94 lines
2.3 KiB
C++
94 lines
2.3 KiB
C++
/*
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* Copyright (c) Facebook, Inc. and its affiliates.
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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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#pragma once
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#include <iterator>
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#include <type_traits>
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#include <boost/iterator/iterator_adaptor.hpp>
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namespace folly {
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template <class BaseIter>
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class BitIterator;
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namespace bititerator_detail {
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// Reference to a bit.
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// Templatize on both parent reference and value types to capture
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// const-ness correctly and to work with the case where Ref is a
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// reference-like type (not T&), just like our BitReference here.
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template <class Ref, class Value>
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class BitReference {
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public:
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BitReference(Ref r, size_t bit) : ref_(r), bit_(bit) {}
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/* implicit */ operator bool() const {
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return ref_ & (one_ << bit_);
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}
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BitReference& operator=(bool b) {
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if (b) {
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set();
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} else {
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clear();
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}
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return *this;
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}
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void set() {
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ref_ |= (one_ << bit_);
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}
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void clear() {
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ref_ &= ~(one_ << bit_);
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}
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void flip() {
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ref_ ^= (one_ << bit_);
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}
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private:
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// shortcut to avoid writing static_cast everywhere
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const static Value one_ = 1;
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Ref ref_;
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size_t bit_;
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};
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template <class BaseIter>
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struct BitIteratorBase {
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static_assert(
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std::is_integral<
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typename std::iterator_traits<BaseIter>::value_type>::value,
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"BitIterator may only be used with integral types");
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typedef boost::iterator_adaptor<
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BitIterator<BaseIter>, // Derived
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BaseIter, // Base
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bool, // Value
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typename std::iterator_traits<
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BaseIter>::iterator_category, // CategoryOrTraversal
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bititerator_detail::BitReference<
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typename std::iterator_traits<BaseIter>::reference,
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typename std::iterator_traits<BaseIter>::value_type>, // Reference
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ssize_t>
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type;
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};
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} // namespace bititerator_detail
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} // namespace folly
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