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package atomics
import (
"sync/atomic"
"unsafe"
)
// String provides user-friendly means of performing atomic operations on string types.
type String struct{ ptr unsafe.Pointer }
// NewString will return a new String instance initialized with zero value.
func NewString() *String {
var v string
return &String{
ptr: unsafe.Pointer(&v),
}
}
// Store will atomically store string value in address contained within v.
func (v *String) Store(val string) {
atomic.StorePointer(&v.ptr, unsafe.Pointer(&val))
}
// Load will atomically load string value at address contained within v.
func (v *String) Load() string {
return *(*string)(atomic.LoadPointer(&v.ptr))
}
// CAS performs a compare-and-swap for a(n) string value at address contained within v.
func (v *String) CAS(cmp, swp string) bool {
for {
// Load current value at address
ptr := atomic.LoadPointer(&v.ptr)
cur := *(*string)(ptr)
// Perform comparison against current
if !(cur == cmp) {
return false
}
// Attempt to replace pointer
if atomic.CompareAndSwapPointer(
&v.ptr,
ptr,
unsafe.Pointer(&swp),
) {
return true
}
}
}
// Swap atomically stores new string value into address contained within v, and returns previous value.
func (v *String) Swap(swp string) string {
ptr := unsafe.Pointer(&swp)
ptr = atomic.SwapPointer(&v.ptr, ptr)
return *(*string)(ptr)
}
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