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//
40package atomic
41
42import (
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.
57func SwapInt32(addr *int32, new int32) (old int32)
58
59// SwapInt64 atomically stores new into *addr and returns the previous *addr value.
60func SwapInt64(addr *int64, new int64) (old int64)
61
62// SwapUint32 atomically stores new into *addr and returns the previous *addr value.
63func SwapUint32(addr *uint32, new uint32) (old uint32)
64
65// SwapUint64 atomically stores new into *addr and returns the previous *addr value.
66func SwapUint64(addr *uint64, new uint64) (old uint64)
67
68// SwapUintptr atomically stores new into *addr and returns the previous *addr value.
69func SwapUintptr(addr *uintptr, new uintptr) (old uintptr)
70
71// SwapPointer atomically stores new into *addr and returns the previous *addr value.
72func SwapPointer(addr *unsafe.Pointer, new unsafe.Pointer) (old unsafe.Pointer)
73
74// CompareAndSwapInt32 executes the compare-and-swap operation for an int32 value.
75func CompareAndSwapInt32(addr *int32, old, new int32) (swapped bool)
76
77// CompareAndSwapInt64 executes the compare-and-swap operation for an int64 value.
78func CompareAndSwapInt64(addr *int64, old, new int64) (swapped bool)
79
80// CompareAndSwapUint32 executes the compare-and-swap operation for a uint32 value.
81func CompareAndSwapUint32(addr *uint32, old, new uint32) (swapped bool)
82
83// CompareAndSwapUint64 executes the compare-and-swap operation for a uint64 value.
84func CompareAndSwapUint64(addr *uint64, old, new uint64) (swapped bool)
85
86// CompareAndSwapUintptr executes the compare-and-swap operation for a uintptr value.
87func CompareAndSwapUintptr(addr *uintptr, old, new uintptr) (swapped bool)
88
89// CompareAndSwapPointer executes the compare-and-swap operation for a unsafe.Pointer value.
90func CompareAndSwapPointer(addr *unsafe.Pointer, old, new unsafe.Pointer) (swapped bool)
91
92// AddInt32 atomically adds delta to *addr and returns the new value.
93func 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)).
98func AddUint32(addr *uint32, delta uint32) (new uint32)
99
100// AddInt64 atomically adds delta to *addr and returns the new value.
101func 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)).
106func AddUint64(addr *uint64, delta uint64) (new uint64)
107
108// AddUintptr atomically adds delta to *addr and returns the new value.
109func AddUintptr(addr *uintptr, delta uintptr) (new uintptr)
110
111// LoadInt32 atomically loads *addr.
112func LoadInt32(addr *int32) (val int32)
113
114// LoadInt64 atomically loads *addr.
115func LoadInt64(addr *int64) (val int64)
116
117// LoadUint32 atomically loads *addr.
118func LoadUint32(addr *uint32) (val uint32)
119
120// LoadUint64 atomically loads *addr.
121func LoadUint64(addr *uint64) (val uint64)
122
123// LoadUintptr atomically loads *addr.
124func LoadUintptr(addr *uintptr) (val uintptr)
125
126// LoadPointer atomically loads *addr.
127func LoadPointer(addr *unsafe.Pointer) (val unsafe.Pointer)
128
129// StoreInt32 atomically stores val into *addr.
130func StoreInt32(addr *int32, val int32)
131
132// StoreInt64 atomically stores val into *addr.
133func StoreInt64(addr *int64, val int64)
134
135// StoreUint32 atomically stores val into *addr.
136func StoreUint32(addr *uint32, val uint32)
137
138// StoreUint64 atomically stores val into *addr.
139func StoreUint64(addr *uint64, val uint64)
140
141// StoreUintptr atomically stores val into *addr.
142func StoreUintptr(addr *uintptr, val uintptr)
143
144// StorePointer atomically stores val into *addr.
145func StorePointer(addr *unsafe.Pointer, val unsafe.Pointer)
146
147// Helper for ARM.  Linker will discard on other systems
148func panic64() {
149	panic("sync/atomic: broken 64-bit atomic operations (buggy QEMU)")
150}
151