# package atomic `import "sync/atomic"` atomic包提供了底層的原子級內存操作，對于同步算法的實現很有用。 這些函數必須謹慎地保證正確使用。除了某些特殊的底層應用，使用通道或者sync包的函數/類型實現同步更好。 應通過通信來共享內存，而不通過共享內存實現通信。 被SwapT系列函數實現的交換操作，在原子性上等價于： ``` old = *addr *addr = new return old ``` CompareAndSwapT系列函數實現的比較-交換操作，在原子性上等價于： ``` if *addr == old { *addr = new return true } return false ``` AddT?系列函數實現加法操作，在原子性上等價于： ``` *addr += delta return *addr ``` LoadT和StoreT系列函數實現的加載和保持操作，在原子性上等價于："return \*addr"和"\*addr = val"。 ## Index * [func LoadInt32(addr \*int32) (val int32)](#LoadInt32) * [func LoadInt64(addr \*int64) (val int64)](#LoadInt64) * [func LoadUint32(addr \*uint32) (val uint32)](#LoadUint32) * [func LoadUint64(addr \*uint64) (val uint64)](#LoadUint64) * [func LoadUintptr(addr \*uintptr) (val uintptr)](#LoadUintptr) * [func LoadPointer(addr \*unsafe.Pointer) (val unsafe.Pointer)](#LoadPointer) * [func StoreInt32(addr \*int32, val int32)](#StoreInt32) * [func StoreInt64(addr \*int64, val int64)](#StoreInt64) * [func StoreUint32(addr \*uint32, val uint32)](#StoreUint32) * [func StoreUint64(addr \*uint64, val uint64)](#StoreUint64) * [func StoreUintptr(addr \*uintptr, val uintptr)](#StoreUintptr) * [func StorePointer(addr \*unsafe.Pointer, val unsafe.Pointer)](#StorePointer) * [func AddInt32(addr \*int32, delta int32) (new int32)](#AddInt32) * [func AddInt64(addr \*int64, delta int64) (new int64)](#AddInt64) * [func AddUint32(addr \*uint32, delta uint32) (new uint32)](#AddUint32) * [func AddUint64(addr \*uint64, delta uint64) (new uint64)](#AddUint64) * [func AddUintptr(addr \*uintptr, delta uintptr) (new uintptr)](#AddUintptr) * [func SwapInt32(addr \*int32, new int32) (old int32)](#SwapInt32) * [func SwapInt64(addr \*int64, new int64) (old int64)](#SwapInt64) * [func SwapUint32(addr \*uint32, new uint32) (old uint32)](#SwapUint32) * [func SwapUint64(addr \*uint64, new uint64) (old uint64)](#SwapUint64) * [func SwapUintptr(addr \*uintptr, new uintptr) (old uintptr)](#SwapUintptr) * [func SwapPointer(addr \*unsafe.Pointer, new unsafe.Pointer) (old unsafe.Pointer)](#SwapPointer) * [func CompareAndSwapInt32(addr \*int32, old, new int32) (swapped bool)](#CompareAndSwapInt32) * [func CompareAndSwapInt64(addr \*int64, old, new int64) (swapped bool)](#CompareAndSwapInt64) * [func CompareAndSwapUint32(addr \*uint32, old, new uint32) (swapped bool)](#CompareAndSwapUint32) * [func CompareAndSwapUint64(addr \*uint64, old, new uint64) (swapped bool)](#CompareAndSwapUint64) * [func CompareAndSwapUintptr(addr \*uintptr, old, new uintptr) (swapped bool)](#CompareAndSwapUintptr) * [func CompareAndSwapPointer(addr \*unsafe.Pointer, old, new unsafe.Pointer) (swapped bool)](#CompareAndSwapPointer) ## func [LoadInt32](https://github.com/golang/go/blob/master/src/sync/atomic/doc.go#L113 "View Source") ``` func LoadInt32(addr *int32) (val int32) ``` LoadInt32原子性的獲取\*addr的值。 ## func [LoadInt64](https://github.com/golang/go/blob/master/src/sync/atomic/doc.go#L116 "View Source") ``` func LoadInt64(addr *int64) (val int64) ``` LoadInt64原子性的獲取\*addr的值。 ## func [LoadUint32](https://github.com/golang/go/blob/master/src/sync/atomic/doc.go#L119 "View Source") ``` func LoadUint32(addr *uint32) (val uint32) ``` LoadUint32原子性的獲取\*addr的值。 ## func [LoadUint64](https://github.com/golang/go/blob/master/src/sync/atomic/doc.go#L122 "View Source") ``` func LoadUint64(addr *uint64) (val uint64) ``` LoadUint64原子性的獲取\*addr的值。 ## func [LoadUintptr](https://github.com/golang/go/blob/master/src/sync/atomic/doc.go#L125 "View Source") ``` func LoadUintptr(addr *uintptr) (val uintptr) ``` LoadUintptr原子性的獲取\*addr的值。 ## func [LoadPointer](https://github.com/golang/go/blob/master/src/sync/atomic/doc.go#L128 "View Source") ``` func LoadPointer(addr *unsafe.Pointer) (val unsafe.Pointer) ``` LoadPointer原子性的獲取\*addr的值。 ## func [StoreInt32](https://github.com/golang/go/blob/master/src/sync/atomic/doc.go#L131 "View Source") ``` func StoreInt32(addr *int32, val int32) ``` StoreInt32原子性的將val的值保存到\*addr。 ## func [StoreInt64](https://github.com/golang/go/blob/master/src/sync/atomic/doc.go#L134 "View Source") ``` func StoreInt64(addr *int64, val int64) ``` StoreInt64原子性的將val的值保存到\*addr。 ## func [StoreUint32](https://github.com/golang/go/blob/master/src/sync/atomic/doc.go#L137 "View Source") ``` func StoreUint32(addr *uint32, val uint32) ``` StoreUint32原子性的將val的值保存到\*addr。 ## func [StoreUint64](https://github.com/golang/go/blob/master/src/sync/atomic/doc.go#L140 "View Source") ``` func StoreUint64(addr *uint64, val uint64) ``` StoreUint64原子性的將val的值保存到\*addr。 ## func [StoreUintptr](https://github.com/golang/go/blob/master/src/sync/atomic/doc.go#L143 "View Source") ``` func StoreUintptr(addr *uintptr, val uintptr) ``` StoreUintptr原子性的將val的值保存到\*addr。 ## func [StorePointer](https://github.com/golang/go/blob/master/src/sync/atomic/doc.go#L146 "View Source") ``` func StorePointer(addr *unsafe.Pointer, val unsafe.Pointer) ``` StorePointer原子性的將val的值保存到\*addr。 ## func [AddInt32](https://github.com/golang/go/blob/master/src/sync/atomic/doc.go#L94 "View Source") ``` func AddInt32(addr *int32, delta int32) (new int32) ``` AddInt32原子性的將val的值添加到\*addr并返回新值。 ## func [AddInt64](https://github.com/golang/go/blob/master/src/sync/atomic/doc.go#L102 "View Source") ``` func AddInt64(addr *int64, delta int64) (new int64) ``` AddInt64原子性的將val的值添加到\*addr并返回新值。 ## func [AddUint32](https://github.com/golang/go/blob/master/src/sync/atomic/doc.go#L99 "View Source") ``` func AddUint32(addr *uint32, delta uint32) (new uint32) ``` AddUint32原子性的將val的值添加到\*addr并返回新值。 如要減去一個值c，調用AddUint32(&x, ^uint32(c-1))；特別的，讓x減1，調用AddUint32(&x, ^uint32(0))。 ## func [AddUint64](https://github.com/golang/go/blob/master/src/sync/atomic/doc.go#L107 "View Source") ``` func AddUint64(addr *uint64, delta uint64) (new uint64) ``` AddUint64原子性的將val的值添加到\*addr并返回新值。 如要減去一個值c，調用AddUint64(&x, ^uint64(c-1))；特別的，讓x減1，調用AddUint64(&x, ^uint64(0))。 ## func [AddUintptr](https://github.com/golang/go/blob/master/src/sync/atomic/doc.go#L110 "View Source") ``` func AddUintptr(addr *uintptr, delta uintptr) (new uintptr) ``` AddUintptr原子性的將val的值添加到\*addr并返回新值。 ## func [SwapInt32](https://github.com/golang/go/blob/master/src/sync/atomic/doc.go#L58 "View Source") ``` func SwapInt32(addr *int32, new int32) (old int32) ``` SwapInt32原子性的將新值保存到\*addr并返回舊值。 ## func [SwapInt64](https://github.com/golang/go/blob/master/src/sync/atomic/doc.go#L61 "View Source") ``` func SwapInt64(addr *int64, new int64) (old int64) ``` SwapInt64原子性的將新值保存到\*addr并返回舊值。 ## func [SwapUint32](https://github.com/golang/go/blob/master/src/sync/atomic/doc.go#L64 "View Source") ``` func SwapUint32(addr *uint32, new uint32) (old uint32) ``` SwapUint32原子性的將新值保存到\*addr并返回舊值。 ## func [SwapUint64](https://github.com/golang/go/blob/master/src/sync/atomic/doc.go#L67 "View Source") ``` func SwapUint64(addr *uint64, new uint64) (old uint64) ``` SwapUint64原子性的將新值保存到\*addr并返回舊值。 ## func [SwapUintptr](https://github.com/golang/go/blob/master/src/sync/atomic/doc.go#L70 "View Source") ``` func SwapUintptr(addr *uintptr, new uintptr) (old uintptr) ``` SwapUintptr原子性的將新值保存到\*addr并返回舊值。 ## func [SwapPointer](https://github.com/golang/go/blob/master/src/sync/atomic/doc.go#L73 "View Source") ``` func SwapPointer(addr *unsafe.Pointer, new unsafe.Pointer) (old unsafe.Pointer) ``` SwapPointer原子性的將新值保存到\*addr并返回舊值。 ## func [CompareAndSwapInt32](https://github.com/golang/go/blob/master/src/sync/atomic/doc.go#L76 "View Source") ``` func CompareAndSwapInt32(addr *int32, old, new int32) (swapped bool) ``` CompareAndSwapInt32原子性的比較\*addr和old，如果相同則將new賦值給\*addr并返回真。 ## func [CompareAndSwapInt64](https://github.com/golang/go/blob/master/src/sync/atomic/doc.go#L79 "View Source") ``` func CompareAndSwapInt64(addr *int64, old, new int64) (swapped bool) ``` CompareAndSwapInt64原子性的比較\*addr和old，如果相同則將new賦值給\*addr并返回真。 ## func [CompareAndSwapUint32](https://github.com/golang/go/blob/master/src/sync/atomic/doc.go#L82 "View Source") ``` func CompareAndSwapUint32(addr *uint32, old, new uint32) (swapped bool) ``` CompareAndSwapUint32原子性的比較\*addr和old，如果相同則將new賦值給\*addr并返回真。 ## func [CompareAndSwapUint64](https://github.com/golang/go/blob/master/src/sync/atomic/doc.go#L85 "View Source") ``` func CompareAndSwapUint64(addr *uint64, old, new uint64) (swapped bool) ``` CompareAndSwapUint64原子性的比較\*addr和old，如果相同則將new賦值給\*addr并返回真。 ## func [CompareAndSwapUintptr](https://github.com/golang/go/blob/master/src/sync/atomic/doc.go#L88 "View Source") ``` func CompareAndSwapUintptr(addr *uintptr, old, new uintptr) (swapped bool) ``` CompareAndSwapUintptr原子性的比較\*addr和old，如果相同則將new賦值給\*addr并返回真。 ## func [CompareAndSwapPointer](https://github.com/golang/go/blob/master/src/sync/atomic/doc.go#L91 "View Source") ``` func CompareAndSwapPointer(addr *unsafe.Pointer, old, new unsafe.Pointer) (swapped bool) ``` CompareAndSwapPointer原子性的比較\*addr和old，如果相同則將new賦值給\*addr并返回真。 ## Bugs [?](https://github.com/golang/go/blob/master/src/sync/atomic/doc.go#L48 "View Source") 在x86-32構架芯片上，64位函數使用的指令在Pentium MMX之前是不可用的；在非Linux的ARM芯片上，64位函數使用的指令在ARMv6k core之前是不可用的。不管是ARM又或x86-32芯片，安排原子性訪問的64位word的64位對齊都是調用者的責任。可以依靠全局變量或申請的切片/結構體的第一個word來實現64位對齊。