process-cpp  3.0.0
A simple convenience library for handling processes in C++11.
cross_process_sync.cpp
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1 /*
2  * Copyright © 2013 Canonical Ltd.
3  *
4  * This program is free software: you can redistribute it and/or modify
5  * it under the terms of the GNU General Public License version 3 as
6  * published by the Free Software Foundation.
7  *
8  * This program is distributed in the hope that it will be useful,
9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
11  * GNU General Public License for more details.
12  *
13  * You should have received a copy of the GNU General Public License
14  * along with this program. If not, see <http://www.gnu.org/licenses/>.
15  *
16  * Authored by: Thomas Voss <thomas.voss@canonical.com>
17  */
18 
20 
21 #include <system_error>
22 
23 #include <poll.h>
24 #include <unistd.h>
25 
26 namespace
27 {
28 const int read_fd = 0;
29 const int write_fd = 1;
30 }
31 
33 {
34  if (::pipe(fds) < 0)
35  throw std::system_error(errno, std::system_category());
36 }
37 
39 {
40  fds[0] = ::dup(rhs.fds[0]);
41  fds[1] = ::dup(rhs.fds[1]);
42 }
43 
45 {
46  ::close(fds[0]);
47  ::close(fds[1]);
48 }
49 
51 {
52  ::close(fds[0]);
53  ::close(fds[1]);
54  fds[0] = ::dup(rhs.fds[0]);
55  fds[1] = ::dup(rhs.fds[1]);
56 
57  counter = rhs.counter;
58 
59  return *this;
60 }
61 
62 void core::testing::CrossProcessSync::try_signal_ready_for(const std::chrono::milliseconds& duration)
63 {
64  static const short empty_revents = 0;
65  pollfd poll_fd[1] = { { fds[write_fd], POLLOUT, empty_revents } };
66  int rc = -1;
67 
68  if ((rc = ::poll(poll_fd, 1, duration.count())) < 0)
69  throw std::system_error(errno, std::system_category());
70  else if (rc == 0)
71  throw Error::Timeout{};
72 
73  static const std::uint32_t value = 1;
74  if (sizeof(value) != write(fds[write_fd], std::addressof(value), sizeof(value)))
75  throw std::system_error(errno, std::system_category());
76 }
77 
78 std::uint32_t core::testing::CrossProcessSync::wait_for_signal_ready_for(const std::chrono::milliseconds& duration)
79 {
80  static const short empty_revents = 0;
81  pollfd poll_fd[1] = { { fds[read_fd], POLLIN, empty_revents } };
82  int rc = -1;
83 
84  if ((rc = ::poll(poll_fd, 1, duration.count())) < 0)
85  throw std::system_error(errno, std::system_category());
86  else if (rc == 0)
87  throw Error::Timeout{};
88 
89  std::uint32_t value = 0;
90  if (sizeof(value) != read(fds[read_fd], std::addressof(value), sizeof(value)))
91  throw std::system_error(errno, std::system_category());
92 
93  if (value != 1)
94  throw std::system_error(errno, std::system_category());
95 
96  counter += value;
97 
98  return counter;
99 }
CrossProcessSync & operator=(const CrossProcessSync &rhs)
operator =, dup&#39;s the underlying fds.
A cross-process synchronization primitive that supports simple wait-condition-like scenarios...
~CrossProcessSync() noexcept
Closes the underlying fds.
void try_signal_ready_for(const std::chrono::milliseconds &duration)
Try to signal the other side that we are ready for at most duration milliseconds. ...
CrossProcessSync()
Constructs a new sync element.
std::uint32_t wait_for_signal_ready_for(const std::chrono::milliseconds &duration)
Wait for the other sides to signal readiness for at most duration milliseconds.
Thrown if any of the *_for functions times out.