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Source file src/sync/atomic/doc.go

Documentation: sync/atomic

  // 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 x86-32, 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 both ARM and x86-32, it is the caller's responsibility to arrange for 64-bit
  // alignment of 64-bit words accessed atomically. The first word in a global
  // variable or in an allocated struct 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)
  
  // Helper for ARM.  Linker will discard on other systems
  func panic64() {
  	panic("sync/atomic: broken 64-bit atomic operations (buggy QEMU)")
  }
  

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