| // Copyright 2024 The Dawn & Tint Authors |
| // |
| // Redistribution and use in source and binary forms, with or without |
| // modification, are permitted provided that the following conditions are met: |
| // |
| // 1. Redistributions of source code must retain the above copyright notice, this |
| // list of conditions and the following disclaimer. |
| // |
| // 2. Redistributions in binary form must reproduce the above copyright notice, |
| // this list of conditions and the following disclaimer in the documentation |
| // and/or other materials provided with the distribution. |
| // |
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| // this software without specific prior written permission. |
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| // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" |
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| |
| #ifndef SRC_TINT_UTILS_CONTAINERS_FILTERED_ITERATOR_H_ |
| #define SRC_TINT_UTILS_CONTAINERS_FILTERED_ITERATOR_H_ |
| |
| #include <utility> |
| |
| namespace tint { |
| |
| /// FilteredIterator is an iterator that skip over elements where the predicate function returns |
| /// false. |
| /// @tparam PREDICATE the filter predicate function |
| /// @tparam ITERATOR the inner iterator type |
| template <typename PREDICATE, typename ITERATOR> |
| class FilteredIterator { |
| public: |
| /// @param current the current iterator. |
| /// @param end the end iterator. |
| FilteredIterator(ITERATOR current, ITERATOR end) : current_(current), end_(end) { |
| // Skip to first element that passes the predicate |
| while (current_ != end && !PREDICATE{}(*current_)) { |
| ++current_; |
| } |
| } |
| |
| /// Copy constructor |
| FilteredIterator(const FilteredIterator&) = default; |
| |
| /// Copy assignment operator |
| FilteredIterator& operator=(const FilteredIterator&) = default; |
| |
| /// Move constructor |
| FilteredIterator(FilteredIterator&&) = default; |
| |
| /// Move assignment operator |
| FilteredIterator& operator=(FilteredIterator&&) = default; |
| |
| /// Increments the iterator until PREDICATE returns true, or the end is reached. |
| /// @return this FilteredIterator |
| FilteredIterator& operator++() { |
| ++current_; |
| while (current_ != end_ && !PREDICATE{}(*current_)) { |
| ++current_; |
| } |
| return *this; |
| } |
| |
| /// @returns the element at the current iterator |
| auto operator*() const { return *current_; } |
| |
| /// @returns the element at the current iterator |
| auto operator->() const { return current_.operator->(); } |
| |
| /// Equality operator |
| /// @returns true if this iterator is equal to @p other |
| bool operator==(const FilteredIterator& other) const { return current_ == other.current_; } |
| |
| /// Inequality operator |
| /// @returns true if this iterator is not equal to @p other |
| bool operator!=(const FilteredIterator& other) const { return current_ != other.current_; } |
| |
| private: |
| /// The current iterator. |
| ITERATOR current_; |
| /// The end iterator. |
| ITERATOR end_; |
| }; |
| |
| /// FilteredIterable is a wrapper around an object with begin() / end() methods, that returns |
| /// iterators that skip over elements where the predicate function returns false. |
| /// @tparam PREDICATE the filter predicate function |
| /// @tparam ITERABLE the inner iterable object type |
| template <typename PREDICATE, typename ITERABLE> |
| struct FilteredIterable { |
| /// The iterator type |
| using iterator = typename std::decay_t<ITERABLE>::iterator; |
| /// The const iterator type |
| using const_iterator = typename std::decay_t<ITERABLE>::const_iterator; |
| |
| /// The wrapped iterable object. |
| ITERABLE iterable; |
| |
| /// @return the filtered start iterator |
| FilteredIterator<PREDICATE, iterator> begin() { return {iterable.begin(), iterable.end()}; } |
| |
| /// @return the filtered end iterator |
| FilteredIterator<PREDICATE, iterator> end() { return {iterable.end(), iterable.end()}; } |
| |
| /// @return the filtered const start iterator |
| FilteredIterator<PREDICATE, const_iterator> begin() const { |
| return {iterable.begin(), iterable.end()}; |
| } |
| |
| /// @return the filtered const end iterator |
| FilteredIterator<PREDICATE, const_iterator> end() const { |
| return {iterable.end(), iterable.end()}; |
| } |
| }; |
| |
| /// @returns a FilteredIterable from the filter function `PREDICATE`, wrapping @p iterable |
| /// @tparam PREDICATE the filter predicate function |
| /// @tparam ITERABLE the inner iterable object type |
| template <typename PREDICATE, typename ITERABLE> |
| FilteredIterable<PREDICATE, ITERABLE&> Filter(ITERABLE& iterable) { |
| return {iterable}; |
| } |
| |
| } // namespace tint |
| |
| #endif // SRC_TINT_UTILS_CONTAINERS_FILTERED_ITERATOR_H_ |