// 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". // 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. // The first word in a variable or in an allocated struct, array, or slice can // be relied upon to be 64-bit aligned. // SwapInt32 atomically stores new into *addr and returns the previous *addr value. func SwapInt32(addr *int32, new int32) (old int32) // SwapInt64 atomically stores new into *addr and returns the previous *addr value. func SwapInt64(addr *int64, new int64) (old int64) // SwapUint32 atomically stores new into *addr and returns the previous *addr value. func SwapUint32(addr *uint32, new uint32) (old uint32) // SwapUint64 atomically stores new into *addr and returns the previous *addr value. func SwapUint64(addr *uint64, new uint64) (old uint64) // SwapUintptr atomically stores new into *addr and returns the previous *addr value. func SwapUintptr(addr *uintptr, new uintptr) (old uintptr) // SwapPointer atomically stores new into *addr and returns the previous *addr value. func SwapPointer(addr *unsafe.Pointer, new unsafe.Pointer) (old unsafe.Pointer) // CompareAndSwapInt32 executes the compare-and-swap operation for an int32 value. func CompareAndSwapInt32(addr *int32, old, new int32) (swapped bool) // CompareAndSwapInt64 executes the compare-and-swap operation for an int64 value. func CompareAndSwapInt64(addr *int64, old, new int64) (swapped bool) // CompareAndSwapUint32 executes the compare-and-swap operation for a uint32 value. func CompareAndSwapUint32(addr *uint32, old, new uint32) (swapped bool) // CompareAndSwapUint64 executes the compare-and-swap operation for a uint64 value. func CompareAndSwapUint64(addr *uint64, old, new uint64) (swapped bool) // CompareAndSwapUintptr executes the compare-and-swap operation for a uintptr value. func CompareAndSwapUintptr(addr *uintptr, old, new uintptr) (swapped bool) // CompareAndSwapPointer executes the compare-and-swap operation for a unsafe.Pointer value. func CompareAndSwapPointer(addr *unsafe.Pointer, old, new unsafe.Pointer) (swapped bool) // AddInt32 atomically adds delta to *addr and returns the new value. 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)). func AddUint32(addr *uint32, delta uint32) (new uint32) // AddInt64 atomically adds delta to *addr and returns the new value. func AddInt64(addr *int64, delta int64) (new int64) // 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 AddUint64(addr *uint64, delta uint64) (new uint64) // AddUintptr atomically adds delta to *addr and returns the new value. func AddUintptr(addr *uintptr, delta uintptr) (new uintptr) // LoadInt32 atomically loads *addr. func LoadInt32(addr *int32) (val int32) // LoadInt64 atomically loads *addr. func LoadInt64(addr *int64) (val int64) // LoadUint32 atomically loads *addr. func LoadUint32(addr *uint32) (val uint32) // LoadUint64 atomically loads *addr. func LoadUint64(addr *uint64) (val uint64) // LoadUintptr atomically loads *addr. func LoadUintptr(addr *uintptr) (val uintptr) // LoadPointer atomically loads *addr. func LoadPointer(addr *unsafe.Pointer) (val unsafe.Pointer) // StoreInt32 atomically stores val into *addr. func StoreInt32(addr *int32, val int32) // StoreInt64 atomically stores val into *addr. func StoreInt64(addr *int64, val int64) // StoreUint32 atomically stores val into *addr. func StoreUint32(addr *uint32, val uint32) // StoreUint64 atomically stores val into *addr. func StoreUint64(addr *uint64, val uint64) // StoreUintptr atomically stores val into *addr. func StoreUintptr(addr *uintptr, val uintptr) // StorePointer atomically stores val into *addr. func StorePointer(addr *unsafe.Pointer, val unsafe.Pointer)