Ichthyostega
eb829e6994
yeah, working with open fire is dangerous... For performace reasons I've undercut the premise to make GenNode / Record immutable. Now I'm dealing with raw storage layout together with this quite hairy distinction between "attribute scope" and "child scope" In hindsight, it might have been better to implement Record as a single list, and to maintain a shortcut pointer to jump to the start of the attributes.
152 lines
4.3 KiB
C++
152 lines
4.3 KiB
C++
/*
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RECORD-CONTENT-MUTATOR.hpp - helper to remould record contents
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Copyright (C) Lumiera.org
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2015, 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 record-content-mutator.hpp
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** Implementation helper for reshaping the contents of a lib::diff::Record.
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** This technical helper is necessary to apply one level of a "Tree Diff"
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** to an object represented as #Record::Mutator. Since records as such are
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** designed as immutable value objects, we build a dedicated #Record::Mutator
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** when it comes to reordering the contents of a given record. The technical
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** details of doing so are highly coupled to the actual storage implementation
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** of #Record, as well as to the actual procedure to apply a diff message, as
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** implemented in lib::diff::DiffApplicationStrategy.
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** @warning this struct is marked "internal" for a reason;
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** it serves the purpose to remove technicalities from usage site,
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** yet it is \em not a proper abstraction. Be sure you understand
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** the storage layout, especially when testing for iteration end.
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** @see generic-record-update-test.cpp
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** @see tree-diff-application-test.cpp
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** @see Record::Mutator
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** @see diff-language.hpp
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**
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*/
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#ifndef LIB_DIFF_RECORD_CONTENT_MUTATOR_H
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#define LIB_DIFF_RECORD_CONTENT_MUTATOR_H
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#include "lib/error.hpp"
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#include <boost/noncopyable.hpp>
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#include <utility>
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namespace lib {
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namespace diff{
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namespace error = lumiera::error;
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using std::move;
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using std::swap;
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/** @internal helper for DiffApplicationStrategy<Rec::Mutator> */
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template<class STO>
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struct RecordContentMutator
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: boost::noncopyable
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{
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using Iter = typename STO::iterator;
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STO attribs;
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STO children;
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Iter pos;
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RecordContentMutator()
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: attribs()
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, children()
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, pos(attribs.begin())
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{ }
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bool
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empty() const
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{
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return attribs.empty()
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and children.empty();
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}
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bool
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currIsAttrib() const
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{
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return & *pos >= & *attribs.begin()
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and & *pos < & *attribs.end();
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}
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bool
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currIsChild() const
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{
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return & *pos >= & *children.begin()
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and & *pos < & *children.end();
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}
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Iter end() { return children.end(); }
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Iter end() const { return children.end(); }
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RecordContentMutator&
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operator++()
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{
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if (pos == children.end())
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throw error::State ("attempt to iterate beyond end of scope"
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,error::LUMIERA_ERROR_ITER_EXHAUST);
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if (pos == attribs.end())
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pos = children.begin();
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else
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++pos;
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if (pos == attribs.end())
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pos = children.begin();
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return *this;
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}
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void
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resetPos()
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{
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if (attribs.empty())
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jumpToChildScope();
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else
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jumpToAttribScope();
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}
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void
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jumpToAttribScope()
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{
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pos = attribs.begin();
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}
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void
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jumpToChildScope()
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{
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pos = children.begin();
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}
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void
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preAllocateStorage(size_t attribCnt, size_t childrenCnt)
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{
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// heuristics for storage pre-allocation (for tree diff application)
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attribs.reserve (attribCnt * 120 / 100);
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children.reserve (childrenCnt * 120 / 100);
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ASSERT (this->empty());
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}
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};
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}} // namespace lib::diff
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#endif /*LIB_DIFF_RECORD_CONTENT_MUTATOR_H*/
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