hal/src/fsfw_hal/linux/CommandExecutor.cpp

@@ -208,6 +208,4 @@ ReturnValue_t CommandExecutor::executeBlocking() {
   return HasReturnvaluesIF::RETURN_OK;
 }
 
-const std::vector<char>& CommandExecutor::getReadVector() const {
+const std::vector<char>& CommandExecutor::getReadVector() const { return readVec; }
-  return readVec;
-}

hal/src/fsfw_hal/linux/spi/ManualCsLockGuard.h

@@ -0,0 +1,43 @@
+#pragma once
+
+#include "fsfw/ipc/MutexIF.h"
+#include "fsfw/returnvalues/HasReturnvaluesIF.h"
+#include "fsfw_hal/common/gpio/GpioIF.h"
+
+class ManualCsLockWrapper : public HasReturnvaluesIF {
+ public:
+  ManualCsLockWrapper(MutexIF* lock, GpioIF* gpioIF, SpiCookie* cookie,
+                      MutexIF::TimeoutType type = MutexIF::TimeoutType::BLOCKING,
+                      uint32_t timeoutMs = 0)
+      : lock(lock), gpioIF(gpioIF), cookie(cookie), type(type), timeoutMs(timeoutMs) {
+    if (cookie == nullptr) {
+      // TODO: Error? Or maybe throw exception..
+      return;
+    }
+    cookie->setCsLockManual(true);
+    lockResult = lock->lockMutex(type, timeoutMs);
+    if (lockResult != RETURN_OK) {
+      return;
+    }
+    gpioResult = gpioIF->pullLow(cookie->getChipSelectPin());
+  }
+
+  ~ManualCsLockWrapper() {
+    if (gpioResult == RETURN_OK) {
+      gpioIF->pullHigh(cookie->getChipSelectPin());
+    }
+    cookie->setCsLockManual(false);
+    if (lockResult == RETURN_OK) {
+      lock->unlockMutex();
+    }
+  }
+  ReturnValue_t lockResult;
+  ReturnValue_t gpioResult;
+
+ private:
+  MutexIF* lock;
+  GpioIF* gpioIF;
+  SpiCookie* cookie;
+  MutexIF::TimeoutType type;
+  uint32_t timeoutMs = 0;
+};

hal/src/fsfw_hal/linux/spi/SpiComIF.cpp

@@ -194,16 +194,22 @@ ReturnValue_t SpiComIF::performRegularSendOperation(SpiCookie* spiCookie, const
 
   bool fullDuplex = spiCookie->isFullDuplex();
   gpioId_t gpioId = spiCookie->getChipSelectPin();
+  bool csLockManual = spiCookie->getCsLockManual();
 
-  /* Pull SPI CS low. For now, no support for active high given  */
+  MutexIF::TimeoutType csType;
-  if (gpioId != gpio::NO_GPIO) {
+  dur_millis_t csTimeout = 0;
-    result = csMutex->lockMutex(timeoutType, timeoutMs);
+  // Pull SPI CS low. For now, no support for active high given
+  if (gpioId != gpio::NO_GPIO and not csLockManual) {
+    spiCookie->getMutexParams(csType, csTimeout);
+    result = csMutex->lockMutex(csType, csTimeout);
     if (result != RETURN_OK) {
 #if FSFW_VERBOSE_LEVEL >= 1
 #if FSFW_CPP_OSTREAM_ENABLED == 1
-      sif::error << "SpiComIF::sendMessage: Failed to lock mutex" << std::endl;
+      sif::error << "SpiComIF::sendMessage: Failed to lock mutex with code "
+                 << "0x" << std::hex << std::setfill('0') << std::setw(4) << result << std::dec
+                 << std::endl;
 #else
-      sif::printError("SpiComIF::sendMessage: Failed to lock mutex\n");
+      sif::printError("SpiComIF::sendMessage: Failed to lock mutex with code %d\n", result);
 #endif
 #endif
       return result;
@@ -249,7 +255,7 @@ ReturnValue_t SpiComIF::performRegularSendOperation(SpiCookie* spiCookie, const
     }
   }
 
-  if (gpioId != gpio::NO_GPIO) {
+  if (gpioId != gpio::NO_GPIO and not csLockManual) {
     gpioComIF->pullHigh(gpioId);
     result = csMutex->unlockMutex();
     if (result != RETURN_OK) {
@@ -292,12 +298,22 @@ ReturnValue_t SpiComIF::performHalfDuplexReception(SpiCookie* spiCookie) {
     return result;
   }
 
+  bool csLockManual = spiCookie->getCsLockManual();
   gpioId_t gpioId = spiCookie->getChipSelectPin();
-  if (gpioId != gpio::NO_GPIO) {
+  MutexIF::TimeoutType csType;
-    result = csMutex->lockMutex(timeoutType, timeoutMs);
+  dur_millis_t csTimeout = 0;
+  if (gpioId != gpio::NO_GPIO and not csLockManual) {
+    spiCookie->getMutexParams(csType, csTimeout);
+    result = csMutex->lockMutex(csType, csTimeout);
     if (result != RETURN_OK) {
+#if FSFW_VERBOSE_LEVEL >= 1
 #if FSFW_CPP_OSTREAM_ENABLED == 1
-      sif::error << "SpiComIF::getSendSuccess: Failed to lock mutex" << std::endl;
+      sif::error << "SpiComIF::sendMessage: Failed to lock mutex with code "
+                 << "0x" << std::hex << std::setfill('0') << std::setw(4) << result << std::dec
+                 << std::endl;
+#else
+      sif::printError("SpiComIF::sendMessage: Failed to lock mutex with code %d\n", result);
+#endif
 #endif
       return result;
     }
@@ -315,7 +331,7 @@ ReturnValue_t SpiComIF::performHalfDuplexReception(SpiCookie* spiCookie) {
     result = HALF_DUPLEX_TRANSFER_FAILED;
   }
 
-  if (gpioId != gpio::NO_GPIO) {
+  if (gpioId != gpio::NO_GPIO and not csLockManual) {
     gpioComIF->pullHigh(gpioId);
     result = csMutex->unlockMutex();
     if (result != RETURN_OK) {
@@ -346,15 +362,7 @@ ReturnValue_t SpiComIF::readReceivedMessage(CookieIF* cookie, uint8_t** buffer,
   return HasReturnvaluesIF::RETURN_OK;
 }
 
-MutexIF* SpiComIF::getMutex(MutexIF::TimeoutType* timeoutType, uint32_t* timeoutMs) {
+MutexIF* SpiComIF::getCsMutex() { return csMutex; }
-  if (timeoutType != nullptr) {
-    *timeoutType = this->timeoutType;
-  }
-  if (timeoutMs != nullptr) {
-    *timeoutMs = this->timeoutMs;
-  }
-  return csMutex;
-}
 
 void SpiComIF::performSpiWiretapping(SpiCookie* spiCookie) {
   if (spiCookie == nullptr) {
@@ -417,9 +425,7 @@ void SpiComIF::getSpiSpeedAndMode(int spiFd, spi::SpiModes& mode, uint32_t& spee
   }
 }
 
-const std::string& SpiComIF::getSpiDev() const {
+const std::string& SpiComIF::getSpiDev() const { return dev; }
-  return dev;
-}
 
 void SpiComIF::updateLinePolarity(int spiFd) {
   clockUpdateTransfer.len = 0;

hal/src/fsfw_hal/linux/spi/SpiComIF.h

@@ -22,15 +22,15 @@ class SpiCookie;
  */
 class SpiComIF : public DeviceCommunicationIF, public SystemObject {
  public:
-  static constexpr uint8_t spiRetvalId = CLASS_ID::HAL_SPI;
+  static constexpr uint8_t CLASS_ID = CLASS_ID::HAL_SPI;
   static constexpr ReturnValue_t OPENING_FILE_FAILED =
-      HasReturnvaluesIF::makeReturnCode(spiRetvalId, 0);
+      HasReturnvaluesIF::makeReturnCode(CLASS_ID, 0);
   /* Full duplex (ioctl) transfer failure */
   static constexpr ReturnValue_t FULL_DUPLEX_TRANSFER_FAILED =
-      HasReturnvaluesIF::makeReturnCode(spiRetvalId, 1);
+      HasReturnvaluesIF::makeReturnCode(CLASS_ID, 1);
   /* Half duplex (read/write) transfer failure */
   static constexpr ReturnValue_t HALF_DUPLEX_TRANSFER_FAILED =
-      HasReturnvaluesIF::makeReturnCode(spiRetvalId, 2);
+      HasReturnvaluesIF::makeReturnCode(CLASS_ID, 2);
 
   SpiComIF(object_id_t objectId, std::string devname, GpioIF* gpioComIF);
 
@@ -44,7 +44,8 @@ class SpiComIF : public DeviceCommunicationIF, public SystemObject {
    * @brief   This function returns the mutex which can be used to protect the spi bus when
    *          the chip select must be driven from outside of the com if.
    */
-  MutexIF* getMutex(MutexIF::TimeoutType* timeoutType = nullptr, uint32_t* timeoutMs = nullptr);
+  MutexIF* getCsMutex();
+  void setMutexParams(MutexIF::TimeoutType timeoutType, uint32_t timeoutMs);
 
   /**
    * Perform a regular send operation using Linux iotcl. This is public so it can be used
@@ -59,6 +60,7 @@ class SpiComIF : public DeviceCommunicationIF, public SystemObject {
 
   GpioIF* getGpioInterface();
   void setSpiSpeedAndMode(int spiFd, spi::SpiModes mode, uint32_t speed);
+  void getSpiSpeedAndMode(int spiFd, spi::SpiModes& mode, uint32_t& speed) const;
 
   /**
    * This updates the SPI clock default polarity. Only setting the mode does not update
@@ -70,7 +72,6 @@ class SpiComIF : public DeviceCommunicationIF, public SystemObject {
    * @param spiFd
    */
   void updateLinePolarity(int spiFd);
-  void getSpiSpeedAndMode(int spiFd, spi::SpiModes& mode, uint32_t& speed) const;
 
   const std::string& getSpiDev() const;
   void performSpiWiretapping(SpiCookie* spiCookie);
@@ -90,8 +91,8 @@ class SpiComIF : public DeviceCommunicationIF, public SystemObject {
    * pulled high
    */
   MutexIF* csMutex = nullptr;
-  MutexIF::TimeoutType timeoutType = MutexIF::TimeoutType::WAITING;
+  // MutexIF::TimeoutType timeoutType = MutexIF::TimeoutType::WAITING;
-  uint32_t timeoutMs = 20;
+  // uint32_t timeoutMs = DEFAULT_MUTEX_TIMEOUT;
   spi_ioc_transfer clockUpdateTransfer = {};
 
   using SpiDeviceMap = std::unordered_map<address_t, SpiInstance>;

hal/src/fsfw_hal/linux/spi/SpiCookie.cpp

@@ -104,3 +104,17 @@ void SpiCookie::getCallback(spi::send_callback_function_t* callback, void** args
   *callback = this->sendCallback;
   *args = this->callbackArgs;
 }
+
+void SpiCookie::setCsLockManual(bool enable) { manualCsLock = enable; }
+
+bool SpiCookie::getCsLockManual() const { return manualCsLock; }
+
+void SpiCookie::getMutexParams(MutexIF::TimeoutType& csTimeoutType, dur_millis_t& csTimeout) const {
+  csTimeoutType = this->csTimeoutType;
+  csTimeout = this->csTimeout;
+}
+
+void SpiCookie::setMutexParams(MutexIF::TimeoutType csTimeoutType, dur_millis_t csTimeout) {
+  this->csTimeoutType = csTimeoutType;
+  this->csTimeout = csTimeout;
+}

hal/src/fsfw_hal/linux/spi/SpiCookie.h

@@ -2,6 +2,8 @@
 #define LINUX_SPI_SPICOOKIE_H_
 
 #include <fsfw/devicehandlers/CookieIF.h>
+#include <fsfw/ipc/MutexIF.h>
+#include <fsfw/timemanager/clockDefinitions.h>
 #include <linux/spi/spidev.h>
 
 #include "../../common/gpio/gpioDefinitions.h"
@@ -20,6 +22,8 @@
  */
 class SpiCookie : public CookieIF {
  public:
+  static constexpr dur_millis_t DEFAULT_MUTEX_TIMEOUT = 20;
+
   /**
    * Each SPI device will have a corresponding cookie. The cookie is used by the communication
    * interface and contains device specific information like the largest expected size to be
@@ -137,9 +141,42 @@ class SpiCookie : public CookieIF {
    */
   void activateCsDeselect(bool deselectCs, uint16_t delayUsecs);
 
+  void getMutexParams(MutexIF::TimeoutType& csTimeoutType, dur_millis_t& csTimeout) const;
+  void setMutexParams(MutexIF::TimeoutType csTimeoutType, dur_millis_t csTimeout);
+
+  void setCsLockManual(bool enable);
+  bool getCsLockManual() const;
+
   spi_ioc_transfer* getTransferStructHandle();
 
  private:
+  address_t spiAddress;
+  gpioId_t chipSelectPin;
+
+  spi::SpiComIfModes comIfMode;
+
+  // Required for regular mode
+  const size_t maxSize;
+  spi::SpiModes spiMode;
+  /**
+   * If this is set to true, the SPI ComIF will not perform any mutex locking for the
+   * CS mechanism. The user is responsible to locking and unlocking the mutex for the
+   * whole duration of the transfers.
+   */
+  bool manualCsLock = false;
+  uint32_t spiSpeed;
+  bool halfDuplex = false;
+
+  MutexIF::TimeoutType csTimeoutType = MutexIF::TimeoutType::WAITING;
+  dur_millis_t csTimeout = DEFAULT_MUTEX_TIMEOUT;
+
+  // Required for callback mode
+  spi::send_callback_function_t sendCallback = nullptr;
+  void* callbackArgs = nullptr;
+
+  struct spi_ioc_transfer spiTransferStruct = {};
+  UncommonParameters uncommonParameters;
+
   /**
    * Internal constructor which initializes every field
    * @param spiAddress
@@ -154,24 +191,6 @@ class SpiCookie : public CookieIF {
   SpiCookie(spi::SpiComIfModes comIfMode, address_t spiAddress, gpioId_t chipSelect,
             const size_t maxSize, spi::SpiModes spiMode, uint32_t spiSpeed,
             spi::send_callback_function_t callback, void* args);
-
-  address_t spiAddress;
-  gpioId_t chipSelectPin;
-
-  spi::SpiComIfModes comIfMode;
-
-  // Required for regular mode
-  const size_t maxSize;
-  spi::SpiModes spiMode;
-  uint32_t spiSpeed;
-  bool halfDuplex = false;
-
-  // Required for callback mode
-  spi::send_callback_function_t sendCallback = nullptr;
-  void* callbackArgs = nullptr;
-
-  struct spi_ioc_transfer spiTransferStruct = {};
-  UncommonParameters uncommonParameters;
 };
 
 #endif /* LINUX_SPI_SPICOOKIE_H_ */

src/fsfw/osal/linux/FixedTimeslotTask.cpp

@@ -14,6 +14,8 @@ FixedTimeslotTask::FixedTimeslotTask(const char* name_, int priority_, size_t st
 
 FixedTimeslotTask::~FixedTimeslotTask() {}
 
+bool FixedTimeslotTask::isEmpty() const { return pst.isEmpty(); }
+
 void* FixedTimeslotTask::taskEntryPoint(void* arg) {
   // The argument is re-interpreted as PollingTask.
   FixedTimeslotTask* originalTask(reinterpret_cast<FixedTimeslotTask*>(arg));
@@ -50,7 +52,7 @@ ReturnValue_t FixedTimeslotTask::addSlot(object_id_t componentId, uint32_t slotT
   return HasReturnvaluesIF::RETURN_FAILED;
 }
 
-ReturnValue_t FixedTimeslotTask::checkSequence() const { return pst.checkSequence(); }
+ReturnValue_t FixedTimeslotTask::checkSequence() { return pst.checkSequence(); }
 
 void FixedTimeslotTask::taskFunctionality() {
   // Like FreeRTOS pthreads are running as soon as they are created

src/fsfw/osal/linux/FixedTimeslotTask.h

@@ -24,15 +24,18 @@ class FixedTimeslotTask : public FixedTimeslotTaskIF, public PosixThread {
   FixedTimeslotTask(const char* name_, int priority_, size_t stackSize_, uint32_t periodMs_);
   virtual ~FixedTimeslotTask();
 
-  virtual ReturnValue_t startTask();
+  ReturnValue_t startTask() override;
 
-  virtual ReturnValue_t sleepFor(uint32_t ms);
+  ReturnValue_t sleepFor(uint32_t ms) override;
 
-  virtual uint32_t getPeriodMs() const;
+  uint32_t getPeriodMs() const override;
 
-  virtual ReturnValue_t addSlot(object_id_t componentId, uint32_t slotTimeMs, int8_t executionStep);
+  ReturnValue_t addSlot(object_id_t componentId, uint32_t slotTimeMs,
+                        int8_t executionStep) override;
 
-  virtual ReturnValue_t checkSequence() const;
+  ReturnValue_t checkSequence() override;
+
+  bool isEmpty() const override;
 
   /**
    * This static function can be used as #deadlineMissedFunc.

src/fsfw/osal/linux/PeriodicPosixTask.cpp

@@ -1,6 +1,7 @@
 #include "fsfw/osal/linux/PeriodicPosixTask.h"
 
-#include <errno.h>
+#include <set>
+#include <cerrno>
 
 #include "fsfw/objectmanager/ObjectManager.h"
 #include "fsfw/serviceinterface/ServiceInterface.h"
@@ -23,15 +24,15 @@ void* PeriodicPosixTask::taskEntryPoint(void* arg) {
   PeriodicPosixTask* originalTask(reinterpret_cast<PeriodicPosixTask*>(arg));
   // The task's functionality is called.
   originalTask->taskFunctionality();
-  return NULL;
+  return nullptr;
 }
 
-ReturnValue_t PeriodicPosixTask::addComponent(object_id_t object) {
+ReturnValue_t PeriodicPosixTask::addComponent(object_id_t object, uint8_t opCode) {
   ExecutableObjectIF* newObject = ObjectManager::instance()->get<ExecutableObjectIF>(object);
-  return addComponent(newObject);
+  return addComponent(newObject, opCode);
 }
 
-ReturnValue_t PeriodicPosixTask::addComponent(ExecutableObjectIF* object) {
+ReturnValue_t PeriodicPosixTask::addComponent(ExecutableObjectIF* object, uint8_t opCode) {
   if (object == nullptr) {
 #if FSFW_CPP_OSTREAM_ENABLED == 1
     sif::error << "PeriodicTask::addComponent: Invalid object. Make sure"
@@ -43,7 +44,7 @@ ReturnValue_t PeriodicPosixTask::addComponent(ExecutableObjectIF* object) {
 #endif
     return HasReturnvaluesIF::RETURN_FAILED;
   }
-  objectList.push_back(object);
+  objectList.push_back({object, opCode});
   object->setTaskIF(this);
 
   return HasReturnvaluesIF::RETURN_OK;
@@ -54,6 +55,9 @@ ReturnValue_t PeriodicPosixTask::sleepFor(uint32_t ms) {
 }
 
 ReturnValue_t PeriodicPosixTask::startTask(void) {
+  if (isEmpty()) {
+    return HasReturnvaluesIF::RETURN_FAILED;
+  }
   started = true;
   PosixThread::createTask(&taskEntryPoint, this);
   return HasReturnvaluesIF::RETURN_OK;
@@ -64,15 +68,13 @@ void PeriodicPosixTask::taskFunctionality(void) {
     suspend();
   }
 
-  for (auto const& object : objectList) {
+  initObjsAfterTaskCreation();
-    object->initializeAfterTaskCreation();
-  }
 
   uint64_t lastWakeTime = getCurrentMonotonicTimeMs();
   // The task's "infinite" inner loop is entered.
   while (1) {
-    for (auto const& object : objectList) {
+    for (auto const& objOpCodePair : objectList) {
-      object->performOperation();
+      objOpCodePair.first->performOperation(objOpCodePair.second);
     }
 
     if (not PosixThread::delayUntil(&lastWakeTime, periodMs)) {
@@ -84,3 +86,25 @@ void PeriodicPosixTask::taskFunctionality(void) {
 }
 
 uint32_t PeriodicPosixTask::getPeriodMs() const { return periodMs; }
+
+bool PeriodicPosixTask::isEmpty() const { return objectList.empty(); }
+
+ReturnValue_t PeriodicPosixTask::initObjsAfterTaskCreation() {
+  std::multiset<ExecutableObjectIF*> uniqueObjects;
+  ReturnValue_t status = HasReturnvaluesIF::RETURN_OK;
+  uint32_t count = 0;
+  for (const auto& obj : objectList) {
+    // Ensure that each unique object is initialized once.
+    if (uniqueObjects.find(obj.first) == uniqueObjects.end()) {
+      ReturnValue_t result = obj.first->initializeAfterTaskCreation();
+      if (result != HasReturnvaluesIF::RETURN_OK) {
+        count++;
+        status = result;
+      }
+      uniqueObjects.emplace(obj.first);
+    }
+  }
+  if (count > 0) {
+  }
+  return status;
+}

src/fsfw/osal/linux/PeriodicPosixTask.h

@@ -40,7 +40,7 @@ class PeriodicPosixTask : public PosixThread, public PeriodicTaskIF {
    * @param object Id of the object to add.
    * @return RETURN_OK on success, RETURN_FAILED if the object could not be added.
    */
-  ReturnValue_t addComponent(object_id_t object) override;
+  ReturnValue_t addComponent(object_id_t object, uint8_t opCode) override;
 
   /**
    * Adds an object to the list of objects to be executed.
@@ -48,14 +48,20 @@ class PeriodicPosixTask : public PosixThread, public PeriodicTaskIF {
    * @param object pointer to the object to add.
    * @return RETURN_OK on success, RETURN_FAILED if the object could not be added.
    */
-  ReturnValue_t addComponent(ExecutableObjectIF* object) override;
+  ReturnValue_t addComponent(ExecutableObjectIF* object, uint8_t opCode) override;
 
   uint32_t getPeriodMs() const override;
 
   ReturnValue_t sleepFor(uint32_t ms) override;
 
+  ReturnValue_t initObjsAfterTaskCreation();
+
+  bool isEmpty() const override;
+
  private:
-  typedef std::vector<ExecutableObjectIF*> ObjectList;  //!< Typedef for the List of objects.
+  //! Typedef for the List of objects. Will contain the objects to execute and their respective
+  //! op codes
+  using ObjectList = std::vector<std::pair<ExecutableObjectIF*, uint8_t>>;
   /**
    * @brief	This attribute holds a list of objects to be executed.
    */

src/fsfw/tasks/FixedSlotSequence.cpp

@@ -164,3 +164,5 @@ ReturnValue_t FixedSlotSequence::intializeSequenceAfterTaskCreation() const {
 void FixedSlotSequence::addCustomCheck(ReturnValue_t (*customCheckFunction)(const SlotList&)) {
   this->customCheckFunction = customCheckFunction;
 }
+
+bool FixedSlotSequence::isEmpty() const { return slotList.empty(); }

src/fsfw/tasks/FixedSlotSequence.h

@@ -159,6 +159,8 @@ class FixedSlotSequence {
    */
   ReturnValue_t intializeSequenceAfterTaskCreation() const;
 
+  bool isEmpty() const;
+
  protected:
   /**
    * @brief	This list contains all PollingSlot objects, defining order and

src/fsfw/tasks/FixedTimeslotTaskIF.h

@@ -30,7 +30,7 @@ class FixedTimeslotTaskIF : public PeriodicTaskIF {
    * Check whether the sequence is valid and perform all other required
    * initialization steps which are needed after task creation
    */
-  virtual ReturnValue_t checkSequence() const = 0;
+  virtual ReturnValue_t checkSequence() = 0;
 };
 
 #endif /* FRAMEWORK_TASKS_FIXEDTIMESLOTTASKIF_H_ */

src/fsfw/tasks/PeriodicTaskIF.h

@@ -31,7 +31,7 @@ class PeriodicTaskIF {
    * Add an object to the task. The object needs to implement ExecutableObjectIF
    * @return
    */
-  virtual ReturnValue_t addComponent(object_id_t object) {
+  virtual ReturnValue_t addComponent(object_id_t object, uint8_t opCode = 0) {
     return HasReturnvaluesIF::RETURN_FAILED;
   };
 
@@ -41,13 +41,15 @@ class PeriodicTaskIF {
    * Add an object to the task.
    * @return
    */
-  virtual ReturnValue_t addComponent(ExecutableObjectIF* object) {
+  virtual ReturnValue_t addComponent(ExecutableObjectIF* object, uint8_t opCode = 0) {
     return HasReturnvaluesIF::RETURN_FAILED;
   };
 
   virtual ReturnValue_t sleepFor(uint32_t ms) = 0;
 
   virtual uint32_t getPeriodMs() const = 0;
+
+  virtual bool isEmpty() const = 0;
 };
 
 #endif /* PERIODICTASKIF_H_ */