Backed out 7 changesets (bug 1839993) for causing build bustages on DecoderTemplate...
[gecko.git] / mfbt / ReverseIterator.h
blobc9e77ffc89a43dc22602037a5a9999c81672d345
1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
3 /* This Source Code Form is subject to the terms of the Mozilla Public
4 * License, v. 2.0. If a copy of the MPL was not distributed with this
5 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
7 /* An iterator that acts like another iterator, but iterating in
8 * the negative direction. (Note that not all iterators can iterate
9 * in the negative direction.) */
11 #ifndef mozilla_ReverseIterator_h
12 #define mozilla_ReverseIterator_h
14 #include <utility>
16 #include "mozilla/Attributes.h"
18 namespace mozilla {
20 // This should only be used in cases where std::reverse_iterator cannot be used,
21 // because the underlying iterator is not a proper bidirectional iterator, but
22 // rather, e.g., a stashing iterator such as IntegerIterator. It is less
23 // efficient than std::reverse_iterator for proper bidirectional iterators.
24 template <typename IteratorT>
25 class ReverseIterator {
26 public:
27 using value_type = typename IteratorT::value_type;
28 using pointer = typename IteratorT::pointer;
29 using reference = typename IteratorT::reference;
30 using difference_type = typename IteratorT::difference_type;
31 using iterator_category = typename IteratorT::iterator_category;
33 explicit ReverseIterator(IteratorT aIter) : mCurrent(std::move(aIter)) {}
35 // The return type is not reference, but rather the return type of
36 // Iterator::operator*(), which might be value_type, to allow this to work
37 // with stashing iterators such as IntegerIterator, see also Bug 1175485.
38 decltype(*std::declval<IteratorT>()) operator*() const {
39 IteratorT tmp = mCurrent;
40 return *--tmp;
43 /* Difference operator */
44 difference_type operator-(const ReverseIterator& aOther) const {
45 return aOther.mCurrent - mCurrent;
48 /* Increments and decrements operators */
50 ReverseIterator& operator++() {
51 --mCurrent;
52 return *this;
54 ReverseIterator& operator--() {
55 ++mCurrent;
56 return *this;
58 ReverseIterator operator++(int) {
59 auto ret = *this;
60 mCurrent--;
61 return ret;
63 ReverseIterator operator--(int) {
64 auto ret = *this;
65 mCurrent++;
66 return ret;
69 /* Comparison operators */
71 template <typename Iterator1, typename Iterator2>
72 friend bool operator==(const ReverseIterator<Iterator1>& aIter1,
73 const ReverseIterator<Iterator2>& aIter2);
74 template <typename Iterator1, typename Iterator2>
75 friend bool operator!=(const ReverseIterator<Iterator1>& aIter1,
76 const ReverseIterator<Iterator2>& aIter2);
77 template <typename Iterator1, typename Iterator2>
78 friend bool operator<(const ReverseIterator<Iterator1>& aIter1,
79 const ReverseIterator<Iterator2>& aIter2);
80 template <typename Iterator1, typename Iterator2>
81 friend bool operator<=(const ReverseIterator<Iterator1>& aIter1,
82 const ReverseIterator<Iterator2>& aIter2);
83 template <typename Iterator1, typename Iterator2>
84 friend bool operator>(const ReverseIterator<Iterator1>& aIter1,
85 const ReverseIterator<Iterator2>& aIter2);
86 template <typename Iterator1, typename Iterator2>
87 friend bool operator>=(const ReverseIterator<Iterator1>& aIter1,
88 const ReverseIterator<Iterator2>& aIter2);
90 private:
91 IteratorT mCurrent;
94 template <typename Iterator1, typename Iterator2>
95 bool operator==(const ReverseIterator<Iterator1>& aIter1,
96 const ReverseIterator<Iterator2>& aIter2) {
97 return aIter1.mCurrent == aIter2.mCurrent;
100 template <typename Iterator1, typename Iterator2>
101 bool operator!=(const ReverseIterator<Iterator1>& aIter1,
102 const ReverseIterator<Iterator2>& aIter2) {
103 return aIter1.mCurrent != aIter2.mCurrent;
106 template <typename Iterator1, typename Iterator2>
107 bool operator<(const ReverseIterator<Iterator1>& aIter1,
108 const ReverseIterator<Iterator2>& aIter2) {
109 return aIter1.mCurrent > aIter2.mCurrent;
112 template <typename Iterator1, typename Iterator2>
113 bool operator<=(const ReverseIterator<Iterator1>& aIter1,
114 const ReverseIterator<Iterator2>& aIter2) {
115 return aIter1.mCurrent >= aIter2.mCurrent;
118 template <typename Iterator1, typename Iterator2>
119 bool operator>(const ReverseIterator<Iterator1>& aIter1,
120 const ReverseIterator<Iterator2>& aIter2) {
121 return aIter1.mCurrent < aIter2.mCurrent;
124 template <typename Iterator1, typename Iterator2>
125 bool operator>=(const ReverseIterator<Iterator1>& aIter1,
126 const ReverseIterator<Iterator2>& aIter2) {
127 return aIter1.mCurrent <= aIter2.mCurrent;
130 namespace detail {
132 template <typename IteratorT,
133 typename ReverseIteratorT = ReverseIterator<IteratorT>>
134 class IteratorRange {
135 public:
136 typedef IteratorT iterator;
137 typedef IteratorT const_iterator;
138 typedef ReverseIteratorT reverse_iterator;
139 typedef ReverseIteratorT const_reverse_iterator;
141 IteratorRange(IteratorT aIterBegin, IteratorT aIterEnd)
142 : mIterBegin(std::move(aIterBegin)), mIterEnd(std::move(aIterEnd)) {}
144 iterator begin() const { return mIterBegin; }
145 const_iterator cbegin() const { return begin(); }
146 iterator end() const { return mIterEnd; }
147 const_iterator cend() const { return end(); }
148 reverse_iterator rbegin() const { return reverse_iterator(mIterEnd); }
149 const_reverse_iterator crbegin() const { return rbegin(); }
150 reverse_iterator rend() const { return reverse_iterator(mIterBegin); }
151 const_reverse_iterator crend() const { return rend(); }
153 IteratorT mIterBegin;
154 IteratorT mIterEnd;
157 } // namespace detail
159 template <typename Range>
160 detail::IteratorRange<typename Range::reverse_iterator> Reversed(
161 Range& aRange) {
162 return {aRange.rbegin(), aRange.rend()};
165 template <typename Range>
166 detail::IteratorRange<typename Range::const_reverse_iterator> Reversed(
167 const Range& aRange) {
168 return {aRange.rbegin(), aRange.rend()};
171 } // namespace mozilla
173 #endif // mozilla_ReverseIterator_h