1 // Copyright 2014 the V8 project authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #ifndef V8_BASE_ITERATOR_H_
6 #define V8_BASE_ITERATOR_H_
7
8 #include <iterator>
9
10 namespace v8 {
11 namespace base {
12
13 template <class Category, class Type, class Diff = std::ptrdiff_t,
14 class Pointer = Type*, class Reference = Type&>
15 struct iterator {
16 using iterator_category = Category;
17 using value_type = Type;
18 using difference_type = Diff;
19 using pointer = Pointer;
20 using reference = Reference;
21 };
22
23 // The intention of the base::iterator_range class is to encapsulate two
24 // iterators so that the range defined by the iterators can be used like
25 // a regular STL container (actually only a subset of the full container
26 // functionality is available usually).
27 template <typename ForwardIterator>
28 class iterator_range {
29 public:
30 using iterator = ForwardIterator;
31 using const_iterator = ForwardIterator;
32 using pointer = typename std::iterator_traits<iterator>::pointer;
33 using reference = typename std::iterator_traits<iterator>::reference;
34 using value_type = typename std::iterator_traits<iterator>::value_type;
35 using difference_type =
36 typename std::iterator_traits<iterator>::difference_type;
37
iterator_range()38 iterator_range() : begin_(), end_() {}
iterator_range(ForwardIterator begin,ForwardIterator end)39 iterator_range(ForwardIterator begin, ForwardIterator end)
40 : begin_(begin), end_(end) {}
41
begin()42 iterator begin() { return begin_; }
end()43 iterator end() { return end_; }
begin()44 const_iterator begin() const { return begin_; }
end()45 const_iterator end() const { return end_; }
cbegin()46 const_iterator cbegin() const { return begin_; }
cend()47 const_iterator cend() const { return end_; }
48
empty()49 bool empty() const { return cbegin() == cend(); }
50
51 // Random Access iterators only.
52 reference operator[](difference_type n) { return begin()[n]; }
size()53 difference_type size() const { return cend() - cbegin(); }
54
55 private:
56 const_iterator const begin_;
57 const_iterator const end_;
58 };
59
60 template <typename ForwardIterator>
make_iterator_range(ForwardIterator begin,ForwardIterator end)61 auto make_iterator_range(ForwardIterator begin, ForwardIterator end) {
62 return iterator_range<ForwardIterator>{begin, end};
63 }
64
65 // {Reversed} returns a container adapter usable in a range-based "for"
66 // statement for iterating a reversible container in reverse order.
67 //
68 // Example:
69 //
70 // std::vector<int> v = ...;
71 // for (int i : base::Reversed(v)) {
72 // // iterates through v from back to front
73 // }
74 template <typename T>
Reversed(T & t)75 auto Reversed(T& t) { // NOLINT(runtime/references): match {rbegin} and {rend}
76 return make_iterator_range(std::rbegin(t), std::rend(t));
77 }
78
79 } // namespace base
80 } // namespace v8
81
82 #endif // V8_BASE_ITERATOR_H_
83