Alexandria  2.22.0
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SemaphorePosix.icpp
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1 /*
2  * Copyright (C) 2012-2021 Euclid Science Ground Segment
3  *
4  * This library is free software; you can redistribute it and/or modify it under
5  * the terms of the GNU Lesser General Public License as published by the Free
6  * Software Foundation; either version 3.0 of the License, or (at your option)
7  * any later version.
8  *
9  * This library is distributed in the hope that it will be useful, but WITHOUT
10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
11  * FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
12  * details.
13  *
14  * You should have received a copy of the GNU Lesser General Public License
15  * along with this library; if not, write to the Free Software Foundation, Inc.,
16  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
17  */
18 
19 #include <cerrno>
20 #include <semaphore.h>
21 #include <system_error>
22 
23 namespace Euclid {
24 class Semaphore::SemaphoreImpl {
25 public:
26  explicit SemaphoreImpl(unsigned int i) {
27  if (sem_init(&m_semaphore, 0, i) < 0) {
28  throw std::system_error(errno, std::system_category());
29  }
30  }
31 
32  ~SemaphoreImpl() {
33  sem_destroy(&m_semaphore);
34  }
35 
36  void post() {
37  if (sem_post(&m_semaphore) < 0) {
38  throw std::system_error(errno, std::system_category());
39  }
40  }
41 
42  void wait() {
43  if (sem_wait(&m_semaphore) != 0) {
44  throw std::system_error(errno, std::system_category());
45  }
46  }
47 
48  bool try_acquire() {
49  if (sem_trywait(&m_semaphore) == 0) {
50  return true;
51  }
52  if (errno == EAGAIN) {
53  return false;
54  }
55  throw std::system_error(errno, std::system_category());
56  }
57 
58  bool try_acquire_until(std::chrono::system_clock::time_point abs_time) {
59  using std::chrono::time_point_cast;
60  auto seconds = time_point_cast<std::chrono::seconds>(abs_time);
61  auto nseconds =
62  time_point_cast<std::chrono::nanoseconds>(abs_time) - time_point_cast<std::chrono::nanoseconds>(seconds);
63 
64  struct timespec timeout;
65  timeout.tv_sec = seconds.time_since_epoch().count();
66  timeout.tv_nsec = nseconds.count();
67  if (sem_timedwait(&m_semaphore, &timeout) == 0) {
68  return true;
69  }
70  if (errno == ETIMEDOUT) {
71  return false;
72  }
73  throw std::system_error(errno, std::system_category());
74  }
75 
76 private:
77  sem_t m_semaphore;
78 };
79 } // namespace Euclid