Documentation
¶
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".
In the terminology of the Go memory model, if the effect of an atomic operation A is observed by atomic operation B, then A “synchronizes before” B. Additionally, all the atomic operations executed in a program behave as though executed in some sequentially consistent order. This definition provides the same semantics as C++'s sequentially consistent atomics and Java's volatile variables.
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 AndInt32(addr *int32, mask int32) (old int32)
- func AndInt64(addr *int64, mask int64) (old int64)
- func AndUint32(addr *uint32, mask uint32) (old uint32)
- func AndUint64(addr *uint64, mask uint64) (old uint64)
- func AndUintptr(addr *uintptr, mask uintptr) (old 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 OrInt32(addr *int32, mask int32) (old int32)
- func OrInt64(addr *int64, mask int64) (old int64)
- func OrUint32(addr *uint32, mask uint32) (old uint32)
- func OrUint64(addr *uint64, mask uint64) (old uint64)
- func OrUintptr(addr *uintptr, mask uintptr) (old 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 Bool
- type Int32
- type Int64
- type Pointer
- type Uint32
- func (x *Uint32) Add(delta uint32) (new uint32)
- func (x *Uint32) And(mask uint32) (old uint32)
- func (x *Uint32) CompareAndSwap(old, new uint32) (swapped bool)
- func (x *Uint32) Load() uint32
- func (x *Uint32) Or(mask uint32) (old uint32)
- func (x *Uint32) Store(val uint32)
- func (x *Uint32) Swap(new uint32) (old uint32)
- type Uint64
- func (x *Uint64) Add(delta uint64) (new uint64)
- func (x *Uint64) And(mask uint64) (old uint64)
- func (x *Uint64) CompareAndSwap(old, new uint64) (swapped bool)
- func (x *Uint64) Load() uint64
- func (x *Uint64) Or(mask uint64) (old uint64)
- func (x *Uint64) Store(val uint64)
- func (x *Uint64) Swap(new uint64) (old uint64)
- type Uintptr
- func (x *Uintptr) Add(delta uintptr) (new uintptr)
- func (x *Uintptr) And(mask uintptr) (old uintptr)
- func (x *Uintptr) CompareAndSwap(old, new uintptr) (swapped bool)
- func (x *Uintptr) Load() uintptr
- func (x *Uintptr) Or(mask uintptr) (old uintptr)
- func (x *Uintptr) Store(val uintptr)
- func (x *Uintptr) Swap(new uintptr) (old uintptr)
- type Value
- Bugs
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
func AddInt32 ¶
AddInt32 atomically adds delta to *addr and returns the new value. Consider using the more ergonomic and less error-prone Int32.Add instead.
func AddInt64 ¶
AddInt64 atomically adds delta to *addr and returns the new value. Consider using the more ergonomic and less error-prone Int64.Add instead (particularly if you target 32-bit platforms; see the bugs section).
func AddUint32 ¶
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)). Consider using the more ergonomic and less error-prone Uint32.Add instead.
func AddUint64 ¶
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)). Consider using the more ergonomic and less error-prone Uint64.Add instead (particularly if you target 32-bit platforms; see the bugs section).
func AddUintptr ¶
AddUintptr atomically adds delta to *addr and returns the new value. Consider using the more ergonomic and less error-prone Uintptr.Add instead.
func AndInt32 ¶
AndInt32 atomically performs a bitwise AND operation on *addr using the bitmask provided as mask and returns the old value. Consider using the more ergonomic and less error-prone Int32.And instead.
func AndInt64 ¶
AndInt64 atomically performs a bitwise AND operation on *addr using the bitmask provided as mask and returns the old value. Consider using the more ergonomic and less error-prone Int64.And instead.
func AndUint32 ¶
AndUint32 atomically performs a bitwise AND operation on *addr using the bitmask provided as mask and returns the old value. Consider using the more ergonomic and less error-prone Uint32.And instead.
func AndUint64 ¶
AndUint64 atomically performs a bitwise AND operation on *addr using the bitmask provided as mask and returns the old. Consider using the more ergonomic and less error-prone Uint64.And instead.
func AndUintptr ¶
AndUintptr atomically performs a bitwise AND operation on *addr using the bitmask provided as mask and returns the old value. Consider using the more ergonomic and less error-prone Uintptr.And instead.
func CompareAndSwapInt32 ¶
CompareAndSwapInt32 executes the compare-and-swap operation for an int32 value. Consider using the more ergonomic and less error-prone Int32.CompareAndSwap instead.
func CompareAndSwapInt64 ¶
CompareAndSwapInt64 executes the compare-and-swap operation for an int64 value. Consider using the more ergonomic and less error-prone Int64.CompareAndSwap instead (particularly if you target 32-bit platforms; see the bugs section).
func CompareAndSwapPointer ¶
CompareAndSwapPointer executes the compare-and-swap operation for a unsafe.Pointer value. Consider using the more ergonomic and less error-prone Pointer.CompareAndSwap instead.
func CompareAndSwapUint32 ¶
CompareAndSwapUint32 executes the compare-and-swap operation for a uint32 value. Consider using the more ergonomic and less error-prone Uint32.CompareAndSwap instead.
func CompareAndSwapUint64 ¶
CompareAndSwapUint64 executes the compare-and-swap operation for a uint64 value. Consider using the more ergonomic and less error-prone Uint64.CompareAndSwap instead (particularly if you target 32-bit platforms; see the bugs section).
func CompareAndSwapUintptr ¶
CompareAndSwapUintptr executes the compare-and-swap operation for a uintptr value. Consider using the more ergonomic and less error-prone Uintptr.CompareAndSwap instead.
func LoadInt32 ¶
LoadInt32 atomically loads *addr. Consider using the more ergonomic and less error-prone Int32.Load instead.
func LoadInt64 ¶
LoadInt64 atomically loads *addr. Consider using the more ergonomic and less error-prone Int64.Load instead (particularly if you target 32-bit platforms; see the bugs section).
func LoadPointer ¶
LoadPointer atomically loads *addr. Consider using the more ergonomic and less error-prone Pointer.Load instead.
func LoadUint32 ¶
LoadUint32 atomically loads *addr. Consider using the more ergonomic and less error-prone Uint32.Load instead.
func LoadUint64 ¶
LoadUint64 atomically loads *addr. Consider using the more ergonomic and less error-prone Uint64.Load instead (particularly if you target 32-bit platforms; see the bugs section).
func LoadUintptr ¶
LoadUintptr atomically loads *addr. Consider using the more ergonomic and less error-prone Uintptr.Load instead.
func OrInt32 ¶
OrInt32 atomically performs a bitwise OR operation on *addr using the bitmask provided as mask and returns the old value. Consider using the more ergonomic and less error-prone Int32.Or instead.
func OrInt64 ¶
OrInt64 atomically performs a bitwise OR operation on *addr using the bitmask provided as mask and returns the old value. Consider using the more ergonomic and less error-prone Int64.Or instead.
func OrUint32 ¶
OrUint32 atomically performs a bitwise OR operation on *addr using the bitmask provided as mask and returns the old value. Consider using the more ergonomic and less error-prone Uint32.Or instead.
func OrUint64 ¶
OrUint64 atomically performs a bitwise OR operation on *addr using the bitmask provided as mask and returns the old value. Consider using the more ergonomic and less error-prone Uint64.Or instead.
func OrUintptr ¶
OrUintptr atomically performs a bitwise OR operation on *addr using the bitmask provided as mask and returns the old value. Consider using the more ergonomic and less error-prone Uintptr.Or instead.
func StoreInt32 ¶
StoreInt32 atomically stores val into *addr. Consider using the more ergonomic and less error-prone Int32.Store instead.
func StoreInt64 ¶
StoreInt64 atomically stores val into *addr. Consider using the more ergonomic and less error-prone Int64.Store instead (particularly if you target 32-bit platforms; see the bugs section).
func StorePointer ¶
StorePointer atomically stores val into *addr. Consider using the more ergonomic and less error-prone Pointer.Store instead.
func StoreUint32 ¶
StoreUint32 atomically stores val into *addr. Consider using the more ergonomic and less error-prone Uint32.Store instead.
func StoreUint64 ¶
StoreUint64 atomically stores val into *addr. Consider using the more ergonomic and less error-prone Uint64.Store instead (particularly if you target 32-bit platforms; see the bugs section).
func StoreUintptr ¶
StoreUintptr atomically stores val into *addr. Consider using the more ergonomic and less error-prone Uintptr.Store instead.
func SwapInt32 ¶
SwapInt32 atomically stores new into *addr and returns the previous *addr value. Consider using the more ergonomic and less error-prone Int32.Swap instead.
func SwapInt64 ¶
SwapInt64 atomically stores new into *addr and returns the previous *addr value. Consider using the more ergonomic and less error-prone Int64.Swap instead (particularly if you target 32-bit platforms; see the bugs section).
func SwapPointer ¶
SwapPointer atomically stores new into *addr and returns the previous *addr value. Consider using the more ergonomic and less error-prone Pointer.Swap instead.
func SwapUint32 ¶
SwapUint32 atomically stores new into *addr and returns the previous *addr value. Consider using the more ergonomic and less error-prone Uint32.Swap instead.
func SwapUint64 ¶
SwapUint64 atomically stores new into *addr and returns the previous *addr value. Consider using the more ergonomic and less error-prone Uint64.Swap instead (particularly if you target 32-bit platforms; see the bugs section).
func SwapUintptr ¶
SwapUintptr atomically stores new into *addr and returns the previous *addr value. Consider using the more ergonomic and less error-prone Uintptr.Swap instead.
Types ¶
type Bool ¶
type Bool struct {
// contains filtered or unexported fields
}
A Bool is an atomic boolean value. The zero value is false.
func (*Bool) CompareAndSwap ¶
CompareAndSwap executes the compare-and-swap operation for the boolean value x.
type Int32 ¶
type Int32 struct {
// contains filtered or unexported fields
}
An Int32 is an atomic int32. The zero value is zero.
func (*Int32) And ¶
And atomically performs a bitwise AND operation on x using the bitmask provided as mask and returns the old value.
func (*Int32) CompareAndSwap ¶
CompareAndSwap executes the compare-and-swap operation for x.
type Int64 ¶
type Int64 struct {
// contains filtered or unexported fields
}
An Int64 is an atomic int64. The zero value is zero.
func (*Int64) And ¶
And atomically performs a bitwise AND operation on x using the bitmask provided as mask and returns the old value.
func (*Int64) CompareAndSwap ¶
CompareAndSwap executes the compare-and-swap operation for x.
type Pointer ¶
type Pointer[T any] struct { // contains filtered or unexported fields }
A Pointer is an atomic pointer of type *T. The zero value is a nil *T.
func (*Pointer[T]) CompareAndSwap ¶
CompareAndSwap executes the compare-and-swap operation for x.
type Uint32 ¶
type Uint32 struct {
// contains filtered or unexported fields
}
A Uint32 is an atomic uint32. The zero value is zero.
func (*Uint32) And ¶
And atomically performs a bitwise AND operation on x using the bitmask provided as mask and returns the old value.
func (*Uint32) CompareAndSwap ¶
CompareAndSwap executes the compare-and-swap operation for x.
type Uint64 ¶
type Uint64 struct {
// contains filtered or unexported fields
}
A Uint64 is an atomic uint64. The zero value is zero.
func (*Uint64) And ¶
And atomically performs a bitwise AND operation on x using the bitmask provided as mask and returns the old value.
func (*Uint64) CompareAndSwap ¶
CompareAndSwap executes the compare-and-swap operation for x.
type Uintptr ¶
type Uintptr struct {
// contains filtered or unexported fields
}
A Uintptr is an atomic uintptr. The zero value is zero.
func (*Uintptr) And ¶
And atomically performs a bitwise AND operation on x using the bitmask provided as mask and returns the old value.
func (*Uintptr) CompareAndSwap ¶
CompareAndSwap executes the compare-and-swap operation for x.
type Value ¶
type Value struct {
// contains filtered or unexported fields
}
A Value provides an atomic load and store of a consistently typed value. The zero value for a Value returns nil from Value.Load. Once Value.Store has been called, a Value must not be copied.
A Value must not be copied after first use.
func (*Value) CompareAndSwap ¶
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 ¶
Load returns the value set by the most recent Store. It returns nil if there has been no call to Store for this Value.
Notes ¶
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 via the primitive atomic functions (types Int64 and Uint64 are automatically aligned). The first word in an allocated struct, array, or slice; in a global variable; or in a local variable (because on 32-bit architectures, the subject of 64-bit atomic operations will escape to the heap) can be relied upon to be 64-bit aligned.
Source Files