/
value.go
66 lines (58 loc) · 1.35 KB
/
value.go
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package atomic
import (
"github.com/ndkimhao/go-xtd/xtd"
)
// Value wrapped a copiable value atomically
// WARNING: Store, Swap, and CompareAndSwap operations do allocate
type Value[T comparable] struct {
_ xtd.NoCopy
p Ptr[T]
}
// NewValue creates a new Value[T].
func NewValue[T comparable](val T) *Value[T] {
v := &Value[T]{}
v.Store(val)
return v
}
// Load atomically loads the wrapped value.
func (v *Value[T]) Load() T {
p := v.p.Load()
if p == nil {
var zero T
return zero
}
return *p
}
// Store atomically stores the passed value.
func (v *Value[T]) Store(val T) {
// Taking address of function argument causes Go to allocate and copy it
v.p.Store(&val)
}
// Swap atomically swaps the wrapped pointer and returns the old value.
func (v *Value[T]) Swap(val T) (old T) {
p := v.p.Swap(&val)
if p == nil {
var zero T
return zero
}
return *p
}
// CompareAndSwap executes the compare-and-swap operation for the wrapped pointer.
func (v *Value[T]) CompareAndSwap(old, new T) (swapped bool) {
p := v.p.Load()
if p == nil {
var zero T
if zero != old {
return false
}
} else if *p != old {
return false
}
if new == old {
return true
}
// We don't need a CAS loop here
// v.p is changed only if the underlying value is changed,
// so if v.p.CompareAndSwap fails, then the value was changed
return v.p.CompareAndSwap(p, &new)
}