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