1 // Copyright © SAS Institute Inc. 2 // Licensed under the Apache License, Version 2.0 (the "License"); 3 // you may not use this file except in compliance with the License. 4 // You may obtain a copy of the License at 5 // 6 // http://www.apache.org/licenses/LICENSE-2.0 7 // 8 // Unless required by applicable law or agreed to in writing, software 9 // distributed under the License is distributed on an "AS IS" BASIS, 10 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 11 // See the License for the specific language governing permissions and 12 // limitations under the License. 13 14 package closeonce 15 16 import ( 17 "sync" 18 "sync/atomic" 19 ) 20 21 type Closed struct { 22 done uintptr 23 mu sync.Mutex 24 err error 25 } 26 27 func (o *Closed) Closed() bool { 28 return atomic.LoadUintptr(&o.done) != 0 29 } 30 31 func (o *Closed) Close(f func() error) error { 32 o.mu.Lock() 33 defer o.mu.Unlock() 34 if o.Closed() { 35 return o.err 36 } 37 o.err = f() 38 atomic.StoreUintptr(&o.done, 1) 39 o.done = 1 40 return o.err 41 } 42