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1 /*
2  * Copyright 2023 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 #pragma once
18 
19 #include <stddef.h>
20 #include <array>
21 
22 namespace android::utils {
23 
24 template <class T, size_t SIZE>
25 class RingBuffer {
26     RingBuffer(const RingBuffer&) = delete;
27     void operator=(const RingBuffer&) = delete;
28 
29 public:
30     RingBuffer() = default;
31     ~RingBuffer() = default;
32 
capacity()33     constexpr size_t capacity() const { return SIZE; }
34 
size()35     size_t size() const { return mCount; }
36 
next()37     T& next() {
38         mHead = static_cast<size_t>(mHead + 1) % SIZE;
39         if (mCount < SIZE) {
40             mCount++;
41         }
42         return mBuffer[static_cast<size_t>(mHead)];
43     }
44 
front()45     T& front() { return (*this)[0]; }
46 
back()47     T& back() { return (*this)[size() - 1]; }
48 
49     T& operator[](size_t index) {
50         return mBuffer[(static_cast<size_t>(mHead + 1) + index) % mCount];
51     }
52 
53     const T& operator[](size_t index) const {
54         return mBuffer[(static_cast<size_t>(mHead + 1) + index) % mCount];
55     }
56 
clear()57     void clear() {
58         mCount = 0;
59         mHead = -1;
60     }
61 
62 private:
63     std::array<T, SIZE> mBuffer;
64     int mHead = -1;
65     size_t mCount = 0;
66 };
67 
68 } // namespace android::utils
69