cross_process_sync.cpp
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/*
* Copyright © 2013 Canonical Ltd.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 3 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* Authored by: Thomas Voss <thomas.voss@canonical.com>
*/
#include <core/testing/cross_process_sync.h>
#include <system_error>
#include <poll.h>
#include <unistd.h>
namespace
{
const int read_fd = 0;
const int write_fd = 1;
}
core::testing::CrossProcessSync::CrossProcessSync() : counter(0)
{
if (::pipe(fds) < 0)
throw std::system_error(errno, std::system_category());
}
core::testing::CrossProcessSync::CrossProcessSync(const CrossProcessSync& rhs) : counter(rhs.counter)
{
fds[0] = ::dup(rhs.fds[0]);
fds[1] = ::dup(rhs.fds[1]);
}
core::testing::CrossProcessSync::~CrossProcessSync() noexcept
{
::close(fds[0]);
::close(fds[1]);
}
core::testing::CrossProcessSync& core::testing::CrossProcessSync::operator=(const core::testing::CrossProcessSync& rhs)
{
::close(fds[0]);
::close(fds[1]);
fds[0] = ::dup(rhs.fds[0]);
fds[1] = ::dup(rhs.fds[1]);
counter = rhs.counter;
return *this;
}
void core::testing::CrossProcessSync::try_signal_ready_for(const std::chrono::milliseconds& duration)
{
static const short empty_revents = 0;
pollfd poll_fd[1] = { { fds[write_fd], POLLOUT, empty_revents } };
int rc = -1;
if ((rc = ::poll(poll_fd, 1, duration.count())) < 0)
throw std::system_error(errno, std::system_category());
else if (rc == 0)
throw Error::Timeout{};
static const std::uint32_t value = 1;
if (sizeof(value) != write(fds[write_fd], std::addressof(value), sizeof(value)))
throw std::system_error(errno, std::system_category());
}
std::uint32_t core::testing::CrossProcessSync::wait_for_signal_ready_for(const std::chrono::milliseconds& duration)
{
static const short empty_revents = 0;
pollfd poll_fd[1] = { { fds[read_fd], POLLIN, empty_revents } };
int rc = -1;
if ((rc = ::poll(poll_fd, 1, duration.count())) < 0)
throw std::system_error(errno, std::system_category());
else if (rc == 0)
throw Error::Timeout{};
std::uint32_t value = 0;
if (sizeof(value) != read(fds[read_fd], std::addressof(value), sizeof(value)))
throw std::system_error(errno, std::system_category());
if (value != 1)
throw std::system_error(errno, std::system_category());
counter += value;
return counter;
}
core::testing::CrossProcessSync
A cross-process synchronization primitive that supports simple wait-condition-like scenarios.
Definition: cross_process_sync.h:36
core::testing::CrossProcessSync::operator=
CrossProcessSync & operator=(const CrossProcessSync &rhs)
operator =, dup's the underlying fds.
Definition: cross_process_sync.cpp:50
core::testing::CrossProcessSync::try_signal_ready_for
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.
Definition: cross_process_sync.cpp:62
core::testing::CrossProcessSync::~CrossProcessSync
~CrossProcessSync() noexcept
Closes the underlying fds.
Definition: cross_process_sync.cpp:44
core::testing::CrossProcessSync::Error::Timeout
Thrown if any of the *_for functions times out.
Definition: cross_process_sync.h:47
core::testing::CrossProcessSync::CrossProcessSync
CrossProcessSync()
Constructs a new sync element.
Definition: cross_process_sync.cpp:32
cross_process_sync.h
core::testing::CrossProcessSync::wait_for_signal_ready_for
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.
Definition: cross_process_sync.cpp:78