1/*
2 * Copyright (c) 2000-2001,2003-2004 Apple Computer, Inc. All Rights Reserved.
3 *
4 * @APPLE_LICENSE_HEADER_START@
5 *
6 * This file contains Original Code and/or Modifications of Original Code
7 * as defined in and that are subject to the Apple Public Source License
8 * Version 2.0 (the 'License'). You may not use this file except in
9 * compliance with the License. Please obtain a copy of the License at
10 * http://www.opensource.apple.com/apsl/ and read it before using this
11 * file.
12 *
13 * The Original Code and all software distributed under the License are
14 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
15 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
16 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
17 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
18 * Please see the License for the specific language governing rights and
19 * limitations under the License.
20 *
21 * @APPLE_LICENSE_HEADER_END@
22 */
23
24
25//
26// threading_internal - internal support classes and functions for threading implementation
27//
28#ifndef _H_THREADING_INTERNAL
29#define _H_THREADING_INTERNAL
30
31#include <security_utilities/utilities.h>
32#include <libkern/OSAtomic.h>
33
34
35namespace Security {
36
37
38//
39// Do we have 64-bit atomic operations?
40//
41#define _HAVE_64BIT_ATOMIC (defined(__ppc64__) || defined(__i386__) || defined(__x86_64__))
42
43
44//
45// The AtomicTypes class is an implementation detail.
46// Do not use it.
47//
48template <unsigned wordsize>
49struct AtomicTypes {
50	// unsupported word size (this will cause compilation errors if used)
51};
52
53template <>
54struct AtomicTypes<32> {
55	typedef int32_t Integer;
56
57	static Integer add(int delta, Integer &base)
58	{ return OSAtomicAdd32(delta, &base); }
59	static Integer addb(int delta, Integer &base) { return OSAtomicAdd32Barrier(delta, &base); }
60
61	static bool cas(Integer oldValue, Integer newValue, Integer &base)
62	{ return OSAtomicCompareAndSwap32(oldValue, newValue, &base); }
63	static bool casb(Integer oldValue, Integer newValue, Integer &base)
64	{ return OSAtomicCompareAndSwap32Barrier(oldValue, newValue, &base); }
65};
66
67#if _HAVE_64BIT_ATOMIC
68
69template <>
70struct AtomicTypes<64> {
71	typedef int64_t Integer;
72
73	static Integer add(int delta, Integer &base) { return OSAtomicAdd64(delta, &base); }
74	static Integer addb(int delta, Integer &base) { return OSAtomicAdd64Barrier(delta, &base); }
75
76	static bool cas(Integer oldValue, Integer newValue, Integer &base)
77	{ return OSAtomicCompareAndSwap64(oldValue, newValue, &base); }
78	static bool casb(Integer oldValue, Integer newValue, Integer &base)
79	{ return OSAtomicCompareAndSwap64Barrier(oldValue, newValue, &base); }
80};
81
82#endif //_HAVE_64BIT_ATOMIC
83
84
85//
86// Atomic<Type> is a set of (static) operations that can atomically access memory.
87// This is not a wrapper object. Think of it as a generator class that produces
88// the proper atomic memory operations for arbitrary data types.
89// If the underlying system does not support atomicity for a particular type
90// (e.g. 64 bits on ppc, or 16 bits anywhere), you will get compilation errors.
91//
92template <class Type>
93class Atomic {
94	typedef AtomicTypes<sizeof(Type) * 8> _Ops;
95	typedef typename _Ops::Integer _Type;
96
97public:
98	static Type add(int delta, Type &store)
99	{ return Type(_Ops::add(delta, (_Type &)store)); }
100	static Type addb(int delta, Type &store)
101	{ return Type(_Ops::addb(delta, (_Type &)store)); }
102
103	static bool cas(Type oldValue, Type newValue, Type &store)
104	{ return _Ops::cas(_Type(oldValue), _Type(newValue), (_Type &)store); }
105	static bool casb(Type oldValue, Type newValue, Type &store)
106	{ return _Ops::casb(_Type(oldValue), _Type(newValue), (_Type &)store); }
107
108	static void barrier() { OSMemoryBarrier(); }
109	static void readBarrier() { OSMemoryBarrier(); }
110	static void writeBarrier() { OSMemoryBarrier(); }
111
112	// convenience additions (expressed in terms above)
113
114	static Type increment(Type &store) { return add(1, store); }
115	static Type decrement(Type &store) { return add(-1, store); }
116
117	static Type load(const Type &store) { readBarrier(); return store; }
118	static Type store(Type value, Type &store)
119	{ while (!casb(store, value, store)) {}; return value; }
120};
121
122
123} // end namespace Security
124
125#endif //_H_THREADING_INTERNAL
126