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/*
* Copyright (C) 2016 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#ifndef ART_LIBARTBASE_BASE_TRANSFORM_ARRAY_REF_H_
#define ART_LIBARTBASE_BASE_TRANSFORM_ARRAY_REF_H_
#include <type_traits>
#include "array_ref.h"
#include "transform_iterator.h"
namespace art {
/**
* @brief An ArrayRef<> wrapper that uses a transformation function for element access.
*/
template <typename BaseType, typename Function>
class TransformArrayRef {
private:
using Iter = TransformIterator<typename ArrayRef<BaseType>::iterator, Function>;
// The Function may take a non-const reference, so const_iterator may not exist.
using FallbackConstIter = std::iterator<std::random_access_iterator_tag, void, void, void, void>;
using PreferredConstIter =
TransformIterator<typename ArrayRef<BaseType>::const_iterator, Function>;
template <typename F, typename = typename std::result_of<F(const BaseType&)>::type>
static PreferredConstIter ConstIterHelper(int&);
template <typename F>
static FallbackConstIter ConstIterHelper(const int&);
using ConstIter = decltype(ConstIterHelper<Function>(*reinterpret_cast<int*>(0)));
public:
using value_type = typename Iter::value_type;
using reference = typename Iter::reference;
using const_reference = typename ConstIter::reference;
using pointer = typename Iter::pointer;
using const_pointer = typename ConstIter::pointer;
using iterator = Iter;
using const_iterator = typename std::conditional<
std::is_same<ConstIter, FallbackConstIter>::value,
void,
ConstIter>::type;
using reverse_iterator = std::reverse_iterator<Iter>;
using const_reverse_iterator = typename std::conditional<
std::is_same<ConstIter, FallbackConstIter>::value,
void,
std::reverse_iterator<ConstIter>>::type;
using difference_type = typename ArrayRef<BaseType>::difference_type;
using size_type = typename ArrayRef<BaseType>::size_type;
// Constructors.
TransformArrayRef(const TransformArrayRef& other) = default;
template <typename OtherBT>
TransformArrayRef(const ArrayRef<OtherBT>& base, Function fn)
: data_(base, fn) { }
template <typename OtherBT,
typename = typename std::enable_if<std::is_same<BaseType, const OtherBT>::value>::type>
TransformArrayRef(const TransformArrayRef<OtherBT, Function>& other)
: TransformArrayRef(other.base(), other.GetFunction()) { }
// Assignment operators.
TransformArrayRef& operator=(const TransformArrayRef& other) = default;
template <typename OtherBT,
typename = typename std::enable_if<std::is_same<BaseType, const OtherBT>::value>::type>
TransformArrayRef& operator=(const TransformArrayRef<OtherBT, Function>& other) {
return *this = TransformArrayRef(other.base(), other.GetFunction());
}
// Destructor.
~TransformArrayRef() = default;
// Iterators.
iterator begin() { return MakeIterator(base().begin()); }
const_iterator begin() const { return MakeIterator(base().cbegin()); }
const_iterator cbegin() const { return MakeIterator(base().cbegin()); }
iterator end() { return MakeIterator(base().end()); }
const_iterator end() const { MakeIterator(base().cend()); }
const_iterator cend() const { return MakeIterator(base().cend()); }
reverse_iterator rbegin() { return reverse_iterator(end()); }
const_reverse_iterator rbegin() const { return const_reverse_iterator(end()); }
const_reverse_iterator crbegin() const { return const_reverse_iterator(cend()); }
reverse_iterator rend() { return reverse_iterator(begin()); }
const_reverse_iterator rend() const { return const_reverse_iterator(begin()); }
const_reverse_iterator crend() const { return const_reverse_iterator(cbegin()); }
// Size.
size_type size() const { return base().size(); }
bool empty() const { return base().empty(); }
// Element access. NOTE: Not providing data().
reference operator[](size_type n) { return GetFunction()(base()[n]); }
const_reference operator[](size_type n) const { return GetFunction()(base()[n]); }
reference front() { return GetFunction()(base().front()); }
const_reference front() const { return GetFunction()(base().front()); }
reference back() { return GetFunction()(base().back()); }
const_reference back() const { return GetFunction()(base().back()); }
TransformArrayRef SubArray(size_type pos) {
return TransformArrayRef(base().subarray(pos), GetFunction());
}
TransformArrayRef SubArray(size_type pos) const {
return TransformArrayRef(base().subarray(pos), GetFunction());
}
TransformArrayRef SubArray(size_type pos, size_type length) const {
return TransformArrayRef(base().subarray(pos, length), GetFunction());
}
// Retrieve the base ArrayRef<>.
ArrayRef<BaseType> base() {
return data_.base_;
}
ArrayRef<const BaseType> base() const {
return ArrayRef<const BaseType>(data_.base_);
}
private:
// Allow EBO for state-less Function.
struct Data : Function {
public:
Data(ArrayRef<BaseType> base, Function fn) : Function(fn), base_(base) { }
ArrayRef<BaseType> base_;
};
const Function& GetFunction() const {
return static_cast<const Function&>(data_);
}
template <typename BaseIterator>
auto MakeIterator(BaseIterator base) const {
return MakeTransformIterator(base, GetFunction());
}
Data data_;
template <typename OtherBT, typename OtherFunction>
friend class TransformArrayRef;
};
template <typename BaseType, typename Function>
bool operator==(const TransformArrayRef<BaseType, Function>& lhs,
const TransformArrayRef<BaseType, Function>& rhs) {
return lhs.size() == rhs.size() && std::equal(lhs.begin(), lhs.end(), rhs.begin());
}
template <typename BaseType, typename Function>
bool operator!=(const TransformArrayRef<BaseType, Function>& lhs,
const TransformArrayRef<BaseType, Function>& rhs) {
return !(lhs == rhs);
}
template <typename ValueType, typename Function>
TransformArrayRef<ValueType, Function> MakeTransformArrayRef(
ArrayRef<ValueType> container, Function f) {
return TransformArrayRef<ValueType, Function>(container, f);
}
template <typename Container, typename Function>
TransformArrayRef<typename Container::value_type, Function> MakeTransformArrayRef(
Container& container, Function f) {
return TransformArrayRef<typename Container::value_type, Function>(
ArrayRef<typename Container::value_type>(container.data(), container.size()), f);
}
template <typename Container, typename Function>
TransformArrayRef<const typename Container::value_type, Function> MakeTransformArrayRef(
const Container& container, Function f) {
return TransformArrayRef<const typename Container::value_type, Function>(
ArrayRef<const typename Container::value_type>(container.data(), container.size()), f);
}
} // namespace art
#endif // ART_LIBARTBASE_BASE_TRANSFORM_ARRAY_REF_H_
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