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..838a76d3a48ecb0d1b2c86b781c9f18c5691bacc
--- /dev/null
+++ b/common/dirwalk/walk_basic.go
@@ -0,0 +1,42 @@
+// 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/ioutil"
+	"os"
+	"path/filepath"
+)
+
+// Trivial implementation of a directory tree walker using the WalkObserver
+// interface.
+func WalkBasic(root string, smallfile_limit int64, obs WalkObserver) {
+	filepath.Walk(root, func(path string, info os.FileInfo, err error) error {
+		if err != nil {
+			obs.Error(path, err)
+			return nil
+		}
+
+		if info.IsDir() {
+			return nil
+		}
+
+		if info.Size() < smallfile_limit {
+			data, err := ioutil.ReadFile(path)
+			if err != nil {
+				obs.Error(path, err)
+				return nil
+			}
+			if int64(len(data)) != info.Size() {
+				panic("file size was wrong!")
+			}
+			obs.SmallFile(path, data)
+		} else {
+			obs.LargeFile(path)
+		}
+		return nil
+	})
+	obs.Finished()
+}