fsfw/ipc/MessageQueueMessage.h
2016-06-15 23:48:49 +02:00

123 lines
4.9 KiB
C++

#ifndef MESSAGEQUEUEMESSAGE_H_
#define MESSAGEQUEUEMESSAGE_H_
#include <framework/osal/OSAL.h>
class MessageQueue;
class MessageQueueSender;
/**
* \brief This class is the representation and data organizer for interprocess messages.
*
* \details To facilitate and standardize interprocess communication, this class was created
* to handle a lightweight "interprocess message protocol". It adds a header with the
* sender's queue id to every sent message and defines the maximum total message size.
* Specialized messages, such as device commanding messages, can be created by inheriting
* from this class and filling the buffer provided by getData with additional content.
* If larger amounts of data must be sent between processes, the data shall be stored in
* the IPC Store object and only the storage id is passed in a queue message.
* The class is used both to generate and send messages and to receive messages from
* other tasks.
* \ingroup message_queue
*/
class MessageQueueMessage {
friend class MessageQueue;
friend class MessageQueueSender;
public:
/**
* \brief This constant defines the maximum size of the data content, excluding the header.
* \details It may be changed if necessary, but in general should be kept as small as possible.
*/
static const size_t MAX_DATA_SIZE = 24;
/**
* \brief This constants defines the size of the header, which is added to every message.
*/
static const size_t HEADER_SIZE = sizeof(MessageQueueId_t);
/**
* \brief This constant defines the maximum total size in bytes of a sent message.
* \details It is the sum of the maximum data and the header size. Be aware that this constant
* is used to define the buffer sizes for every message queue in the system. So, a change
* here may have significant impact on the required resources.
*/
static const size_t MAX_MESSAGE_SIZE = MAX_DATA_SIZE + HEADER_SIZE;
private:
/**
* \brief This is the internal buffer that contains the actual message data.
*/
uint8_t internalBuffer[MAX_MESSAGE_SIZE];
protected:
/**
* \brief This method is used to set the sender's message queue id information prior to
* sending the message.
* \param setId The message queue id that identifies the sending message queue.
*/
void setSender(MessageQueueId_t setId);
/**
* \brief This helper function is used by the MessageQueue class to check the size of an
* incoming message.
* \details The method must be overwritten by child classes if size checks shall be more strict.
* @return The default implementation returns HEADER_SIZE.
*/
virtual size_t getMinimumMessageSize();
public:
/**
* \brief The size information of each message is stored in this attribute.
* \details It is public to simplify usage and to allow for passing the variable's address as a
* pointer. Care must be taken when inheriting from this class, as every child class is
* responsible for managing the size information by itself. When using the class to
* receive a message, the size information is updated automatically.
*/
size_t messageSize;
/**
* \brief The class is initialized empty with this constructor.
* \details The messageSize attribute is set to the header's size and the whole content is set to
* zero.
*/
MessageQueueMessage();
/**
* \brief With this constructor the class is initialized with the given content.
* \details If the passed message size fits into the buffer, the passed data is copied to the
* internal buffer and the messageSize information is set. Otherwise, messageSize
* is set to the header's size and the whole content is set to zero.
* \param data The data to be put in the message.
* \param size Size of the data to be copied. Must be smaller than MAX_MESSAGE_SIZE.
*/
MessageQueueMessage(uint8_t* data, uint32_t size);
/**
* \brief As no memory is allocated in this class, the destructor is empty.
*/
virtual ~MessageQueueMessage();
/**
* \brief This method is used to get the complete data of the message.
*/
const uint8_t* getBuffer() const;
/**
* \brief This method is used to get the complete data of the message.
*/
uint8_t* getBuffer();
/**
* \brief This method is used to fetch the data content of the message.
* \details It shall be used by child classes to add data at the right position.
*/
const uint8_t* getData() const;
/**
* \brief This method is used to fetch the data content of the message.
* \details It shall be used by child classes to add data at the right position.
*/
uint8_t* getData();
/**
* \brief This method is used to extract the sender's message queue id information from a
* received message.
*/
MessageQueueId_t getSender() const;
/**
* \brief With this method, the whole content and the message size is set to zero.
*/
void clear();
/**
* \brief This is a debug method that prints the content (till messageSize) to the debug output.
*/
void print();
};
#endif /* MESSAGEQUEUEMESSAGE_H_ */