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 15 package testutil 16 17 import ( 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. 25 func 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. 31 type lockedSource struct { 32 mu sync.Mutex 33 src rand.Source 34 } 35 36 func (ls *lockedSource) Int63() int64 { 37 ls.mu.Lock() 38 defer ls.mu.Unlock() 39 return ls.src.Int63() 40 } 41 42 func (ls *lockedSource) Seed(int64) { 43 panic("shouldn't be calling Seed") 44 } 45