Ichthyostega
c791763890
this compiles just fine. But we still need to define the concrete closures to make it work with the actual contents of GenNode
104 lines
4.2 KiB
C++
104 lines
4.2 KiB
C++
/*
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TREE-MUTATOR-GEN-NODE-BINDING.hpp - diff::TreeMutator implementation building block
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Copyright (C) Lumiera.org
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2016, Hermann Vosseler <Ichthyostega@web.de>
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License as
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published by the Free Software Foundation; either version 2 of
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the License, or (at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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/** @file tree-mutator-gen-node-binding.hpp
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** Special binding implementation for TreeMutator, allowing to map
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** tree diff operations onto an »External Tree Description«. Such is is a
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** DOM like representation of tree like structures, comprised of GenNode elements.
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** TreeMutator is a customisable intermediary, which enables otherwise opaque
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** implementation data structures to receive and respond to generic structural
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** change messages ("tree diff").
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**
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** Each concrete TreeMutator instance will be configured differently, and this
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** adaptation is done by implementing binding templates, in the way of building
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** blocks, layered on top of each other. This header defines a special setup, based
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** on the two layered bindings for STL collections. The reason is that our »External
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** Tree Description« of object-like structures is comprised of recursively nested
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** Record<GenNode> to represent "objects", and this representation is actually implemented
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** internally based on two collections -- one to hold the _attributes_ and one to hold the
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** _children._ So this special setup relies on implementation inside knowledge to apply
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** structural changes to such a representation. There is an implicit convention that
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** "objects" are to be spelled out by first giving the metadata, then enumerating the
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** attributes (key-value properties) and finally the child elements located within the
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** scope of this "object" node. This implicit convention is in accordance with the
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** structure of our _diff language_ -- thus it is sufficient just to layer two collection
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** bindings, together with suitable closures (lambdas) for layer selection, matching, etc.
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**
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** @note the header tree-mutator-collection-binding.hpp with specific builder templates
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** is included way down, after the class definitions. This is done so for sake
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** of readability.
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**
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** @see tree-mutator-test.cpp
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** @see TreeMutator::build()
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**
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*/
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#ifndef LIB_DIFF_TREE_MUTATOR_GEN_NODE_BINDING_H
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#define LIB_DIFF_TREE_MUTATOR_GEN_NODE_BINDING_H
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#ifndef LIB_DIFF_TREE_MUTATOR_H
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#error "this header shall not be used standalone (see tree-mutator.hpp)"
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#endif
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//== anonymous namespace...
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using lib::diff::GenNode;
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using Storage = RecordSetup<GenNode>::Storage;
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inline Storage&
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accessAttribs (Rec::Mutator& targetTree)
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{
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return std::get<0> (targetTree.exposeToDiff());
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}
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inline Storage&
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accessChildren (Rec::Mutator& targetTree)
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{
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return std::get<1> (targetTree.exposeToDiff());
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}
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/**
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* Attach to GenNode tree: Special setup to build a concrete `TreeMutator`.
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* This decorator is already outfitted with the necessary closures to work on
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* a diff::Record<GenNode> -- which is typically used as "meta representation"
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* of object-like structures. Thus this binding allows to apply a diff message
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* onto such a given »External Tree Description«, mutating it into new shape.
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*/
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template<class PAR>
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inline auto
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twoLayeredGenNodeTreeMutator (Rec::Mutator& targetTree, PAR&& builderBase)
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{
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return builderBase
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.attach (collection (accessChildren(targetTree)))
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.attach (collection (accessAttribs(targetTree)));
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}
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#endif /*LIB_DIFF_TREE_MUTATOR_GEN_NODE_BINDING_H*/
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