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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);
+ }
+}