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
+
+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)
+        }
+}