Home | History | Annotate | Download | only in base 
      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 
     24 namespace art {
     25 
     26 template<typename T>
     27 class 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 
    121 template <typename T>
    122 StrideIterator<T> operator+(typename StrideIterator<T>::difference_type dist,
    123                             const StrideIterator<T>& it) {
    124   return it + dist;
    125 }
    126 
    127 template <typename T>
    128 bool operator<(const StrideIterator<T>& lhs, const StrideIterator<T>& rhs) {
    129   DCHECK_EQ(lhs.stride_, rhs.stride_);
    130   return lhs.ptr_ < rhs.ptr_;
    131 }
    132 
    133 template <typename T>
    134 bool operator>(const StrideIterator<T>& lhs, const StrideIterator<T>& rhs) {
    135   return rhs < lhs;
    136 }
    137 
    138 template <typename T>
    139 bool operator<=(const StrideIterator<T>& lhs, const StrideIterator<T>& rhs) {
    140   return !(rhs < lhs);
    141 }
    142 
    143 template <typename T>
    144 bool 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