log/sinks/sink.hpp

0001 /*
0002  *          Copyright Andrey Semashev 2007 - 2015.
0003  * Distributed under the Boost Software License, Version 1.0.
0004  *    (See accompanying file LICENSE_1_0.txt or copy at
0005  *          http://www.boost.org/LICENSE_1_0.txt)
0006  */
0007 /*!
0008  * \file   sink.hpp
0009  * \author Andrey Semashev
0010  * \date   22.04.2007
0011  *
0012  * The header contains an interface declaration for all sinks. This interface is used by the
0013  * logging core to feed log records to sinks.
0014  */
0015
0016 #ifndef BOOST_LOG_SINKS_SINK_HPP_INCLUDED_
0017 #define BOOST_LOG_SINKS_SINK_HPP_INCLUDED_
0018
0019 #include <string>
0020 #include <boost/log/detail/config.hpp>
0021 #include <boost/log/detail/light_function.hpp>
0022 #include <boost/log/core/record_view.hpp>
0023 #include <boost/log/attributes/attribute_value_set.hpp>
0024 #include <boost/log/detail/header.hpp>
0025
0026 #ifdef BOOST_HAS_PRAGMA_ONCE
0027 #pragma once
0028 #endif
0029
0030 namespace boost {
0031
0032 BOOST_LOG_OPEN_NAMESPACE
0033
0034 namespace sinks {
0035
0036 //! A base class for a logging sink frontend
0037 class BOOST_LOG_NO_VTABLE sink
0038 {
0039 public:
0040     //! An exception handler type
0041     typedef boost::log::aux::light_function< void () > exception_handler_type;
0042
0043 private:
0044     //! The flag indicates that the sink passes log records across thread boundaries
0045     const bool m_cross_thread;
0046
0047 public:
0048     /*!
0049      * Default constructor
0050      */
0051     explicit sink(bool cross_thread) : m_cross_thread(cross_thread)
0052     {
0053     }
0054
0055     /*!
0056      * Virtual destructor
0057      */
0058     virtual ~sink() {}
0059
0060     /*!
0061      * The method returns \c true if no filter is set or the attribute values pass the filter
0062      *
0063      * \param attributes A set of attribute values of a logging record
0064      */
0065     virtual bool will_consume(attribute_value_set const& attributes) = 0;
0066
0067     /*!
0068      * The method puts logging record to the sink
0069      *
0070      * \param rec Logging record to consume
0071      */
0072     virtual void consume(record_view const& rec) = 0;
0073
0074     /*!
0075      * The method attempts to put logging record to the sink. The method may be used by the
0076      * core in order to determine the most efficient order of sinks to feed records to in
0077      * case of heavy contention. Sink implementations may implement try/backoff logic in
0078      * order to improve overall logging throughput.
0079      *
0080      * \param rec Logging record to consume
0081      * \return \c true, if the record was consumed, \c false, if not.
0082      */
0083     virtual bool try_consume(record_view const& rec)
0084     {
0085         consume(rec);
0086         return true;
0087     }
0088
0089     /*!
0090      * The method performs flushing of any internal buffers that may hold log records. The method
0091      * may take considerable time to complete and may block both the calling thread and threads
0092      * attempting to put new records into the sink while this call is in progress.
0093      */
0094     virtual void flush() = 0;
0095
0096     /*!
0097      * The method indicates that the sink passes log records between different threads. This information is
0098      * needed by the logging core to detach log records from all thread-specific resources before passing it
0099      * to the sink.
0100      */
0101     bool is_cross_thread() const BOOST_NOEXCEPT { return m_cross_thread; }
0102
0103     BOOST_DELETED_FUNCTION(sink(sink const&))
0104     BOOST_DELETED_FUNCTION(sink& operator= (sink const&))
0105 };
0106
0107 } // namespace sinks
0108
0109 BOOST_LOG_CLOSE_NAMESPACE // namespace log
0110
0111 } // namespace boost
0112
0113 #include <boost/log/detail/footer.hpp>
0114
0115 #endif // BOOST_LOG_SINKS_SINK_HPP_INCLUDED_