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package mutexes
import (
"sync/atomic"
)
// WithSafety wrapps the supplied Mutex to protect unlock fns
// from being called multiple times
func WithSafety(mu Mutex) Mutex {
return &safeMutex{mu: mu}
}
// WithSafetyRW wrapps the supplied RWMutex to protect unlock
// fns from being called multiple times
func WithSafetyRW(mu RWMutex) RWMutex {
return &safeRWMutex{mu: mu}
}
// safeMutex simply wraps a Mutex to add multi-unlock safety
type safeMutex struct{ mu Mutex }
func (mu *safeMutex) Lock() func() {
unlock := mu.mu.Lock()
return once(unlock)
}
// safeRWMutex simply wraps a RWMutex to add multi-unlock safety
type safeRWMutex struct{ mu RWMutex }
func (mu *safeRWMutex) Lock() func() {
unlock := mu.mu.Lock()
return once(unlock)
}
func (mu *safeRWMutex) RLock() func() {
unlock := mu.mu.RLock()
return once(unlock)
}
// once will perform 'do' only once, this is safe for unlocks
// as 2 functions calling 'unlock()' don't need absolute guarantees
// that by the time it is completed the unlock was finished.
func once(do func()) func() {
var done uint32
return func() {
if atomic.CompareAndSwapUint32(&done, 0, 1) {
do()
}
}
}
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