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/*
* Copyright 2022 WebAssembly Community Group participants
*
* 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 wasm_support_parent_index_iterator_h
#define wasm_support_parent_index_iterator_h
#include <cstddef>
#include <iterator>
namespace wasm {
// A helper for defining iterators that contain references to some parent object
// and indices into that parent object. Provides operator implementations for
// equality, inequality, index updates, and index differences, but not for
// dereferencing.
//
// Users of this utility should subclass ParentIndexIterator<...> and define the
// following members in the subclass:
//
// - using value_type = ...
// - using pointer = ...
// - using reference = ...
// - reference operator*() const
//
// `Parent` is the parent type that the iterator contains and is being indexed
// into and `Iterator` is the subclass of ParentIndexIterator<...> that is being
// defined.
template<typename Parent, typename Iterator> struct ParentIndexIterator {
using iterator_category = std::random_access_iterator_tag;
using difference_type = std::ptrdiff_t;
Parent parent;
size_t index;
const Iterator& self() const { return *static_cast<const Iterator*>(this); }
Iterator& self() { return *static_cast<Iterator*>(this); }
bool operator==(const ParentIndexIterator& other) const {
return index == other.index && parent == other.parent;
}
bool operator!=(const ParentIndexIterator& other) const {
return !(*this == other);
}
Iterator& operator++() {
++index;
return self();
}
Iterator& operator--() {
--index;
return self();
}
Iterator operator++(int) {
auto it = self();
index++;
return it;
}
Iterator operator--(int) {
auto it = self();
index--;
return it;
}
Iterator& operator+=(difference_type off) {
index += off;
return self();
}
Iterator operator+(difference_type off) const {
return Iterator(self()) += off;
}
Iterator& operator-=(difference_type off) {
index -= off;
return self();
}
Iterator operator-(difference_type off) const {
return Iterator(self()) -= off;
}
difference_type operator-(const Iterator& other) const {
assert(parent == other.parent);
return index - other.index;
}
};
} // namespace wasm
#endif // wasm_support_parent_index_iterator_h
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