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// ossig.h - written and placed in the public domain by Jeffrey Walton
//
/// \file ossig.h
/// \brief Utility class for trapping OS signals.
/// \since Crypto++ 5.6.5
#ifndef CRYPTOPP_OS_SIGNAL_H
#define CRYPTOPP_OS_SIGNAL_H
#include "config.h"
#if defined(UNIX_SIGNALS_AVAILABLE)
# include <signal.h>
#endif
NAMESPACE_BEGIN(CryptoPP)
// ************** Unix and Linux compatibles ***************
#if defined(UNIX_SIGNALS_AVAILABLE) || defined(CRYPTOPP_DOXYGEN_PROCESSING)
/// \brief Signal handler function pointer
/// \details SignalHandlerFn is provided as a stand alone function pointer with external "C" linkage
/// \sa SignalHandler, NullSignalHandler
extern "C" {
typedef void (*SignalHandlerFn) (int);
}
/// \brief Null signal handler function
/// \param unused the signal number
/// \details NullSignalHandler is provided as a stand alone function with external "C" linkage
/// and not a static member function due to the member function's implicit
/// external "C++" linkage.
/// \sa SignalHandler, SignalHandlerFn
extern "C" {
inline void NullSignalHandler(int unused) {CRYPTOPP_UNUSED(unused);}
}
/// Signal handler for Linux and Unix compatibles
/// \tparam S Signal number
/// \tparam O Flag indicating if an existing handler should be overwritten
/// \details SignalHandler() can be used to install a signal handler with the signature
/// <tt>void handler_fn(int)</tt>. If <tt>SignalHandlerFn</tt> is not <tt>NULL</tt>, then
/// the sigaction is set to the function and the sigaction flags is set to the flags.
/// If <tt>SignalHandlerFn</tt> is <tt>NULL</tt>, then a default handler is installed
/// using sigaction flags set to 0. The default handler only returns from the call.
/// \details Upon destruction the previous signal handler is restored if the former signal handler
/// was replaced.
/// \details On Cygwin systems using Newlib, you should define <tt>_XOPEN_SOURCE=700</tt> or
/// <tt>_GNU_SOURCE</tt>; or use <tt>-std=gnu++03</tt>, <tt>-std=gnu++11</tt>, or similar. If
/// you compile with <tt>-std=c++03</tt>, <tt>-std=c++11</tt> or similar, then define
/// <tt>_XOPEN_SOURCE=700</tt>.
/// \warning Do not use SignalHandler in a code block that uses <tt>setjmp</tt> or <tt>longjmp</tt>
/// because the destructor may not run.
/// \since Crypto++ 5.6.5
/// \sa NullSignalHandler, SignalHandlerFn, \ref CRYPTOPP_ASSERT "CRYPTOPP_ASSERT", DebugTrapHandler
template <int S, bool O=false>
struct SignalHandler
{
/// \brief Construct a signal handler
/// \param pfn Pointer to a signal handler function
/// \param flags Flags to use with the signal handler
/// \details SignalHandler() installs a signal handler with the signature
/// <tt>void handler_fn(int)</tt>. If <tt>SignalHandlerFn</tt> is not <tt>NULL</tt>, then
/// the sigaction is set to the function and the sigaction flags is set to the flags.
/// If <tt>SignalHandlerFn</tt> is <tt>NULL</tt>, then a default handler is installed
/// using sigaction flags set to 0. The default handler only returns from the call.
/// \details Upon destruction the previous signal handler is restored if the former signal handler
/// was overwritten.
/// \details On Cygwin systems using Newlib, you should define <tt>_XOPEN_SOURCE=700</tt> or
/// <tt>_GNU_SOURCE</tt>; or use <tt>-std=gnu++03</tt>, <tt>-std=gnu++11</tt>, or similar. If
/// you compile with <tt>-std=c++03</tt>, <tt>-std=c++11</tt> or similar, then define
/// <tt>_XOPEN_SOURCE=700</tt>.
/// \warning Do not use SignalHandler in a code block that uses <tt>setjmp</tt> or <tt>longjmp</tt>
/// because the destructor may not run. <tt>setjmp</tt> is why cpu.cpp does not use SignalHandler
/// during CPU feature testing.
/// \since Crypto++ 5.6.5
SignalHandler(SignalHandlerFn pfn = NULLPTR, int flags = 0) : m_installed(false)
{
// http://pubs.opengroup.org/onlinepubs/007908799/xsh/sigaction.html
struct sigaction new_handler;
do
{
int ret = 0;
ret = sigaction (S, 0, &m_old);
if (ret != 0) break; // Failed
// Don't step on another's handler if Overwrite=false
if (m_old.sa_handler != 0 && !O) break;
// Cygwin/Newlib requires -D_XOPEN_SOURCE=700
ret = sigemptyset (&new_handler.sa_mask);
if (ret != 0) break; // Failed
new_handler.sa_handler = (pfn ? pfn : &NullSignalHandler);
new_handler.sa_flags = (pfn ? flags : 0);
// Install it
ret = sigaction (S, &new_handler, 0);
if (ret != 0) break; // Failed
m_installed = true;
} while(0);
}
~SignalHandler()
{
if (m_installed)
sigaction (S, &m_old, 0);
}
private:
struct sigaction m_old;
bool m_installed;
private:
// Not copyable
SignalHandler(const SignalHandler &);
void operator=(const SignalHandler &);
};
#endif
NAMESPACE_END
#endif // CRYPTOPP_OS_SIGNAL_H
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