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Source file src/sync/atomic/doc.go

Documentation: sync/atomic

     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  // Package atomic provides low-level atomic memory primitives
     6  // useful for implementing synchronization algorithms.
     7  //
     8  // These functions require great care to be used correctly.
     9  // Except for special, low-level applications, synchronization is better
    10  // done with channels or the facilities of the sync package.
    11  // Share memory by communicating;
    12  // don't communicate by sharing memory.
    13  //
    14  // The swap operation, implemented by the SwapT functions, is the atomic
    15  // equivalent of:
    16  //
    17  //	old = *addr
    18  //	*addr = new
    19  //	return old
    20  //
    21  // The compare-and-swap operation, implemented by the CompareAndSwapT
    22  // functions, is the atomic equivalent of:
    23  //
    24  //	if *addr == old {
    25  //		*addr = new
    26  //		return true
    27  //	}
    28  //	return false
    29  //
    30  // The add operation, implemented by the AddT functions, is the atomic
    31  // equivalent of:
    32  //
    33  //	*addr += delta
    34  //	return *addr
    35  //
    36  // The load and store operations, implemented by the LoadT and StoreT
    37  // functions, are the atomic equivalents of "return *addr" and
    38  // "*addr = val".
    39  //
    40  package atomic
    41  
    42  import (
    43  	"unsafe"
    44  )
    45  
    46  // BUG(rsc): On x86-32, the 64-bit functions use instructions unavailable before the Pentium MMX.
    47  //
    48  // On non-Linux ARM, the 64-bit functions use instructions unavailable before the ARMv6k core.
    49  //
    50  // On ARM, x86-32, and 32-bit MIPS,
    51  // it is the caller's responsibility to arrange for 64-bit
    52  // alignment of 64-bit words accessed atomically. The first word in a
    53  // variable or in an allocated struct, array, or slice can be relied upon to be
    54  // 64-bit aligned.
    55  
    56  // SwapInt32 atomically stores new into *addr and returns the previous *addr value.
    57  func SwapInt32(addr *int32, new int32) (old int32)
    58  
    59  // SwapInt64 atomically stores new into *addr and returns the previous *addr value.
    60  func SwapInt64(addr *int64, new int64) (old int64)
    61  
    62  // SwapUint32 atomically stores new into *addr and returns the previous *addr value.
    63  func SwapUint32(addr *uint32, new uint32) (old uint32)
    64  
    65  // SwapUint64 atomically stores new into *addr and returns the previous *addr value.
    66  func SwapUint64(addr *uint64, new uint64) (old uint64)
    67  
    68  // SwapUintptr atomically stores new into *addr and returns the previous *addr value.
    69  func SwapUintptr(addr *uintptr, new uintptr) (old uintptr)
    70  
    71  // SwapPointer atomically stores new into *addr and returns the previous *addr value.
    72  func SwapPointer(addr *unsafe.Pointer, new unsafe.Pointer) (old unsafe.Pointer)
    73  
    74  // CompareAndSwapInt32 executes the compare-and-swap operation for an int32 value.
    75  func CompareAndSwapInt32(addr *int32, old, new int32) (swapped bool)
    76  
    77  // CompareAndSwapInt64 executes the compare-and-swap operation for an int64 value.
    78  func CompareAndSwapInt64(addr *int64, old, new int64) (swapped bool)
    79  
    80  // CompareAndSwapUint32 executes the compare-and-swap operation for a uint32 value.
    81  func CompareAndSwapUint32(addr *uint32, old, new uint32) (swapped bool)
    82  
    83  // CompareAndSwapUint64 executes the compare-and-swap operation for a uint64 value.
    84  func CompareAndSwapUint64(addr *uint64, old, new uint64) (swapped bool)
    85  
    86  // CompareAndSwapUintptr executes the compare-and-swap operation for a uintptr value.
    87  func CompareAndSwapUintptr(addr *uintptr, old, new uintptr) (swapped bool)
    88  
    89  // CompareAndSwapPointer executes the compare-and-swap operation for a unsafe.Pointer value.
    90  func CompareAndSwapPointer(addr *unsafe.Pointer, old, new unsafe.Pointer) (swapped bool)
    91  
    92  // AddInt32 atomically adds delta to *addr and returns the new value.
    93  func AddInt32(addr *int32, delta int32) (new int32)
    94  
    95  // AddUint32 atomically adds delta to *addr and returns the new value.
    96  // To subtract a signed positive constant value c from x, do AddUint32(&x, ^uint32(c-1)).
    97  // In particular, to decrement x, do AddUint32(&x, ^uint32(0)).
    98  func AddUint32(addr *uint32, delta uint32) (new uint32)
    99  
   100  // AddInt64 atomically adds delta to *addr and returns the new value.
   101  func AddInt64(addr *int64, delta int64) (new int64)
   102  
   103  // AddUint64 atomically adds delta to *addr and returns the new value.
   104  // To subtract a signed positive constant value c from x, do AddUint64(&x, ^uint64(c-1)).
   105  // In particular, to decrement x, do AddUint64(&x, ^uint64(0)).
   106  func AddUint64(addr *uint64, delta uint64) (new uint64)
   107  
   108  // AddUintptr atomically adds delta to *addr and returns the new value.
   109  func AddUintptr(addr *uintptr, delta uintptr) (new uintptr)
   110  
   111  // LoadInt32 atomically loads *addr.
   112  func LoadInt32(addr *int32) (val int32)
   113  
   114  // LoadInt64 atomically loads *addr.
   115  func LoadInt64(addr *int64) (val int64)
   116  
   117  // LoadUint32 atomically loads *addr.
   118  func LoadUint32(addr *uint32) (val uint32)
   119  
   120  // LoadUint64 atomically loads *addr.
   121  func LoadUint64(addr *uint64) (val uint64)
   122  
   123  // LoadUintptr atomically loads *addr.
   124  func LoadUintptr(addr *uintptr) (val uintptr)
   125  
   126  // LoadPointer atomically loads *addr.
   127  func LoadPointer(addr *unsafe.Pointer) (val unsafe.Pointer)
   128  
   129  // StoreInt32 atomically stores val into *addr.
   130  func StoreInt32(addr *int32, val int32)
   131  
   132  // StoreInt64 atomically stores val into *addr.
   133  func StoreInt64(addr *int64, val int64)
   134  
   135  // StoreUint32 atomically stores val into *addr.
   136  func StoreUint32(addr *uint32, val uint32)
   137  
   138  // StoreUint64 atomically stores val into *addr.
   139  func StoreUint64(addr *uint64, val uint64)
   140  
   141  // StoreUintptr atomically stores val into *addr.
   142  func StoreUintptr(addr *uintptr, val uintptr)
   143  
   144  // StorePointer atomically stores val into *addr.
   145  func StorePointer(addr *unsafe.Pointer, val unsafe.Pointer)
   146  
   147  // Helper for ARM.  Linker will discard on other systems
   148  func panic64() {
   149  	panic("sync/atomic: broken 64-bit atomic operations (buggy QEMU)")
   150  }
   151  

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