adding ReadDir() and Walk()

dir.go

@@ -3,6 +3,7 @@ package vfs
 import (
 	"fmt"
 	"os"
+	"sort"
 	"strings"
 )
 
@@ -44,3 +45,19 @@ func MkdirAll(fs FileSystem, path string, perm os.FileMode) error {
 
 	return nil
 }
+
+func ReadDir(fs FileSystem, path string) ([]os.FileInfo, error) {
+	f, err := fs.Open(path)
+	if err != nil {
+		return nil, err
+	}
+
+	res, err := f.Readdir(-1)
+	f.Close()
+	if err != nil {
+		return nil, err
+	}
+
+	sort.Slice(res, func(i, j int) bool { return res[i].Name() < res[j].Name() })
+	return res, nil
+}

walk.go

@@ -0,0 +1,40 @@
+package vfs
+
+import (
+	"os"
+	"path/filepath"
+)
+
+func walk(fs FileSystem, path string, walkFn filepath.WalkFunc, info os.FileInfo, err error) error {
+	if err != nil {
+		return walkFn(path, info, err)
+	}
+	err = walkFn(path, info, nil)
+	if !info.IsDir() {
+		return err
+	}
+	if err == filepath.SkipDir {
+		return nil
+	}
+	// note: ReadDir returns results sorted by name
+	infos, err := ReadDir(fs, path)
+	if err != nil {
+		return err
+	}
+	for _, info := range infos {
+		name := info.Name()
+		if name == "." || name == ".." {
+			continue
+		}
+		if err := walk(fs, filepath.Join(path, info.Name()), walkFn, info, nil); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// Walk is the equivalent of filepath.Walk
+func Walk(fs FileSystem, path string, walkFn filepath.WalkFunc) error {
+	info, err := fs.Lstat(path)
+	return walk(fs, path, walkFn, info, err)
+}