Program Listing for File circular_buffer.h

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// Copyright The OpenTelemetry Authors
// SPDX-License-Identifier: Apache-2.0

#pragma once

#include "opentelemetry/nostd/variant.h"

#include <cstdint>
#include <limits>
#include <vector>

OPENTELEMETRY_BEGIN_NAMESPACE
namespace sdk
{
namespace metrics
{

class AdaptingIntegerArray
{
public:
  // Construct an adapting integer array of a given size.
  explicit AdaptingIntegerArray(size_t size) : backing_(std::vector<uint8_t>(size, 0)) {}
  AdaptingIntegerArray(const AdaptingIntegerArray &other) = default;
  AdaptingIntegerArray(AdaptingIntegerArray &&other)      = default;
  AdaptingIntegerArray &operator=(const AdaptingIntegerArray &other) = default;
  AdaptingIntegerArray &operator=(AdaptingIntegerArray &&other) = default;

  void Increment(size_t index, uint64_t count);

  uint64_t Get(size_t index) const;

  size_t Size() const;

  void Clear();

private:
  void EnlargeToFit(uint64_t value);

  nostd::variant<std::vector<uint8_t>,
                 std::vector<uint16_t>,
                 std::vector<uint32_t>,
                 std::vector<uint64_t>>
      backing_;
};

class AdaptingCircularBufferCounter
{
public:
  explicit AdaptingCircularBufferCounter(size_t max_size) : backing_(max_size) {}
  AdaptingCircularBufferCounter(const AdaptingCircularBufferCounter &other) = default;
  AdaptingCircularBufferCounter(AdaptingCircularBufferCounter &&other)      = default;
  AdaptingCircularBufferCounter &operator=(const AdaptingCircularBufferCounter &other) = default;
  AdaptingCircularBufferCounter &operator=(AdaptingCircularBufferCounter &&other) = default;

  int32_t StartIndex() const { return start_index_; }

  int32_t EndIndex() const { return end_index_; }

  bool Empty() const { return base_index_ == kNullIndex; }

  size_t MaxSize() const { return backing_.Size(); }

  void Clear();

  bool Increment(int32_t index, uint64_t delta);

  uint64_t Get(int32_t index);

private:
  size_t ToBufferIndex(int32_t index) const;

  static constexpr int32_t kNullIndex = std::numeric_limits<int32_t>::min();

  // Index of the first populated element, may be kNullIndex if container is empty.
  int32_t start_index_ = kNullIndex;
  // Index of the last populated element, may be kNullIndex if container is empty.
  int32_t end_index_ = kNullIndex;
  // Index corresponding to the element located at the start of the backing array, may be kNullIndex
  // if container is empty.
  int32_t base_index_ = kNullIndex;
  AdaptingIntegerArray backing_;
};

}  // namespace metrics
}  // namespace sdk
OPENTELEMETRY_END_NAMESPACE