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

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

Index: common/dirwalk/tests/tools/walkdir/fileprocessor_size.go
diff --git a/common/dirwalk/tests/tools/walkdir/fileprocessor_size.go b/common/dirwalk/tests/tools/walkdir/fileprocessor_size.go
new file mode 100644
index 0000000000000000000000000000000000000000..bcb1fd6aaa1b365fadf1f06f05fa59603003230d
--- /dev/null
+++ b/common/dirwalk/tests/tools/walkdir/fileprocessor_size.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 main
+
+import (
+	"fmt"
+	"io"
+	"io/ioutil"
+	"os"
+)
+
+// SizeFileProcessor implements FileProcessor. It prints the size of every file.
+type SizeFileProcessor struct {
+	BaseFileProcessor
+	obuf io.Writer
+}
+
+func (p *SizeFileProcessor) SizeFile(path string, size int64) {
+	fmt.Fprintf(p.obuf, "%s: %d\n", path, size)
+}
+
+func (p *SizeFileProcessor) SmallFile(path string, r io.ReadCloser) {
+	bytes, err := io.Copy(ioutil.Discard, r)
+	if err != nil {
+		p.Error(path, err)
+	}
+	p.SizeFile(path, int64(bytes))
+
+	p.BaseFileProcessor.SmallFile(path, r)
+}
+
+func (p *SizeFileProcessor) LargeFile(path string, r io.ReadCloser) {
+	fi, err := os.Stat(path)
+	if err != nil {
+		p.Error(path, err)
+	} else {
+		p.SizeFile(path, fi.Size())
+	}
+	p.BaseFileProcessor.LargeFile(path, r)
+}