| // Copyright 2011 The Go Authors. All rights reserved. | |
| // Use of this source code is governed by a BSD-style | |
| // license that can be found in the LICENSE file. | |
| // 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. | |
| // | |
| // [the Go memory model]: https://go.dev/ref/mem | |
| package atomic | |
| import ( | |
| "unsafe" | |
| ) | |
| // BUG(rsc): 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. | |
| // SwapInt32 atomically stores new into *addr and returns the previous *addr value. | |
| // Consider using the more ergonomic and less error-prone [Int32.Swap] instead. | |
| // | |
| //go:noescape | |
| func SwapInt32(addr *int32, new int32) (old int32) | |
| // SwapUint32 atomically stores new into *addr and returns the previous *addr value. | |
| // Consider using the more ergonomic and less error-prone [Uint32.Swap] instead. | |
| // | |
| //go:noescape | |
| func SwapUint32(addr *uint32, new uint32) (old uint32) | |
| // SwapUintptr atomically stores new into *addr and returns the previous *addr value. | |
| // Consider using the more ergonomic and less error-prone [Uintptr.Swap] instead. | |
| // | |
| //go:noescape | |
| func SwapUintptr(addr *uintptr, new uintptr) (old uintptr) | |
| // 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 SwapPointer(addr *unsafe.Pointer, new unsafe.Pointer) (old unsafe.Pointer) | |
| // CompareAndSwapInt32 executes the compare-and-swap operation for an int32 value. | |
| // Consider using the more ergonomic and less error-prone [Int32.CompareAndSwap] instead. | |
| // | |
| //go:noescape | |
| func CompareAndSwapInt32(addr *int32, old, new int32) (swapped bool) | |
| // CompareAndSwapUint32 executes the compare-and-swap operation for a uint32 value. | |
| // Consider using the more ergonomic and less error-prone [Uint32.CompareAndSwap] instead. | |
| // | |
| //go:noescape | |
| func CompareAndSwapUint32(addr *uint32, old, new uint32) (swapped bool) | |
| // CompareAndSwapUintptr executes the compare-and-swap operation for a uintptr value. | |
| // Consider using the more ergonomic and less error-prone [Uintptr.CompareAndSwap] instead. | |
| // | |
| //go:noescape | |
| func CompareAndSwapUintptr(addr *uintptr, old, new uintptr) (swapped bool) | |
| // 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 CompareAndSwapPointer(addr *unsafe.Pointer, old, new unsafe.Pointer) (swapped bool) | |
| // AddInt32 atomically adds delta to *addr and returns the new value. | |
| // Consider using the more ergonomic and less error-prone [Int32.Add] instead. | |
| // | |
| //go:noescape | |
| func AddInt32(addr *int32, delta int32) (new int32) | |
| // 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. | |
| // | |
| //go:noescape | |
| func AddUint32(addr *uint32, delta uint32) (new uint32) | |
| // AddUintptr atomically adds delta to *addr and returns the new value. | |
| // Consider using the more ergonomic and less error-prone [Uintptr.Add] instead. | |
| // | |
| //go:noescape | |
| func AddUintptr(addr *uintptr, delta uintptr) (new uintptr) | |
| // 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. | |
| // | |
| //go:noescape | |
| func AndInt32(addr *int32, mask int32) (old int32) | |
| // 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. | |
| // | |
| //go:noescape | |
| func AndUint32(addr *uint32, mask uint32) (old uint32) | |
| // 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. | |
| // | |
| //go:noescape | |
| func AndUintptr(addr *uintptr, mask uintptr) (old uintptr) | |
| // 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. | |
| // | |
| //go:noescape | |
| func OrInt32(addr *int32, mask int32) (old int32) | |
| // 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. | |
| // | |
| //go:noescape | |
| func OrUint32(addr *uint32, mask uint32) (old uint32) | |
| // 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. | |
| // | |
| //go:noescape | |
| func OrUintptr(addr *uintptr, mask uintptr) (old uintptr) | |
| // LoadInt32 atomically loads *addr. | |
| // Consider using the more ergonomic and less error-prone [Int32.Load] instead. | |
| // | |
| //go:noescape | |
| func LoadInt32(addr *int32) (val int32) | |
| // LoadUint32 atomically loads *addr. | |
| // Consider using the more ergonomic and less error-prone [Uint32.Load] instead. | |
| // | |
| //go:noescape | |
| func LoadUint32(addr *uint32) (val uint32) | |
| // LoadUintptr atomically loads *addr. | |
| // Consider using the more ergonomic and less error-prone [Uintptr.Load] instead. | |
| // | |
| //go:noescape | |
| func LoadUintptr(addr *uintptr) (val uintptr) | |
| // LoadPointer atomically loads *addr. | |
| // Consider using the more ergonomic and less error-prone [Pointer.Load] instead. | |
| func LoadPointer(addr *unsafe.Pointer) (val unsafe.Pointer) | |
| // StoreInt32 atomically stores val into *addr. | |
| // Consider using the more ergonomic and less error-prone [Int32.Store] instead. | |
| // | |
| //go:noescape | |
| func StoreInt32(addr *int32, val int32) | |
| // StoreUint32 atomically stores val into *addr. | |
| // Consider using the more ergonomic and less error-prone [Uint32.Store] instead. | |
| // | |
| //go:noescape | |
| func StoreUint32(addr *uint32, val uint32) | |
| // StoreUintptr atomically stores val into *addr. | |
| // Consider using the more ergonomic and less error-prone [Uintptr.Store] instead. | |
| // | |
| //go:noescape | |
| func StoreUintptr(addr *uintptr, val uintptr) | |
| // StorePointer atomically stores val into *addr. | |
| // Consider using the more ergonomic and less error-prone [Pointer.Store] instead. | |
| func StorePointer(addr *unsafe.Pointer, val unsafe.Pointer) | |