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

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

+// 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)
+}