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// Copyright 2020 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef V8_BASE_BITS_ITERATOR_H_
#define V8_BASE_BITS_ITERATOR_H_
#include <type_traits>
#include "src/base/bits.h"
#include "src/base/iterator.h"
namespace v8 {
namespace base {
namespace bits {
template <typename T, bool kMSBFirst = false>
class BitsIterator : public iterator<std::forward_iterator_tag, int> {
STATIC_ASSERT(std::is_integral<T>::value);
public:
explicit BitsIterator(T bits) : bits_(bits) {}
int operator*() const {
return kMSBFirst ? 8 * sizeof(T) - 1 - CountLeadingZeros(bits_)
: CountTrailingZeros(bits_);
}
BitsIterator& operator++() {
bits_ &= ~(T{1} << **this);
return *this;
}
bool operator==(BitsIterator other) { return bits_ == other.bits_; }
bool operator!=(BitsIterator other) { return bits_ != other.bits_; }
private:
T bits_;
};
// Returns an iterable over the bits in {bits}, from LSB to MSB.
template <typename T>
auto IterateBits(T bits) {
return make_iterator_range(BitsIterator<T>{bits}, BitsIterator<T>{0});
}
// Returns an iterable over the bits in {bits}, from MSB to LSB.
template <typename T>
auto IterateBitsBackwards(T bits) {
return make_iterator_range(BitsIterator<T, true>{bits},
BitsIterator<T, true>{0});
}
} // namespace bits
} // namespace base
} // namespace v8
#endif // V8_BASE_BITS_ITERATOR_H_
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