[wpilibc] Refactor Tracer functionality out of Watchdog class (#2456)

wpilibc/src/main/native/include/frc/Tracer.h

@@ -0,0 +1,66 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2020 FIRST. All Rights Reserved.                             */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#pragma once
+
+#include <chrono>
+
+#include <hal/cpp/fpga_clock.h>
+#include <units/units.h>
+#include <wpi/StringMap.h>
+#include <wpi/StringRef.h>
+
+namespace frc {
+/**
+ * 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(wpi::StringRef epochName);
+
+  /**
+   * Prints list of epochs added so far and their times.
+   */
+  void PrintEpochs();
+
+ private:
+  static constexpr std::chrono::milliseconds kMinPrintPeriod{1000};
+
+  hal::fpga_clock::time_point m_startTime;
+  hal::fpga_clock::time_point m_lastEpochsPrintTime = hal::fpga_clock::epoch();
+
+  wpi::StringMap<std::chrono::nanoseconds> m_epochs;
+};
+}  // namespace frc

wpilibc/src/main/native/include/frc/Watchdog.h

@@ -14,10 +14,11 @@
 #include <hal/cpp/fpga_clock.h>
 #include <units/units.h>
 #include <wpi/SafeThread.h>
-#include <wpi/StringMap.h>
 #include <wpi/StringRef.h>
 #include <wpi/deprecated.h>
 
+#include "frc/Tracer.h"
+
 namespace frc {
 
 /**
@@ -155,9 +156,8 @@ class Watchdog {
   hal::fpga_clock::time_point m_expirationTime;
   std::function<void()> m_callback;
   hal::fpga_clock::time_point m_lastTimeoutPrintTime = hal::fpga_clock::epoch();
-  hal::fpga_clock::time_point m_lastEpochsPrintTime = hal::fpga_clock::epoch();
 
-  wpi::StringMap<std::chrono::nanoseconds> m_epochs;
+  Tracer m_tracer;
   bool m_isExpired = false;
 
   bool m_suppressTimeoutMessage = false;