95 lines
3.0 KiB
C++
95 lines
3.0 KiB
C++
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/*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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* Copyright 2017 Danny Robson <danny@nerdcruft.net>
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*/
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#ifndef CRUFT_UTIL_SARRAY_HPP
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#define CRUFT_UTIL_SARRAY_HPP
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#include "./iterator.hpp"
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#include <cstdlib>
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namespace util {
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/// An array with constant maximum size, but with actual used storage
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/// capacity fixed at construction time.
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///
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/// \tparam S maximum number of elements
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/// \tparam T data type of elements
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template <std::size_t S, typename T>
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class sarray {
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public:
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//---------------------------------------------------------------------
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template <typename ContainerT>
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explicit
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sarray (const ContainerT &_data):
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m_size (std::size (_data))
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{
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if (m_size > S)
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throw std::length_error("exceeded maximum size");
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// I'd like to use izip and structured bindings here, but we run
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// afoul of clang#3349 so we use a seperate index variable.
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std::size_t i = 0;
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for (auto &d: _data) {
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::new (&m_data.objects[i++]) (T) (d);
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}
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}
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~sarray ()
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{
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for (std::size_t i = 0; i < m_size; ++i)
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m_data.objects[i].~T ();
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}
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//---------------------------------------------------------------------
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std::size_t size (void) const
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{
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return m_size;
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}
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//---------------------------------------------------------------------
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T& operator[] (std::size_t i)& { return m_data.objects[i]; }
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const T& operator[] (std::size_t i) const& { return m_data.objects[i]; }
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auto begin (void) { return std::begin (m_data.objects); };
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auto end (void) { return begin () + m_size; }
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auto begin (void) const { return std::begin (m_data.objects); };
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auto end (void) const { return begin () + m_size; }
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auto cbegin (void) const { return std::cbegin (m_data.objects); };
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auto cend (void) const { return cbegin () + m_size; }
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private:
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union alignas (T) data_t {
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// we manually define a trivial constructor/destructor to appease
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// gcc which doesn't like us using non-trivial T as the stored
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// object.
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//
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// we're explicitly controlling the lifetime ourselves so this
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// isn't a functional issue.
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data_t () { };
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~data_t () { };
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char store[sizeof (T) * S];
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T objects[S];
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} m_data;
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const std::size_t m_size;
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};
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}
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#endif
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