vendor/kyua/0.13-a685f91vendor/kyua

1 files changed, 138 insertions, 0 deletions

diff --git a/utils/signals/programmer.cpp b/utils/signals/programmer.cpp
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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);
+    }
+}