1 | // Copyright(c) 2015-present, Gabi Melman & spdlog contributors. |
2 | // Distributed under the MIT License (http://opensource.org/licenses/MIT) |
3 | |
4 | // circular q view of std::vector. |
5 | #pragma once |
6 | |
7 | #include <vector> |
8 | #include <cassert> |
9 | |
10 | namespace spdlog { |
11 | namespace details { |
12 | template<typename T> |
13 | class circular_q |
14 | { |
15 | size_t max_items_ = 0; |
16 | typename std::vector<T>::size_type head_ = 0; |
17 | typename std::vector<T>::size_type tail_ = 0; |
18 | size_t overrun_counter_ = 0; |
19 | std::vector<T> v_; |
20 | |
21 | public: |
22 | using value_type = T; |
23 | |
24 | // empty ctor - create a disabled queue with no elements allocated at all |
25 | circular_q() = default; |
26 | |
27 | explicit circular_q(size_t max_items) |
28 | : max_items_(max_items + 1) // one item is reserved as marker for full q |
29 | , v_(max_items_) |
30 | {} |
31 | |
32 | circular_q(const circular_q &) = default; |
33 | circular_q &operator=(const circular_q &) = default; |
34 | |
35 | // move cannot be default, |
36 | // since we need to reset head_, tail_, etc to zero in the moved object |
37 | circular_q(circular_q &&other) SPDLOG_NOEXCEPT |
38 | { |
39 | copy_moveable(std::move(other)); |
40 | } |
41 | |
42 | circular_q &operator=(circular_q &&other) SPDLOG_NOEXCEPT |
43 | { |
44 | copy_moveable(std::move(other)); |
45 | return *this; |
46 | } |
47 | |
48 | // push back, overrun (oldest) item if no room left |
49 | void push_back(T &&item) |
50 | { |
51 | if (max_items_ > 0) |
52 | { |
53 | v_[tail_] = std::move(item); |
54 | tail_ = (tail_ + 1) % max_items_; |
55 | |
56 | if (tail_ == head_) // overrun last item if full |
57 | { |
58 | head_ = (head_ + 1) % max_items_; |
59 | ++overrun_counter_; |
60 | } |
61 | } |
62 | } |
63 | |
64 | // Return reference to the front item. |
65 | // If there are no elements in the container, the behavior is undefined. |
66 | const T &front() const |
67 | { |
68 | return v_[head_]; |
69 | } |
70 | |
71 | T &front() |
72 | { |
73 | return v_[head_]; |
74 | } |
75 | |
76 | // Return number of elements actually stored |
77 | size_t size() const |
78 | { |
79 | if (tail_ >= head_) |
80 | { |
81 | return tail_ - head_; |
82 | } |
83 | else |
84 | { |
85 | return max_items_ - (head_ - tail_); |
86 | } |
87 | } |
88 | |
89 | // Return const reference to item by index. |
90 | // If index is out of range 0…size()-1, the behavior is undefined. |
91 | const T &at(size_t i) const |
92 | { |
93 | assert(i < size()); |
94 | return v_[(head_ + i) % max_items_]; |
95 | } |
96 | |
97 | // Pop item from front. |
98 | // If there are no elements in the container, the behavior is undefined. |
99 | void pop_front() |
100 | { |
101 | head_ = (head_ + 1) % max_items_; |
102 | } |
103 | |
104 | bool empty() const |
105 | { |
106 | return tail_ == head_; |
107 | } |
108 | |
109 | bool full() const |
110 | { |
111 | // head is ahead of the tail by 1 |
112 | if (max_items_ > 0) |
113 | { |
114 | return ((tail_ + 1) % max_items_) == head_; |
115 | } |
116 | return false; |
117 | } |
118 | |
119 | size_t overrun_counter() const |
120 | { |
121 | return overrun_counter_; |
122 | } |
123 | |
124 | void reset_overrun_counter() |
125 | { |
126 | overrun_counter_ = 0; |
127 | } |
128 | |
129 | private: |
130 | // copy from other&& and reset it to disabled state |
131 | void copy_moveable(circular_q &&other) SPDLOG_NOEXCEPT |
132 | { |
133 | max_items_ = other.max_items_; |
134 | head_ = other.head_; |
135 | tail_ = other.tail_; |
136 | overrun_counter_ = other.overrun_counter_; |
137 | v_ = std::move(other.v_); |
138 | |
139 | // put &&other in disabled, but valid state |
140 | other.max_items_ = 0; |
141 | other.head_ = other.tail_ = 0; |
142 | other.overrun_counter_ = 0; |
143 | } |
144 | }; |
145 | } // namespace details |
146 | } // namespace spdlog |
147 | |