ring_buffer.hpp

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#pragma once
 
 
#include <array>
#include <cstddef>
#include <optional>
 
namespace loon {
 
template <typename T, size_t N>
class RingBuffer {
 public:
  RingBuffer() = default;
 
  explicit RingBuffer(bool override_when_full) : override(override_when_full) {}
 
  bool push(const T& value) {
    if (full()) {
      if (!override) {
        return false;
      }
      // advance read pointer to discard oldest
      read = (read + 1) % N;
    } else {
      ++count;
    }
    buffer[write] = value;
    write = (write + 1) % N;
 
    return true;
  }
 
  std::optional<T> pop() {
    if (empty()) {
      return std::nullopt;
    }
    T value = buffer[read];
    read = (read + 1) % N;
    --count;
    return value;
  }
 
  std::optional<T> front() {
    if (empty()) {
      return std::nullopt;
    }
    return buffer[read];
  }
 
  std::optional<T> back() {
    if (empty()) {
      return std::nullopt;
    }
    return buffer[(write - 1 + N) % N];
  }
 
  bool discard() {
    if (empty()) {
      return false;
    }
    read = (read + 1) % N;
    --count;
    return true;
  }
 
  [[nodiscard]] size_t capacity() const { return N; }
 
  [[nodiscard]] bool empty() const { return count == 0; }
 
  [[nodiscard]] bool full() const { return count == N; }
 
  [[nodiscard]] bool overrides() const { return override; }
 
  [[nodiscard]] size_t size() const { return count; }
 
 private:
  std::array<T, N> buffer;
  size_t write = 0;
  size_t read = 0;
  size_t count = 0;
  bool override = false;
};
 
} // namespace loon