85 lines
2.6 KiB
C++
85 lines
2.6 KiB
C++
///@file
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/// Compare lists and get differences
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///
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// Copyright (C) 2013 Thomas Geymayer <tomgey@gmail.com>
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//
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// This library is free software; you can redistribute it and/or
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// modify it under the terms of the GNU Library General Public
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// License as published by the Free Software Foundation; either
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// version 2 of the License, or (at your option) any later version.
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//
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// This library 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 GNU
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// Library General Public License for more details.
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//
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// You should have received a copy of the GNU Library General Public
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// License along with this library; if not, write to the Free Software
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// Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
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#ifndef SG_LISTDIFF_HXX_
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#define SG_LISTDIFF_HXX_
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#include <vector>
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namespace simgear
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{
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template<class T>
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struct ListDiff
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{
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typedef std::vector<T> List;
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typedef std::function<void (T)> Callback;
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/**
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* Perform list diff in-place (modifies both lists) and call cb_add for
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* every element in new_list not in old_list and cb_remove for every element
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* in old_list not in new_list.
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*/
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static void inplace( List& old_list,
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List& new_list,
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Callback cb_add,
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Callback cb_remove )
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{
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// Check which elements have been removed. (Removing first and adding
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// second should keep the memory usage lower - not for this function, but
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// probably for users of this function which use the callbacks to delete
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// and create objects)
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while( !old_list.empty() )
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{
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T& old_el = old_list.front();
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typename List::iterator new_el =
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std::find(new_list.begin(), new_list.end(), old_el);
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if( new_el == new_list.end() )
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{
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if( cb_remove )
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cb_remove(old_el);
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}
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else
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{
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// Element is in both lists -> just ignore
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*new_el = new_list.back();
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new_list.pop_back();
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}
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old_list.front() = old_list.back();
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old_list.pop_back();
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}
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// All remaing elements in new_list have not been in old_list, so call
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// the add callback for every element if required.
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if( cb_add )
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{
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for( typename List::iterator it = new_list.begin();
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it != new_list.end();
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++it )
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cb_add(*it);
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}
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}
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};
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} // namespace simgear
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#endif /* SG_LISTDIFF_HXX_ */
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