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197 lines
7.3 KiB
197 lines
7.3 KiB
/*
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* Copyright (C) 2016 The Android Open Source Project
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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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#ifndef ART_LIBARTBASE_BASE_TRANSFORM_ARRAY_REF_H_
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#define ART_LIBARTBASE_BASE_TRANSFORM_ARRAY_REF_H_
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#include <type_traits>
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#include "array_ref.h"
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#include "transform_iterator.h"
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namespace art {
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/**
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* @brief An ArrayRef<> wrapper that uses a transformation function for element access.
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*/
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template <typename BaseType, typename Function>
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class TransformArrayRef {
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private:
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using Iter = TransformIterator<typename ArrayRef<BaseType>::iterator, Function>;
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// The Function may take a non-const reference, so const_iterator may not exist.
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using FallbackConstIter = std::iterator<std::random_access_iterator_tag, void, void, void, void>;
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using PreferredConstIter =
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TransformIterator<typename ArrayRef<BaseType>::const_iterator, Function>;
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template <typename F, typename = typename std::result_of<F(const BaseType&)>::type>
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static PreferredConstIter ConstIterHelper(int&);
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template <typename F>
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static FallbackConstIter ConstIterHelper(const int&);
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using ConstIter = decltype(ConstIterHelper<Function>(*reinterpret_cast<int*>(0)));
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public:
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using value_type = typename Iter::value_type;
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using reference = typename Iter::reference;
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using const_reference = typename ConstIter::reference;
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using pointer = typename Iter::pointer;
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using const_pointer = typename ConstIter::pointer;
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using iterator = Iter;
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using const_iterator = typename std::conditional<
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std::is_same<ConstIter, FallbackConstIter>::value,
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void,
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ConstIter>::type;
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using reverse_iterator = std::reverse_iterator<Iter>;
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using const_reverse_iterator = typename std::conditional<
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std::is_same<ConstIter, FallbackConstIter>::value,
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void,
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std::reverse_iterator<ConstIter>>::type;
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using difference_type = typename ArrayRef<BaseType>::difference_type;
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using size_type = typename ArrayRef<BaseType>::size_type;
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// Constructors.
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TransformArrayRef(const TransformArrayRef& other) = default;
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template <typename OtherBT>
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TransformArrayRef(const ArrayRef<OtherBT>& base, Function fn)
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: data_(base, fn) { }
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template <typename OtherBT,
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typename = typename std::enable_if<std::is_same<BaseType, const OtherBT>::value>::type>
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TransformArrayRef(const TransformArrayRef<OtherBT, Function>& other)
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: TransformArrayRef(other.base(), other.GetFunction()) { }
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// Assignment operators.
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TransformArrayRef& operator=(const TransformArrayRef& other) = default;
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template <typename OtherBT,
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typename = typename std::enable_if<std::is_same<BaseType, const OtherBT>::value>::type>
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TransformArrayRef& operator=(const TransformArrayRef<OtherBT, Function>& other) {
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return *this = TransformArrayRef(other.base(), other.GetFunction());
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}
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// Destructor.
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~TransformArrayRef() = default;
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// Iterators.
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iterator begin() { return MakeIterator(base().begin()); }
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const_iterator begin() const { return MakeIterator(base().cbegin()); }
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const_iterator cbegin() const { return MakeIterator(base().cbegin()); }
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iterator end() { return MakeIterator(base().end()); }
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const_iterator end() const { return MakeIterator(base().cend()); }
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const_iterator cend() const { return MakeIterator(base().cend()); }
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reverse_iterator rbegin() { return reverse_iterator(end()); }
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const_reverse_iterator rbegin() const { return const_reverse_iterator(end()); }
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const_reverse_iterator crbegin() const { return const_reverse_iterator(cend()); }
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reverse_iterator rend() { return reverse_iterator(begin()); }
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const_reverse_iterator rend() const { return const_reverse_iterator(begin()); }
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const_reverse_iterator crend() const { return const_reverse_iterator(cbegin()); }
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// Size.
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size_type size() const { return base().size(); }
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bool empty() const { return base().empty(); }
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// Element access. NOTE: Not providing data().
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reference operator[](size_type n) { return GetFunction()(base()[n]); }
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const_reference operator[](size_type n) const { return GetFunction()(base()[n]); }
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reference front() { return GetFunction()(base().front()); }
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const_reference front() const { return GetFunction()(base().front()); }
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reference back() { return GetFunction()(base().back()); }
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const_reference back() const { return GetFunction()(base().back()); }
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TransformArrayRef SubArray(size_type pos) {
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return TransformArrayRef(base().subarray(pos), GetFunction());
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}
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TransformArrayRef SubArray(size_type pos) const {
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return TransformArrayRef(base().subarray(pos), GetFunction());
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}
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TransformArrayRef SubArray(size_type pos, size_type length) const {
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return TransformArrayRef(base().subarray(pos, length), GetFunction());
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}
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// Retrieve the base ArrayRef<>.
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ArrayRef<BaseType> base() {
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return data_.base_;
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}
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ArrayRef<const BaseType> base() const {
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return ArrayRef<const BaseType>(data_.base_);
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}
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private:
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// Allow EBO for state-less Function.
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struct Data : Function {
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public:
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Data(ArrayRef<BaseType> base, Function fn) : Function(fn), base_(base) { }
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ArrayRef<BaseType> base_;
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};
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const Function& GetFunction() const {
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return static_cast<const Function&>(data_);
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}
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template <typename BaseIterator>
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auto MakeIterator(BaseIterator base) const {
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return MakeTransformIterator(base, GetFunction());
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}
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Data data_;
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template <typename OtherBT, typename OtherFunction>
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friend class TransformArrayRef;
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};
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template <typename BaseType, typename Function>
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bool operator==(const TransformArrayRef<BaseType, Function>& lhs,
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const TransformArrayRef<BaseType, Function>& rhs) {
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return lhs.size() == rhs.size() && std::equal(lhs.begin(), lhs.end(), rhs.begin());
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}
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template <typename BaseType, typename Function>
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bool operator!=(const TransformArrayRef<BaseType, Function>& lhs,
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const TransformArrayRef<BaseType, Function>& rhs) {
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return !(lhs == rhs);
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}
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template <typename ValueType, typename Function>
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TransformArrayRef<ValueType, Function> MakeTransformArrayRef(
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ArrayRef<ValueType> container, Function f) {
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return TransformArrayRef<ValueType, Function>(container, f);
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}
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template <typename Container, typename Function>
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TransformArrayRef<typename Container::value_type, Function> MakeTransformArrayRef(
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Container& container, Function f) {
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return TransformArrayRef<typename Container::value_type, Function>(
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ArrayRef<typename Container::value_type>(container.data(), container.size()), f);
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}
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template <typename Container, typename Function>
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TransformArrayRef<const typename Container::value_type, Function> MakeTransformArrayRef(
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const Container& container, Function f) {
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return TransformArrayRef<const typename Container::value_type, Function>(
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ArrayRef<const typename Container::value_type>(container.data(), container.size()), f);
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}
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} // namespace art
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#endif // ART_LIBARTBASE_BASE_TRANSFORM_ARRAY_REF_H_
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