Ichthyostega
ad6d348d8f
since we're moving elements around to apply the diff, dangerous situation might arise in case anyone takes a copy of the mutator. Thus we effectively limit the possible usage pattern and only allow to build an anonymous TreeMutator subclass through the Builder-DSL. The concrete "onion layers" of the TreeMutator are now limited - to be created by the chaining operations of the Builder DSl - to be moved into target location, retaining ownership.
515 lines
18 KiB
C++
515 lines
18 KiB
C++
/*
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TREE-MUTATOR-COLLECTION-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-collection-binding.hpp
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** Special binding implementation for TreeMutator, allowing to map
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** tree diff operations onto a STL collection of native implementation objects.
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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, attached and customised through lambdas. It is possible to layer
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** several bindings on top of a single TreeMutator -- and this header defines
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** a building block for one such layer, especially for binding to a representation
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** of "child objects" managed within a typical STL container.
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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_COLLECTION_BINDING_H
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#define LIB_DIFF_TREE_MUTATOR_COLLECTION_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::meta::Strip;
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using lib::diff::GenNode;
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using lib::iter_stl::eachElm;
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/** verify the installed functors or lambdas expose the expected signature */
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#define ASSERT_VALID_SIGNATURE(_FUN_, _SIG_) \
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static_assert (has_Sig<_FUN_, _SIG_>::value, "Function " STRINGIFY(_FUN_) " unsuitable, expected signature: " STRINGIFY(_SIG_));
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/**
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* Attach to collection: Concrete binding setup.
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* This record holds all the actual binding and closures
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* used to attach the tree mutator to an external pre-existing
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* STL container with child elements/objects. It serves as flexible
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* connection, configuration and adaptation element, and will be embedded
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* as a whole into the (\ref ChildCollectionMutator), which in turn implements
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* the `TreeMutator` interface. The resulting compound is able to consume
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* tree diff messages and apply the respective changes and mutations to
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* an otherwise opaque implementation data structure.
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*
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* @tparam COLL a STL compliant collection type holding "child elements"
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* @tparam MAT a closure to determine if a child matches a diff spec (GenNode)
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* @tparam CTR a closure to construct a new child element from a given diff spec
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* @tparam SEL predicate to determine if this binding layer has to process a diff message
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* @tparam ASS a closure to assign / set a new value from a given diff spec
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* @tparam MUT a closure to construct a nested mutator for some child element
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*/
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template<class COLL, class MAT, class CTR, class SEL, class ASS, class MUT>
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struct CollectionBinding
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{
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using Coll = typename Strip<COLL>::TypeReferred;
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using Elm = typename Coll::value_type;
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using iterator = typename lib::iter_stl::_SeqT<Coll>::Range;
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using const_iterator = typename lib::iter_stl::_SeqT<const Coll>::Range;
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ASSERT_VALID_SIGNATURE (MAT, bool(GenNode const& spec, Elm const& elm))
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ASSERT_VALID_SIGNATURE (CTR, Elm (GenNode const&))
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ASSERT_VALID_SIGNATURE (SEL, bool(GenNode const&))
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ASSERT_VALID_SIGNATURE (ASS, bool(Elm&, GenNode const&))
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ASSERT_VALID_SIGNATURE (MUT, bool(Elm&, TreeMutator::MutatorBuffer))
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Coll& collection;
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MAT matches;
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CTR construct;
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SEL isApplicable;
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ASS assign;
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MUT openSub;
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CollectionBinding(Coll& coll, MAT m, CTR c, SEL s, ASS a, MUT u)
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: collection(coll)
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, matches(m)
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, construct(c)
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, isApplicable(s)
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, assign(a)
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, openSub(u)
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{ }
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/* === content manipulation API === */
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Coll contentBuffer;
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iterator
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initMutation ()
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{
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contentBuffer.clear();
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swap (collection, contentBuffer);
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return eachElm (contentBuffer);
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}
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void
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inject (Elm&& elm)
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{
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collection.emplace_back (forward<Elm>(elm));
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}
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iterator
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search (GenNode const& targetSpec, iterator pos)
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{
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while (pos and not matches(targetSpec, *pos))
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++pos;
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return pos;
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}
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#if false /////////////////////////////////////////////////////////////////////////////////////////////////////////////UNIMPLEMENTED :: TICKET #992
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iterator
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locate (GenNode::ID const& targetID)
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{
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if (!empty() and content_.back().matches(targetID))
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return lastElm();
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else
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return search (targetID, eachElm(content_));
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}
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#endif /////////////////////////////////////////////////////////////////////////////////////////////////////////////UNIMPLEMENTED :: TICKET #992
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};
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/**
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* Attach to collection: Building block for a concrete `TreeMutator`.
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* This decorator will be outfitted with actual binding and closures
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* and then layered on top of the (\ref TreeMutaor) base. The resulting
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* compound is able to consume tree diff messages and apply the respective
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* changes and mutations to an otherwise opaque implementation data structure.
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* @remarks in practice, this is the most relevant and typical `TreeMutator` setup.
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*/
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template<class PAR, class BIN>
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class ChildCollectionMutator
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: public PAR
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{
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using Iter = typename BIN::iterator;
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BIN binding_;
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Iter pos_;
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public:
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ChildCollectionMutator(BIN wiringClosures, PAR&& chain)
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: PAR(std::forward<PAR>(chain))
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, binding_(wiringClosures)
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, pos_(binding_.initMutation())
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{ }
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/* ==== re-Implementation of the operation API ==== */
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/** skip next pending src element,
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* causing this element to be discarded
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*/
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virtual void
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skipSrc () override
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{
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if (pos_)
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++pos_;
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}
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/** fabricate a new element, based on
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* the given specification (GenNode),
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* and insert it at current position
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* into the target sequence.
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*/
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virtual void
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injectNew (GenNode const& n) override
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{
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binding_.inject (binding_.construct(n));
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}
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virtual bool
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emptySrc () override
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{
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return !pos_;
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}
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/** ensure the next recorded source element
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* matches on a formal level with given spec */
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virtual bool
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matchSrc (GenNode const& spec) override
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{
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return pos_? binding_.matches (spec, *pos_)
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: false;
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}
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/** accept existing element, when matching the given spec */
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virtual bool
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acceptSrc (GenNode const& n) override
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{
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bool isSrcMatch = ChildCollectionMutator::matchSrc(n);
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if (isSrcMatch) // NOTE: crucial to call our own method here, not the virtual function
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{
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binding_.inject (move(*pos_));
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++pos_;
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}
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return isSrcMatch;
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}
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/** locate designated element and accept it at current position */
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virtual bool
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findSrc (GenNode const& refSpec) override
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{
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Iter found = binding_.search (refSpec, pos_);
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if (found)
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{
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binding_.inject (move(*found));
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}
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return found;
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}
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#if false /////////////////////////////////////////////////////////////////////////////////////////////////////////////UNIMPLEMENTED :: TICKET #992
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/** repeatedly accept, until after the designated location */
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virtual bool
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accept_until (GenNode const& spec)
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{
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bool foundTarget = true;
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if (spec.matches (Ref::END))
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for ( ; pos_; ++pos_)
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target_.inject (move(*pos_), "accept_until END");
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else
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{
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string logMsg{"accept_until "+spec.idi.getSym()};
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while (pos_ and not TestWireTap::matchSrc(spec))
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{
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target_.inject (move(*pos_), logMsg);
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++pos_;
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}
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if (TestWireTap::matchSrc(spec))
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{
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target_.inject (move(*pos_), logMsg);
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++pos_;
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}
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else
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foundTarget = false;
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}
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return PAR::accept_until(spec)
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or foundTarget;
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}
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/** locate element already accepted into the target sequence
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* and assign the designated payload value to it. */
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virtual bool
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assignElm (GenNode const& spec)
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{
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Iter targetElm = target_.locate (spec.idi);
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if (targetElm)
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{
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string logOldPayload{render(targetElm->data)};
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*targetElm = spec;
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target_.logAssignment (*targetElm, logOldPayload);
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}
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return PAR::assignElm(spec)
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or targetElm;
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}
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/** locate the designated target element and build a suitable
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* sub-mutator for this element into the provided target buffer */
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virtual bool
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mutateChild (GenNode const& spec, TreeMutator::MutatorBuffer targetBuff)
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{
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if (PAR::mutateChild (spec, targetBuff))
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return true;
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else // Test mode only --
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{ // no other layer was able to provide a mutator
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Iter targetElm = target_.locate (spec.idi);
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if (targetElm)
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{
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targetBuff.create (TreeMutator::build());
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target_.logMutation (*targetElm);
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return true;
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}
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return false;
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}
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}
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#endif /////////////////////////////////////////////////////////////////////////////////////////////////////////////UNIMPLEMENTED :: TICKET #992
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};
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/**
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* Nested DSL to define the specifics of a collection binding.
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*/
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template<class COLL, class MAT, class CTR, class SEL, class ASS, class MUT>
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struct CollectionBindingBuilder
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: CollectionBinding<COLL,MAT,CTR,SEL,ASS,MUT>
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{
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using CollectionBinding<COLL,MAT,CTR,SEL,ASS,MUT>::CollectionBinding;
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template<class FUN>
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CollectionBindingBuilder<COLL, FUN ,CTR,SEL,ASS,MUT>
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matchElement(FUN matcher)
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{
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return { this->collection
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, matcher
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, this->construct
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, this->isApplicable
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, this->assign
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, this->openSub
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};
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}
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template<class FUN>
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CollectionBindingBuilder<COLL,MAT, FUN ,SEL,ASS,MUT>
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constructFrom(FUN constructor)
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{
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return { this->collection
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, this->matches
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, constructor
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, this->isApplicable
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, this->assign
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, this->openSub
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};
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}
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template<class FUN>
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CollectionBindingBuilder<COLL,MAT,CTR, FUN ,ASS,MUT>
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isApplicableIf(FUN selector)
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{
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return { this->collection
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, this->matches
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, this->construct
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, selector
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, this->assign
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, this->openSub
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};
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}
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template<class FUN>
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CollectionBindingBuilder<COLL,MAT,CTR,SEL, FUN ,MUT>
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assignElement(FUN setter)
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{
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return { this->collection
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, this->matches
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, this->construct
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, this->isApplicable
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, setter
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, this->openSub
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};
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}
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template<class FUN>
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CollectionBindingBuilder<COLL,MAT,CTR,SEL,ASS, FUN >
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buildChildMutator(FUN childMutationBuilder)
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{
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return { this->collection
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, this->matches
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, this->construct
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, this->isApplicable
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, this->assign
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, childMutationBuilder
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};
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}
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};
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using lib::meta::enable_if;
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using lib::diff::can_wrap_in_GenNode;
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template<typename ELM, typename SEL =void>
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struct _DefaultPayload
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{
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static bool
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match (GenNode const&, ELM const&)
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{
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throw error::Logic ("unable to build a sensible default matching predicate");
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}
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static ELM
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construct (GenNode const&)
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{
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throw error::Logic ("unable to build a sensible default for creating new elements");
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}
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};
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template<typename ELM>
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struct _DefaultPayload<ELM, enable_if<can_wrap_in_GenNode<ELM>>>
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{
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static bool
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match (GenNode const& spec, ELM const& elm)
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{
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return spec.matches(elm);
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}
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static ELM
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construct (GenNode const& spec)
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{
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return spec.data.get<ELM>();
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}
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};
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/**
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* starting point for configuration of a binding to STL container.
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* When using the "nested DSL" to setup a binding to child elements
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* managed within a STL collection, all the variable and flexible
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* aspects of the binding are preconfigured to a more or less
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* disabled and inactive state. The resulting binding layer
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* offers just minimal functionality. Typically you'd use
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* the created (\ref CollectionBindingBuilder) to replace
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* those defaults with lambdas tied into the actual
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* implementation of the target data structure.
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*/
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template<class COLL>
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struct _DefaultBinding
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{
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using Coll = typename Strip<COLL>::TypeReferred;
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using Elm = typename Coll::value_type;
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using Payload = _DefaultPayload<Elm>;
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static bool
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disable_selector (GenNode const&)
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{
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return false;
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}
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static bool
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disable_assignment (Elm&, GenNode const&)
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{
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return false;
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}
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static bool
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disable_childMutation (Elm&, TreeMutator::MutatorBuffer)
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{
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return false;
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}
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using FallbackBindingConfiguration
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= CollectionBindingBuilder<Coll
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,decltype(&Payload::match)
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,decltype(&Payload::construct)
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,decltype(&disable_selector)
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,decltype(&disable_assignment)
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,decltype(&disable_childMutation)
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>;
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static FallbackBindingConfiguration
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attachTo (Coll& coll)
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{
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return FallbackBindingConfiguration{ coll
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, Payload::match
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, Payload::construct
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, disable_selector
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, disable_assignment
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, disable_childMutation
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};
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}
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};
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/**
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* Entry point to a nested DSL
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* for setup and configuration of a collection binding.
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* This function shall be used right within Builder::attach()
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* and wrap a language reference to the concrete collection
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* implementing the "object children". The result is a default configured
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* binding, which should be further adapted with the builder functions,
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* using lambdas as callback into the otherwise opaque implementation code.
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*/
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template<class COLL>
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auto
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collection (COLL& coll) -> decltype(_DefaultBinding<COLL>::attachTo(coll))
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{
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return _DefaultBinding<COLL>::attachTo(coll);
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}
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#endif /*LIB_DIFF_TREE_MUTATOR_COLLECTION_BINDING_H*/
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