59 lines
1.8 KiB
C++
59 lines
1.8 KiB
C++
/*
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/.
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*
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* Copyright 2010-2018 Danny Robson <danny@nerdcruft.net>
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*/
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#pragma once
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#include <memory>
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namespace cruft::iterator {
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///////////////////////////////////////////////////////////////////////////
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/// Counts the number of times the iterator is assigned to.
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///
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/// It currently uses a shared_ptr to allow for value copying of the iterator
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/// (as tends to often happen in places such as <algorithm>)
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struct counting_output_iterator {
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// An internal proxy value which is returned when the iterator is
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// dereferenced. It increments the assignment value in the host
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// iterator.
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//
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// The internals of this object are not a stable interface.
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struct assignable {
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assignable (std::size_t &_count)
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: m_count (_count)
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{ ; }
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template <typename Arg>
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void
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operator= (Arg&&)
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{
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++m_count;
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}
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private:
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std::size_t &m_count;
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};
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using value_type = assignable;
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using iterator_category = std::output_iterator_tag;
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using reference = assignable&;
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counting_output_iterator ()
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: m_count (std::make_shared<std::size_t> (0))
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{ ; }
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counting_output_iterator& operator++ () { return *this; }
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assignable operator* () { return assignable (*m_count); }
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/// Returns the number of times the iterator has been assigned to.
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std::size_t count (void) const { return *m_count; }
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private:
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std::shared_ptr<std::size_t> m_count;
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};
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}
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