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wait_at_least.go
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wait_at_least.go
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// Copyright (c) 2018 Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
package lib
import (
"sync"
)
// WaitAtLeast wait group signals the wait channel when at least the added
// count are done. This avoids sync.WaitGroup panic when count is negative.
//
// Usage:
// wg := WaitAtLeast{}
// wg.Add(1)
// wg.Wait()
// go func() {
// wg.Done()
// }()
//
type WaitAtLeast struct {
mutex sync.Mutex
wg sync.WaitGroup
add int
done int
}
// Add positive wait count.
func (w *WaitAtLeast) Add(count int) {
w.mutex.Lock()
defer w.mutex.Unlock()
if count <= 0 {
panic("non-positive count")
}
w.add += count
w.wg.Add(count)
// complete matching add/done
done := w.done
if w.add < w.done {
done = w.add
}
for i := 0; i < done; i++ {
w.done--
w.add--
w.wg.Done()
}
}
// Done subtracts one from the wait count.
func (w *WaitAtLeast) Done() {
w.mutex.Lock()
defer w.mutex.Unlock()
// complete matching add/done
if w.add > 0 {
w.add--
w.wg.Done()
return
}
w.done++
}
// Wait for matching add/done.
func (w *WaitAtLeast) Wait() {
w.wg.Wait()
}