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package atomics
import (
"sync/atomic"
"unsafe"
)
// Error provides user-friendly means of performing atomic operations on error types.
type Error struct{ ptr unsafe.Pointer }
// NewError will return a new Error instance initialized with zero value.
func NewError() *Error {
var v error
return &Error{
ptr: unsafe.Pointer(&v),
}
}
// Store will atomically store error value in address contained within v.
func (v *Error) Store(val error) {
atomic.StorePointer(&v.ptr, unsafe.Pointer(&val))
}
// Load will atomically load error value at address contained within v.
func (v *Error) Load() error {
return *(*error)(atomic.LoadPointer(&v.ptr))
}
// CAS performs a compare-and-swap for a(n) error value at address contained within v.
func (v *Error) CAS(cmp, swp error) bool {
for {
// Load current value at address
ptr := atomic.LoadPointer(&v.ptr)
cur := *(*error)(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 error value into address contained within v, and returns previous value.
func (v *Error) Swap(swp error) error {
ptr := unsafe.Pointer(&swp)
ptr = atomic.SwapPointer(&v.ptr, ptr)
return *(*error)(ptr)
}
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