381 lines
16 KiB
C++
381 lines
16 KiB
C++
|
/*
|
||
|
|
* 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 attribute_value.hpp
|
||
|
|
* \author Andrey Semashev
|
||
|
|
* \date 21.05.2010
|
||
|
|
*
|
||
|
|
* The header contains \c attribute_value class definition.
|
||
|
|
*/
|
||
|
|
|
||
|
|
#ifndef BOOST_LOG_ATTRIBUTE_VALUE_HPP_INCLUDED_
|
||
|
|
#define BOOST_LOG_ATTRIBUTE_VALUE_HPP_INCLUDED_
|
||
|
|
|
||
|
|
#include <boost/type_index.hpp>
|
||
|
|
#include <boost/move/core.hpp>
|
||
|
|
#include <boost/smart_ptr/intrusive_ptr.hpp>
|
||
|
|
#include <boost/log/detail/config.hpp>
|
||
|
|
#include <boost/utility/explicit_operator_bool.hpp>
|
||
|
|
#include <boost/log/utility/type_dispatch/type_dispatcher.hpp>
|
||
|
|
#include <boost/log/attributes/attribute.hpp>
|
||
|
|
#include <boost/log/attributes/value_extraction_fwd.hpp>
|
||
|
|
#include <boost/log/attributes/value_visitation_fwd.hpp>
|
||
|
|
#include <boost/log/detail/header.hpp>
|
||
|
|
|
||
|
|
#ifdef BOOST_HAS_PRAGMA_ONCE
|
||
|
|
#pragma once
|
||
|
|
#endif
|
||
|
|
|
||
|
|
namespace boost {
|
||
|
|
|
||
|
|
BOOST_LOG_OPEN_NAMESPACE
|
||
|
|
|
||
|
|
/*!
|
||
|
|
* \brief An attribute value class
|
||
|
|
*
|
||
|
|
* An attribute value is an object that contains a piece of data that represents an attribute state
|
||
|
|
* at the point of the value acquisition. All major operations with log records, such as filtering and
|
||
|
|
* formatting, involve attribute values contained in a single view. Most likely an attribute value is
|
||
|
|
* implemented as a simple holder of some typed value. This holder implements the
|
||
|
|
* \c attribute_value::implementation interface and acts as a pimpl for the \c attribute_value
|
||
|
|
* object. The \c attribute_value class provides type dispatching support in order to allow
|
||
|
|
* to extract the value from the holder.
|
||
|
|
*
|
||
|
|
* Normally, attributes and their values shall be designed in order to exclude as much interference as
|
||
|
|
* reasonable. Such approach allows to have more than one attribute value simultaneously, which improves
|
||
|
|
* scalability and allows to implement generating attributes.
|
||
|
|
*
|
||
|
|
* However, there are cases when this approach does not help to achieve the required level of independency
|
||
|
|
* of attribute values and attribute itself from each other at a reasonable performance tradeoff.
|
||
|
|
* For example, an attribute or its values may use thread-specific data, which is global and shared
|
||
|
|
* between all the instances of the attribute/value. Passing such an attribute value to another thread
|
||
|
|
* would be a disaster. To solve this the library defines an additional method for attribute values,
|
||
|
|
* namely \c detach_from_thread. The \c attribute_value class forwards the call to its pimpl,
|
||
|
|
* which is supposed to ensure that it no longer refers to any thread-specific data after the call.
|
||
|
|
* The pimpl can create a new holder as a result of this method and return it to the \c attribute_value
|
||
|
|
* wrapper, which will keep the returned reference for any further calls.
|
||
|
|
* This method is called for all attribute values that are passed to another thread.
|
||
|
|
*/
|
||
|
|
class attribute_value
|
||
|
|
{
|
||
|
|
BOOST_COPYABLE_AND_MOVABLE(attribute_value)
|
||
|
|
|
||
|
|
public:
|
||
|
|
/*!
|
||
|
|
* \brief A base class for an attribute value implementation
|
||
|
|
*
|
||
|
|
* All attribute value holders should derive from this interface.
|
||
|
|
*/
|
||
|
|
struct BOOST_LOG_NO_VTABLE impl :
|
||
|
|
public attribute::impl
|
||
|
|
{
|
||
|
|
public:
|
||
|
|
/*!
|
||
|
|
* The method dispatches the value to the given object.
|
||
|
|
*
|
||
|
|
* \param dispatcher The object that attempts to dispatch the stored value.
|
||
|
|
* \return true if \a dispatcher was capable to consume the real attribute value type and false otherwise.
|
||
|
|
*/
|
||
|
|
virtual bool dispatch(type_dispatcher& dispatcher) = 0;
|
||
|
|
|
||
|
|
/*!
|
||
|
|
* The method is called when the attribute value is passed to another thread (e.g.
|
||
|
|
* in case of asynchronous logging). The value should ensure it properly owns all thread-specific data.
|
||
|
|
*
|
||
|
|
* \return An actual pointer to the attribute value. It may either point to this object or another.
|
||
|
|
* In the latter case the returned pointer replaces the pointer used by caller to invoke this
|
||
|
|
* method and is considered to be a functional equivalent to the previous pointer.
|
||
|
|
*/
|
||
|
|
virtual intrusive_ptr< impl > detach_from_thread()
|
||
|
|
{
|
||
|
|
return this;
|
||
|
|
}
|
||
|
|
|
||
|
|
/*!
|
||
|
|
* \return The attribute value that refers to self implementation.
|
||
|
|
*/
|
||
|
|
virtual attribute_value get_value() { return attribute_value(this); }
|
||
|
|
|
||
|
|
/*!
|
||
|
|
* \return The attribute value type
|
||
|
|
*/
|
||
|
|
virtual typeindex::type_index get_type() const { return typeindex::type_index(); }
|
||
|
|
};
|
||
|
|
|
||
|
|
private:
|
||
|
|
//! Pointer to the value implementation
|
||
|
|
intrusive_ptr< impl > m_pImpl;
|
||
|
|
|
||
|
|
public:
|
||
|
|
/*!
|
||
|
|
* Default constructor. Creates an empty (absent) attribute value.
|
||
|
|
*/
|
||
|
|
BOOST_DEFAULTED_FUNCTION(attribute_value(), {})
|
||
|
|
|
||
|
|
/*!
|
||
|
|
* Copy constructor
|
||
|
|
*/
|
||
|
|
attribute_value(attribute_value const& that) BOOST_NOEXCEPT : m_pImpl(that.m_pImpl) {}
|
||
|
|
|
||
|
|
/*!
|
||
|
|
* Move constructor
|
||
|
|
*/
|
||
|
|
attribute_value(BOOST_RV_REF(attribute_value) that) BOOST_NOEXCEPT { m_pImpl.swap(that.m_pImpl); }
|
||
|
|
|
||
|
|
/*!
|
||
|
|
* Initializing constructor. Creates an attribute value that refers to the specified holder.
|
||
|
|
*
|
||
|
|
* \param p A pointer to the attribute value holder.
|
||
|
|
*/
|
||
|
|
explicit attribute_value(intrusive_ptr< impl > p) BOOST_NOEXCEPT { m_pImpl.swap(p); }
|
||
|
|
|
||
|
|
/*!
|
||
|
|
* Copy assignment
|
||
|
|
*/
|
||
|
|
attribute_value& operator= (BOOST_COPY_ASSIGN_REF(attribute_value) that) BOOST_NOEXCEPT
|
||
|
|
{
|
||
|
|
m_pImpl = that.m_pImpl;
|
||
|
|
return *this;
|
||
|
|
}
|
||
|
|
|
||
|
|
/*!
|
||
|
|
* Move assignment
|
||
|
|
*/
|
||
|
|
attribute_value& operator= (BOOST_RV_REF(attribute_value) that) BOOST_NOEXCEPT
|
||
|
|
{
|
||
|
|
m_pImpl.swap(that.m_pImpl);
|
||
|
|
return *this;
|
||
|
|
}
|
||
|
|
|
||
|
|
/*!
|
||
|
|
* The operator checks if the attribute value is empty
|
||
|
|
*/
|
||
|
|
BOOST_EXPLICIT_OPERATOR_BOOL_NOEXCEPT()
|
||
|
|
/*!
|
||
|
|
* The operator checks if the attribute value is empty
|
||
|
|
*/
|
||
|
|
bool operator! () const BOOST_NOEXCEPT { return !m_pImpl; }
|
||
|
|
|
||
|
|
/*!
|
||
|
|
* The method returns the type information of the stored value of the attribute.
|
||
|
|
* The returned type info wrapper may be empty if the attribute value is empty or
|
||
|
|
* the information cannot be provided. If the returned value is not empty, the type
|
||
|
|
* can be used for value extraction.
|
||
|
|
*/
|
||
|
|
typeindex::type_index get_type() const
|
||
|
|
{
|
||
|
|
if (m_pImpl.get())
|
||
|
|
return m_pImpl->get_type();
|
||
|
|
else
|
||
|
|
return typeindex::type_index();
|
||
|
|
}
|
||
|
|
|
||
|
|
/*!
|
||
|
|
* The method is called when the attribute value is passed to another thread (e.g.
|
||
|
|
* in case of asynchronous logging). The value should ensure it properly owns all thread-specific data.
|
||
|
|
*
|
||
|
|
* \post The attribute value no longer refers to any thread-specific resources.
|
||
|
|
*/
|
||
|
|
void detach_from_thread()
|
||
|
|
{
|
||
|
|
if (m_pImpl.get())
|
||
|
|
m_pImpl->detach_from_thread().swap(m_pImpl);
|
||
|
|
}
|
||
|
|
|
||
|
|
/*!
|
||
|
|
* The method dispatches the value to the given object. This method is a low level interface for
|
||
|
|
* attribute value visitation and extraction. For typical usage these interfaces may be more convenient.
|
||
|
|
*
|
||
|
|
* \param dispatcher The object that attempts to dispatch the stored value.
|
||
|
|
* \return \c true if the value is not empty and the \a dispatcher was capable to consume
|
||
|
|
* the real attribute value type and \c false otherwise.
|
||
|
|
*/
|
||
|
|
bool dispatch(type_dispatcher& dispatcher) const
|
||
|
|
{
|
||
|
|
if (m_pImpl.get())
|
||
|
|
return m_pImpl->dispatch(dispatcher);
|
||
|
|
else
|
||
|
|
return false;
|
||
|
|
}
|
||
|
|
|
||
|
|
#if !defined(BOOST_LOG_DOXYGEN_PASS)
|
||
|
|
#if !defined(BOOST_NO_CXX11_FUNCTION_TEMPLATE_DEFAULT_ARGS)
|
||
|
|
#define BOOST_LOG_AUX_VOID_DEFAULT = void
|
||
|
|
#else
|
||
|
|
#define BOOST_LOG_AUX_VOID_DEFAULT
|
||
|
|
#endif
|
||
|
|
#endif // !defined(BOOST_LOG_DOXYGEN_PASS)
|
||
|
|
|
||
|
|
/*!
|
||
|
|
* The method attempts to extract the stored value, assuming the value has the specified type.
|
||
|
|
* One can specify either a single type or an MPL type sequence, in which case the stored value
|
||
|
|
* is checked against every type in the sequence.
|
||
|
|
*
|
||
|
|
* \note Include <tt>value_extraction.hpp</tt> prior to using this method.
|
||
|
|
*
|
||
|
|
* \return The extracted value, if the attribute value is not empty and the value is the same
|
||
|
|
* as specified. Otherwise returns an empty value. See description of the \c result_of::extract
|
||
|
|
* metafunction for information on the nature of the result value.
|
||
|
|
*/
|
||
|
|
template< typename T, typename TagT BOOST_LOG_AUX_VOID_DEFAULT >
|
||
|
|
typename result_of::extract< T, TagT >::type extract() const;
|
||
|
|
|
||
|
|
/*!
|
||
|
|
* The method attempts to extract the stored value, assuming the value has the specified type.
|
||
|
|
* One can specify either a single type or an MPL type sequence, in which case the stored value
|
||
|
|
* is checked against every type in the sequence.
|
||
|
|
*
|
||
|
|
* \note Include <tt>value_extraction.hpp</tt> prior to using this method.
|
||
|
|
*
|
||
|
|
* \return The extracted value, if the attribute value is not empty and the value is the same
|
||
|
|
* as specified. Otherwise an exception is thrown. See description of the \c result_of::extract_or_throw
|
||
|
|
* metafunction for information on the nature of the result value.
|
||
|
|
*/
|
||
|
|
template< typename T, typename TagT BOOST_LOG_AUX_VOID_DEFAULT >
|
||
|
|
typename result_of::extract_or_throw< T, TagT >::type extract_or_throw() const;
|
||
|
|
|
||
|
|
/*!
|
||
|
|
* The method attempts to extract the stored value, assuming the value has the specified type.
|
||
|
|
* One can specify either a single type or an MPL type sequence, in which case the stored value
|
||
|
|
* is checked against every type in the sequence. If extraction fails, the default value is returned.
|
||
|
|
*
|
||
|
|
* \note Include <tt>value_extraction.hpp</tt> prior to using this method.
|
||
|
|
*
|
||
|
|
* \param def_value Default value.
|
||
|
|
*
|
||
|
|
* \return The extracted value, if the attribute value is not empty and the value is the same
|
||
|
|
* as specified. Otherwise returns the default value. See description of the \c result_of::extract_or_default
|
||
|
|
* metafunction for information on the nature of the result value.
|
||
|
|
*/
|
||
|
|
template< typename T, typename TagT BOOST_LOG_AUX_VOID_DEFAULT >
|
||
|
|
typename result_of::extract_or_default< T, T, TagT >::type extract_or_default(T const& def_value) const;
|
||
|
|
|
||
|
|
/*!
|
||
|
|
* The method attempts to extract the stored value, assuming the value has the specified type.
|
||
|
|
* One can specify either a single type or an MPL type sequence, in which case the stored value
|
||
|
|
* is checked against every type in the sequence. If extraction fails, the default value is returned.
|
||
|
|
*
|
||
|
|
* \note Include <tt>value_extraction.hpp</tt> prior to using this method.
|
||
|
|
*
|
||
|
|
* \param def_value Default value.
|
||
|
|
*
|
||
|
|
* \return The extracted value, if the attribute value is not empty and the value is the same
|
||
|
|
* as specified. Otherwise returns the default value. See description of the \c result_of::extract_or_default
|
||
|
|
* metafunction for information on the nature of the result value.
|
||
|
|
*/
|
||
|
|
template< typename T, typename TagT BOOST_LOG_AUX_VOID_DEFAULT, typename DefaultT >
|
||
|
|
typename result_of::extract_or_default< T, DefaultT, TagT >::type extract_or_default(DefaultT const& def_value) const;
|
||
|
|
|
||
|
|
#if defined(BOOST_NO_CXX11_FUNCTION_TEMPLATE_DEFAULT_ARGS)
|
||
|
|
/*!
|
||
|
|
* The method attempts to extract the stored value, assuming the value has the specified type.
|
||
|
|
* One can specify either a single type or an MPL type sequence, in which case the stored value
|
||
|
|
* is checked against every type in the sequence.
|
||
|
|
*
|
||
|
|
* \note Include <tt>value_extraction.hpp</tt> prior to using this method.
|
||
|
|
*
|
||
|
|
* \return The extracted value, if the attribute value is not empty and the value is the same
|
||
|
|
* as specified. Otherwise returns an empty value. See description of the \c result_of::extract
|
||
|
|
* metafunction for information on the nature of the result value.
|
||
|
|
*/
|
||
|
|
template< typename T >
|
||
|
|
typename result_of::extract< T >::type extract() const;
|
||
|
|
|
||
|
|
/*!
|
||
|
|
* The method attempts to extract the stored value, assuming the value has the specified type.
|
||
|
|
* One can specify either a single type or an MPL type sequence, in which case the stored value
|
||
|
|
* is checked against every type in the sequence.
|
||
|
|
*
|
||
|
|
* \note Include <tt>value_extraction.hpp</tt> prior to using this method.
|
||
|
|
*
|
||
|
|
* \return The extracted value, if the attribute value is not empty and the value is the same
|
||
|
|
* as specified. Otherwise an exception is thrown. See description of the \c result_of::extract_or_throw
|
||
|
|
* metafunction for information on the nature of the result value.
|
||
|
|
*/
|
||
|
|
template< typename T >
|
||
|
|
typename result_of::extract_or_throw< T >::type extract_or_throw() const;
|
||
|
|
|
||
|
|
/*!
|
||
|
|
* The method attempts to extract the stored value, assuming the value has the specified type.
|
||
|
|
* One can specify either a single type or an MPL type sequence, in which case the stored value
|
||
|
|
* is checked against every type in the sequence. If extraction fails, the default value is returned.
|
||
|
|
*
|
||
|
|
* \note Include <tt>value_extraction.hpp</tt> prior to using this method.
|
||
|
|
*
|
||
|
|
* \param def_value Default value.
|
||
|
|
*
|
||
|
|
* \return The extracted value, if the attribute value is not empty and the value is the same
|
||
|
|
* as specified. Otherwise returns the default value. See description of the \c result_of::extract_or_default
|
||
|
|
* metafunction for information on the nature of the result value.
|
||
|
|
*/
|
||
|
|
template< typename T >
|
||
|
|
typename result_of::extract_or_default< T, T >::type extract_or_default(T const& def_value) const;
|
||
|
|
|
||
|
|
/*!
|
||
|
|
* The method attempts to extract the stored value, assuming the value has the specified type.
|
||
|
|
* One can specify either a single type or an MPL type sequence, in which case the stored value
|
||
|
|
* is checked against every type in the sequence. If extraction fails, the default value is returned.
|
||
|
|
*
|
||
|
|
* \note Include <tt>value_extraction.hpp</tt> prior to using this method.
|
||
|
|
*
|
||
|
|
* \param def_value Default value.
|
||
|
|
*
|
||
|
|
* \return The extracted value, if the attribute value is not empty and the value is the same
|
||
|
|
* as specified. Otherwise returns the default value. See description of the \c result_of::extract_or_default
|
||
|
|
* metafunction for information on the nature of the result value.
|
||
|
|
*/
|
||
|
|
template< typename T, typename DefaultT >
|
||
|
|
typename result_of::extract_or_default< T, DefaultT >::type extract_or_default(DefaultT const& def_value) const;
|
||
|
|
#endif // defined(BOOST_NO_CXX11_FUNCTION_TEMPLATE_DEFAULT_ARGS)
|
||
|
|
|
||
|
|
#undef BOOST_LOG_AUX_VOID_DEFAULT
|
||
|
|
|
||
|
|
/*!
|
||
|
|
* The method attempts to extract the stored value, assuming the value has the specified type,
|
||
|
|
* and pass it to the \a visitor function object.
|
||
|
|
* One can specify either a single type or an MPL type sequence, in which case the stored value
|
||
|
|
* is checked against every type in the sequence.
|
||
|
|
*
|
||
|
|
* \note Include <tt>value_visitation.hpp</tt> prior to using this method.
|
||
|
|
*
|
||
|
|
* \param visitor A function object that will be invoked on the extracted attribute value.
|
||
|
|
* The visitor should be capable to be called with a single argument of
|
||
|
|
* any type of the specified types in \c T.
|
||
|
|
*
|
||
|
|
* \return The result of visitation.
|
||
|
|
*/
|
||
|
|
template< typename T, typename VisitorT >
|
||
|
|
visitation_result visit(VisitorT visitor) const;
|
||
|
|
|
||
|
|
/*!
|
||
|
|
* The method swaps two attribute values
|
||
|
|
*/
|
||
|
|
void swap(attribute_value& that) BOOST_NOEXCEPT
|
||
|
|
{
|
||
|
|
m_pImpl.swap(that.m_pImpl);
|
||
|
|
}
|
||
|
|
};
|
||
|
|
|
||
|
|
/*!
|
||
|
|
* The function swaps two attribute values
|
||
|
|
*/
|
||
|
|
inline void swap(attribute_value& left, attribute_value& right) BOOST_NOEXCEPT
|
||
|
|
{
|
||
|
|
left.swap(right);
|
||
|
|
}
|
||
|
|
|
||
|
|
BOOST_LOG_CLOSE_NAMESPACE // namespace log
|
||
|
|
|
||
|
|
} // namespace boost
|
||
|
|
|
||
|
|
#include <boost/log/detail/footer.hpp>
|
||
|
|
#if defined(BOOST_LOG_ATTRIBUTES_ATTRIBUTE_HPP_INCLUDED_)
|
||
|
|
#include <boost/log/detail/attribute_get_value_impl.hpp>
|
||
|
|
#endif
|
||
|
|
|
||
|
|
#endif // BOOST_LOG_ATTRIBUTE_VALUE_HPP_INCLUDED_
|