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type
SharedPtr*[T] = object
val: ptr tuple[atomicCounter: int, value: T]
proc `=destroy`*[T](p: var SharedPtr[T]) =
mixin `=destroy`
if p.val != nil:
let c = atomicDec(p.val[].atomicCounter)
if c == 0:
`=destroy`(p.val.value)
freeShared(p.val)
p.val = nil
proc `=`*[T](dest: var SharedPtr[T], src: SharedPtr[T]) {.inline.} =
if dest.val != src.val:
if dest.val != nil:
`=destroy`(dest)
if src.val != nil:
discard atomicInc(src.val[].atomicCounter)
dest.val = src.val
proc newSharedPtr*[T](val: sink T): SharedPtr[T] =
result.val = cast[type(result.val)](allocShared0(sizeof(result.val[])))
result.val.atomicCounter = 1
result.val.value = val
func get*[T](p: SharedPtr[T]): var T {.inline.} =
p.val.value
func isNil*[T](p: SharedPtr[T]): bool {.inline.} =
p.val == nil
proc cas*[T](p, old_val: var SharedPtr[T], new_val: SharedPtr[T]): bool {.inline.} =
if old_val.val == new_val.val:
result = true
else:
result = cas(p.val.addr, old_val.val, new_val.val)
if result:
`=destroy`(old_val)
if new_val.val != nil:
discard atomicInc(new_val.val[].atomicCounter)
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