allwpilib/wpilibc/sim/src/Timer.cpp

/*----------------------------------------------------------------------------*/
/* Copyright (c) FIRST 2008-2016. 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.                                                               */
/*----------------------------------------------------------------------------*/

#include "Timer.h"

#include "Utility.h"
#include "simulation/simTime.h"

// Internal stuff
#include "simulation/MainNode.h"
#include "simulation/SimFloatInput.h"
namespace wpilib {
namespace internal {
double simTime = 0;
std::condition_variable time_wait;
std::mutex time_wait_mutex;

void time_callback(const msgs::ConstFloat64Ptr& msg) {
  simTime = msg->data();
  time_wait.notify_all();
}
}
}  // namespace wpilib

/**
 * 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(double seconds) {
  if (seconds < 0.0) return;

  double start = wpilib::internal::simTime;

  std::unique_lock<std::mutex> lock(wpilib::internal::time_wait_mutex);
  while ((wpilib::internal::simTime - start) < seconds) {
    wpilib::internal::time_wait.wait(lock);
  }
}

/*
 * Return the FPGA system clock time in seconds.
 *
 * This is deprecated and just forwards to Timer::GetFPGATimestamp().
 *
 * @returns Robot running time in seconds.
 */
double GetClock() { return Timer::GetFPGATimestamp(); }

/**
 * @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 (except in simulation).
 */
double GetTime() {
  return Timer::GetFPGATimestamp();  // The epoch starts when Gazebo starts
}

// for compatibility with msvc12--see C2864
const double Timer::kRolloverTime = (1ll << 32) / 1e6;
/**
 * 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::Timer() : m_startTime(0.0), m_accumulatedTime(0.0), m_running(false) {
  // Creates a semaphore to control access to critical regions.
  // Initially 'open'
  Reset();
}

/**
 * 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
 */
double Timer::Get() const {
  double result;
  double currentTime = GetFPGATimestamp();

  std::lock_guard<priority_mutex> sync(m_mutex);
  if (m_running) {
    // This math won't work if the timer rolled over (71 minutes after boot).
    // TODO: Check for it and compensate.
    result = (currentTime - m_startTime) + m_accumulatedTime;
  } else {
    result = m_accumulatedTime;
  }

  return result;
}

/**
 * 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 Timer::Reset() {
  std::lock_guard<priority_mutex> sync(m_mutex);
  m_accumulatedTime = 0;
  m_startTime = GetFPGATimestamp();
}

/**
 * Start the timer running.
 *
 * Just set the running flag to true indicating that all time requests should be
 * relative to the system clock.
 */
void Timer::Start() {
  std::lock_guard<priority_mutex> sync(m_mutex);
  if (!m_running) {
    m_startTime = GetFPGATimestamp();
    m_running = true;
  }
}

/**
 * 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 Timer::Stop() {
  double temp = Get();

  std::lock_guard<priority_mutex> sync(m_mutex);
  if (m_running) {
    m_accumulatedTime = temp;
    m_running = false;
  }
}

/**
 * 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 (in seconds).
 * @return If the period has passed.
 */
bool Timer::HasPeriodPassed(double period) {
  if (Get() > period) {
    std::lock_guard<priority_mutex> sync(m_mutex);
    // Advance the start time by the period.
    // Don't set it to the current time... we want to avoid drift.
    m_startTime += period;
    return true;
  }
  return false;
}

/*
 * 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.
 *
 * @return Robot running time in seconds.
 */
double Timer::GetFPGATimestamp() {
  // FPGA returns the timestamp in microseconds
  // Call the helper GetFPGATime() in Utility.cpp
  return wpilib::internal::simTime;
}

/*
 * Not in a match.
 */
double Timer::GetMatchTime() { return Timer::GetFPGATimestamp(); }