ring_buffer.h

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// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
 
#ifndef RUNTIME_VM_RING_BUFFER_H_
#define RUNTIME_VM_RING_BUFFER_H_
 
#include "platform/assert.h"
#include "platform/utils.h"
 
namespace dart {
 
// Fixed-capacity ring buffer.
template <typename T, int N>
class RingBuffer {
 public:
  RingBuffer() : count_(0) {}
 
  void Add(const T& t) { data_[count_++ & kMask] = t; }
 
  // Returns the i'th most recently added element. Requires 0 <= i < Size().
  const T& Get(int i) const {
    ASSERT(0 <= i && i < Size());
    return data_[(count_ - i - 1) & kMask];
  }
 
  // Returns the number of elements currently stored in this buffer (at most N).
  int64_t Size() const {
    return Utils::Minimum(count_, static_cast<int64_t>(N));
  }
 
 private:
  static constexpr int kMask = N - 1;
  COMPILE_ASSERT((N & kMask) == 0);
  T data_[N];
  int64_t count_;
};
 
}  // namespace dart
 
#endif  // RUNTIME_VM_RING_BUFFER_H_