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

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

Index: common/dirwalk/tests/tools/walkdir/walkers_hash.go
diff --git a/common/dirwalk/tests/tools/walkdir/walkers_hash.go b/common/dirwalk/tests/tools/walkdir/walkers_hash.go
new file mode 100644
index 0000000000000000000000000000000000000000..f88ebb09b6f98a4579931e8242a590f1bcd79d0b
--- /dev/null
+++ b/common/dirwalk/tests/tools/walkdir/walkers_hash.go
@@ -0,0 +1,34 @@
+// 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"
+
+	"github.com/luci/luci-go/common/isolated"
+)
+
+// HashWalker implements Walker. It generates a hash for the contents of each
+// found file.
+type HashWalker struct {
+	BaseWalker
+	obuf io.Writer
+}
+
+func (h *HashWalker) HashedFile(filename string, digest isolated.HexDigest) {
+	fmt.Fprintf(h.obuf, "%s: %v\n", filename, digest)
+}
+
+func (h *HashWalker) SmallFile(filename string, alldata []byte) {
+	h.BaseWalker.SmallFile(filename, alldata)
+	h.HashedFile(filename, isolated.HashBytes(alldata))
+}
+
+func (h *HashWalker) LargeFile(filename string) {
+	h.BaseWalker.LargeFile(filename)
+	d, _ := isolated.HashFile(filename)
+	h.HashedFile(filename, isolated.HexDigest(d.Digest))
+}