Definitions.ih

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//
// Copyright (c) 2020 Fraunhofer Institute for Applied Information Technology (FIT)
//                    Network Research Group (NET)
//                    Schloss Birlinghoven, 53754 Sankt Augustin, GERMANY
//                    Contact: support@wiback.org
//
// This file is part of the SENF code tree.
// It is licensed under the 3-clause BSD License (aka New BSD License).
// See LICENSE.txt in the top level directory for details or visit
// https://opensource.org/licenses/BSD-3-Clause
//


/** \file
    \brief Definitions internal header */

#ifndef IH_SENF_Utils_Logger_Definitions_
#define IH_SENF_Utils_Logger_Definitions_ 1

// Custom includes

//-/////////////////////////////////////////////////////////////////////////////////////////////////

// Implementation details concerning SENF_LOG_CLASS_AREA
//
// The SENF_LOG_CLASS_AREA statement shall declare the containing class as it's own default area. Of
// course, we cannot make the containing class into an area. Therefore we need to trick around a bit:
//
// We begin by defining an area SENFLogArea with in the class. This area however is hacked, so that
// it's name() member will return the name of the containing class (which is simple: just cut of the
// last couple of characters of the name since the name will always end in '::SENFLogArea').
//
// This however does not allow the use of the containing class as an area. There are several places
// which need to be adjusted to allow using the containing class as an area: The logging statements
// (SENF_LOG), the compile time configuration via SENF_LOG_CONF and the runtime configuration via
// route statements.
//
// Lets begin with the compile time configuration. The compile time configuration is done using
// specialization of the senf::log::detail::Config template. This doesn't care, what the area
// template argument really is. Therefore, compile-time configuration just uses the containing class
// as is. So we need to make sure, that the logging statements use the containing class when
// checking the compile-time limit whereas they need to use the nested SENFLogArea when calling the
// targets.
//
// So let's look at the logging statements. The central logic for parsing the logging parameters is
// in SENF_LOG_MERGE_PARAMETERS in Parameters.ih. Here we have a special case which detects classes
// with a SENFLogArea member and then set's things up correctly: It uses the containing class for
// compile time checking (this is, what 'area_base' typedef is for) while using the nested
// SENFLogArea for routing (this is, what the 'area' typedef is for).
//
// So the last thing which needs to be adjusted is the routing which is part of the Target
// class. Here for each template taking an area as an argument we really provide TWO templates, one
// taking the area directly, the other checking for a nested SENFLogArea member. We can
// differentiate these overloads using boost::enable_if and friends.
//
// This setup makes a class with SENF_LOG_CLASS_AREA() look like an ordinary area even though the
// implementation is somewhat different.

#define SENF_LOG_DEFINE_AREA_I(area, decls)                                                       \
    struct area                                                                                   \
        : public senf::log::detail::AreaBase, public senf::singleton<area>                        \
    {                                                                                             \
        static std::string name() { return instance().v_name(); }                                 \
        using senf::singleton<area>::instance;                                                    \
        decls                                                                                     \
    private:                                                                                      \
        area() { init(); }                                                                        \
        friend class senf::singleton<area>;                                                       \
    }

namespace senf {
namespace log {
namespace detail {

    /// Internal: Alias base class
    struct AliasBase {};

}}}

//-/////////////////////////////////////////////////////////////////////////////////////////////////
#endif


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