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

common/dirwalk/tests/tools/gendir/random_utils.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 (
+        "math/rand"
+)
+
+var textChars = []rune("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-.")
+
+func randChar(r *rand.Rand, runes []rune) rune {
+        return runes[r.Intn(len(runes))]
+}
+
+func randStr(r *rand.Rand, length uint64, runes []rune) string {
+        str := make([]rune, length)
+        for i := range str {
+                str[i] = randChar(r, runes)
+        }
+        return string(str)
+}
+
+func randBetween(r *rand.Rand, min uint64, max uint64) uint64 {
+        if min == max {
+                return min
+        }
+        return uint64(r.Int63n(int64(max-min))) + min
+}
+
+// FIXME: Maybe some UTF-8 characters?
+var fileNameChars = []rune("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789-")
+
+func fileNameRandom(r *rand.Rand, length uint64) string {
+        return randStr(r, length, fileNameChars)
+}