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

common/dirwalk/walk_basic.go

Index: common/dirwalk/walk_basic.go
diff --git a/common/dirwalk/walk_basic.go b/common/dirwalk/walk_basic.go
new file mode 100644
index 0000000000000000000000000000000000000000..b179af5aa828aeee8db1650375f56bbe6a766330
--- /dev/null
+++ b/common/dirwalk/walk_basic.go
@@ -0,0 +1,49 @@
+// 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 (
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+// WalkBasic is the trivial implementation of a directory tree walker using
+// built in filepath.Walk function.
+func WalkBasic(root string, callback WalkFunc) {
+	dirs := newStringStack()
+	dirs.push("")
+	filepath.Walk(root, func(path string, info os.FileInfo, err error) error {
+		if err != nil {
+			callback(path, -1, nil, err)
+			return nil
+		}
+
+		for true {
+			if strings.HasPrefix(path, dirs.peek()) {
+				break
+			}
+			callback(dirs.pop(), -1, nil, nil)
+		}
+
+		if info.IsDir() {
+			dirs.push(path)
+		} else {
+			f, err := os.Open(path)
+			if err != nil {
+				callback(path, -1, nil, err)
+				return nil
+			}
+			callback(path, info.Size(), f, nil)
+		}
+		return nil
+	})
+	for true {
+		if dirs.peek() == "" {
+			break
+		}
+		callback(dirs.pop(), -1, nil, nil)
+	}
+}