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lock.go
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lock.go
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// Copyright (c) 2017 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 locks
import (
"context"
"sync"
"sync/atomic"
)
type (
// Mutex accepts a context in its Lock method.
// It blocks the goroutine until either the lock is acquired or the context
// is closed.
Mutex interface {
Lock(context.Context) error
Unlock()
}
mutexImpl struct {
sync.Mutex
}
)
const (
acquiring = iota
acquired
bailed
)
// NewMutex creates a new RWMutex
func NewMutex() Mutex {
return &mutexImpl{}
}
func (m *mutexImpl) Lock(ctx context.Context) error {
return m.lockInternal(ctx)
}
func (m *mutexImpl) lockInternal(ctx context.Context) error {
var state int32 = acquiring
acquiredCh := make(chan struct{})
go func() {
m.Mutex.Lock()
if !atomic.CompareAndSwapInt32(&state, acquiring, acquired) {
// already bailed due to context closing
m.Unlock()
}
close(acquiredCh)
}()
select {
case <-acquiredCh:
return nil
case <-ctx.Done():
{
if !atomic.CompareAndSwapInt32(&state, acquiring, bailed) {
return nil
}
return ctx.Err()
}
}
}