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Package atomic

import "sync/atomic"
Overview
Index
Examples

Overview ▾

Package atomic provides low-level atomic memory primitives useful for implementing synchronization algorithms.

These functions require great care to be used correctly. Except for special, low-level applications, synchronization is better done with channels or the facilities of the sync package. Share memory by communicating; don't communicate by sharing memory.

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".

Index ▾

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)
func CompareAndSwapInt32(addr *int32, old, new int32) (swapped bool)
func CompareAndSwapInt64(addr *int64, old, new int64) (swapped bool)
func CompareAndSwapPointer(addr *unsafe.Pointer, old, new unsafe.Pointer) (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 LoadInt32(addr *int32) (val int32)
func LoadInt64(addr *int64) (val int64)
func LoadPointer(addr *unsafe.Pointer) (val unsafe.Pointer)
func LoadUint32(addr *uint32) (val uint32)
func LoadUint64(addr *uint64) (val uint64)
func LoadUintptr(addr *uintptr) (val uintptr)
func StoreInt32(addr *int32, val int32)
func StoreInt64(addr *int64, val int64)
func StorePointer(addr *unsafe.Pointer, val unsafe.Pointer)
func StoreUint32(addr *uint32, val uint32)
func StoreUint64(addr *uint64, val uint64)
func StoreUintptr(addr *uintptr, val uintptr)
func SwapInt32(addr *int32, new int32) (old int32)
func SwapInt64(addr *int64, new int64) (old int64)
func SwapPointer(addr *unsafe.Pointer, new unsafe.Pointer) (old unsafe.Pointer)
func SwapUint32(addr *uint32, new uint32) (old uint32)
func SwapUint64(addr *uint64, new uint64) (old uint64)
func SwapUintptr(addr *uintptr, new uintptr) (old uintptr)
type Value
    func (v *Value) Load() (x interface{})
    func (v *Value) Store(x interface{})
Bugs

Examples

Value (Config)
Value (ReadMostly)

Package files

doc.go value.go

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
}

Example (Config)

The following example shows how to use Value for periodic program config updates and propagation of the changes to worker goroutines.

Example (ReadMostly)

The following example shows how to maintain a scalable frequently read, but infrequently updated data structure using copy-on-write idiom.

func (*Value) Load 1.4

func (v *Value) Load() (x 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(x 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).

Bugs