| // Copyright 2017 The Dawn Authors |
| // |
| // 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 SRC_DAWN_COMMON_BITSETITERATOR_H_ |
| #define SRC_DAWN_COMMON_BITSETITERATOR_H_ |
| |
| #include <bitset> |
| #include <limits> |
| |
| #include "dawn/common/Assert.h" |
| #include "dawn/common/Math.h" |
| #include "dawn/common/UnderlyingType.h" |
| |
| namespace dawn { |
| |
| // This is ANGLE's BitSetIterator class with a customizable return type. |
| // Types have been updated to be more specific. |
| // TODO(crbug.com/dawn/306): it could be optimized, in particular when N <= 64 |
| |
| template <typename T> |
| T roundUp(const T value, const T alignment) { |
| auto temp = value + alignment - static_cast<T>(1); |
| return temp - temp % alignment; |
| } |
| |
| template <size_t N, typename T> |
| class BitSetIterator final { |
| public: |
| explicit BitSetIterator(const std::bitset<N>& bitset); |
| BitSetIterator(const BitSetIterator& other); |
| BitSetIterator& operator=(const BitSetIterator& other); |
| |
| class Iterator final { |
| public: |
| explicit Iterator(const std::bitset<N>& bits); |
| Iterator& operator++(); |
| |
| bool operator==(const Iterator& other) const; |
| bool operator!=(const Iterator& other) const; |
| |
| T operator*() const { |
| using U = UnderlyingType<T>; |
| DAWN_ASSERT(static_cast<U>(mCurrentBit) <= std::numeric_limits<U>::max()); |
| return static_cast<T>(static_cast<U>(mCurrentBit)); |
| } |
| |
| private: |
| uint32_t getNextBit(); |
| |
| static constexpr size_t kBitsPerWord = sizeof(uint32_t) * 8; |
| std::bitset<N> mBits; |
| uint32_t mCurrentBit; |
| uint32_t mOffset; |
| }; |
| |
| Iterator begin() const { return Iterator(mBits); } |
| Iterator end() const { return Iterator(std::bitset<N>(0)); } |
| |
| private: |
| const std::bitset<N> mBits; |
| }; |
| |
| template <size_t N, typename T> |
| BitSetIterator<N, T>::BitSetIterator(const std::bitset<N>& bitset) : mBits(bitset) {} |
| |
| template <size_t N, typename T> |
| BitSetIterator<N, T>::BitSetIterator(const BitSetIterator& other) : mBits(other.mBits) {} |
| |
| template <size_t N, typename T> |
| BitSetIterator<N, T>& BitSetIterator<N, T>::operator=(const BitSetIterator& other) { |
| mBits = other.mBits; |
| return *this; |
| } |
| |
| template <size_t N, typename T> |
| BitSetIterator<N, T>::Iterator::Iterator(const std::bitset<N>& bits) |
| : mBits(bits), mCurrentBit(0), mOffset(0) { |
| if (bits.any()) { |
| mCurrentBit = getNextBit(); |
| } else { |
| mOffset = static_cast<uint32_t>(roundUp(N, kBitsPerWord)); |
| } |
| } |
| |
| template <size_t N, typename T> |
| typename BitSetIterator<N, T>::Iterator& BitSetIterator<N, T>::Iterator::operator++() { |
| DAWN_ASSERT(mBits.any()); |
| mBits.set(mCurrentBit - mOffset, 0); |
| mCurrentBit = getNextBit(); |
| return *this; |
| } |
| |
| template <size_t N, typename T> |
| bool BitSetIterator<N, T>::Iterator::operator==(const Iterator& other) const { |
| return mOffset == other.mOffset && mBits == other.mBits; |
| } |
| |
| template <size_t N, typename T> |
| bool BitSetIterator<N, T>::Iterator::operator!=(const Iterator& other) const { |
| return !(*this == other); |
| } |
| |
| template <size_t N, typename T> |
| uint32_t BitSetIterator<N, T>::Iterator::getNextBit() { |
| static std::bitset<N> wordMask(std::numeric_limits<uint32_t>::max()); |
| |
| while (mOffset < N) { |
| uint32_t wordBits = static_cast<uint32_t>((mBits & wordMask).to_ulong()); |
| if (wordBits != 0ul) { |
| return ScanForward(wordBits) + mOffset; |
| } |
| |
| mBits >>= kBitsPerWord; |
| mOffset += kBitsPerWord; |
| } |
| return 0; |
| } |
| |
| // Helper to avoid needing to specify the template parameter size |
| template <size_t N> |
| BitSetIterator<N, uint32_t> IterateBitSet(const std::bitset<N>& bitset) { |
| return BitSetIterator<N, uint32_t>(bitset); |
| } |
| |
| } // namespace dawn |
| |
| #endif // SRC_DAWN_COMMON_BITSETITERATOR_H_ |