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| 1 // Copyright 2013 The Chromium 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 CC_DEBUG_RING_BUFFER_H_ | |
| 6 #define CC_DEBUG_RING_BUFFER_H_ | |
| 7 | |
| 8 #include "base/logging.h" | |
| 9 | |
| 10 namespace cc { | |
| 11 | |
| 12 template<typename T, size_t kSize> | |
| 13 class RingBuffer { | |
| 14 public: | |
| 15 RingBuffer() : current_index_(0) {} | |
| 16 | |
| 17 size_t BufferSize() const { | |
| 18 return kSize; | |
| 19 } | |
| 20 | |
| 21 size_t CurrentIndex() const { | |
| 22 return current_index_; | |
| 23 } | |
| 24 | |
| 25 // tests if a value was saved to this index | |
| 26 bool IsFilledIndex(size_t n) const { | |
| 27 return BufferIndex(n) < current_index_; | |
| 28 } | |
| 29 | |
| 30 // n = 0 returns the oldest value and | |
| 31 // n = bufferSize() - 1 returns the most recent value. | |
| 32 const T& ReadBuffer(size_t n) const { | |
| 33 DCHECK(IsFilledIndex(n)); | |
| 34 return buffer_[BufferIndex(n)]; | |
| 35 } | |
| 36 | |
| 37 T* MutableReadBuffer(size_t n) { | |
| 38 DCHECK(IsFilledIndex(n)); | |
| 39 return &buffer_[BufferIndex(n)]; | |
| 40 } | |
| 41 | |
| 42 void SaveToBuffer(const T& value) { | |
| 43 buffer_[BufferIndex(0)] = value; | |
| 44 current_index_++; | |
| 45 } | |
| 46 | |
| 47 void Clear() { | |
| 48 current_index_ = 0; | |
| 49 } | |
| 50 | |
| 51 // Iterator has const access to the RingBuffer it got retrieved from. | |
| 52 class Iterator { | |
| 53 public: | |
| 54 size_t index() const { return index_; } | |
| 55 | |
| 56 const T* operator->() const { return &buffer_.ReadBuffer(index_); } | |
| 57 const T* operator*() const { return &buffer_.ReadBuffer(index_); } | |
| 58 | |
| 59 Iterator& operator++() { | |
| 60 index_++; | |
| 61 if (index_ == kSize) | |
| 62 out_of_range_ = true; | |
| 63 return *this; | |
| 64 } | |
| 65 | |
| 66 Iterator& operator--() { | |
| 67 if (index_ == 0) | |
| 68 out_of_range_ = true; | |
| 69 index_--; | |
| 70 return *this; | |
| 71 } | |
| 72 | |
| 73 operator bool() const { | |
| 74 return buffer_.IsFilledIndex(index_) && !out_of_range_; | |
| 75 } | |
| 76 | |
| 77 private: | |
| 78 Iterator(const RingBuffer<T, kSize>& buffer, size_t index) | |
| 79 : buffer_(buffer), | |
| 80 index_(index), | |
| 81 out_of_range_(false) { | |
| 82 } | |
| 83 | |
| 84 const RingBuffer<T, kSize>& buffer_; | |
| 85 size_t index_; | |
| 86 bool out_of_range_; | |
| 87 | |
| 88 friend class RingBuffer<T, kSize>; | |
| 89 }; | |
| 90 | |
| 91 // Returns an Iterator pointing to the oldest value in the buffer. | |
| 92 // Example usage (iterate from oldest to newest value): | |
| 93 // for (RingBuffer<T, kSize>::Iterator it = ring_buffer.Begin(); it; ++it) {} | |
| 94 Iterator Begin() const { | |
| 95 if (current_index_ < kSize) | |
| 96 return Iterator(*this, kSize - current_index_); | |
| 97 return Iterator(*this, 0); | |
| 98 } | |
| 99 | |
| 100 // Returns an Iterator pointing to the newest value in the buffer. | |
| 101 // Example usage (iterate backwards from newest to oldest value): | |
| 102 // for (RingBuffer<T, kSize>::Iterator it = ring_buffer.End(); it; --it) {} | |
| 103 Iterator End() const { | |
| 104 return Iterator(*this, kSize - 1); | |
| 105 } | |
| 106 | |
| 107 private: | |
| 108 inline size_t BufferIndex(size_t n) const { | |
| 109 return (current_index_ + n) % kSize; | |
| 110 } | |
| 111 | |
| 112 T buffer_[kSize]; | |
| 113 size_t current_index_; | |
| 114 | |
| 115 DISALLOW_COPY_AND_ASSIGN(RingBuffer); | |
| 116 }; | |
| 117 | |
| 118 } // namespace cc | |
| 119 | |
| 120 #endif // CC_DEBUG_RING_BUFFER_H_ | |
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