luci-go/common/dirwalk: Code for walking a directory tree efficiently

common/dirwalk/util.go

Index: common/dirwalk/util.go
diff --git a/common/dirwalk/util.go b/common/dirwalk/util.go
new file mode 100644
index 0000000000000000000000000000000000000000..3047ced495d6d43eb7307bfc8e75f74a541aa16f
--- /dev/null
+++ b/common/dirwalk/util.go
@@ -0,0 +1,51 @@
+// Copyright 2016 The LUCI Authors. All rights reserved.
+// Use of this source code is governed under the Apache License, Version 2.0
+// that can be found in the LICENSE file.
+
+package dirwalk
+
+import "io"
+
+type multiReadCloser struct {
+	io.Reader
+	closers []io.Closer
+}
+
+func (mrc multiReadCloser) Close() error {
+	for _, c := range mrc.closers {
+		if err := c.Close(); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+type stringStack struct {
+	elements []string
+}
+
+func (s *stringStack) push(v string) {
+	s.elements = append(s.elements, v)
+}
+
+func (s *stringStack) pop() string {
+	var v string
+	v, s.elements = s.elements[s.last()], s.elements[:s.last()]
+	return v
+}
+
+func (s *stringStack) peek() string {
+	return s.elements[s.last()]
+}
+
+func (s *stringStack) size() int {
+	return len(s.elements)
+}
+
+func (s *stringStack) last() int {
+	return len(s.elements) - 1
+}
+
+func newStringStack() *stringStack {
+	return &stringStack{elements: make([]string, 0)}
+}