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

common/dirwalk/tests/tools/gendir/main.go

Index: common/dirwalk/tests/tools/gendir/main.go
diff --git a/common/dirwalk/tests/tools/gendir/main.go b/common/dirwalk/tests/tools/gendir/main.go
new file mode 100644
index 0000000000000000000000000000000000000000..6ea952a37c29d6709afbe79c351232f1ec348583
--- /dev/null
+++ b/common/dirwalk/tests/tools/gendir/main.go
@@ -0,0 +1,81 @@
+// 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 (
+	"encoding/json"
+	"errors"
+	"flag"
+	"fmt"
+	"io/ioutil"
+	"log"
+	"math/rand"
+	"os"
+)
+
+type testSettings struct {
+	Name    string
+	Comment string
+	Seed    int64
+	Tree    treeSettings
+}
+
+func mainImpl() error {
+	config := flag.String("config", "", "JSON config file for generating test file.")
+	outdir := flag.String("outdir", "", "Where to write the output.")
+	seed := flag.Int64("seed", 4, "Seed for random.")
+	verbose := flag.Bool("v", false, "verbose mode")
+
+	flag.Parse()
+
+	if !*verbose {
+		log.SetOutput(ioutil.Discard)
+	}
+
+	var settings testSettings
+	settings.Seed = *seed
+
+	configdata, err := ioutil.ReadFile(*config)
+	if err != nil {
+		return err
+	}
+
+	if err := json.Unmarshal(configdata, &settings); err != nil {
+		return err
+	}
+
+	fmt.Printf("%s: %s\n", settings.Name, settings.Comment)
+	fmt.Println("===============================================")
+	fmt.Println()
+
+	if len(*outdir) == 0 {
+		return errors.New("no output directory supplied")
+	}
+
+	if _, err := os.Stat(*outdir); !os.IsNotExist(err) {
+		return errors.New("directory exists")
+	}
+
+	if *seed != 4 && settings.Seed != *seed {
+		return errors.New("seed supplied by test config")
+	}
+
+	r := rand.New(rand.NewSource(settings.Seed))
+
+	// Create the root directory
+	if err := os.MkdirAll(*outdir, 0700); err != nil {
+		return err
+	}
+
+	generateTree(r, *outdir, &settings.Tree)
+	return nil
+}
+
+func main() {
+	if err := mainImpl(); err != nil {
+		fmt.Fprintf(os.Stderr, "gendir: %s.\n", err)
+		os.Exit(1)
+	}
+}