github.com/timstclair/heapster@v0.20.0-alpha1/Godeps/_workspace/src/k8s.io/kubernetes/pkg/util/atomic_value.go (about) 1 /* 2 Copyright 2015 The Kubernetes Authors All rights reserved. 3 4 Licensed under the Apache License, Version 2.0 (the "License"); 5 you may not use this file except in compliance with the License. 6 You may obtain a copy of the License at 7 8 http://www.apache.org/licenses/LICENSE-2.0 9 10 Unless required by applicable law or agreed to in writing, software 11 distributed under the License is distributed on an "AS IS" BASIS, 12 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 See the License for the specific language governing permissions and 14 limitations under the License. 15 */ 16 17 package util 18 19 import ( 20 "sync" 21 "sync/atomic" 22 ) 23 24 // TODO(ArtfulCoder) 25 // sync/atomic/Value was added in golang 1.4 26 // Once support is dropped for go 1.3, this type must be deprecated in favor of sync/atomic/Value. 27 // The functions are named Load/Store to match sync/atomic/Value function names. 28 type AtomicValue struct { 29 value interface{} 30 valueMutex sync.RWMutex 31 } 32 33 func (at *AtomicValue) Store(val interface{}) { 34 at.valueMutex.Lock() 35 defer at.valueMutex.Unlock() 36 at.value = val 37 } 38 39 func (at *AtomicValue) Load() interface{} { 40 at.valueMutex.RLock() 41 defer at.valueMutex.RUnlock() 42 return at.value 43 } 44 45 // HighWaterMark is a thread-safe object for tracking the maximum value seen 46 // for some quantity. 47 type HighWaterMark int64 48 49 // Check returns true if and only if 'current' is the highest value ever seen. 50 func (hwm *HighWaterMark) Check(current int64) bool { 51 for { 52 old := atomic.LoadInt64((*int64)(hwm)) 53 if current <= old { 54 return false 55 } 56 if atomic.CompareAndSwapInt64((*int64)(hwm), old, current) { 57 return true 58 } 59 } 60 }