ceph/src/boost/libs/log/include/boost/log/attributes/attribute_cast.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   attribute_cast.hpp
   9  * \author Andrey Semashev
  10  * \date   06.08.2010
  11  *
  12  * The header contains utilities for casting between attribute factories.
  13  */
  14
  15 #ifndef BOOST_LOG_ATTRIBUTES_ATTRIBUTE_CAST_HPP_INCLUDED_
  16 #define BOOST_LOG_ATTRIBUTES_ATTRIBUTE_CAST_HPP_INCLUDED_
  17
  18 #include <boost/log/detail/config.hpp>
  19 #include <boost/log/attributes/attribute.hpp>
  20 #include <boost/log/detail/header.hpp>
  21
  22 #ifdef BOOST_HAS_PRAGMA_ONCE
  23 #pragma once
  24 #endif
  25
  26 namespace boost {
  27
  28 BOOST_LOG_OPEN_NAMESPACE
  29
  30 namespace attributes {
  31
  32 /*!
  33  * The class holds a reference to the attribute factory implementation being casted
  34  */
  35 class cast_source
  36 {
  37 private:
  38     attribute::impl* m_pImpl;
  39
  40 public:
  41     /*!
  42      * Initializing constructor. Creates a source that refers to the specified factory implementation.
  43      */
  44     explicit cast_source(attribute::impl* p) : m_pImpl(p)
  45     {
  46     }
  47
  48     /*!
  49      * The function attempts to cast the aggregated pointer to the implementation to the specified type.
  50      *
  51      * \return The converted pointer or \c NULL, if the conversion fails.
  52      */
  53     template< typename T >
  54     T* as() const { return dynamic_cast< T* >(m_pImpl); }
  55 };
  56
  57 } // namespace attributes
  58
  59 /*!
  60  * The function casts one attribute factory to another
  61  */
  62 template< typename T >
  63 inline T attribute_cast(attribute const& attr)
  64 {
  65     return T(attributes::cast_source(attr.get_impl()));
  66 }
  67
  68 BOOST_LOG_CLOSE_NAMESPACE // namespace log
  69
  70 } // namespace boost
  71
  72 #include <boost/log/detail/footer.hpp>
  73
  74 #endif // BOOST_LOG_ATTRIBUTES_ATTRIBUTE_CAST_HPP_INCLUDED_