Ichthyostega
6b32d1f37d
while it's still not really clear how we'll use this helper and if we need it at all -- some weeks ago I changed its semantics to be strictly based on the delta to a reference level. Now this means, we could go below level zero, but this doesn't make any sense in the context of navigating a tree. Actually, our test case triggered this situation, which caused the reference level to wrap around, since it is stored in an unsigned variable. Thus I'll add a precondition to keep the level positive, and I'll change the test to comply.
134 lines
3.4 KiB
C++
134 lines
3.4 KiB
C++
/*
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HIERARCHY-ORIENTATION-INDICATOR.hpp - helper to mark level on tree navigation
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Copyright (C) Lumiera.org
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2013, 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 hierarchy-orientation-indicator.hpp
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** Helper to support navigating a tree structure.
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** The OrientationIndicator records reference levels (depth into the tree)
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** and can then be used to determine the relative orientation between the
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** previously marked reference level and the current reference level.
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** This simple state capturing mechanism can be used to track the path
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** of a tree visitation, or to sync an external stack with a currently
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** investigated tree level.
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**
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** The relative orientation value can be retrieved through an int conversion;
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** to ease recursive programming, this statefull value can be incremented and
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** decremented without influencing the captured reference level.
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**
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** @see job-ticket.hpp usage example
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** @see HierarchyOrientationIndicator_test
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**
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*/
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#ifndef HIERARCHY_ORIENTATION_INDICATOR_H
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#define HIERARCHY_ORIENTATION_INDICATOR_H
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#include <cstddef>
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#include <limits>
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#include <string>
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namespace lib {
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using std::string;
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class OrientationIndicator
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{
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size_t refLevel_;
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ptrdiff_t offset_;
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public:
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OrientationIndicator()
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: refLevel_(0)
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, offset_(0)
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{ }
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// using default copy/assignment
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operator ptrdiff_t() const
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{
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return offset_;
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}
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void
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markRefLevel (size_t newRefLevel)
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{
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REQUIRE (newRefLevel < size_t(std::numeric_limits<ptrdiff_t>::max()) );
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offset_ -= newRefLevel - refLevel_;
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refLevel_ = newRefLevel;
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}
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/** define the current offset as new reference point */
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OrientationIndicator&
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markRefLevel ()
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{
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REQUIRE (0 < ptrdiff_t(refLevel_) + offset_);
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markRefLevel (refLevel_ + offset_);
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ENSURE (offset_ == 0);
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return *this;
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}
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OrientationIndicator&
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resetToRef ()
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{
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offset_ = 0;
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return *this;
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}
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OrientationIndicator&
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operator+= (int adj)
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{
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offset_ += adj;
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return *this;
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}
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OrientationIndicator&
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operator-= (int adj)
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{
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offset_ -= adj;
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return *this;
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}
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OrientationIndicator&
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operator++ ()
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{
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this->operator +=(1);
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return *this;
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}
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OrientationIndicator&
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operator-- ()
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{
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this->operator -=(1);
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return *this;
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}
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};
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} // namespace lib
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#endif /*HIERARCHY_ORIENTATION_INDICATOR_HPP_*/
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