ring-buffer.h

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// Copyright 2016 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
 
#ifndef V8_BASE_RING_BUFFER_H_
#define V8_BASE_RING_BUFFER_H_
 
#include <cstdint>
 
namespace v8::base {
 
template <typename T, uint8_t _SIZE = 10>
class RingBuffer final {
 public:
  static constexpr uint8_t kSize = _SIZE;
 
  constexpr RingBuffer() = default;
 
  RingBuffer(const RingBuffer&) = delete;
  RingBuffer& operator=(const RingBuffer&) = delete;
 
  constexpr void Push(const T& value) {
    elements_[pos_++] = value;
    if (pos_ == kSize) {
      pos_ = 0;
      is_full_ = true;
    }
  }
 
  constexpr uint8_t Size() const { return is_full_ ? kSize : pos_; }
 
  constexpr bool Empty() const { return Size() == 0; }
 
  constexpr void Clear() {
    pos_ = 0;
    is_full_ = false;
  }
 
  template <typename Callback>
  constexpr T Reduce(Callback callback, const T& initial) const {
    T result = initial;
    for (uint8_t i = pos_; i > 0; --i) {
      result = callback(result, elements_[i - 1]);
    }
    if (!is_full_) {
      return result;
    }
    for (uint8_t i = kSize; i > pos_; --i) {
      result = callback(result, elements_[i - 1]);
    }
    return result;
  }
 
 private:
  T elements_[kSize];
  uint8_t pos_ = 0;
  bool is_full_ = false;
};
 
}  // namespace v8::base
 
#endif  // V8_BASE_RING_BUFFER_H_