Tracer.hpp

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// Copyright (c) FIRST and other WPILib contributors.
// Open Source Software; you can modify and/or share it under the terms of
// the WPILib BSD license file in the root directory of this project.
 
#pragma once
 
#include <chrono>
#include <string_view>
 
#include "wpi/hal/cpp/fpga_clock.hpp"
#include "wpi/util/StringMap.hpp"
 
namespace wpi::util {
class raw_ostream;
}  // namespace wpi::util
 
namespace wpi {
/**
 * A class for keeping track of how much time it takes for different parts of
 * code to execute. This is done with epochs, that are added to calls to
 * AddEpoch() and can be printed with a call to PrintEpochs().
 *
 * Epochs are a way to partition the time elapsed so that when overruns occur,
 * one can determine which parts of an operation consumed the most time.
 */
class Tracer {
 public:
  /**
   * Constructs a Tracer instance.
   */
  Tracer();
 
  /**
   * Restarts the epoch timer.
   */
  void ResetTimer();
 
  /**
   * Clears all epochs.
   */
  void ClearEpochs();
 
  /**
   * Adds time since last epoch to the list printed by PrintEpochs().
   *
   * Epochs are a way to partition the time elapsed so that when overruns occur,
   * one can determine which parts of an operation consumed the most time.
   *
   * @param epochName The name to associate with the epoch.
   */
  void AddEpoch(std::string_view epochName);
 
  /**
   * Prints list of epochs added so far and their times to the DriverStation.
   */
  void PrintEpochs();
 
  /**
   * Prints list of epochs added so far and their times to a stream.
   *
   * @param os output stream
   */
  void PrintEpochs(wpi::util::raw_ostream& os);
 
 private:
  static constexpr std::chrono::milliseconds kMinPrintPeriod{1000};
 
  wpi::hal::fpga_clock::time_point m_startTime;
  wpi::hal::fpga_clock::time_point m_lastEpochsPrintTime =
      wpi::hal::fpga_clock::epoch();
 
  wpi::util::StringMap<std::chrono::nanoseconds> m_epochs;
};
}  // namespace wpi