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114 lines
3.4 KiB
114 lines
3.4 KiB
/*
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* Copyright (C) 2015 The Android Open Source Project
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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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*/
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#ifndef ART_LIBARTBASE_BASE_BIT_UTILS_ITERATOR_H_
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#define ART_LIBARTBASE_BASE_BIT_UTILS_ITERATOR_H_
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#include <iterator>
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#include <limits>
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#include <type_traits>
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#include <android-base/logging.h>
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#include "bit_utils.h"
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#include "iteration_range.h"
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#include "stl_util.h"
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namespace art {
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// Using the Curiously Recurring Template Pattern to implement everything shared
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// by LowToHighBitIterator and HighToLowBitIterator, i.e. everything but operator*().
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template <typename T, typename Iter>
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class BitIteratorBase
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: public std::iterator<std::forward_iterator_tag, uint32_t, ptrdiff_t, void, void> {
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static_assert(std::is_integral<T>::value, "T must be integral");
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static_assert(std::is_unsigned<T>::value, "T must be unsigned");
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static_assert(sizeof(T) == sizeof(uint32_t) || sizeof(T) == sizeof(uint64_t), "Unsupported size");
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public:
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BitIteratorBase() : bits_(0u) { }
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explicit BitIteratorBase(T bits) : bits_(bits) { }
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Iter& operator++() {
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DCHECK_NE(bits_, 0u);
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uint32_t bit = *static_cast<Iter&>(*this);
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bits_ &= ~(static_cast<T>(1u) << bit);
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return static_cast<Iter&>(*this);
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}
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Iter& operator++(int) {
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Iter tmp(static_cast<Iter&>(*this));
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++*this;
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return tmp;
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}
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protected:
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T bits_;
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template <typename U, typename I>
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friend bool operator==(const BitIteratorBase<U, I>& lhs, const BitIteratorBase<U, I>& rhs);
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};
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template <typename T, typename Iter>
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bool operator==(const BitIteratorBase<T, Iter>& lhs, const BitIteratorBase<T, Iter>& rhs) {
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return lhs.bits_ == rhs.bits_;
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}
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template <typename T, typename Iter>
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bool operator!=(const BitIteratorBase<T, Iter>& lhs, const BitIteratorBase<T, Iter>& rhs) {
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return !(lhs == rhs);
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}
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template <typename T>
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class LowToHighBitIterator : public BitIteratorBase<T, LowToHighBitIterator<T>> {
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public:
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using BitIteratorBase<T, LowToHighBitIterator<T>>::BitIteratorBase;
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uint32_t operator*() const {
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DCHECK_NE(this->bits_, 0u);
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return CTZ(this->bits_);
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}
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};
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template <typename T>
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class HighToLowBitIterator : public BitIteratorBase<T, HighToLowBitIterator<T>> {
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public:
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using BitIteratorBase<T, HighToLowBitIterator<T>>::BitIteratorBase;
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uint32_t operator*() const {
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DCHECK_NE(this->bits_, 0u);
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static_assert(std::numeric_limits<T>::radix == 2, "Unexpected radix!");
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return std::numeric_limits<T>::digits - 1u - CLZ(this->bits_);
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}
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};
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template <typename T>
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IterationRange<LowToHighBitIterator<T>> LowToHighBits(T bits) {
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return IterationRange<LowToHighBitIterator<T>>(
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LowToHighBitIterator<T>(bits), LowToHighBitIterator<T>());
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}
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template <typename T>
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IterationRange<HighToLowBitIterator<T>> HighToLowBits(T bits) {
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return IterationRange<HighToLowBitIterator<T>>(
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HighToLowBitIterator<T>(bits), HighToLowBitIterator<T>());
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}
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} // namespace art
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#endif // ART_LIBARTBASE_BASE_BIT_UTILS_ITERATOR_H_
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