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// 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 COMMON_BITSETITERATOR_H_
#define COMMON_BITSETITERATOR_H_
#include "common/Assert.h"
#include "common/Math.h"
#include "common/UnderlyingType.h"
#include <bitset>
#include <limits>
// This is ANGLE's BitSetIterator class with a customizable return type
// 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:
BitSetIterator(const std::bitset<N>& bitset);
BitSetIterator(const BitSetIterator& other);
BitSetIterator& operator=(const BitSetIterator& other);
class Iterator final {
public:
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>;
ASSERT(static_cast<U>(mCurrentBit) <= std::numeric_limits<U>::max());
return static_cast<T>(static_cast<U>(mCurrentBit));
}
private:
unsigned long getNextBit();
static constexpr size_t kBitsPerWord = sizeof(uint32_t) * 8;
std::bitset<N> mBits;
unsigned long mCurrentBit;
unsigned long 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<unsigned long>(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>
unsigned long 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);
}
#endif // COMMON_BITSETITERATOR_H_