Boost C++ Libraries

boost/system/detail/error_category_impl.hpp

#ifndef BOOST_SYSTEM_DETAIL_ERROR_CATEGORY_IMPL_HPP_INCLUDED
#define BOOST_SYSTEM_DETAIL_ERROR_CATEGORY_IMPL_HPP_INCLUDED

//  Copyright Beman Dawes 2006, 2007
//  Copyright Christoper Kohlhoff 2007
//  Copyright Peter Dimov 2017, 2018
//
//  Distributed under the Boost Software License, Version 1.0. (See accompanying
//  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//
//  See library home page at http://www.boost.org/libs/system

#include <boost/system/detail/error_category.hpp>
#include <boost/system/detail/error_condition.hpp>
#include <boost/system/detail/error_code.hpp>
#include <boost/system/detail/snprintf.hpp>
#include <boost/system/detail/config.hpp>
#include <boost/config.hpp>
#include <string>
#include <cstring>

namespace boost
{
namespace system
{

// error_category default implementation

inline error_condition error_category::default_error_condition( int ev ) const BOOST_NOEXCEPT
{
    return error_condition( ev, *this );
}

inline bool error_category::equivalent( int code, const error_condition & condition ) const BOOST_NOEXCEPT
{
    return default_error_condition( code ) == condition;
}

inline bool error_category::equivalent( const error_code & code, int condition ) const BOOST_NOEXCEPT
{
    return code.equals( condition, *this );
}

inline char const * error_category::message( int ev, char * buffer, std::size_t len ) const BOOST_NOEXCEPT
{
    if( len == 0 )
    {
        return buffer;
    }

    if( len == 1 )
    {
        buffer[0] = 0;
        return buffer;
    }

#if !defined(BOOST_NO_EXCEPTIONS)
    try
#endif
    {
        std::string m = this->message( ev );

# if defined( BOOST_MSVC )
#  pragma warning( push )
#  pragma warning( disable: 4996 )
# elif defined(__clang__) && defined(__has_warning)
#  pragma clang diagnostic push
#  if __has_warning("-Wdeprecated-declarations")
#   pragma clang diagnostic ignored "-Wdeprecated-declarations"
#  endif
# endif

        std::strncpy( buffer, m.c_str(), len - 1 );
        buffer[ len-1 ] = 0;

# if defined( BOOST_MSVC )
#  pragma warning( pop )
# elif defined(__clang__) && defined(__has_warning)
#  pragma clang diagnostic pop
# endif

        return buffer;
    }
#if !defined(BOOST_NO_EXCEPTIONS)
    catch( ... )
    {
        detail::snprintf( buffer, len, "No message text available for error %d", ev );
        return buffer;
    }
#endif
}

} // namespace system
} // namespace boost

// interoperability with std::error_code, std::error_condition

#if defined(BOOST_SYSTEM_HAS_SYSTEM_ERROR)

#include <boost/system/detail/std_category.hpp>

namespace boost
{
namespace system
{

inline error_category::operator std::error_category const & () const
{
    if( id_ == detail::generic_category_id )
    {
// This condition must be the same as the one in error_condition.hpp
#if defined(BOOST_SYSTEM_AVOID_STD_GENERIC_CATEGORY)

    static const boost::system::detail::std_category generic_instance( this, 0x1F4D3 );
    return generic_instance;

#else

    return std::generic_category();

#endif
    }

    if( id_ == detail::system_category_id )
    {
// This condition must be the same as the one in error_code.hpp
#if defined(BOOST_SYSTEM_AVOID_STD_SYSTEM_CATEGORY)

    static const boost::system::detail::std_category system_instance( this, 0x1F4D7 );
    return system_instance;

#else

    return std::system_category();

#endif
    }

    detail::std_category* p = ps_.load( std::memory_order_acquire );

    if( p != 0 )
    {
        return *p;
    }

    // One `std_category` object is allocated for every
    // user-defined `error_category` that is converted to
    // `std::error_category`.
    //
    // This one-time allocation will show up on leak checkers.
    // That's unavoidable. There is no way to deallocate the
    // `std_category` object because first, `error_category`
    // is a literal type (so it can't have a destructor) and
    // second, `error_category` needs to be usable during program
    // shutdown.
    //
    // https://github.com/boostorg/system/issues/78

    detail::std_category* q = new detail::std_category( this, 0 );

    if( ps_.compare_exchange_strong( p, q, std::memory_order_release, std::memory_order_acquire ) )
    {
        return *q;
    }
    else
    {
        delete q;
        return *p;
    }
}

} // namespace system
} // namespace boost

#endif // #if defined(BOOST_SYSTEM_HAS_SYSTEM_ERROR)

#endif // #ifndef BOOST_SYSTEM_DETAIL_ERROR_CATEGORY_IMPL_HPP_INCLUDED