Class MessageQueue

Defined in File message_queue.hpp

Inheritance Relationships

Base Type

public DesignPattern::Creation< MessageQueue, IpcChannelError > (Template Class Creation)

Class Documentation

class MessageQueue : public DesignPattern::Creation<MessageQueue, IpcChannelError>

Wrapper class for posix message queue.

Template Parameters:

NON_BLOCKING – specifies the type of message queue. A non-blocking message queue will immediately return from a send/receive call if the queue is full/empty. A blocking message has member functions timedSend and timedReceive which allow to specify a maximum timeout duration.

auto mq = posix::MessageQueue<true>::CreateMessageQueue("/MqName123");
if (mq.has_value())
{
    mq->send("important message, bla.");
    // ...
    std::string str;
    mq->receive(str);
}

Public Functions

MessageQueue() noexcept: default constructor. The result is an invalid MessageQueue object which can be reassigned later by using the move constructor.

MessageQueue(const MessageQueue &other) = delete

MessageQueue(MessageQueue &&other) noexcept

MessageQueue &operator=(const MessageQueue &other) = delete

MessageQueue &operator=(MessageQueue &&other) noexcept

~MessageQueue() noexcept

cxx::expected<IpcChannelError> destroy() noexcept: close and remove message queue.

cxx::expected<IpcChannelError> send(const std::string &msg) const noexcept

send a message to queue using std::string.

Returns:: true if sent without errors, false otherwise

cxx::expected<std::string, IpcChannelError> receive() const noexcept

receive message from queue using std::string.

Todo:: zero copy receive with receive(cxx::string&); cxx::string would be the buffer for mq_receive

Returns:: number of characters received. In case of an error, returns -1 and msg is empty.

cxx::expected<std::string, IpcChannelError> timedReceive(const units::Duration &timeout) const noexcept

try to receive message from queue for a given timeout duration using std::string. Only defined for NON_BLOCKING == false.

Returns:: optional containing the received string. In case of an error, nullopt type is returned.

cxx::expected<IpcChannelError> timedSend(const std::string &msg, const units::Duration &timeout) const noexcept: try to send a message to the queue for a given timeout duration using std::string

cxx::expected<bool, IpcChannelError> isOutdated() noexcept

Public Static Functions

static cxx::expected<bool, IpcChannelError> unlinkIfExists(const IpcChannelName_t &name) noexcept

Public Static Attributes

static constexpr mqd_t INVALID_DESCRIPTOR = std::numeric_limits<mqd_t>::max()

static constexpr int32_t ERROR_CODE = -1

static constexpr size_t SHORTEST_VALID_QUEUE_NAME = 2

static constexpr size_t NULL_TERMINATOR_SIZE = 1

static constexpr size_t MAX_MESSAGE_SIZE = 4096

Friends

friend class DesignPattern::Creation< MessageQueue, IpcChannelError >