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

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

Index: common/dirwalk/tests/tools/gendir/random_utils.go
diff --git a/common/dirwalk/tests/tools/gendir/random_utils.go b/common/dirwalk/tests/tools/gendir/random_utils.go
new file mode 100644
index 0000000000000000000000000000000000000000..1a39b994c4a810ed63595a17871f65f96b85bbf8
--- /dev/null
+++ b/common/dirwalk/tests/tools/gendir/random_utils.go
@@ -0,0 +1,37 @@
+// 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)
+}