1/*
2 * Copyright (C) 2015 The Android Open Source Project
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#ifndef ART_LIBARTBASE_BASE_STRIDE_ITERATOR_H_
18#define ART_LIBARTBASE_BASE_STRIDE_ITERATOR_H_
19
20#include <iterator>
21
22#include <android-base/logging.h>
23
24namespace art {
25
26template<typename T>
27class StrideIterator : public std::iterator<std::random_access_iterator_tag, T> {
28 public:
29  using difference_type =
30      typename std::iterator<std::random_access_iterator_tag, T>::difference_type;
31
32  StrideIterator(const StrideIterator&) = default;
33  StrideIterator(StrideIterator&&) = default;
34  StrideIterator& operator=(const StrideIterator&) = default;
35  StrideIterator& operator=(StrideIterator&&) = default;
36
37  StrideIterator(T* ptr, size_t stride)
38      : ptr_(reinterpret_cast<uintptr_t>(ptr)),
39        stride_(stride) {}
40
41  bool operator==(const StrideIterator& other) const {
42    DCHECK_EQ(stride_, other.stride_);
43    return ptr_ == other.ptr_;
44  }
45
46  bool operator!=(const StrideIterator& other) const {
47    return !(*this == other);
48  }
49
50  StrideIterator& operator++() {  // Value after modification.
51    ptr_ += stride_;
52    return *this;
53  }
54
55  StrideIterator operator++(int) {
56    StrideIterator<T> temp = *this;
57    ++*this;
58    return temp;
59  }
60
61  StrideIterator& operator--() {  // Value after modification.
62    ptr_ -= stride_;
63    return *this;
64  }
65
66  StrideIterator operator--(int) {
67    StrideIterator<T> temp = *this;
68    --*this;
69    return temp;
70  }
71
72  StrideIterator& operator+=(difference_type delta) {
73    ptr_ += static_cast<ssize_t>(stride_) * delta;
74    return *this;
75  }
76
77  StrideIterator operator+(difference_type delta) const {
78    StrideIterator<T> temp = *this;
79    temp += delta;
80    return temp;
81  }
82
83  StrideIterator& operator-=(difference_type delta) {
84    ptr_ -= static_cast<ssize_t>(stride_) * delta;
85    return *this;
86  }
87
88  StrideIterator operator-(difference_type delta) const {
89    StrideIterator<T> temp = *this;
90    temp -= delta;
91    return temp;
92  }
93
94  difference_type operator-(const StrideIterator& rhs) {
95    DCHECK_EQ(stride_, rhs.stride_);
96    DCHECK_EQ((ptr_ - rhs.ptr_) % stride_, 0u);
97    return (ptr_ - rhs.ptr_) / stride_;
98  }
99
100  T& operator*() const {
101    return *reinterpret_cast<T*>(ptr_);
102  }
103
104  T* operator->() const {
105    return &**this;
106  }
107
108  T& operator[](difference_type n) {
109    return *(*this + n);
110  }
111
112 private:
113  uintptr_t ptr_;
114  // Not const for operator=.
115  size_t stride_;
116
117  template <typename U>
118  friend bool operator<(const StrideIterator<U>& lhs, const StrideIterator<U>& rhs);
119};
120
121template <typename T>
122StrideIterator<T> operator+(typename StrideIterator<T>::difference_type dist,
123                            const StrideIterator<T>& it) {
124  return it + dist;
125}
126
127template <typename T>
128bool operator<(const StrideIterator<T>& lhs, const StrideIterator<T>& rhs) {
129  DCHECK_EQ(lhs.stride_, rhs.stride_);
130  return lhs.ptr_ < rhs.ptr_;
131}
132
133template <typename T>
134bool operator>(const StrideIterator<T>& lhs, const StrideIterator<T>& rhs) {
135  return rhs < lhs;
136}
137
138template <typename T>
139bool operator<=(const StrideIterator<T>& lhs, const StrideIterator<T>& rhs) {
140  return !(rhs < lhs);
141}
142
143template <typename T>
144bool operator>=(const StrideIterator<T>& lhs, const StrideIterator<T>& rhs) {
145  return !(lhs < rhs);
146}
147
148}  // namespace art
149
150#endif  // ART_LIBARTBASE_BASE_STRIDE_ITERATOR_H_
151