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

common/dirwalk/tests/tools/walkdir/walkers_size.go

Index: common/dirwalk/tests/tools/walkdir/walkers_size.go
diff --git a/common/dirwalk/tests/tools/walkdir/walkers_size.go b/common/dirwalk/tests/tools/walkdir/walkers_size.go
new file mode 100644
index 0000000000000000000000000000000000000000..5f1973ca80d4e35343e96a13f558a9b6fe5184bd
--- /dev/null
+++ b/common/dirwalk/tests/tools/walkdir/walkers_size.go
@@ -0,0 +1,36 @@
+// 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 main
+
+import (
+	"fmt"
+	"io"
+	"os"
+)
+
+// SizeWalker implements Walker. It prints the size of every file.
+type SizeWalker struct {
+	BaseWalker
+	obuf io.Writer
+}
+
+func (s *SizeWalker) SizeFile(filename string, size int64) {
+	fmt.Fprintf(s.obuf, "%s: %d\n", filename, size)
+}
+
+func (s *SizeWalker) SmallFile(filename string, alldata []byte) {
+	s.BaseWalker.SmallFile(filename, alldata)
+	s.SizeFile(filename, int64(len(alldata)))
+}
+
+func (s *SizeWalker) LargeFile(filename string) {
+	s.BaseWalker.LargeFile(filename)
+	stat, err := os.Stat(filename)
+	if err != nil {
+		s.Error(filename, err)
+	} else {
+		s.SizeFile(filename, stat.Size())
+	}
+}