1/*
2 * Copyright 2011-present Facebook, Inc.
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#pragma once
18
19#include <iterator>
20#include <type_traits>
21
22#include <boost/iterator/iterator_adaptor.hpp>
23
24namespace folly {
25
26template <class BaseIter>
27class BitIterator;
28
29namespace bititerator_detail {
30
31// Reference to a bit.
32// Templatize on both parent reference and value types to capture
33// const-ness correctly and to work with the case where Ref is a
34// reference-like type (not T&), just like our BitReference here.
35template <class Ref, class Value>
36class BitReference {
37 public:
38 BitReference(Ref r, size_t bit) : ref_(r), bit_(bit) {}
39
40 /* implicit */ operator bool() const {
41 return ref_ & (one_ << bit_);
42 }
43
44 BitReference& operator=(bool b) {
45 if (b) {
46 set();
47 } else {
48 clear();
49 }
50 return *this;
51 }
52
53 void set() {
54 ref_ |= (one_ << bit_);
55 }
56
57 void clear() {
58 ref_ &= ~(one_ << bit_);
59 }
60
61 void flip() {
62 ref_ ^= (one_ << bit_);
63 }
64
65 private:
66 // shortcut to avoid writing static_cast everywhere
67 const static Value one_ = 1;
68
69 Ref ref_;
70 size_t bit_;
71};
72
73template <class BaseIter>
74struct BitIteratorBase {
75 static_assert(
76 std::is_integral<
77 typename std::iterator_traits<BaseIter>::value_type>::value,
78 "BitIterator may only be used with integral types");
79 typedef boost::iterator_adaptor<
80 BitIterator<BaseIter>, // Derived
81 BaseIter, // Base
82 bool, // Value
83 boost::use_default, // CategoryOrTraversal
84 bititerator_detail::BitReference<
85 typename std::iterator_traits<BaseIter>::reference,
86 typename std::iterator_traits<BaseIter>::value_type>, // Reference
87 ssize_t>
88 type;
89};
90
91} // namespace bititerator_detail
92} // namespace folly
93