Package atomic

old = *addr
*addr = new
return old

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

*addr += delta
return *addr

func AddInt32 ¶

func AddInt32(addr *int32, delta int32) (new int32)

AddInt32 atomically adds delta to *addr and returns the new value.

func AddInt64 ¶

func AddInt64(addr *int64, delta int64) (new int64)

AddInt64 atomically adds delta to *addr and returns the new value.

func AddUint32 ¶

func AddUint32(addr *uint32, delta uint32) (new uint32)

AddUint32 atomically adds delta to *addr and returns the new value. To subtract a signed positive constant value c from x, do AddUint32(&x, ^uint32(c-1)). In particular, to decrement x, do AddUint32(&x, ^uint32(0)).

func AddUint64 ¶

func AddUint64(addr *uint64, delta uint64) (new uint64)

AddUint64 atomically adds delta to *addr and returns the new value. To subtract a signed positive constant value c from x, do AddUint64(&x, ^uint64(c-1)). In particular, to decrement x, do AddUint64(&x, ^uint64(0)).

func AddUintptr ¶

func AddUintptr(addr *uintptr, delta uintptr) (new uintptr)

AddUintptr atomically adds delta to *addr and returns the new value.

func CompareAndSwapInt32 ¶

func CompareAndSwapInt32(addr *int32, old, new int32) (swapped bool)

CompareAndSwapInt32 executes the compare-and-swap operation for an int32 value.

func CompareAndSwapInt64 ¶

func CompareAndSwapInt64(addr *int64, old, new int64) (swapped bool)

CompareAndSwapInt64 executes the compare-and-swap operation for an int64 value.

func CompareAndSwapPointer ¶

func CompareAndSwapPointer(addr *unsafe.Pointer, old, new unsafe.Pointer) (swapped bool)

CompareAndSwapPointer executes the compare-and-swap operation for a unsafe.Pointer value.

func CompareAndSwapUint32 ¶

func CompareAndSwapUint32(addr *uint32, old, new uint32) (swapped bool)

CompareAndSwapUint32 executes the compare-and-swap operation for a uint32 value.

func CompareAndSwapUint64 ¶

func CompareAndSwapUint64(addr *uint64, old, new uint64) (swapped bool)

CompareAndSwapUint64 executes the compare-and-swap operation for a uint64 value.

func CompareAndSwapUintptr ¶

func CompareAndSwapUintptr(addr *uintptr, old, new uintptr) (swapped bool)

CompareAndSwapUintptr executes the compare-and-swap operation for a uintptr value.

func LoadInt32 ¶

func LoadInt32(addr *int32) (val int32)

LoadInt32 atomically loads *addr.

func LoadInt64 ¶

func LoadInt64(addr *int64) (val int64)

LoadInt64 atomically loads *addr.

func LoadPointer ¶

func LoadPointer(addr *unsafe.Pointer) (val unsafe.Pointer)

LoadPointer atomically loads *addr.

func LoadUint32 ¶

func LoadUint32(addr *uint32) (val uint32)

LoadUint32 atomically loads *addr.

func LoadUint64 ¶

func LoadUint64(addr *uint64) (val uint64)

LoadUint64 atomically loads *addr.

func LoadUintptr ¶

func LoadUintptr(addr *uintptr) (val uintptr)

LoadUintptr atomically loads *addr.

func StoreInt32 ¶

func StoreInt32(addr *int32, val int32)

StoreInt32 atomically stores val into *addr.

func StoreInt64 ¶

func StoreInt64(addr *int64, val int64)

StoreInt64 atomically stores val into *addr.

func StorePointer ¶

func StorePointer(addr *unsafe.Pointer, val unsafe.Pointer)

StorePointer atomically stores val into *addr.

func StoreUint32 ¶

func StoreUint32(addr *uint32, val uint32)

StoreUint32 atomically stores val into *addr.

func StoreUint64 ¶

func StoreUint64(addr *uint64, val uint64)

StoreUint64 atomically stores val into *addr.

func StoreUintptr ¶

func StoreUintptr(addr *uintptr, val uintptr)

StoreUintptr atomically stores val into *addr.

func SwapInt32 ¶ 1.2

func SwapInt32(addr *int32, new int32) (old int32)

SwapInt32 atomically stores new into *addr and returns the previous *addr value.

func SwapInt64 ¶ 1.2

func SwapInt64(addr *int64, new int64) (old int64)

SwapInt64 atomically stores new into *addr and returns the previous *addr value.

func SwapPointer ¶ 1.2

func SwapPointer(addr *unsafe.Pointer, new unsafe.Pointer) (old unsafe.Pointer)

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

func SwapUint32 ¶ 1.2

func SwapUint32(addr *uint32, new uint32) (old uint32)

SwapUint32 atomically stores new into *addr and returns the previous *addr value.

func SwapUint64 ¶ 1.2

func SwapUint64(addr *uint64, new uint64) (old uint64)

SwapUint64 atomically stores new into *addr and returns the previous *addr value.

func SwapUintptr ¶ 1.2

func SwapUintptr(addr *uintptr, new uintptr) (old uintptr)

SwapUintptr atomically stores new into *addr and returns the previous *addr value.

type Value ¶ 1.4

A Value provides an atomic load and store of a consistently typed value. The zero value for a Value returns nil from Load. Once Store has been called, a Value must not be copied.

A Value must not be copied after first use.

type Value struct {
		// contains filtered or unexported fields
}

var config atomic.Value // holds current server configuration
// Create initial config value and store into config.
config.Store(loadConfig())
go func() {
		// Reload config every 10 seconds
		// and update config value with the new version.
		for {
				time.Sleep(10 * time.Second)
				config.Store(loadConfig())
		}
}()
// Create worker goroutines that handle incoming requests
// using the latest config value.
for i := 0; i < 10; i++ {
		go func() {
				for r := range requests() {
						c := config.Load()
						// Handle request r using config c.
						_, _ = r, c
				}
		}()
}

type Map map[string]string
var m atomic.Value
m.Store(make(Map))
var mu sync.Mutex // used only by writers
// read function can be used to read the data without further synchronization
read := func(key string) (val string) {
		m1 := m.Load().(Map)
		return m1[key]
}
// insert function can be used to update the data without further synchronization
insert := func(key, val string) {
		mu.Lock() // synchronize with other potential writers
		defer mu.Unlock()
		m1 := m.Load().(Map) // load current value of the data structure
		m2 := make(Map)			// create a new value
		for k, v := range m1 {
				m2[k] = v // copy all data from the current object to the new one
		}
		m2[key] = val // do the update that we need
		m.Store(m2)	 // atomically replace the current object with the new one
		// At this point all new readers start working with the new version.
		// The old version will be garbage collected once the existing readers
		// (if any) are done with it.
}
_, _ = read, insert

func (*Value) CompareAndSwap ¶ 1.17

func (v *Value) CompareAndSwap(old, new interface{}) (swapped bool)

CompareAndSwap executes the compare-and-swap operation for the Value.

All calls to CompareAndSwap for a given Value must use values of the same concrete type. CompareAndSwap of an inconsistent type panics, as does CompareAndSwap(old, nil).

func (*Value) Load ¶ 1.4

func (v *Value) Load() (val interface{})

Load returns the value set by the most recent Store. It returns nil if there has been no call to Store for this Value.

func (*Value) Store ¶ 1.4

func (v *Value) Store(val interface{})

Store sets the value of the Value to x. All calls to Store for a given Value must use values of the same concrete type. Store of an inconsistent type panics, as does Store(nil).

func (*Value) Swap ¶ 1.17

func (v *Value) Swap(new interface{}) (old interface{})

Swap stores new into Value and returns the previous value. It returns nil if the Value is empty.

All calls to Swap for a given Value must use values of the same concrete type. Swap of an inconsistent type panics, as does Swap(nil).

Bugs

• ☞

  On 386, the 64-bit functions use instructions unavailable before the Pentium MMX.

  On non-Linux ARM, the 64-bit functions use instructions unavailable before the ARMv6k core.

  On ARM, 386, and 32-bit MIPS, it is the caller's responsibility to arrange for 64-bit alignment of 64-bit words accessed atomically. The first word in a variable or in an allocated struct, array, or slice can be relied upon to be 64-bit aligned.