Class SubscriptionIntraProcessBase

Defined in File subscription_intra_process_base.hpp

Inheritance Relationships

Base Type

public rclcpp::Waitable (Class Waitable)

Derived Types

public rclcpp::experimental::SubscriptionROSMsgIntraProcessBuffer< SubscribedType, allocator::AllocRebind< SubscribedType, std::allocator< SubscribedType > >::allocator_type, allocator::Deleter< allocator::AllocRebind< SubscribedType, std::allocator< SubscribedType > >::allocator_type, SubscribedType > > (Template Class SubscriptionROSMsgIntraProcessBuffer)
public rclcpp::experimental::SubscriptionROSMsgIntraProcessBuffer< RosMessageT, Alloc, Deleter > (Template Class SubscriptionROSMsgIntraProcessBuffer)

Class Documentation

class SubscriptionIntraProcessBase : public rclcpp::Waitable 

Subclassed by rclcpp::experimental::SubscriptionROSMsgIntraProcessBuffer< SubscribedType, allocator::AllocRebind< SubscribedType, std::allocator< SubscribedType > >::allocator_type, allocator::Deleter< allocator::AllocRebind< SubscribedType, std::allocator< SubscribedType > >::allocator_type, SubscribedType > >, rclcpp::experimental::SubscriptionROSMsgIntraProcessBuffer< RosMessageT, Alloc, Deleter >

Public Types

enum class EntityType : std::size_t

Values:

enumerator Subscription

Public Functions

inline SubscriptionIntraProcessBase(rclcpp::Context::SharedPtr context, const std::string &topic_name, const rclcpp::QoS &qos_profile)

virtual ~SubscriptionIntraProcessBase()

inline virtual size_t get_number_of_ready_guard_conditions() override

Get the number of ready guard_conditions.

Returns a value of 0 by default. This should be overridden if the Waitable contains one or more guard_conditions.

Returns:: The number of guard_conditions associated with the Waitable.

virtual void add_to_wait_set(rcl_wait_set_t *wait_set) override

Add the Waitable to a wait set.

Parameters:: wait_set – [in] A handle to the wait set to add the Waitable to.
Throws:: rclcpp::execptions::RCLError – from rcl_wait_set_add_*()

virtual bool is_ready(rcl_wait_set_t *wait_set) override = 0

Check if the Waitable is ready.

The input wait set should be the same that was used in a previously call to add_to_wait_set(). The wait set should also have been previously waited on with rcl_wait().

Parameters:: wait_set – [in] A handle to the wait set the Waitable was previously added to and that has been waited on.
Returns:: true if the Waitable is ready, false otherwise.

virtual std::shared_ptr<void> take_data() override = 0

Take the data so that it can be consumed with execute.

NOTE: take_data is a partial fix to a larger design issue with the multithreaded executor. This method is likely to be removed when a more permanent fix is implemented. A longterm fix is currently being discussed here: https://github.com/ros2/rclcpp/pull/1276

This method takes the data from the underlying data structure and writes it to the void shared pointer data that is passed into the method. The data can then be executed with the execute method.

Before calling this method, the Waitable should be added to a wait set, waited on, and then updated.

Example usage:

// ... create a wait set and a Waitable
// Add the Waitable to the wait set
waitable.add_to_wait_set(wait_set);
// Wait
rcl_ret_t wait_ret = rcl_wait(wait_set);
// ... error handling
// Update the Waitable
waitable.update(wait_set);
// Execute any entities of the Waitable that may be ready
std::shared_ptr<void> data = waitable.take_data();

inline virtual std::shared_ptr<void> take_data_by_entity_id(size_t id) override

Take the data so that it can be consumed with execute.

This function allows to specify an entity ID to take the data from. Entity IDs are identifiers that can be defined by waitable-derived classes that are composed of several distinct entities. The main use-case is in conjunction with the listener APIs.

See also

rclcpp::Waitable::set_on_ready_callback

Parameters:: id – [in] the id of the entity from which to take
Returns:: the type-erased data taken from entity specified

virtual void execute(std::shared_ptr<void> &data) override = 0

Execute data that is passed in.

Before calling this method, the Waitable should be added to a wait set, waited on, and then updated - and the take_data method should be called.

Example usage:

// ... create a wait set and a Waitable
// Add the Waitable to the wait set
waitable.add_to_wait_set(wait_set);
// Wait
rcl_ret_t wait_ret = rcl_wait(wait_set);
// ... error handling
// Update the Waitable
waitable.update(wait_set);
// Execute any entities of the Waitable that may be ready
std::shared_ptr<void> data = waitable.take_data();
waitable.execute(data);

virtual bool use_take_shared_method() const = 0

const char *get_topic_name() const

QoS get_actual_qos() const

inline virtual void set_on_ready_callback(std::function<void(size_t, int)> callback) override

Set a callback to be called when each new message arrives.

The callback receives a size_t which is the number of messages received since the last time this callback was called. Normally this is 1, but can be > 1 if messages were received before any callback was set.

The callback also receives an int identifier argument. This is needed because a Waitable may be composed of several distinct entities, such as subscriptions, services, etc. The application should provide a generic callback function that will be then forwarded by the waitable to all of its entities. Before forwarding, a different value for the identifier argument will be bound to the function. This implies that the provided callback can use the identifier to behave differently depending on which entity triggered the waitable to become ready.

Calling it again will clear any previously set callback.

An exception will be thrown if the callback is not callable.

This function is thread-safe.

If you want more information available in the callback, like the subscription or other information, you may use a lambda with captures or std::bind.

Parameters:: callback – [in] functor to be called when a new message is received.

inline virtual void clear_on_ready_callback() override: Unset the callback registered for new messages, if any.

Protected Functions

virtual void trigger_guard_condition() = 0

inline void invoke_on_new_message()

Protected Attributes

std::recursive_mutex callback_mutex_

std::function<void(size_t)> on_new_message_callback_ = {nullptr}

size_t unread_count_ = {0}

rclcpp::GuardCondition gc_