github.com/xushiwei/go@v0.0.0-20130601165731-2b9d83f45bc9/src/pkg/sync/atomic/doc.go (about)

     1  // Copyright 2011 The Go Authors.  All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // +build !race
     6  
     7  // Package atomic provides low-level atomic memory primitives
     8  // useful for implementing synchronization algorithms.
     9  //
    10  // These functions require great care to be used correctly.
    11  // Except for special, low-level applications, synchronization is better
    12  // done with channels or the facilities of the sync package.
    13  // Share memory by communicating;
    14  // don't communicate by sharing memory.
    15  //
    16  // The compare-and-swap operation, implemented by the CompareAndSwapT
    17  // functions, is the atomic equivalent of:
    18  //
    19  //	if *addr == old {
    20  //		*addr = new
    21  //		return true
    22  //	}
    23  //	return false
    24  //
    25  // The add operation, implemented by the AddT functions, is the atomic
    26  // equivalent of:
    27  //
    28  //	*addr += delta
    29  //	return *addr
    30  //
    31  // The load and store operations, implemented by the LoadT and StoreT
    32  // functions, are the atomic equivalents of "return *addr" and
    33  // "*addr = val".
    34  //
    35  package atomic
    36  
    37  import (
    38  	"unsafe"
    39  )
    40  
    41  // BUG(rsc): On x86-32, the 64-bit functions use instructions unavailable before the Pentium MMX.
    42  //
    43  // On both ARM and x86-32, it is the caller's responsibility to arrange for 64-bit
    44  // alignment of 64-bit words accessed atomically. The first word in a global
    45  // variable or in an allocated struct or slice can be relied upon to be
    46  // 64-bit aligned.
    47  
    48  // CompareAndSwapInt32 executes the compare-and-swap operation for an int32 value.
    49  func CompareAndSwapInt32(addr *int32, old, new int32) (swapped bool)
    50  
    51  // CompareAndSwapInt64 executes the compare-and-swap operation for an int64 value.
    52  func CompareAndSwapInt64(addr *int64, old, new int64) (swapped bool)
    53  
    54  // CompareAndSwapUint32 executes the compare-and-swap operation for a uint32 value.
    55  func CompareAndSwapUint32(addr *uint32, old, new uint32) (swapped bool)
    56  
    57  // CompareAndSwapUint64 executes the compare-and-swap operation for a uint64 value.
    58  func CompareAndSwapUint64(addr *uint64, old, new uint64) (swapped bool)
    59  
    60  // CompareAndSwapUintptr executes the compare-and-swap operation for a uintptr value.
    61  func CompareAndSwapUintptr(addr *uintptr, old, new uintptr) (swapped bool)
    62  
    63  // CompareAndSwapPointer executes the compare-and-swap operation for a unsafe.Pointer value.
    64  func CompareAndSwapPointer(addr *unsafe.Pointer, old, new unsafe.Pointer) (swapped bool)
    65  
    66  // AddInt32 atomically adds delta to *addr and returns the new value.
    67  func AddInt32(addr *int32, delta int32) (new int32)
    68  
    69  // AddUint32 atomically adds delta to *addr and returns the new value.
    70  func AddUint32(addr *uint32, delta uint32) (new uint32)
    71  
    72  // AddInt64 atomically adds delta to *addr and returns the new value.
    73  func AddInt64(addr *int64, delta int64) (new int64)
    74  
    75  // AddUint64 atomically adds delta to *addr and returns the new value.
    76  func AddUint64(addr *uint64, delta uint64) (new uint64)
    77  
    78  // AddUintptr atomically adds delta to *addr and returns the new value.
    79  func AddUintptr(addr *uintptr, delta uintptr) (new uintptr)
    80  
    81  // LoadInt32 atomically loads *addr.
    82  func LoadInt32(addr *int32) (val int32)
    83  
    84  // LoadInt64 atomically loads *addr.
    85  func LoadInt64(addr *int64) (val int64)
    86  
    87  // LoadUint32 atomically loads *addr.
    88  func LoadUint32(addr *uint32) (val uint32)
    89  
    90  // LoadUint64 atomically loads *addr.
    91  func LoadUint64(addr *uint64) (val uint64)
    92  
    93  // LoadUintptr atomically loads *addr.
    94  func LoadUintptr(addr *uintptr) (val uintptr)
    95  
    96  // LoadPointer atomically loads *addr.
    97  func LoadPointer(addr *unsafe.Pointer) (val unsafe.Pointer)
    98  
    99  // StoreInt32 atomically stores val into *addr.
   100  func StoreInt32(addr *int32, val int32)
   101  
   102  // StoreInt64 atomically stores val into *addr.
   103  func StoreInt64(addr *int64, val int64)
   104  
   105  // StoreUint32 atomically stores val into *addr.
   106  func StoreUint32(addr *uint32, val uint32)
   107  
   108  // StoreUint64 atomically stores val into *addr.
   109  func StoreUint64(addr *uint64, val uint64)
   110  
   111  // StoreUintptr atomically stores val into *addr.
   112  func StoreUintptr(addr *uintptr, val uintptr)
   113  
   114  // StorePointer atomically stores val into *addr.
   115  func StorePointer(addr *unsafe.Pointer, val unsafe.Pointer)
   116  
   117  // Helper for ARM.  Linker will discard on other systems
   118  func panic64() {
   119  	panic("sync/atomic: broken 64-bit atomic operations (buggy QEMU)")
   120  }