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

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

Index: common/dirwalk/tests/tools/walkdir/walkers_base.go
diff --git a/common/dirwalk/tests/tools/walkdir/walkers_base.go b/common/dirwalk/tests/tools/walkdir/walkers_base.go
new file mode 100644
index 0000000000000000000000000000000000000000..6efb2987741c42663e3041682838035fb0536e54
--- /dev/null
+++ b/common/dirwalk/tests/tools/walkdir/walkers_base.go
@@ -0,0 +1,28 @@
+// 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 (
+	"log"
+	"sync/atomic"
+)
+
+// BaseWalker implements Walker. It counts the number of files of each type.
+type BaseWalker struct {
+	smallfiles uint64
+	largefiles uint64
+}
+
+func (n *BaseWalker) SmallFile(filename string, alldata []byte) {
+	atomic.AddUint64(&n.smallfiles, 1)
+}
+func (n *BaseWalker) LargeFile(filename string) {
+	atomic.AddUint64(&n.largefiles, 1)
+}
+func (n *BaseWalker) Error(pathname string, err error) {
+	log.Fatalf("%s:%s", pathname, err)
+}
+func (n *BaseWalker) Finished() {
+}