boost/log/attributes/value_extraction.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 value_extraction.hpp
* \author Andrey Semashev
* \date 01.03.2008
*
* The header contains implementation of tools for extracting an attribute value
* from the view.
*/
#ifndef BOOST_LOG_ATTRIBUTES_VALUE_EXTRACTION_HPP_INCLUDED_
#define BOOST_LOG_ATTRIBUTES_VALUE_EXTRACTION_HPP_INCLUDED_
#include <boost/mpl/vector.hpp>
#include <boost/mpl/joint_view.hpp>
#include <boost/mpl/if.hpp>
#include <boost/mpl/eval_if.hpp>
#include <boost/mpl/identity.hpp>
#include <boost/mpl/is_sequence.hpp>
#include <boost/mpl/contains.hpp>
#include <boost/mpl/push_back.hpp>
#include <boost/type_traits/is_same.hpp>
#include <boost/utility/enable_if.hpp>
#include <boost/log/detail/config.hpp>
#include <boost/log/exceptions.hpp>
#include <boost/log/core/record.hpp>
#include <boost/log/attributes/attribute_name.hpp>
#include <boost/log/attributes/attribute_value.hpp>
#include <boost/log/attributes/attribute.hpp>
#include <boost/log/attributes/attribute_value_set.hpp>
#include <boost/log/attributes/value_extraction_fwd.hpp>
#include <boost/log/attributes/fallback_policy.hpp>
#include <boost/log/expressions/keyword_fwd.hpp>
#include <boost/log/utility/value_ref.hpp>
#include <boost/log/utility/type_dispatch/static_type_dispatcher.hpp>
#include <boost/log/detail/header.hpp>
#ifdef BOOST_HAS_PRAGMA_ONCE
#pragma once
#endif
namespace boost {
BOOST_LOG_OPEN_NAMESPACE
namespace result_of {
/*!
* \brief A metafunction that allows to acquire the result of the value extraction
*
* The metafunction results in a type that is in form of <tt>T const&</tt>, if \c T is
* not an MPL type sequence and <tt>DefaultT</tt> is the same as <tt>T</tt>,
* or <tt>value_ref< TypesT, TagT ></tt> otherwise, with
* \c TypesT being a type sequence comprising the types from sequence \c T and \c DefaultT,
* if it is not present in \c T already.
*/
template< typename T, typename DefaultT, typename TagT >
struct extract_or_default
{
typedef typename mpl::eval_if<
mpl::is_sequence< T >,
mpl::eval_if<
mpl::contains< T, DefaultT >,
mpl::identity< T >,
mpl::push_back< T, DefaultT >
>,
mpl::if_<
is_same< T, DefaultT >,
T,
mpl::vector2< T, DefaultT >
>
>::type extracted_type;
typedef typename mpl::if_<
mpl::is_sequence< extracted_type >,
value_ref< extracted_type, TagT >,
extracted_type const&
>::type type;
};
/*!
* \brief A metafunction that allows to acquire the result of the value extraction
*
* The metafunction results in a type that is in form of <tt>T const&</tt>, if \c T is
* not an MPL type sequence, or <tt>value_ref< T, TagT ></tt> otherwise. In the latter
* case the value reference shall never be empty.
*/
template< typename T, typename TagT >
struct extract_or_throw
{
typedef typename mpl::if_<
mpl::is_sequence< T >,
value_ref< T, TagT >,
T const&
>::type type;
};
/*!
* \brief A metafunction that allows to acquire the result of the value extraction
*
* The metafunction results in a type that is in form of <tt>value_ref< T, TagT ></tt>.
*/
template< typename T, typename TagT >
struct extract
{
typedef value_ref< T, TagT > type;
};
} // namespace result_of
namespace aux {
//! The function object initializes the value reference
template< typename RefT >
struct value_ref_initializer
{
typedef void result_type;
value_ref_initializer(RefT& ref) : m_ref(ref)
{
}
template< typename ArgT >
result_type operator() (ArgT const& arg) const
{
m_ref = RefT(arg);
}
private:
RefT& m_ref;
};
//! The function unwraps \c value_ref, if possible
template< typename T, typename TagT >
BOOST_FORCEINLINE typename enable_if< mpl::is_sequence< T >, value_ref< T, TagT > >::type
unwrap_value_ref(value_ref< T, TagT > const& r)
{
return r;
}
template< typename T, typename TagT >
BOOST_FORCEINLINE typename disable_if< mpl::is_sequence< T >, T const& >::type
unwrap_value_ref(value_ref< T, TagT > const& r)
{
return r.get();
}
} // namespace aux
/*!
* \brief Generic attribute value extractor
*
* Attribute value extractor is a functional object that attempts to find and extract the stored
* attribute value from the attribute values view or a log record. The extracted value is returned
* from the extractor.
*/
template< typename T, typename FallbackPolicyT, typename TagT >
class value_extractor :
private FallbackPolicyT
{
public:
//! Fallback policy
typedef FallbackPolicyT fallback_policy;
//! Attribute value types
typedef T value_type;
//! Function object result type
typedef value_ref< value_type, TagT > result_type;
public:
/*!
* Default constructor
*/
BOOST_DEFAULTED_FUNCTION(value_extractor(), {})
/*!
* Copy constructor
*/
value_extractor(value_extractor const& that) : fallback_policy(static_cast< fallback_policy const& >(that))
{
}
/*!
* Constructor
*
* \param arg Fallback policy constructor argument
*/
template< typename U >
explicit value_extractor(U const& arg) : fallback_policy(arg) {}
/*!
* Extraction operator. Attempts to acquire the stored value of one of the supported types. If extraction succeeds,
* the extracted value is returned.
*
* \param attr The attribute value to extract from.
* \return The extracted value, if extraction succeeded, an empty value otherwise.
*/
result_type operator() (attribute_value const& attr) const
{
result_type res;
aux::value_ref_initializer< result_type > initializer(res);
if (!!attr)
{
static_type_dispatcher< value_type > disp(initializer);
if (!attr.dispatch(disp) && !fallback_policy::apply_default(initializer))
fallback_policy::on_invalid_type(attr.get_type());
}
else if (!fallback_policy::apply_default(initializer))
{
fallback_policy::on_missing_value();
}
return res;
}
/*!
* Extraction operator. Looks for an attribute value with the specified name
* and tries to acquire the stored value of one of the supported types. If extraction succeeds,
* the extracted value is returned.
*
* \param name Attribute value name.
* \param attrs A set of attribute values in which to look for the specified attribute value.
* \return The extracted value, if extraction succeeded, an empty value otherwise.
*/
result_type operator() (attribute_name const& name, attribute_value_set const& attrs) const
{
try
{
attribute_value_set::const_iterator it = attrs.find(name);
if (it != attrs.end())
return operator() (it->second);
else
return operator() (attribute_value());
}
catch (exception& e)
{
// Attach the attribute name to the exception
boost::log::aux::attach_attribute_name_info(e, name);
throw;
}
}
/*!
* Extraction operator. Looks for an attribute value with the specified name
* and tries to acquire the stored value of one of the supported types. If extraction succeeds,
* the extracted value is returned.
*
* \param name Attribute value name.
* \param rec A log record. The attribute value will be sought among those associated with the record.
* \return The extracted value, if extraction succeeded, an empty value otherwise.
*/
result_type operator() (attribute_name const& name, record const& rec) const
{
return operator() (name, rec.attribute_values());
}
/*!
* Extraction operator. Looks for an attribute value with the specified name
* and tries to acquire the stored value of one of the supported types. If extraction succeeds,
* the extracted value is returned.
*
* \param name Attribute value name.
* \param rec A log record view. The attribute value will be sought among those associated with the record.
* \return The extracted value, if extraction succeeded, an empty value otherwise.
*/
result_type operator() (attribute_name const& name, record_view const& rec) const
{
return operator() (name, rec.attribute_values());
}
/*!
* \returns Fallback policy
*/
fallback_policy const& get_fallback_policy() const
{
return *static_cast< fallback_policy const* >(this);
}
};
#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 function extracts an attribute value from the view. The user has to explicitly specify the
* type or set of possible types of the attribute value to be extracted.
*
* \param name The name of the attribute value to extract.
* \param attrs A set of attribute values in which to look for the specified attribute value.
* \return A \c value_ref that refers to the extracted value, if found. An empty value otherwise.
*/
template< typename T, typename TagT BOOST_LOG_AUX_VOID_DEFAULT >
inline typename result_of::extract< T, TagT >::type extract(attribute_name const& name, attribute_value_set const& attrs)
{
value_extractor< T, fallback_to_none, TagT > extractor;
return extractor(name, attrs);
}
/*!
* The function extracts an attribute value from the view. The user has to explicitly specify the
* type or set of possible types of the attribute value to be extracted.
*
* \param name The name of the attribute value to extract.
* \param rec A log record. The attribute value will be sought among those associated with the record.
* \return A \c value_ref that refers to the extracted value, if found. An empty value otherwise.
*/
template< typename T, typename TagT BOOST_LOG_AUX_VOID_DEFAULT >
inline typename result_of::extract< T, TagT >::type extract(attribute_name const& name, record const& rec)
{
value_extractor< T, fallback_to_none, TagT > extractor;
return extractor(name, rec);
}
/*!
* The function extracts an attribute value from the view. The user has to explicitly specify the
* type or set of possible types of the attribute value to be extracted.
*
* \param name The name of the attribute value to extract.
* \param rec A log record view. The attribute value will be sought among those associated with the record.
* \return A \c value_ref that refers to the extracted value, if found. An empty value otherwise.
*/
template< typename T, typename TagT BOOST_LOG_AUX_VOID_DEFAULT >
inline typename result_of::extract< T, TagT >::type extract(attribute_name const& name, record_view const& rec)
{
value_extractor< T, fallback_to_none, TagT > extractor;
return extractor(name, rec);
}
/*!
* The function extracts an attribute value from the view. The user has to explicitly specify the
* type or set of possible types of the attribute value to be extracted.
*
* \param value Attribute value.
* \return A \c value_ref that refers to the extracted value, if found. An empty value otherwise.
*/
template< typename T, typename TagT BOOST_LOG_AUX_VOID_DEFAULT >
inline typename result_of::extract< T, TagT >::type extract(attribute_value const& value)
{
value_extractor< T, fallback_to_none, TagT > extractor;
return extractor(value);
}
/*!
* The function extracts an attribute value from the view. The user has to explicitly specify the
* type or set of possible types of the attribute value to be extracted.
*
* \param name The name of the attribute value to extract.
* \param attrs A set of attribute values in which to look for the specified attribute value.
* \return The extracted value or a non-empty \c value_ref that refers to the value.
* \throws An exception is thrown if the requested value cannot be extracted.
*/
template< typename T, typename TagT BOOST_LOG_AUX_VOID_DEFAULT >
inline typename result_of::extract_or_throw< T, TagT >::type extract_or_throw(attribute_name const& name, attribute_value_set const& attrs)
{
value_extractor< T, fallback_to_throw, TagT > extractor;
return aux::unwrap_value_ref(extractor(name, attrs));
}
/*!
* The function extracts an attribute value from the view. The user has to explicitly specify the
* type or set of possible types of the attribute value to be extracted.
*
* \param name The name of the attribute value to extract.
* \param rec A log record. The attribute value will be sought among those associated with the record.
* \return The extracted value or a non-empty \c value_ref that refers to the value.
* \throws An exception is thrown if the requested value cannot be extracted.
*/
template< typename T, typename TagT BOOST_LOG_AUX_VOID_DEFAULT >
inline typename result_of::extract_or_throw< T, TagT >::type extract_or_throw(attribute_name const& name, record const& rec)
{
value_extractor< T, fallback_to_throw, TagT > extractor;
return aux::unwrap_value_ref(extractor(name, rec));
}
/*!
* The function extracts an attribute value from the view. The user has to explicitly specify the
* type or set of possible types of the attribute value to be extracted.
*
* \param name The name of the attribute value to extract.
* \param rec A log record view. The attribute value will be sought among those associated with the record.
* \return The extracted value or a non-empty \c value_ref that refers to the value.
* \throws An exception is thrown if the requested value cannot be extracted.
*/
template< typename T, typename TagT BOOST_LOG_AUX_VOID_DEFAULT >
inline typename result_of::extract_or_throw< T, TagT >::type extract_or_throw(attribute_name const& name, record_view const& rec)
{
value_extractor< T, fallback_to_throw, TagT > extractor;
return aux::unwrap_value_ref(extractor(name, rec));
}
/*!
* The function extracts an attribute value from the view. The user has to explicitly specify the
* type or set of possible types of the attribute value to be extracted.
*
* \param value Attribute value.
* \return The extracted value or a non-empty \c value_ref that refers to the value.
* \throws An exception is thrown if the requested value cannot be extracted.
*/
template< typename T, typename TagT BOOST_LOG_AUX_VOID_DEFAULT >
inline typename result_of::extract_or_throw< T, TagT >::type extract_or_throw(attribute_value const& value)
{
value_extractor< T, fallback_to_throw, TagT > extractor;
return aux::unwrap_value_ref(extractor(value));
}
/*!
* The function extracts an attribute value from the view. The user has to explicitly specify the
* type or set of possible types of the attribute value to be extracted.
*
* \note Caution must be exercised if the default value is a temporary object. Because the function returns
* a reference, if the temporary object is destroyed, the reference may become dangling.
*
* \param name The name of the attribute value to extract.
* \param attrs A set of attribute values in which to look for the specified attribute value.
* \param def_val The default value
* \return The extracted value, if found. The default value otherwise.
*/
template< typename T, typename TagT BOOST_LOG_AUX_VOID_DEFAULT, typename DefaultT >
inline typename result_of::extract_or_default< T, DefaultT, TagT >::type
extract_or_default(attribute_name const& name, attribute_value_set const& attrs, DefaultT const& def_val)
{
typedef typename result_of::extract_or_default< T, DefaultT, TagT >::extracted_type extracted_type;
value_extractor< extracted_type, fallback_to_default< DefaultT const& >, TagT > extractor(def_val);
return aux::unwrap_value_ref(extractor(name, attrs));
}
/*!
* The function extracts an attribute value from the view. The user has to explicitly specify the
* type or set of possible types of the attribute value to be visited.
*
* \note Caution must be exercised if the default value is a temporary object. Because the function returns
* a reference, if the temporary object is destroyed, the reference may become dangling.
*
* \param name The name of the attribute value to extract.
* \param rec A log record. The attribute value will be sought among those associated with the record.
* \param def_val The default value
* \return The extracted value, if found. The default value otherwise.
*/
template< typename T, typename TagT BOOST_LOG_AUX_VOID_DEFAULT, typename DefaultT >
inline typename result_of::extract_or_default< T, DefaultT, TagT >::type
extract_or_default(attribute_name const& name, record const& rec, DefaultT const& def_val)
{
typedef typename result_of::extract_or_default< T, DefaultT, TagT >::extracted_type extracted_type;
value_extractor< extracted_type, fallback_to_default< DefaultT const& >, TagT > extractor(def_val);
return aux::unwrap_value_ref(extractor(name, rec));
}
/*!
* The function extracts an attribute value from the view. The user has to explicitly specify the
* type or set of possible types of the attribute value to be visited.
*
* \note Caution must be exercised if the default value is a temporary object. Because the function returns
* a reference, if the temporary object is destroyed, the reference may become dangling.
*
* \param name The name of the attribute value to extract.
* \param rec A log record view. The attribute value will be sought among those associated with the record.
* \param def_val The default value
* \return The extracted value, if found. The default value otherwise.
*/
template< typename T, typename TagT BOOST_LOG_AUX_VOID_DEFAULT, typename DefaultT >
inline typename result_of::extract_or_default< T, DefaultT, TagT >::type
extract_or_default(attribute_name const& name, record_view const& rec, DefaultT const& def_val)
{
typedef typename result_of::extract_or_default< T, DefaultT, TagT >::extracted_type extracted_type;
value_extractor< extracted_type, fallback_to_default< DefaultT const& >, TagT > extractor(def_val);
return aux::unwrap_value_ref(extractor(name, rec));
}
/*!
* The function extracts an attribute value from the view. The user has to explicitly specify the
* type or set of possible types of the attribute value to be visited.
*
* \note Caution must be exercised if the default value is a temporary object. Because the function returns
* a reference, if the temporary object is destroyed, the reference may become dangling.
*
* \param value Attribute value.
* \param def_val The default value
* \return The extracted value, if found. The default value otherwise.
*/
template< typename T, typename TagT BOOST_LOG_AUX_VOID_DEFAULT, typename DefaultT >
inline typename result_of::extract_or_default< T, DefaultT, TagT >::type extract_or_default(attribute_value const& value, DefaultT const& def_val)
{
typedef typename result_of::extract_or_default< T, DefaultT, TagT >::extracted_type extracted_type;
value_extractor< extracted_type, fallback_to_default< DefaultT const& >, TagT > extractor(def_val);
return aux::unwrap_value_ref(extractor(value));
}
#if defined(BOOST_NO_CXX11_FUNCTION_TEMPLATE_DEFAULT_ARGS)
template< typename T >
inline typename result_of::extract< T >::type extract(attribute_name const& name, attribute_value_set const& attrs)
{
value_extractor< T, fallback_to_none > extractor;
return extractor(name, attrs);
}
template< typename T >
inline typename result_of::extract< T >::type extract(attribute_name const& name, record const& rec)
{
value_extractor< T, fallback_to_none > extractor;
return extractor(name, rec);
}
template< typename T >
inline typename result_of::extract< T >::type extract(attribute_name const& name, record_view const& rec)
{
value_extractor< T, fallback_to_none > extractor;
return extractor(name, rec);
}
template< typename T >
inline typename result_of::extract< T >::type extract(attribute_value const& value)
{
value_extractor< T, fallback_to_none > extractor;
return extractor(value);
}
template< typename T >
inline typename result_of::extract_or_throw< T >::type extract_or_throw(attribute_name const& name, attribute_value_set const& attrs)
{
value_extractor< T, fallback_to_throw > extractor;
return aux::unwrap_value_ref(extractor(name, attrs));
}
template< typename T >
inline typename result_of::extract_or_throw< T >::type extract_or_throw(attribute_name const& name, record const& rec)
{
value_extractor< T, fallback_to_throw > extractor;
return aux::unwrap_value_ref(extractor(name, rec));
}
template< typename T >
inline typename result_of::extract_or_throw< T >::type extract_or_throw(attribute_name const& name, record_view const& rec)
{
value_extractor< T, fallback_to_throw > extractor;
return aux::unwrap_value_ref(extractor(name, rec));
}
template< typename T >
inline typename result_of::extract_or_throw< T >::type extract_or_throw(attribute_value const& value)
{
value_extractor< T, fallback_to_throw > extractor;
return aux::unwrap_value_ref(extractor(value));
}
template< typename T, typename DefaultT >
inline typename result_of::extract_or_default< T, DefaultT >::type extract_or_default(
attribute_name const& name, attribute_value_set const& attrs, DefaultT const& def_val)
{
typedef typename result_of::extract_or_default< T, DefaultT >::extracted_type extracted_type;
value_extractor< extracted_type, fallback_to_default< DefaultT const& > > extractor(def_val);
return aux::unwrap_value_ref(extractor(name, attrs));
}
template< typename T, typename DefaultT >
inline typename result_of::extract_or_default< T, DefaultT >::type extract_or_default(
attribute_name const& name, record const& rec, DefaultT const& def_val)
{
typedef typename result_of::extract_or_default< T, DefaultT >::extracted_type extracted_type;
value_extractor< extracted_type, fallback_to_default< DefaultT const& > > extractor(def_val);
return aux::unwrap_value_ref(extractor(name, rec));
}
template< typename T, typename DefaultT >
inline typename result_of::extract_or_default< T, DefaultT >::type extract_or_default(
attribute_name const& name, record_view const& rec, DefaultT const& def_val)
{
typedef typename result_of::extract_or_default< T, DefaultT >::extracted_type extracted_type;
value_extractor< extracted_type, fallback_to_default< DefaultT const& > > extractor(def_val);
return aux::unwrap_value_ref(extractor(name, rec));
}
template< typename T, typename DefaultT >
inline typename result_of::extract_or_default< T, DefaultT >::type extract_or_default(attribute_value const& value, DefaultT const& def_val)
{
typedef typename result_of::extract_or_default< T, DefaultT >::extracted_type extracted_type;
value_extractor< extracted_type, fallback_to_default< DefaultT const& > > extractor(def_val);
return aux::unwrap_value_ref(extractor(value));
}
#endif // defined(BOOST_NO_CXX11_FUNCTION_TEMPLATE_DEFAULT_ARGS)
/*!
* The function extracts an attribute value from the view. The user has to explicitly specify the
* type or set of possible types of the attribute value to be extracted.
*
* \param keyword The keyword of the attribute value to extract.
* \param attrs A set of attribute values in which to look for the specified attribute value.
* \return A \c value_ref that refers to the extracted value, if found. An empty value otherwise.
*/
template< typename DescriptorT, template< typename > class ActorT >
inline typename result_of::extract< typename DescriptorT::value_type, DescriptorT >::type
extract(expressions::attribute_keyword< DescriptorT, ActorT > const& keyword, attribute_value_set const& attrs)
{
value_extractor< typename DescriptorT::value_type, fallback_to_none, DescriptorT > extractor;
return extractor(keyword.get_name(), attrs);
}
/*!
* The function extracts an attribute value from the view. The user has to explicitly specify the
* type or set of possible types of the attribute value to be extracted.
*
* \param keyword The keyword of the attribute value to extract.
* \param rec A log record. The attribute value will be sought among those associated with the record.
* \return A \c value_ref that refers to the extracted value, if found. An empty value otherwise.
*/
template< typename DescriptorT, template< typename > class ActorT >
inline typename result_of::extract< typename DescriptorT::value_type, DescriptorT >::type
extract(expressions::attribute_keyword< DescriptorT, ActorT > const& keyword, record const& rec)
{
value_extractor< typename DescriptorT::value_type, fallback_to_none, DescriptorT > extractor;
return extractor(keyword.get_name(), rec);
}
/*!
* The function extracts an attribute value from the view. The user has to explicitly specify the
* type or set of possible types of the attribute value to be extracted.
*
* \param keyword The keyword of the attribute value to extract.
* \param rec A log record view. The attribute value will be sought among those associated with the record.
* \return A \c value_ref that refers to the extracted value, if found. An empty value otherwise.
*/
template< typename DescriptorT, template< typename > class ActorT >
inline typename result_of::extract< typename DescriptorT::value_type, DescriptorT >::type
extract(expressions::attribute_keyword< DescriptorT, ActorT > const& keyword, record_view const& rec)
{
value_extractor< typename DescriptorT::value_type, fallback_to_none, DescriptorT > extractor;
return extractor(keyword.get_name(), rec);
}
/*!
* The function extracts an attribute value from the view. The user has to explicitly specify the
* type or set of possible types of the attribute value to be extracted.
*
* \param keyword The keyword of the attribute value to extract.
* \param attrs A set of attribute values in which to look for the specified attribute value.
* \return The extracted value or a non-empty \c value_ref that refers to the value.
* \throws An exception is thrown if the requested value cannot be extracted.
*/
template< typename DescriptorT, template< typename > class ActorT >
inline typename result_of::extract_or_throw< typename DescriptorT::value_type, DescriptorT >::type
extract_or_throw(expressions::attribute_keyword< DescriptorT, ActorT > const& keyword, attribute_value_set const& attrs)
{
value_extractor< typename DescriptorT::value_type, fallback_to_throw, DescriptorT > extractor;
return aux::unwrap_value_ref(extractor(keyword.get_name(), attrs));
}
/*!
* The function extracts an attribute value from the view. The user has to explicitly specify the
* type or set of possible types of the attribute value to be extracted.
*
* \param keyword The keyword of the attribute value to extract.
* \param rec A log record. The attribute value will be sought among those associated with the record.
* \return The extracted value or a non-empty \c value_ref that refers to the value.
* \throws An exception is thrown if the requested value cannot be extracted.
*/
template< typename DescriptorT, template< typename > class ActorT >
inline typename result_of::extract_or_throw< typename DescriptorT::value_type, DescriptorT >::type
extract_or_throw(expressions::attribute_keyword< DescriptorT, ActorT > const& keyword, record const& rec)
{
value_extractor< typename DescriptorT::value_type, fallback_to_throw, DescriptorT > extractor;
return aux::unwrap_value_ref(extractor(keyword.get_name(), rec));
}
/*!
* The function extracts an attribute value from the view. The user has to explicitly specify the
* type or set of possible types of the attribute value to be extracted.
*
* \param keyword The keyword of the attribute value to extract.
* \param rec A log record view. The attribute value will be sought among those associated with the record.
* \return The extracted value or a non-empty \c value_ref that refers to the value.
* \throws An exception is thrown if the requested value cannot be extracted.
*/
template< typename DescriptorT, template< typename > class ActorT >
inline typename result_of::extract_or_throw< typename DescriptorT::value_type, DescriptorT >::type
extract_or_throw(expressions::attribute_keyword< DescriptorT, ActorT > const& keyword, record_view const& rec)
{
value_extractor< typename DescriptorT::value_type, fallback_to_throw, DescriptorT > extractor;
return aux::unwrap_value_ref(extractor(keyword.get_name(), rec));
}
/*!
* The function extracts an attribute value from the view. The user has to explicitly specify the
* type or set of possible types of the attribute value to be extracted.
*
* \note Caution must be exercised if the default value is a temporary object. Because the function returns
* a reference, if the temporary object is destroyed, the reference may become dangling.
*
* \param keyword The keyword of the attribute value to extract.
* \param attrs A set of attribute values in which to look for the specified attribute value.
* \param def_val The default value
* \return The extracted value, if found. The default value otherwise.
*/
template< typename DescriptorT, template< typename > class ActorT, typename DefaultT >
inline typename result_of::extract_or_default< typename DescriptorT::value_type, DefaultT, DescriptorT >::type
extract_or_default(expressions::attribute_keyword< DescriptorT, ActorT > const& keyword, attribute_value_set const& attrs, DefaultT const& def_val)
{
typedef typename result_of::extract_or_default< typename DescriptorT::value_type, DefaultT, DescriptorT >::extracted_type extracted_type;
value_extractor< extracted_type, fallback_to_default< DefaultT const& >, DescriptorT > extractor(def_val);
return aux::unwrap_value_ref(extractor(keyword.get_name(), attrs));
}
/*!
* The function extracts an attribute value from the view. The user has to explicitly specify the
* type or set of possible types of the attribute value to be visited.
*
* \note Caution must be exercised if the default value is a temporary object. Because the function returns
* a reference, if the temporary object is destroyed, the reference may become dangling.
*
* \param keyword The keyword of the attribute value to extract.
* \param rec A log record. The attribute value will be sought among those associated with the record.
* \param def_val The default value
* \return The extracted value, if found. The default value otherwise.
*/
template< typename DescriptorT, template< typename > class ActorT, typename DefaultT >
inline typename result_of::extract_or_default< typename DescriptorT::value_type, DefaultT, DescriptorT >::type
extract_or_default(expressions::attribute_keyword< DescriptorT, ActorT > const& keyword, record const& rec, DefaultT const& def_val)
{
typedef typename result_of::extract_or_default< typename DescriptorT::value_type, DefaultT, DescriptorT >::extracted_type extracted_type;
value_extractor< extracted_type, fallback_to_default< DefaultT const& >, DescriptorT > extractor(def_val);
return aux::unwrap_value_ref(extractor(keyword.get_name(), rec));
}
/*!
* The function extracts an attribute value from the view. The user has to explicitly specify the
* type or set of possible types of the attribute value to be visited.
*
* \note Caution must be exercised if the default value is a temporary object. Because the function returns
* a reference, if the temporary object is destroyed, the reference may become dangling.
*
* \param keyword The keyword of the attribute value to extract.
* \param rec A log record view. The attribute value will be sought among those associated with the record.
* \param def_val The default value
* \return The extracted value, if found. The default value otherwise.
*/
template< typename DescriptorT, template< typename > class ActorT, typename DefaultT >
inline typename result_of::extract_or_default< typename DescriptorT::value_type, DefaultT, DescriptorT >::type
extract_or_default(expressions::attribute_keyword< DescriptorT, ActorT > const& keyword, record_view const& rec, DefaultT const& def_val)
{
typedef typename result_of::extract_or_default< typename DescriptorT::value_type, DefaultT, DescriptorT >::extracted_type extracted_type;
value_extractor< extracted_type, fallback_to_default< DefaultT const& >, DescriptorT > extractor(def_val);
return aux::unwrap_value_ref(extractor(keyword.get_name(), rec));
}
#if !defined(BOOST_LOG_DOXYGEN_PASS)
template< typename T, typename TagT >
inline typename result_of::extract< T, TagT >::type attribute_value::extract() const
{
return boost::log::extract< T, TagT >(*this);
}
template< typename T, typename TagT >
inline typename result_of::extract_or_throw< T, TagT >::type attribute_value::extract_or_throw() const
{
return boost::log::extract_or_throw< T, TagT >(*this);
}
template< typename T, typename TagT >
inline typename result_of::extract_or_default< T, T, TagT >::type attribute_value::extract_or_default(T const& def_value) const
{
return boost::log::extract_or_default< T, TagT >(*this, def_value);
}
template< typename T, typename TagT, typename DefaultT >
inline typename result_of::extract_or_default< T, DefaultT, TagT >::type attribute_value::extract_or_default(DefaultT const& def_value) const
{
return boost::log::extract_or_default< T, TagT >(*this, def_value);
}
#if defined(BOOST_NO_CXX11_FUNCTION_TEMPLATE_DEFAULT_ARGS)
template< typename T >
inline typename result_of::extract< T >::type attribute_value::extract() const
{
return boost::log::extract< T >(*this);
}
template< typename T >
inline typename result_of::extract_or_throw< T >::type attribute_value::extract_or_throw() const
{
return boost::log::extract_or_throw< T >(*this);
}
template< typename T >
inline typename result_of::extract_or_default< T, T >::type attribute_value::extract_or_default(T const& def_value) const
{
return boost::log::extract_or_default< T >(*this, def_value);
}
template< typename T, typename DefaultT >
inline typename result_of::extract_or_default< T, DefaultT >::type attribute_value::extract_or_default(DefaultT const& def_value) const
{
return boost::log::extract_or_default< T >(*this, def_value);
}
#endif // defined(BOOST_NO_CXX11_FUNCTION_TEMPLATE_DEFAULT_ARGS)
#endif // !defined(BOOST_LOG_DOXYGEN_PASS)
#undef BOOST_LOG_AUX_VOID_DEFAULT
BOOST_LOG_CLOSE_NAMESPACE // namespace log
} // namespace boost
#include <boost/log/detail/footer.hpp>
#endif // BOOST_LOG_ATTRIBUTES_VALUE_EXTRACTION_HPP_INCLUDED_