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

common/dirwalk/observer.go

Index: common/dirwalk/observer.go
diff --git a/common/dirwalk/observer.go b/common/dirwalk/observer.go
new file mode 100644
index 0000000000000000000000000000000000000000..f855c05df0191afdf9546af85d94e1361788608e
--- /dev/null
+++ b/common/dirwalk/observer.go
@@ -0,0 +1,23 @@
+// 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
+
+// Interface for receiving the results of walking a directory tree.
+//
+// For performance reasons, small files and large files are treated
+// differently.
+//
+// SmallFile and LargeFile must be called in sorted order.
+type WalkObserver interface {
+	SmallFile(filename string, alldata []byte)
+	LargeFile(filename string)
+
+	//StartDir(dirname string) error
+	//FinishDir(dirname string)
+
+	Error(pathname string, err error)
+
+	Finished()
+}