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/*
* Copyright 2012 Facebook, Inc.
*
* 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 FOLLY_DETAIL_BITITERATORDETAIL_H_
#define FOLLY_DETAIL_BITITERATORDETAIL_H_
#include <iterator>
#include <type_traits>
#include <boost/iterator/iterator_adaptor.hpp>
namespace folly {
template <class BaseIter> class BitIterator;
namespace bititerator_detail {
// Reference to a bit.
// Templatize on both parent reference and value types to capture
// const-ness correctly and to work with the case where Ref is a
// reference-like type (not T&), just like our BitReference here.
template <class Ref, class Value>
class BitReference {
public:
BitReference(Ref r, size_t bit) : ref_(r), bit_(bit) { }
operator bool() const {
return ref_ & (one_ << bit_);
}
BitReference& operator=(bool b) {
if (b) {
set();
} else {
clear();
}
return *this;
}
void set() {
ref_ |= (one_ << bit_);
}
void clear() {
ref_ &= ~(one_ << bit_);
}
void flip() {
ref_ ^= (one_ << bit_);
}
private:
// shortcut to avoid writing static_cast everywhere
const static Value one_ = 1;
Ref ref_;
size_t bit_;
};
template <class BaseIter>
struct BitIteratorBase {
static_assert(std::is_integral<typename BaseIter::value_type>::value,
"BitIterator may only be used with integral types");
typedef boost::iterator_adaptor<
BitIterator<BaseIter>, // Derived
BaseIter, // Base
bool, // Value
boost::use_default, // CategoryOrTraversal
bititerator_detail::BitReference<
typename std::iterator_traits<BaseIter>::reference,
typename std::iterator_traits<BaseIter>::value_type
>, // Reference
ssize_t> type;
};
} // namespace bititerator_detail
} // namespace folly
#endif /* FOLLY_DETAIL_BITITERATORDETAIL_H_ */
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