69 lines
1.5 KiB
Go
69 lines
1.5 KiB
Go
// Copyright 2019 The Hugo Authors. All rights reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package lazy
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import (
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"sync"
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"sync/atomic"
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)
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// onceMore is similar to sync.Once.
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//
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// Additional features are:
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// * it can be reset, so the action can be repeated if needed
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// * it has methods to check if it's done or in progress
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//
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type onceMore struct {
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mu sync.Mutex
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lock uint32
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done uint32
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}
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func (t *onceMore) Do(f func()) {
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if atomic.LoadUint32(&t.done) == 1 {
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return
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}
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// f may call this Do and we would get a deadlock.
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locked := atomic.CompareAndSwapUint32(&t.lock, 0, 1)
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if !locked {
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return
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}
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defer atomic.StoreUint32(&t.lock, 0)
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t.mu.Lock()
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defer t.mu.Unlock()
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// Double check
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if t.done == 1 {
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return
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}
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defer atomic.StoreUint32(&t.done, 1)
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f()
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}
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func (t *onceMore) InProgress() bool {
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return atomic.LoadUint32(&t.lock) == 1
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}
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func (t *onceMore) Done() bool {
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return atomic.LoadUint32(&t.done) == 1
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}
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func (t *onceMore) ResetWithLock() *sync.Mutex {
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t.mu.Lock()
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defer atomic.StoreUint32(&t.done, 0)
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return &t.mu
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}
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