1// Copyright 2018 Google LLC
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7//      http://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14
15package testutil
16
17import (
18	"math/rand"
19	"sync"
20	"time"
21)
22
23// NewRand creates a new *rand.Rand seeded with t. The return value is safe for use
24// with multiple goroutines.
25func NewRand(t time.Time) *rand.Rand {
26	s := &lockedSource{src: rand.NewSource(t.UnixNano())}
27	return rand.New(s)
28}
29
30// lockedSource makes a rand.Source safe for use by multiple goroutines.
31type lockedSource struct {
32	mu  sync.Mutex
33	src rand.Source
34}
35
36func (ls *lockedSource) Int63() int64 {
37	ls.mu.Lock()
38	defer ls.mu.Unlock()
39	return ls.src.Int63()
40}
41
42func (ls *lockedSource) Seed(int64) {
43	panic("shouldn't be calling Seed")
44}
45