ceph/src/boost/libs/log/include/boost/log/attributes/fallback_policy_fwd.hpp

   1 /*
   2  *          Copyright Andrey Semashev 2007 - 2015.
   3  * Distributed under the Boost Software License, Version 1.0.
   4  *    (See accompanying file LICENSE_1_0.txt or copy at
   5  *          http://www.boost.org/LICENSE_1_0.txt)
   6  */
   7 /*!
   8  * \file   fallback_policy_fwd.hpp
   9  * \author Andrey Semashev
  10  * \date   18.08.2012
  11  *
  12  * The header contains forward declaration of fallback policies when attribute value visitation or extraction fails.
  13  */
  14
  15 #ifndef BOOST_LOG_ATTRIBUTES_FALLBACK_POLICY_FWD_HPP_INCLUDED_
  16 #define BOOST_LOG_ATTRIBUTES_FALLBACK_POLICY_FWD_HPP_INCLUDED_
  17
  18 #include <boost/log/detail/config.hpp>
  19
  20 #ifdef BOOST_HAS_PRAGMA_ONCE
  21 #pragma once
  22 #endif
  23
  24 namespace boost {
  25
  26 BOOST_LOG_OPEN_NAMESPACE
  27
  28 /*!
  29  * The \c fallback_to_none policy results in returning an empty value reference if the attribute value cannot be extracted.
  30  */
  31 struct fallback_to_none;
  32
  33 /*!
  34  * The \c fallback_to_throw policy results in throwing an exception if the attribute value cannot be extracted.
  35  */
  36 struct fallback_to_throw;
  37
  38 /*!
  39  * The \c fallback_to_default policy results in a default value if the attribute value cannot be extracted.
  40  */
  41 template< typename DefaultT >
  42 struct fallback_to_default;
  43
  44 BOOST_LOG_CLOSE_NAMESPACE // namespace log
  45
  46 } // namespace boost
  47
  48 #endif // BOOST_LOG_ATTRIBUTES_FALLBACK_POLICY_FWD_HPP_INCLUDED_