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// Copyright 2010 The Kyua Authors.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the distribution.
// * Neither the name of Google Inc. nor the names of its contributors
// may be used to endorse or promote products derived from this software
// without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#include "utils/signals/programmer.hpp"
extern "C" {
#include <signal.h>
}
#include <cerrno>
#include "utils/format/macros.hpp"
#include "utils/logging/macros.hpp"
#include "utils/noncopyable.hpp"
#include "utils/sanity.hpp"
#include "utils/signals/exceptions.hpp"
namespace utils {
namespace signals {
/// Internal implementation for the signals::programmer class.
struct programmer::impl : utils::noncopyable {
/// The number of the signal managed by this programmer.
int signo;
/// Whether the signal is currently programmed by us or not.
bool programmed;
/// The signal handler that we replaced; to be restored on unprogramming.
struct ::sigaction old_sa;
/// Initializes the internal implementation of the programmer.
///
/// \param signo_ The signal number.
impl(const int signo_) :
signo(signo_),
programmed(false)
{
}
};
} // namespace signals
} // namespace utils
namespace signals = utils::signals;
/// Programs a signal handler.
///
/// \param signo The signal for which to install the handler.
/// \param handler The handler to install.
///
/// \throw signals::system_error If there is an error programming the signal.
signals::programmer::programmer(const int signo, const handler_type handler) :
_pimpl(new impl(signo))
{
struct ::sigaction sa;
sa.sa_handler = handler;
sigemptyset(&sa.sa_mask);
sa.sa_flags = SA_RESTART;
if (::sigaction(_pimpl->signo, &sa, &_pimpl->old_sa) == -1) {
const int original_errno = errno;
throw system_error(F("Could not install handler for signal %s") %
_pimpl->signo, original_errno);
} else
_pimpl->programmed = true;
}
/// Destructor; unprograms the signal handler if still programmed.
///
/// Given that this is a destructor and it can't report errors back to the
/// caller, the caller must attempt to call unprogram() on its own.
signals::programmer::~programmer(void)
{
if (_pimpl->programmed) {
LW("Destroying still-programmed signals::programmer object");
try {
unprogram();
} catch (const system_error& e) {
UNREACHABLE;
}
}
}
/// Unprograms the signal handler.
///
/// \pre The signal handler is programmed (i.e. this can only be called once).
///
/// \throw system_error If unprogramming the signal failed. If this happens,
/// the signal is left programmed, this object forgets about the signal and
/// therefore there is no way to restore the original handler.
void
signals::programmer::unprogram(void)
{
PRE(_pimpl->programmed);
// If we fail, we don't want the destructor to attempt to unprogram the
// handler again, as it would result in a crash.
_pimpl->programmed = false;
if (::sigaction(_pimpl->signo, &_pimpl->old_sa, NULL) == -1) {
const int original_errno = errno;
throw system_error(F("Could not reset handler for signal %s") %
_pimpl->signo, original_errno);
}
}
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