[wpilib] Add timestamp getters with configurable time base (#7378)

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

@@ -6,6 +6,7 @@
 
 #include <stdint.h>
 
+#include <functional>
 #include <string>
 
 #include <units/temperature.h>
@@ -78,6 +79,24 @@ class RobotController {
    */
   static int32_t GetTeamNumber();
 
+  /**
+   * Sets a new source to provide the clock time in microseconds. Changing this
+   * affects the return value of {@code GetTime}.
+   *
+   * @param supplier Function to return the time in microseconds.
+   */
+  static void SetTimeSource(std::function<uint64_t()> supplier);
+
+  /**
+   * Read the microsecond timestamp. By default, the time is based on the FPGA
+   * hardware clock in microseconds since the FPGA started. However, the return
+   * value of this method may be modified to use any time base, including
+   * non-monotonic and non-continuous time bases.
+   *
+   * @return The current time in microseconds.
+   */
+  static uint64_t GetTime();
+
   /**
    * Read the microsecond-resolution timer on the FPGA.
    *
@@ -320,6 +339,9 @@ class RobotController {
    * @return The status of the CAN bus
    */
   static CANStatus GetCANStatus();
+
+ private:
+  static std::function<uint64_t()> m_timeSource;
 };
 
 }  // namespace frc

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

@@ -56,6 +56,17 @@ class TimedRobot : public IterativeRobotBase {
 
   ~TimedRobot() override;
 
+  /**
+   * Return the system clock time in micrseconds for the start of the current
+   * periodic loop. This is in the same time base as Timer.GetFPGATimestamp(),
+   * but is stable through a loop. It is updated at the beginning of every
+   * periodic callback (including the normal periodic loop).
+   *
+   * @return Robot running time in microseconds, as of the start of the current
+   * periodic function.
+   */
+  uint64_t GetLoopStartTime();
+
   /**
    * Add a callback to run at a specific period with a starting time offset.
    *
@@ -103,6 +114,7 @@ class TimedRobot : public IterativeRobotBase {
 
   hal::Handle<HAL_NotifierHandle, HAL_CleanNotifier> m_notifier;
   std::chrono::microseconds m_startTime;
+  uint64_t m_loopStartTimeUs = 0;
 
   wpi::priority_queue<Callback, std::vector<Callback>, std::greater<Callback>>
       m_callbacks;

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

@@ -118,6 +118,16 @@ class Timer {
    */
   bool IsRunning() const;
 
+  /**
+   * Return the clock time in seconds. By default, the time is based on the FPGA
+   * hardware clock in seconds since the FPGA started. However, the return value
+   * of this method may be modified to use any time base, including
+   * non-monotonic time bases.
+   *
+   * @returns Robot running time in seconds.
+   */
+  static units::second_t GetTimestamp();
+
   /**
    * Return the FPGA system clock time in seconds.
    *