Panda3D

atomicAdjustPosixImpl.I
Go to the documentation of this file.
1 /**
2 * PANDA 3D SOFTWARE
3 * Copyright (c) Carnegie Mellon University. All rights reserved.
4 *
5 * All use of this software is subject to the terms of the revised BSD
6 * license. You should have received a copy of this license along
7 * with this source code in a file named "LICENSE."
8 *
9 * @file atomicAdjustPosixImpl.I
10 * @author drose
11 * @date 2006-02-10
12 */
13
14 /**
15 * Atomically increments the indicated variable.
16 */
17 INLINE void AtomicAdjustPosixImpl::
18 inc(TVOLATILE AtomicAdjustPosixImpl::Integer &var) {
19 pthread_mutex_lock(&_mutex);
20 ++var;
21 pthread_mutex_unlock(&_mutex);
22 }
23
24 /**
25 * Atomically decrements the indicated variable and returns true if the new
26 * value is nonzero, false if it is zero.
27 */
28 INLINE bool AtomicAdjustPosixImpl::
29 dec(TVOLATILE AtomicAdjustPosixImpl::Integer &var) {
30 pthread_mutex_lock(&_mutex);
31 Integer result = --var;
32 pthread_mutex_unlock(&_mutex);
33 return (result != 0);
34 }
35
36 /**
37 * Atomically computes var += delta. It is legal for delta to be negative.
38 * Returns the result of the addition.
39 */
40 INLINE AtomicAdjustPosixImpl::Integer AtomicAdjustPosixImpl::
41 add(TVOLATILE AtomicAdjustPosixImpl::Integer &var,
42 AtomicAdjustPosixImpl::Integer delta) {
43 pthread_mutex_lock(&_mutex);
44 Integer new_value = var + delta;
45 var = new_value;
46 pthread_mutex_unlock(&_mutex);
47 return new_value;
48 }
49
50 /**
51 * Atomically changes the indicated variable and returns the original value.
52 */
53 INLINE AtomicAdjustPosixImpl::Integer AtomicAdjustPosixImpl::
54 set(TVOLATILE AtomicAdjustPosixImpl::Integer &var,
55 AtomicAdjustPosixImpl::Integer new_value) {
56 pthread_mutex_lock(&_mutex);
57 Integer orig_value = var;
58 var = new_value;
59 pthread_mutex_unlock(&_mutex);
60 return orig_value;
61 }
62
63 /**
64 * Atomically retrieves the snapshot value of the indicated variable. This is
65 * the only guaranteed safe way to retrieve the value that other threads might
66 * be asynchronously setting, incrementing, or decrementing (via other
67 * AtomicAjust methods).
68 */
69 INLINE AtomicAdjustPosixImpl::Integer AtomicAdjustPosixImpl::
70 get(const TVOLATILE AtomicAdjustPosixImpl::Integer &var) {
71 pthread_mutex_lock(&_mutex);
72 Integer orig_value = var;
73 pthread_mutex_unlock(&_mutex);
74 return orig_value;
75 }
76
77 /**
78 * Atomically changes the indicated variable and returns the original value.
79 */
80 INLINE AtomicAdjustPosixImpl::Pointer AtomicAdjustPosixImpl::
81 set_ptr(TVOLATILE AtomicAdjustPosixImpl::Pointer &var,
82 AtomicAdjustPosixImpl::Pointer new_value) {
83 pthread_mutex_lock(&_mutex);
84 Pointer orig_value = var;
85 var = new_value;
86 pthread_mutex_unlock(&_mutex);
87 return orig_value;
88 }
89
90 /**
91 * Atomically retrieves the snapshot value of the indicated variable. This is
92 * the only guaranteed safe way to retrieve the value that other threads might
93 * be asynchronously setting, incrementing, or decrementing (via other
94 * AtomicAjust methods).
95 */
96 INLINE AtomicAdjustPosixImpl::Pointer AtomicAdjustPosixImpl::
97 get_ptr(const TVOLATILE AtomicAdjustPosixImpl::Pointer &var) {
98 pthread_mutex_lock(&_mutex);
99 Pointer orig_value = var;
100 pthread_mutex_unlock(&_mutex);
101 return orig_value;
102 }
103
104 /**
105 * Atomic compare and exchange.
106 *
107 * If mem is equal to old_value, store new_value in mem. In either case,
108 * return the original value of mem. The caller can test for success by
109 * comparing return_value == old_value.
110 *
111 * The atomic function expressed in pseudo-code:
112 *
113 * orig_value = mem; if (mem == old_value) { mem = new_value; } return
114 * orig_value;
115 *
116 */
117 INLINE AtomicAdjustPosixImpl::Integer AtomicAdjustPosixImpl::
118 compare_and_exchange(TVOLATILE AtomicAdjustPosixImpl::Integer &mem,
119 AtomicAdjustPosixImpl::Integer old_value,
120 AtomicAdjustPosixImpl::Integer new_value) {
121 pthread_mutex_lock(&_mutex);
122 Integer orig_value = mem;
123 if (mem == old_value) {
124 mem = new_value;
125 }
126 pthread_mutex_unlock(&_mutex);
127 return orig_value;
128 }
129
130 /**
131 * Atomic compare and exchange.
132 *
133 * As above, but works on pointers instead of integers.
134 */
135 INLINE AtomicAdjustPosixImpl::Pointer AtomicAdjustPosixImpl::
136 compare_and_exchange_ptr(TVOLATILE AtomicAdjustPosixImpl::Pointer &mem,
137 AtomicAdjustPosixImpl::Pointer old_value,
138 AtomicAdjustPosixImpl::Pointer new_value) {
139 pthread_mutex_lock(&_mutex);
140 Pointer orig_value = mem;
141 if (mem == old_value) {
142 mem = new_value;
143 }
144 pthread_mutex_unlock(&_mutex);
145 return orig_value;
146 }