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