提供原子操作，同步，直接操作指针地址

• The swap operation, implemented by the SwapT functions, is the atomic equivalent of:

    old = *addr
    *addr = new
    return old

• The compare-and-swap operation, implemented by the CompareAndSwapT functions, is the atomic equivalent of:

   if *addr == old {
   *addr = new
   return true
   }
   return false
  

• The add operation, implemented by the AddT functions, is the atomic equivalent of:

   *addr += delta
   return *addr
  

• The load and store operations, implemented by the LoadT and StoreT functions, are the atomic equivalents of "return addr" and "addr = val".

atomic.swappoint()

// SwapPointer atomically stores new into addr and returns the previous addr value.

var arr = make([]int, 0)

func main() {
    //atomic.LoadPointer()
    f1()
}
//错误用法
func f1() {
    arr = append(arr, 10)
    arr = append(arr, 11)
    arr = append(arr, 12)
    arr = append(arr, 13)
    arr = append(arr, 14)

    fmt.Printf("%p,%v\n", &arr, arr)
    add := unsafe.Pointer(&arr)
    //addradd := &add
    new := 34
    snew := unsafe.Pointer(&new)
    old := atomic.SwapPointer(&add, snew)
    fmt.Println((*[]int)(old))
    fmt.Printf("%p\n", &old)
    fmt.Println(arr)
    fmt.Println(*(*int)(add))

}

//正确用法
直接将需要原子操作的变量定义为unsafe.pointer类型
var arr2 = new()
func New() unsafe.Pointer {
    a := make([]int, 0)
    return unsafe.Pointer(&a)
}

func Get() []int  {

    a := (*[]int)(atomic.LoadPointer(&arr2))
return *a
}

func Swap() []int  {
    old :=(*[]int)(atomic.SwapPointer(&arr2,new()))
    return *old
}