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// Copyright 2017 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.
//
// 3. Neither the name of the copyright holder nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
// DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
// SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#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_