Ichthyostega
4356315021
each language token of our "linearised diff representation" carries a payload data element, which typically is the piece of data to be altered (added, mutated, etc). Basically, these elements have value semantics and are "sent over wire", and thus it seems natural when the language interpreter functions accept that piece of payload by-value. But since we're now sending GenNode elements as parameter data in our diff, which typically are of the size of 10 data elements (640 bit on a 64bit machine), it seems more resonable to pass these argument elements by const& through the interpreter function. This still means we can (and will indeed) copy the mutated data values when applying the diff, but we're able to relay the data more efficiently to the point where it's consumed.
101 lines
3.6 KiB
C++
101 lines
3.6 KiB
C++
/*
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LIST-DIFF.hpp - language to describe differences between list like sequences
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Copyright (C) Lumiera.org
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2014, 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 list-diff.hpp
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** A token language to represent changes in a list of elements.
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** In combination with the #DiffLanguage framework, this building block
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** defines the set of operations to express changes in a given list of elements.
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** By implementing the #ListDiffInterpreter interface (visitor), a concrete usage
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** can receive such a diff description and e.g. apply it to a target data structure.
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**
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** @see diff-language.cpp
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** @see diff-list-application-test.cpp
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** @see VerbToken
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**
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*/
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#ifndef LIB_DIFF_LIST_DIFF_H
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#define LIB_DIFF_LIST_DIFF_H
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#include "lib/diff/diff-language.hpp"
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namespace lib {
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namespace diff{
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/**
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* Interpreter interface to define the operations ("verbs"),
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* which describe differences or changes in a given list of data elements.
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* The meaning of the verbs is as follows:
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* - \c ins prompts to insert the given argument element at the \em current
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* processing position into the target sequence. This operation
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* allows to inject new data
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* - \c del requires to delete the \em next element at \em current position.
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* For sake of verification, the element to be deleted is also
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* included as argument (redundancy).
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* - \c pick just accepts the \em next element at \em current position into
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* the resulting altered sequence. The element is given redundantly.
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* - \c find effect a re-ordering of the target list contents: it requires
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* to \em search for the (next respective single occurrence of the)
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* given element further down into the remainder of the list,
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* to bring it forward and insert it as the next element.
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* - \c skip processing hint, emitted at the position where an element
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* previously extracted by a \c find verb happened to sit within
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* the old order. This allows an optimising implementation to “fetch”
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* a copy and just drop or skip the original, thereby avoiding to
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* shift any other elements.
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*/
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template<typename E>
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class ListDiffInterpreter
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{
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public:
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virtual ~ListDiffInterpreter() { } ///< this is an interface
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virtual void ins (E const& e) =0;
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virtual void del (E const& e) =0;
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virtual void pick(E const& e) =0;
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virtual void find(E const& e) =0;
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virtual void skip(E const& e) =0;
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};
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template<typename E>
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struct ListDiffLanguage
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: DiffLanguage<ListDiffInterpreter<E>, E>
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{
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using Interpreter = ListDiffInterpreter<E>;
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DiffStep_CTOR(ins);
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DiffStep_CTOR(del);
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DiffStep_CTOR(pick);
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DiffStep_CTOR(find);
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DiffStep_CTOR(skip);
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};
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}} // namespace lib::diff
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#endif /*LIB_DIFF_LIST_DIFF_H*/
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