code review 173100044: x/net/webdav: add a Dir type, analogous to http.Dir.

webdav/file.go

 // Copyright 2014 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
 package webdav
 
 import (
         "io"
         "net/http"
         "os"
+        "path"
+        "path/filepath"
+        "strings"
 )
 
-// TODO: comment that paths are always "/"-separated, even for Windows servers.
-
+// A FileSystem implements access to a collection of named files. The elements
+// in a file path are separated by slash ('/', U+002F) characters, regardless
+// of host operating system convention.
+//
+// Each method has the same semantics as the os package's function of the same
+// name.
 type FileSystem interface {
-        Mkdir(path string, perm os.FileMode) error
-        OpenFile(path string, flag int, perm os.FileMode) (File, error)
-        RemoveAll(path string) error
-        Stat(path string) (os.FileInfo, error)
+        Mkdir(name string, perm os.FileMode) error
+        OpenFile(name string, flag int, perm os.FileMode) (File, error)
+        RemoveAll(name string) error
+        Stat(name string) (os.FileInfo, error)
 }
 
+// A File is returned by a FileSystem's OpenFile method and can be served by a
+// Handler.
 type File interface {
         http.File
         io.Writer
 }
 
+// A Dir implements FileSystem using the native file system restricted to a
+// specific directory tree.
+//
+// While the FileSystem.OpenFile method takes '/'-separated paths, a Dir's
+// string value is a filename on the native file system, not a URL, so it is
+// separated by filepath.Separator, which isn't necessarily '/'.
+//
+// An empty Dir is treated as ".".
+type Dir string
+
+func (d Dir) resolve(name string) string {
+        // This implementation is based on Dir.Open's code in the standard net/http package.
+        if filepath.Separator != '/' && strings.IndexRune(name, filepath.Separator) >= 0 ||
+                strings.Contains(name, "\x00") {
+                return ""
+        }
+        dir := string(d)
+        if dir == "" {
+                dir = "."
+        }
+        return filepath.Join(dir, filepath.FromSlash(path.Clean("/"+name)))
+}
+
+func (d Dir) Mkdir(name string, perm os.FileMode) error {
+        if name = d.resolve(name); name == "" {
+                return os.ErrNotExist
+        }
+        return os.Mkdir(name, perm)
+}
+
+func (d Dir) OpenFile(name string, flag int, perm os.FileMode) (File, error) {
+        if name = d.resolve(name); name == "" {
+                return nil, os.ErrNotExist
+        }
+        return os.OpenFile(name, flag, perm)
+}
+
+func (d Dir) RemoveAll(name string) error {
+        if name = d.resolve(name); name == "" {
+                return os.ErrNotExist
+        }
+        if name == filepath.Clean(string(d)) {
+                // Prohibit removing the virtual root directory.
+                return os.ErrInvalid
+        }
+        return os.RemoveAll(name)
+}
+
+func (d Dir) Stat(name string) (os.FileInfo, error) {
+        if name = d.resolve(name); name == "" {
+                return nil, os.ErrNotExist
+        }
+        return os.Stat(name)
+}
+
 // TODO: a MemFS implementation.
-// TODO: a RealFS implementation, backed by the real, OS-provided file system.