atomic
最后更新于：2022-04-02 02:46:08
[TOC]
> [参考](https://mp.weixin.qq.com/s?__biz=MzAxMTA4Njc0OQ==&mid=2651438345&idx=3&sn=b03e06d6bef1de2bcae561e8f607e0d4&chksm=80bb63fbb7cceaedf344010a30547122b2912d806763f268dbd4eea55a079936fe16ab55c8ed&scene=21#wechat_redirect)
## 原子性
cpu 在操作中不会切换任务的最小操作单元叫做原子,在并发系统中采用原子才可避免使用互斥锁
## 语法
```
// 获取
func LoadInt32(addr *int32) (val int32)
func LoadInt64(addr *int64) (val int64)
func LoadUint32(addr *uint32) (val uint32)
func LoadUint64(addr *uint64) (val uint64)
func LoadUintptr(addr *uintptr) (val uintptr)
func LoadPointer(addr *unsafe.Pointer) (val unsafe.Pointer)
// 赋值
func StoreInt32(addr *int32, val int32)
func StoreInt64(addr *int64, val int64)
func StoreUint32(addr *uint32, val uint32)
func StoreUint64(addr *uint64, val uint64)
func StoreUintptr(addr *uintptr, val uintptr)
func StorePointer(addr *unsafe.Pointer, val unsafe.Pointer)
// 增加
func AddInt32(addr *int32, delta int32) (new int32)
func AddInt64(addr *int64, delta int64) (new int64)
func AddUint32(addr *uint32, delta uint32) (new uint32)
func AddUint64(addr *uint64, delta uint64) (new uint64)
func AddUintptr(addr *uintptr, delta uintptr) (new uintptr)
// 交换两个值,并返回旧的值
func SwapInt32(addr *int32, new int32) (old int32)
func SwapInt64(addr *int64, new int64) (old int64)
func SwapUint32(addr *uint32, new uint32) (old uint32)
func SwapUint64(addr *uint64, new uint64) (old uint64)
func SwapUintptr(addr *uintptr, new uintptr) (old uintptr)
func SwapPointer(addr *unsafe.Pointer, new unsafe.Pointer) (old unsafe.Pointer)
// 原子性的比较*addr和old，如果相同则将new赋值给*addr并返回真
func CompareAndSwapInt32(addr *int32, old, new int32) (swapped bool)
func CompareAndSwapInt64(addr *int64, old, new int64) (swapped bool)
func CompareAndSwapUint32(addr *uint32, old, new uint32) (swapped bool)
func CompareAndSwapUint64(addr *uint64, old, new uint64) (swapped bool)
func CompareAndSwapUintptr(addr *uintptr, old, new uintptr) (swapped bool)
func CompareAndSwapPointer(addr *unsafe.Pointer, old, new unsafe.Pointer) (swapped bool)
```
## 实例
### 原子操作
```
var i int32
atomic.StoreInt32(&i, 3) // i=3
atomic.AddInt32(&i, 1) // i=4
l := atomic.LoadInt32(&i)
fmt.Printf("%+v\n", l) // 4
var j int32
j = 11
res := atomic.SwapInt32(&i, j) // i=11
fmt.Printf("%+v\n", res) // 4
atomic.CompareAndSwapInt32(&i, 11, 12) // i=12
```
## atomic.Value
注意:
1. 存储值不能是 nil；
2. 再次存储时,值类型必须相等
如果违背这两条，编译时会抛出 panic
```
type People struct {
Name string
}
p := People{
Name: "ccc",
}
var a atomic.Value
a.Store(p)
l := a.Load().(People)
fmt.Printf("%+v\n", l.Name)
```
### 当作mpa
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