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dekker.one
1/* -*- mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*- */
2/*
3 * Main authors:
4 * Christian Schulte <schulte@gecode.org>
5 *
6 * Copyright:
7 * Christian Schulte, 2017
8 *
9 * This file is part of Gecode, the generic constraint
10 * development environment:
11 * http://www.gecode.org
12 *
13 * Permission is hereby granted, free of charge, to any person obtaining
14 * a copy of this software and associated documentation files (the
15 * "Software"), to deal in the Software without restriction, including
16 * without limitation the rights to use, copy, modify, merge, publish,
17 * distribute, sublicense, and/or sell copies of the Software, and to
18 * permit persons to whom the Software is furnished to do so, subject to
19 * the following conditions:
20 *
21 * The above copyright notice and this permission notice shall be
22 * included in all copies or substantial portions of the Software.
23 *
24 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
25 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
26 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
27 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
28 * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
29 * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
30 * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
31 *
32 */
33
34#include <atomic>
35
36namespace Gecode { namespace Support {
37
38 /// A class for thread-safe reference counting
39 class RefCount {
40 protected:
41 /// The reference count
42 std::atomic_ulong n;
43 public:
44 /// Initialize
45 RefCount(unsigned long int n);
46 /// Increment counter
47 void inc(void);
48 /// Decrement counter and return true if it hits zero
49 bool dec(void);
50 /// Test whether reference count is non-zero
51 operator bool(void) const;
52 };
53
54 forceinline
55 RefCount::RefCount(unsigned long int n0) {
56 n.store(n0,std::memory_order_release);
57 }
58 forceinline void
59 RefCount::inc(void) {
60 (void) n.fetch_add(1U,std::memory_order_relaxed);
61 }
62 forceinline bool
63 RefCount::dec(void) {
64 return n.fetch_sub(1U,std::memory_order_acq_rel) == 1U;
65 }
66 forceinline
67 RefCount::operator bool(void) const {
68 return n.load(std::memory_order_acquire) > 0U;
69 }
70
71}}
72
73// STATISTICS: support-any