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..9dd86ae39272369ac3d67133dc3d57bc7609f79c
--- /dev/null
+++ b/common/dirwalk/tests/tools/gendir/main.go
@@ -0,0 +1,69 @@
+// 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
+
+// Generate directory tree following a given structure.
+
+import (
+	"encoding/json"
+	"flag"
+	"fmt"
+	"io/ioutil"
+	"log"
+	"math/rand"
+	"os"
+)
+
+type TestSettings struct {
+	Name    string
+	Comment string
+	Seed    int64
+	Tree    TreeSettings
+}
+
+var config = flag.String("config", "", "JSON config file for generating test file.")
+var outdir = flag.String("outdir", "", "Where to write the output.")
+var seed = flag.Int64("seed", 4, "Seed for random.")
+
+func main() {
+	flag.Parse()
+
+	var settings TestSettings
+	settings.Seed = *seed
+
+	configdata, err := ioutil.ReadFile(*config)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	if err := json.Unmarshal(configdata, &settings); err != nil {
+		log.Fatal(err)
+	}
+
+	fmt.Printf("%s: %s\n", settings.Name, settings.Comment)
+	fmt.Println("===============================================")
+	fmt.Println()
+
+	if len(*outdir) == 0 {
+		log.Fatal("No output directory supplied.")
+	}
+
+	if _, err := os.Stat(*outdir); !os.IsNotExist(err) {
+		log.Fatal("directory exists!")
+	}
+
+	if *seed != 4 && settings.Seed != *seed {
+		log.Fatal("Seed supplied by test config.")
+	}
+
+	r := rand.New(rand.NewSource(settings.Seed))
+
+	// Create the root directory
+	if err := os.MkdirAll(*outdir, 0755); err != nil {
+		log.Fatal(err)
+	}
+
+	GenerateTree(r, *outdir, &settings.Tree)
+}