ceph/src/boost/libs/log/include/boost/log/attributes/counter.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   counter.hpp
   9  * \author Andrey Semashev
  10  * \date   01.05.2007
  11  *
  12  * The header contains implementation of the counter attribute.
  13  */
  14
  15 #ifndef BOOST_LOG_ATTRIBUTES_COUNTER_HPP_INCLUDED_
  16 #define BOOST_LOG_ATTRIBUTES_COUNTER_HPP_INCLUDED_
  17
  18 #include <boost/static_assert.hpp>
  19 #include <boost/type_traits/is_integral.hpp>
  20 #include <boost/log/detail/config.hpp>
  21 #include <boost/log/attributes/attribute.hpp>
  22 #include <boost/log/attributes/attribute_cast.hpp>
  23 #include <boost/log/attributes/attribute_value_impl.hpp>
  24 #ifndef BOOST_LOG_NO_THREADS
  25 #include <boost/memory_order.hpp>
  26 #include <boost/atomic/atomic.hpp>
  27 #endif // BOOST_LOG_NO_THREADS
  28 #include <boost/log/detail/header.hpp>
  29
  30 #ifdef BOOST_HAS_PRAGMA_ONCE
  31 #pragma once
  32 #endif
  33
  34 namespace boost {
  35
  36 BOOST_LOG_OPEN_NAMESPACE
  37
  38 namespace attributes {
  39
  40 /*!
  41  * \brief A class of an attribute that counts an integral value
  42  *
  43  * This attribute acts as a counter - it returns a monotonously
  44  * changing value each time requested. The attribute value type can be specified
  45  * as a template parameter. The type must be an integral type.
  46  */
  47 template< typename T >
  48 class counter :
  49     public attribute
  50 {
  51     BOOST_STATIC_ASSERT_MSG(is_integral< T >::value, "Boost.Log: Only integral types are supported by the counter attribute");
  52
  53 public:
  54     //! A counter value type
  55     typedef T value_type;
  56
  57 protected:
  58     //! Factory implementation
  59     class BOOST_SYMBOL_VISIBLE impl :
  60         public attribute::impl
  61     {
  62     private:
  63 #ifndef BOOST_LOG_NO_THREADS
  64         boost::atomic< value_type > m_counter;
  65 #else
  66         value_type m_counter;
  67 #endif
  68         const value_type m_step;
  69
  70     public:
  71         impl(value_type initial, value_type step) BOOST_NOEXCEPT :
  72             m_counter(initial), m_step(step)
  73         {
  74         }
  75
  76         attribute_value get_value()
  77         {
  78 #ifndef BOOST_LOG_NO_THREADS
  79             value_type value = m_counter.fetch_add(m_step, boost::memory_order_relaxed);
  80 #else
  81             value_type value = m_counter;
  82             m_counter += m_step;
  83 #endif
  84             return make_attribute_value(value);
  85         }
  86     };
  87
  88 public:
  89     /*!
  90      * Constructor
  91      *
  92      * \param initial Initial value of the counter
  93      * \param step Changing step of the counter. Each value acquired from the attribute
  94      *        will be greater than the previous one by this amount.
  95      */
  96     explicit counter(value_type initial = (value_type)0, value_type step = (value_type)1) :
  97         attribute(new impl(initial, step))
  98     {
  99     }
 100
 101     /*!
 102      * Constructor for casting support
 103      */
 104     explicit counter(cast_source const& source) :
 105         attribute(source.as< impl >())
 106     {
 107     }
 108 };
 109
 110 } // namespace attributes
 111
 112 BOOST_LOG_CLOSE_NAMESPACE // namespace log
 113
 114 } // namespace boost
 115
 116 #include <boost/log/detail/footer.hpp>
 117
 118 #endif // BOOST_LOG_ATTRIBUTES_COUNTER_HPP_INCLUDED_