Add frc2::Timer (#1968)

This is a unit-safe version of frc::Timer.
Undo previous (#1815) deprecation of parts of frc::Timer.

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

@@ -12,11 +12,10 @@
 #include <wpi/mutex.h>
 
 #include "frc/Base.h"
+#include "frc2/Timer.h"
 
 namespace frc {
 
-using TimerInterruptHandler = void (*)(void* param);
-
 /**
  * Pause the task for a specified time.
  *
@@ -57,10 +56,10 @@ class Timer {
 
   virtual ~Timer() = default;
 
-  Timer(const Timer& rhs);
-  Timer& operator=(const Timer& rhs);
-  Timer(Timer&& rhs);
-  Timer& operator=(Timer&& rhs);
+  Timer(const Timer& rhs) = default;
+  Timer& operator=(const Timer& rhs) = default;
+  Timer(Timer&& rhs) = default;
+  Timer& operator=(Timer&& rhs) = default;
 
   /**
    * Get the current time from the timer. If the clock is running it is derived
@@ -104,19 +103,8 @@ class Timer {
    * @param period The period to check for (in seconds).
    * @return       True if the period has passed.
    */
-  WPI_DEPRECATED("Use unit-safe HasPeriodPassed method instead.")
   bool HasPeriodPassed(double period);
 
-  /**
-   * Check if the period specified has passed and if it has, advance the start
-   * time by that period. This is useful to decide if it's time to do periodic
-   * work without drifting later by the time it took to get around to checking.
-   *
-   * @param period The period to check for.
-   * @return       True if the period has passed.
-   */
-  bool HasPeriodPassed(units::second_t period);
-
   /**
    * Return the FPGA system clock time in seconds.
    *
@@ -148,10 +136,7 @@ class Timer {
   static const double kRolloverTime;
 
  private:
-  double m_startTime = 0.0;
-  double m_accumulatedTime = 0.0;
-  bool m_running = false;
-  mutable wpi::mutex m_mutex;
+  frc2::Timer m_timer;
 };
 
 }  // namespace frc

wpilibc/src/main/native/include/frc2/Timer.h

@@ -0,0 +1,138 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2008-2019 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 <units/units.h>
+#include <wpi/deprecated.h>
+#include <wpi/mutex.h>
+
+#include "frc/Base.h"
+
+namespace frc2 {
+
+/**
+ * Pause the task for a specified time.
+ *
+ * Pause the execution of the program for a specified period of time given in
+ * seconds. Motors will continue to run at their last assigned values, and
+ * sensors will continue to update. Only the task containing the wait will pause
+ * until the wait time is expired.
+ *
+ * @param seconds Length of time to pause, in seconds.
+ */
+void Wait(units::second_t seconds);
+
+/**
+ * @brief  Gives real-time clock system time with nanosecond resolution
+ * @return The time, just in case you want the robot to start autonomous at 8pm
+ *         on Saturday.
+ */
+units::second_t GetTime();
+
+/**
+ * A wrapper for the frc::Timer class that returns unit-typed values.
+ */
+class Timer {
+ public:
+  /**
+   * Create a new timer object.
+   *
+   * Create a new timer object and reset the time to zero. The timer is
+   * initially not running and must be started.
+   */
+  Timer();
+
+  virtual ~Timer() = default;
+
+  Timer(const Timer& rhs);
+  Timer& operator=(const Timer& rhs);
+  Timer(Timer&& rhs);
+  Timer& operator=(Timer&& rhs);
+
+  /**
+   * Get the current time from the timer. If the clock is running it is derived
+   * from the current system clock the start time stored in the timer class. If
+   * the clock is not running, then return the time when it was last stopped.
+   *
+   * @return Current time value for this timer in seconds
+   */
+  units::second_t Get() const;
+
+  /**
+   * Reset the timer by setting the time to 0.
+   *
+   * Make the timer startTime the current time so new requests will be relative
+   * to now.
+   */
+  void Reset();
+
+  /**
+   * Start the timer running.
+   *
+   * Just set the running flag to true indicating that all time requests should
+   * be relative to the system clock.
+   */
+  void Start();
+
+  /**
+   * Stop the timer.
+   *
+   * This computes the time as of now and clears the running flag, causing all
+   * subsequent time requests to be read from the accumulated time rather than
+   * looking at the system clock.
+   */
+  void Stop();
+
+  /**
+   * Check if the period specified has passed and if it has, advance the start
+   * time by that period. This is useful to decide if it's time to do periodic
+   * work without drifting later by the time it took to get around to checking.
+   *
+   * @param period The period to check for.
+   * @return       True if the period has passed.
+   */
+  bool HasPeriodPassed(units::second_t period);
+
+  /**
+   * Return the FPGA system clock time in seconds.
+   *
+   * Return the time from the FPGA hardware clock in seconds since the FPGA
+   * started. Rolls over after 71 minutes.
+   *
+   * @returns Robot running time in seconds.
+   */
+  static units::second_t GetFPGATimestamp();
+
+  /**
+   * Return the approximate match time.
+   *
+   * The FMS does not send an official match time to the robots, but does send
+   * an approximate match time. The value will count down the time remaining in
+   * the current period (auto or teleop).
+   *
+   * Warning: This is not an official time (so it cannot be used to dispute ref
+   * calls or guarantee that a function will trigger before the match ends).
+   *
+   * The Practice Match function of the DS approximates the behavior seen on the
+   * field.
+   *
+   * @return Time remaining in current match period (auto or teleop)
+   */
+  static units::second_t GetMatchTime();
+
+  // The time, in seconds, at which the 32-bit FPGA timestamp rolls over to 0
+  static const units::second_t kRolloverTime;
+
+ private:
+  units::second_t m_startTime = 0_s;
+  units::second_t m_accumulatedTime = 0_s;
+  bool m_running = false;
+  mutable wpi::mutex m_mutex;
+};
+
+}  // namespace frc2

wpilibc/src/main/native/include/frc2/command/WaitCommand.h

@@ -12,7 +12,7 @@
 
 #include "CommandBase.h"
 #include "CommandHelper.h"
-#include "frc/Timer.h"
+#include "frc2/Timer.h"
 
 namespace frc2 {
 /**
@@ -43,7 +43,7 @@ class WaitCommand : public CommandHelper<CommandBase, WaitCommand> {
   bool RunsWhenDisabled() const override;
 
  protected:
-  frc::Timer m_timer;
+  Timer m_timer;
 
  private:
   units::second_t m_duration;