针对整数数据类型（int32、uint32、int64、uint64）我们还可以使用原子操作来保证并发安全，通常直接使用原子操作比使用锁操作效率更高。Go语言中原子操作由内置的标准库sync/atomic提供。
atomic包
| 方法 | 解释 |
|---|---|
| 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) |
读取操作 |
| 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) |
写入操作 |
| 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) |
修改操作 |
| 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) |
交换操作 |
| 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) |
比较并交换操作 |
package main
import (
"fmt"
"sync"
"sync/atomic"
"time"
)
type Counter interface {
Inc()
Load() int64
}
// 普通版
type CommonCounter struct {
counter int64
}
func (c CommonCounter) Inc() {
c.counter++
}
func (c CommonCounter) Load() int64 {
return c.counter
}
// 互斥锁版
type MutexCounter struct {
counter int64
lock sync.Mutex
}
func (m *MutexCounter) Inc() {
m.lock.Lock()
defer m.lock.Unlock()
m.counter++
}
func (m *MutexCounter) Load() int64 {
m.lock.Lock()
defer m.lock.Unlock()
return m.counter
}
// 原子操作版
type AtomicCounter struct {
counter int64
}
func (a *AtomicCounter) Inc() {
atomic.AddInt64(&a.counter, 1)
}
func (a *AtomicCounter) Load() int64 {
return atomic.LoadInt64(&a.counter)
}
func test(c Counter) {
var wg sync.WaitGroup
start := time.Now()
for i := 0; i < 1000; i++ {
wg.Add(1)
go func() {
c.Inc()
wg.Done()
}()
}
wg.Wait()
end := time.Now()
fmt.Println(c.Load(), end.Sub(start))
}
func main() {
c1 := CommonCounter{} // 非并发安全
test(c1)
c2 := MutexCounter{} // 使用互斥锁实现并发安全
test(&c2)
c3 := AtomicCounter{} // 并发安全且比互斥锁效率更高
test(&c3)
}
atomic包提供了底层的原子级内存操作，对于同步算法的实现很有用。这些函数必须谨慎地保证正确使用。除了某些特殊的底层应用，使用通道或者 sync 包的函数/类型实现同步更好。