (0666 etc.) if applicable. If successful, methods on the returned
+	// File can be used for I/O. If there is an error, it will be of type
+	// *PathError.
 	OpenFile(filename string, flag int, perm os.FileMode) (File, error)
-	// Stat returns a FileInfo describing the named file.
+	// Stat returns a FileInfo describing the named file. If there is an error,
+	// it will be of type *PathError.
 	Stat(filename string) (FileInfo, error)
+	// Rename renames (moves) oldpath to newpath. If newpath already exists and
+	// is not a directory, Rename replaces it. OS-specific restrictions may
+	// apply when oldpath and newpath are in different directories. If there is
+	// an error, it will be of type *LinkError.
+	Rename(oldpath, newpath string) error
+	// Remove removes the named file or directory. If there is an error, it will
+	// be of type *PathError.
+	Remove(filename string) error
+	// Join joins any number of path elements into a single path, adding a
+	// Separator if necessary. Join calls filepath.Clean on the result; in
+	// particular, all empty strings are ignored. On Windows, the result is a
+	// UNC path if and only if the first path element is a UNC path.
+	Join(elem ...string) string
+}
+
+type TempFile interface {
+	// TempDir returns the default directory to use for temporary files.
+	//TempDir() string
+	TempFile(dir, prefix string) (File, error)
+}
+
+// Dir abstract the dir related operations in a storage-agnostic interface as
+// an extension to the Basic interface.
+type Dir interface {
+	ReadDir(path string) ([]FileInfo, error)
+	// MkdirAll creates a directory named path, along with any necessary
+	// parents, and returns nil, or else returns an error. The permission bits
+	// perm are used for all directories that MkdirAll creates. If path is/
+	// already a directory, MkdirAll does nothing and returns nil.
+	MkdirAll(filename string, perm os.FileMode) error
+}
+
+// Symlink abstract the symlink related operations in a storage-agnostic
+// interface as an extension to the Basic interface.
+type Symlink interface {
 	// Lstat returns a FileInfo describing the named file. If the file is a
 	// symbolic link, the returned FileInfo describes the symbolic link. Lstat
-	// makes no attempt to follow the link.
+	// makes no attempt to follow the link. If there is an error, it will be of
+	// type *PathError.
 	Lstat(filename string) (FileInfo, error)
-	ReadDir(path string) ([]FileInfo, error)
-	TempFile(dir, prefix string) (File, error)
-	Rename(from, to string) error
-	Remove(filename string) error
-	MkdirAll(filename string, perm os.FileMode) error
-	Join(elem ...string) string
-	Dir(path string) Filesystem
 	// Symlink creates a symbolic-link from link to target. target may be an
 	// absolute or relative path, and need not refer to an existing node.
-	// Parent directories of link are created as necessary.
+	// Parent directories of link are created as necessary. If there is an
+	// error, it will be of type *LinkError.
 	Symlink(target, link string) error
-	// Readlink returns the target path of link. An error is returned if link is
-	// not a symbolic-link.
+	// Readlink returns the target path of link. If there is an error, it will
+	// be of type *PathError.
 	Readlink(link string) (string, error)
-	Base() string
+}
+
+// Change abstract the FileInfo change related operations in a storage-agnostic
+// interface as an extension to the Basic interface
+type Change interface {
+	// 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. If there is an
+	// error, it will be of type *PathError.
+	Chmod(name string, mode os.FileMode) error
+	// Lchown 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 itself. If there
+	// is an error, it will be of type *PathError.
+	Lchown(name string, uid, gid int) 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. If there
+	// is an error, it will be of type *PathError.
+	Chown(name string, uid, gid int) error
+	// Chtimes changes the access and modification times of the named file,
+	// similar to the Unix utime() or utimes() functions.
+	//
+	// The underlying filesystem may truncate or round the values to a less
+	// precise time unit. If there is an error, it will be of type *PathError.
+	Chtimes(name string, atime time.Time, mtime time.Time) error
 }
 
 // File implements io.Closer, io.Reader, io.Seeker, and io.Writer>

utils.go

@@ -5,10 +5,9 @@ import (
 	"os"
 )
 
-// RemoveAll removes path and any children it contains.
-// It removes everything it can but returns the first error
-// it encounters. If the path does not exist, RemoveAll
-// returns nil (no error).
+// RemoveAll removes path and any children it contains. It removes everything it
+// can but returns the first error it encounters. If the path does not exist,
+// RemoveAll returns nil (no error).
 func RemoveAll(fs Filesystem, path string) error {
 	r, ok := fs.(removerAll)
 	if ok {
@@ -81,7 +80,7 @@ func removeAll(fs Filesystem, path string) error {
 // WriteFile writes data to a file named by filename in the given filesystem.
 // If the file does not exist, WriteFile creates it with permissions perm;
 // otherwise WriteFile truncates it before writing.
-func WriteFile(fs Filesystem, filename string, data []byte, perm os.FileMode) error {
+func WriteFile(fs Basic, filename string, data []byte, perm os.FileMode) error {
 	f, err := fs.OpenFile(filename, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, perm)
 	if err != nil {
 		return err