Implemented the stopwatch class and methods

Marlin/stopwatch.cpp

+/*
+ * Marlin 3D Printer Firmware
+ * Copyright (C) 2016 MarlinFirmware [https://github.com/MarlinFirmware/Marlin]
+ *
+ * Based on Sprinter and grbl.
+ * Copyright (C) 2011 Camiel Gubbels / Erik van der Zalm
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include "Marlin.h"
+#include "stopwatch.h"
+
+stopwatch::stopwatch() {
+   this->reset();
+ }
+
+void stopwatch::stop() {
+  if (DEBUGGING(INFO)) SERIAL_ECHOLNPGM("stopwatch::stop()");
+  if (!this->isRunning()) return;
+
+  this->status = STPWTCH_STOPPED;
+  this->stopTimestamp = millis();
+}
+
+void stopwatch::pause() {
+  if (DEBUGGING(INFO)) SERIAL_ECHOLNPGM("stopwatch::pause()");
+  if (!this->isRunning()) return;
+
+  this->status = STPWTCH_PAUSED;
+  this->stopTimestamp = millis();
+}
+
+void stopwatch::start() {
+  if (DEBUGGING(INFO)) SERIAL_ECHOLNPGM("stopwatch::start()");
+  if (this->isRunning()) return;
+
+  if (this->isPaused()) this->accumulator = this->duration();
+  else this->reset();
+
+  this->status = STPWTCH_RUNNING;
+  this->startTimestamp = millis();
+}
+
+void stopwatch::reset() {
+  if (DEBUGGING(INFO)) SERIAL_ECHOLNPGM("stopwatch::reset()");
+
+  this->status = STPWTCH_STOPPED;
+  this->startTimestamp = 0;
+  this->stopTimestamp = 0;
+  this->accumulator = 0;
+}
+
+bool stopwatch::isRunning() {
+  return (this->status == STPWTCH_RUNNING) ? true : false;
+}
+
+bool stopwatch::isPaused() {
+  return (this->status == STPWTCH_PAUSED) ? true : false;
+}
+
+uint16_t stopwatch::duration() {
+  return (((this->isRunning()) ? millis() : this->stopTimestamp)
+          - this->startTimestamp) / 1000 + this->accumulator;
+}

Marlin/stopwatch.h

+/*
+ * Marlin 3D Printer Firmware
+ * Copyright (C) 2016 MarlinFirmware [https://github.com/MarlinFirmware/Marlin]
+ *
+ * Based on Sprinter and grbl.
+ * Copyright (C) 2011 Camiel Gubbels / Erik van der Zalm
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#ifndef STOPWATCH_H
+#define STOPWATCH_H
+
+enum stopwatch_s {
+  STPWTCH_STOPPED = 0x0,
+  STPWTCH_RUNNING = 0x1,
+  STPWTCH_PAUSED  = 0x2
+};
+
+/**
+ * @brief Stopwatch class
+ * @details This class acts as a timer proving stopwatch functionality including
+ * the ability to pause the running time counter.
+ */
+class stopwatch {
+  private:
+    stopwatch_s status;
+    uint16_t accumulator;
+    uint32_t startTimestamp;
+    uint32_t stopTimestamp;
+
+  public:
+    /**
+     * @brief Class constructor
+     */
+    stopwatch();
+
+    /**
+     * @brief Stops the stopwatch
+     * @details Stops the running timer, it will silently ignore the request if
+     * no timer is currently running.
+     */
+    void stop();
+
+    /**
+     * @brief Pauses the stopwatch
+     * @details Pauses the running timer, it will silently ignore the request if
+     * no timer is currently running.
+     */
+    void pause();
+
+    /**
+     * @brief Starts the stopwatch
+     * @details Starts the timer, it will silently ignore the request if the
+     * timer is already running.
+     */
+    void start();
+
+    /**
+     * @brief Resets the stopwatch
+     * @details Resets all settings to their default values.
+     */
+    void reset();
+
+    /**
+     * @brief Checks if the timer is running
+     * @details Returns true if the timer is currently running, false otherwise.
+     * @return bool
+     */
+    bool isRunning();
+
+    /**
+     * @brief Checks if the timer is paused
+     * @details Returns true if the timer is currently paused, false otherwise.
+     * @return bool
+     */
+    bool isPaused();
+
+    /**
+     * @brief Gets the running time
+     * @details Returns the total number of seconds the timer has been running.
+     * @return uint16_t
+     */
+    uint16_t duration();
+};
+
+#endif //STOPWATCH_H