boost/log/attributes/counter.hpp
/*
* Copyright Andrey Semashev 2007 - 2015.
* 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)
*/
/*!
* \file counter.hpp
* \author Andrey Semashev
* \date 01.05.2007
*
* The header contains implementation of the counter attribute.
*/
#ifndef BOOST_LOG_ATTRIBUTES_COUNTER_HPP_INCLUDED_
#define BOOST_LOG_ATTRIBUTES_COUNTER_HPP_INCLUDED_
#include <boost/type_traits/is_integral.hpp>
#include <boost/log/detail/config.hpp>
#include <boost/log/attributes/attribute.hpp>
#include <boost/log/attributes/attribute_cast.hpp>
#include <boost/log/attributes/attribute_value_impl.hpp>
#ifndef BOOST_LOG_NO_THREADS
#include <boost/memory_order.hpp>
#include <boost/atomic/atomic.hpp>
#endif // BOOST_LOG_NO_THREADS
#include <boost/log/detail/header.hpp>
#ifdef BOOST_HAS_PRAGMA_ONCE
#pragma once
#endif
namespace boost {
BOOST_LOG_OPEN_NAMESPACE
namespace attributes {
/*!
* \brief A class of an attribute that counts an integral value
*
* This attribute acts as a counter - it returns a monotonously
* changing value each time requested. The attribute value type can be specified
* as a template parameter. The type must be an integral type.
*/
template< typename T >
class counter :
public attribute
{
static_assert(is_integral< T >::value, "Boost.Log: Only integral types are supported by the counter attribute");
public:
//! A counter value type
typedef T value_type;
protected:
//! Factory implementation
class BOOST_SYMBOL_VISIBLE impl :
public attribute::impl
{
private:
#ifndef BOOST_LOG_NO_THREADS
boost::atomic< value_type > m_counter;
#else
value_type m_counter;
#endif
const value_type m_step;
public:
impl(value_type initial, value_type step) BOOST_NOEXCEPT :
m_counter(initial), m_step(step)
{
}
attribute_value get_value()
{
#ifndef BOOST_LOG_NO_THREADS
value_type value = m_counter.fetch_add(m_step, boost::memory_order_relaxed);
#else
value_type value = m_counter;
m_counter += m_step;
#endif
return make_attribute_value(value);
}
};
public:
/*!
* Constructor
*
* \param initial Initial value of the counter
* \param step Changing step of the counter. Each value acquired from the attribute
* will be greater than the previous one by this amount.
*/
explicit counter(value_type initial = (value_type)0, value_type step = (value_type)1) :
attribute(new impl(initial, step))
{
}
/*!
* Constructor for casting support
*/
explicit counter(cast_source const& source) :
attribute(source.as< impl >())
{
}
};
} // namespace attributes
BOOST_LOG_CLOSE_NAMESPACE // namespace log
} // namespace boost
#include <boost/log/detail/footer.hpp>
#endif // BOOST_LOG_ATTRIBUTES_COUNTER_HPP_INCLUDED_