rmw.h File Reference

#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include "rcutils/types.h"
#include "rosidl_generator_c/message_bounds_struct.h"
#include "rosidl_generator_c/message_type_support_struct.h"
#include "rosidl_generator_c/service_type_support_struct.h"
#include "rmw/init.h"
#include "rmw/macros.h"
#include "rmw/qos_profiles.h"
#include "rmw/subscription_options.h"
#include "rmw/types.h"
#include "rmw/visibility_control.h"

Include dependency graph for rmw.h:

Go to the source code of this file.

Functions
const char *	rmw_get_implementation_identifier (void)
const char *	rmw_get_serialization_format (void)
	Get the unique serialization format for this middleware. More...
rmw_node_t *	rmw_create_node (rmw_context_t *context, const char *name, const char *namespace_, size_t domain_id, const rmw_node_security_options_t *security_options, bool localhost_only)
	Create a node and return a handle to that node. More...
rmw_ret_t	rmw_destroy_node (rmw_node_t *node)
	Finalize a given node handle, reclaim the resources, and deallocate the node handle. More...
rmw_ret_t	rmw_node_assert_liveliness (const rmw_node_t *node)
	Manually assert that this node is alive (for RMW_QOS_POLICY_LIVELINESS_MANUAL_BY_NODE) More...
const rmw_guard_condition_t *	rmw_node_get_graph_guard_condition (const rmw_node_t *node)
	Return a guard condition which is triggered when the ROS graph changes. More...
rmw_ret_t	rmw_init_publisher_allocation (const rosidl_message_type_support_t *type_support, const rosidl_message_bounds_t *message_bounds, rmw_publisher_allocation_t *allocation)
	Initialize a publisher allocation to be used with later publications. More...
rmw_ret_t	rmw_fini_publisher_allocation (rmw_publisher_allocation_t *allocation)
	Destroy a publisher allocation object. More...
rmw_publisher_options_t	rmw_get_default_publisher_options (void)
	Return a rmw_publisher_options_t initialized with default values. More...
rmw_publisher_t *	rmw_create_publisher (const rmw_node_t *node, const rosidl_message_type_support_t *type_support, const char *topic_name, const rmw_qos_profile_t *qos_policies, const rmw_publisher_options_t *publisher_options)
	Create and return an rmw publisher. More...
rmw_ret_t	rmw_destroy_publisher (rmw_node_t *node, rmw_publisher_t *publisher)
rmw_ret_t	rmw_borrow_loaned_message (const rmw_publisher_t *publisher, const rosidl_message_type_support_t *type_support, void **ros_message)
	Borrow a loaned message. More...
rmw_ret_t	rmw_return_loaned_message_from_publisher (const rmw_publisher_t *publisher, void *loaned_message)
	Return a loaned message previously borrow from a publisher. More...
rmw_ret_t	rmw_publish (const rmw_publisher_t *publisher, const void *ros_message, rmw_publisher_allocation_t *allocation)
	Publish a given ros_message. More...
rmw_ret_t	rmw_publish_loaned_message (const rmw_publisher_t *publisher, void *ros_message, rmw_publisher_allocation_t *allocation)
	Publish a loaned ros_message. More...
rmw_ret_t	rmw_publisher_count_matched_subscriptions (const rmw_publisher_t *publisher, size_t *subscription_count)
	Retrieve the number of matched subscriptions to a publisher. More...
rmw_ret_t	rmw_publisher_get_actual_qos (const rmw_publisher_t *publisher, rmw_qos_profile_t *qos)
	Retrieve the actual qos settings of the publisher. More...
rmw_ret_t	rmw_publish_serialized_message (const rmw_publisher_t *publisher, const rmw_serialized_message_t *serialized_message, rmw_publisher_allocation_t *allocation)
	Publish an already serialized message. More...
rmw_ret_t	rmw_get_serialized_message_size (const rosidl_message_type_support_t *type_support, const rosidl_message_bounds_t *message_bounds, size_t *size)
	Compute the size of a serialized message. More...
rmw_ret_t	rmw_publisher_assert_liveliness (const rmw_publisher_t *publisher)
	Manually assert that this Publisher is alive (for RMW_QOS_POLICY_LIVELINESS_MANUAL_BY_TOPIC) More...
rmw_ret_t	rmw_serialize (const void *ros_message, const rosidl_message_type_support_t *type_support, rmw_serialized_message_t *serialized_message)
	Serialize a ROS message into a rmw_serialized_message_t. More...
rmw_ret_t	rmw_deserialize (const rmw_serialized_message_t *serialized_message, const rosidl_message_type_support_t *type_support, void *ros_message)
	Deserialize a ROS message. More...
rmw_ret_t	rmw_init_subscription_allocation (const rosidl_message_type_support_t *type_support, const rosidl_message_bounds_t *message_bounds, rmw_subscription_allocation_t *allocation)
	Initialize a subscription allocation to be used with later takes. More...
rmw_ret_t	rmw_fini_subscription_allocation (rmw_subscription_allocation_t *allocation)
	Destroy a publisher allocation object. More...
rmw_subscription_t *	rmw_create_subscription (const rmw_node_t *node, const rosidl_message_type_support_t *type_support, const char *topic_name, const rmw_qos_profile_t *qos_policies, const rmw_subscription_options_t *subscription_options)
	Create and return an rmw subscription. More...
rmw_ret_t	rmw_destroy_subscription (rmw_node_t *node, rmw_subscription_t *subscription)
rmw_ret_t	rmw_subscription_count_matched_publishers (const rmw_subscription_t *subscription, size_t *publisher_count)
	Retrieve the number of matched publishers to a subscription. More...
rmw_ret_t	rmw_subscription_get_actual_qos (const rmw_subscription_t *subscription, rmw_qos_profile_t *qos)
	Retrieve the actual qos settings of the subscription. More...
rmw_ret_t	rmw_take (const rmw_subscription_t *subscription, void *ros_message, bool *taken, rmw_subscription_allocation_t *allocation)
	Take an incoming message from a subscription. More...
rmw_ret_t	rmw_take_with_info (const rmw_subscription_t *subscription, void *ros_message, bool *taken, rmw_message_info_t *message_info, rmw_subscription_allocation_t *allocation)
	Take an incoming message from a subscription with additional metadata. More...
rmw_ret_t	rmw_take_serialized_message (const rmw_subscription_t *subscription, rmw_serialized_message_t *serialized_message, bool *taken, rmw_subscription_allocation_t *allocation)
	Take a message without deserializing it. More...
rmw_ret_t	rmw_take_serialized_message_with_info (const rmw_subscription_t *subscription, rmw_serialized_message_t *serialized_message, bool *taken, rmw_message_info_t *message_info, rmw_subscription_allocation_t *allocation)
	Take a message without deserializing it and with its additional message information. More...
rmw_ret_t	rmw_take_loaned_message (const rmw_subscription_t *subscription, void **loaned_message, bool *taken, rmw_subscription_allocation_t *allocation)
	Take a loaned message. More...
rmw_ret_t	rmw_take_loaned_message_with_info (const rmw_subscription_t *subscription, void **loaned_message, bool *taken, rmw_message_info_t *message_info, rmw_subscription_allocation_t *allocation)
	Take a loaned message and with its additional message information. More...
rmw_ret_t	rmw_return_loaned_message_from_subscription (const rmw_subscription_t *subscription, void *loaned_message)
	Return a loaned message previously taken from a subscription. More...
rmw_client_t *	rmw_create_client (const rmw_node_t *node, const rosidl_service_type_support_t *type_support, const char *service_name, const rmw_qos_profile_t *qos_policies)
rmw_ret_t	rmw_destroy_client (rmw_node_t *node, rmw_client_t *client)
rmw_ret_t	rmw_send_request (const rmw_client_t *client, const void *ros_request, int64_t *sequence_id)
rmw_ret_t	rmw_take_response (const rmw_client_t *client, rmw_request_id_t *request_header, void *ros_response, bool *taken)
rmw_service_t *	rmw_create_service (const rmw_node_t *node, const rosidl_service_type_support_t *type_support, const char *service_name, const rmw_qos_profile_t *qos_policies)
rmw_ret_t	rmw_destroy_service (rmw_node_t *node, rmw_service_t *service)
rmw_ret_t	rmw_take_request (const rmw_service_t *service, rmw_request_id_t *request_header, void *ros_request, bool *taken)
rmw_ret_t	rmw_send_response (const rmw_service_t *service, rmw_request_id_t *request_header, void *ros_response)
rmw_guard_condition_t *	rmw_create_guard_condition (rmw_context_t *context)
	Create a guard condition and return a handle to that guard condition. More...
rmw_ret_t	rmw_destroy_guard_condition (rmw_guard_condition_t *guard_condition)
	Finalize a given guard condition handle, reclaim the resources, and deallocate the handle. More...
rmw_ret_t	rmw_trigger_guard_condition (const rmw_guard_condition_t *guard_condition)
rmw_wait_set_t *	rmw_create_wait_set (rmw_context_t *context, size_t max_conditions)
	Create a wait set to store conditions that the middleware will block on. More...
rmw_ret_t	rmw_destroy_wait_set (rmw_wait_set_t *wait_set)
rmw_ret_t	rmw_wait (rmw_subscriptions_t *subscriptions, rmw_guard_conditions_t *guard_conditions, rmw_services_t *services, rmw_clients_t *clients, rmw_events_t *events, rmw_wait_set_t *wait_set, const rmw_time_t *wait_timeout)
	Waits on sets of different waitable entities and returns when one is ready. More...
rmw_ret_t	rmw_get_node_names (const rmw_node_t *node, rcutils_string_array_t *node_names, rcutils_string_array_t *node_namespaces)
	Return a list of node name and namespaces discovered via a node. More...
rmw_ret_t	rmw_count_publishers (const rmw_node_t *node, const char *topic_name, size_t *count)
rmw_ret_t	rmw_count_subscribers (const rmw_node_t *node, const char *topic_name, size_t *count)
rmw_ret_t	rmw_get_gid_for_publisher (const rmw_publisher_t *publisher, rmw_gid_t *gid)
rmw_ret_t	rmw_compare_gids_equal (const rmw_gid_t *gid1, const rmw_gid_t *gid2, bool *result)
rmw_ret_t	rmw_service_server_is_available (const rmw_node_t *node, const rmw_client_t *client, bool *is_available)
	Check if a service server is available for the given service client. More...
rmw_ret_t	rmw_set_log_severity (rmw_log_severity_t severity)

Function Documentation

rmw_get_implementation_identifier()

const char* rmw_get_implementation_identifier

(

void

)

rmw_get_serialization_format()

const char* rmw_get_serialization_format

(

void

)

Get the unique serialization format for this middleware.

Return the format in which binary data is serialized. One middleware can only have one encoding. In contrast to the implementation identifier, the serialization format can be equal between multiple RMW implementations. This means, that the same binary messages can be deserialized by RMW implementations with the same format.

See also

rmw_serialize

rmw_deserialize

Returns

serialization format

rmw_create_node()

rmw_node_t* rmw_create_node	(	rmw_context_t *	context,
		const char *	name,
		const char *	namespace_,
		size_t	domain_id,
		const rmw_node_security_options_t *	security_options,
		bool	localhost_only
	)

Create a node and return a handle to that node.

This function can fail, and therefore return NULL, if:

• context, name, namespace_, or security_options is NULL
• context, security_options is invalid
• memory allocation fails during node creation
• an unspecified error occurs

The context must be non-null and valid, i.e. it has been initialized by rmw_init() and has not been finalized by rmw_shutdown().

The name and namespace_ should be valid node name and namespace, and this should be asserted by the caller (e.g. rcl).

The domain ID should be used to physically separate nodes at the communication graph level by the middleware. For RTPS/DDS this maps naturally to their concept of domain id.

The security options should always be non-null and encapsulate the essential security configurations for the node and its entities.

---

Attribute	Adherence
Allocates Memory	Yes
Thread-Safe	No
Uses Atomics	No [1]
Lock-Free	No [1]

[1] rmw implementation defined, check the implementation documentation

This should be defined by the rmw implementation.

Parameters

[in]	context	init context that this node should be associated with
[in]	name	the node name
[in]	namespace_	the node namespace
[in]	domain_id	the id of the domain that the node should join
[in]	security_options	the security configurations for the node
[in]	localhost_only	whenever to use loopback only for communication or default network interfaces.

Returns

rmw node handle or NULL if there was an error

rmw_destroy_node()

rmw_ret_t rmw_destroy_node

(

rmw_node_t *

node

)

Finalize a given node handle, reclaim the resources, and deallocate the node handle.

Parameters

node	the node handle to be destroyed

Returns

RMW_RET_OK if successful, or

RMW_RET_INVALID_ARGUMENT if node is null, or

RMW_RET_ERROR if an unexpected error occurs.

rmw_node_assert_liveliness()

rmw_ret_t rmw_node_assert_liveliness

(

const rmw_node_t *

node

)

Manually assert that this node is alive (for RMW_QOS_POLICY_LIVELINESS_MANUAL_BY_NODE)

If the rmw Liveliness policy is set to RMW_QOS_POLICY_LIVELINESS_MANUAL_BY_NODE, the creator of this node may manually call assert_liveliness at some point in time to signal to the rest of the system that this Node is still alive.

---

Attribute	Adherence
Allocates Memory	No
Thread-Safe	Yes
Uses Atomics	No
Lock-Free	Yes

Parameters

[in]

node

handle to the node that needs liveliness to be asserted

Returns

RMW_RET_OK if the liveliness assertion was completed successfully, or

RMW_RET_ERROR if an unspecified error occurs, or

RMW_RET_UNSUPPORTED if the rmw implementation does not support asserting liveliness.

rmw_node_get_graph_guard_condition()

const rmw_guard_condition_t* rmw_node_get_graph_guard_condition

(

const rmw_node_t *

node

)

Return a guard condition which is triggered when the ROS graph changes.

The handle returned is a pointer to an internally held rmw guard condition. This function can fail, and therefore return NULL, if:

• node is NULL
• node is invalid

The returned handle is made invalid if the node is destroyed or if rmw_shutdown() is called.

The guard condition will be triggered anytime a change to the ROS graph occurs. A ROS graph change includes things like (but not limited to) a new publisher advertises, a new subscription is created, a new service becomes available, a subscription is canceled, etc.

---

Attribute	Adherence
Allocates Memory	No
Thread-Safe	Yes
Uses Atomics	No
Lock-Free	Yes

Parameters

[in]

node

pointer to the rmw node

Returns

rmw guard condition handle if successful, otherwise NULL

rmw_init_publisher_allocation()

rmw_ret_t rmw_init_publisher_allocation	(	const rosidl_message_type_support_t *	type_support,
		const rosidl_message_bounds_t *	message_bounds,
		rmw_publisher_allocation_t *	allocation
	)

Initialize a publisher allocation to be used with later publications.

This creates an allocation object that can be used in conjunction with the rmw_publish method to perform more carefully control memory allocations.

This will allow the middleware to preallocate the correct amount of memory for a given message type and message bounds. As allocation is performed in this method, it will not be necessary to allocate in the rmw_publish method.

Parameters

[in]	type_support	Type support of the message to be preallocated.
[in]	message_bounds	Bounds structure of the message to be preallocated.
[out]	allocation	Allocation structure to be passed to rmw_publish.

Returns

RMW_RET_OK if successful, or

RMW_RET_INVALID_ARGUMENT if an argument is null, or

RMW_RET_ERROR if an unexpected error occurs.

rmw_fini_publisher_allocation()

rmw_ret_t rmw_fini_publisher_allocation

(

rmw_publisher_allocation_t *

allocation

)

Destroy a publisher allocation object.

This deallocates any memory allocated by rmw_init_publisher_allocation.

Parameters

[in]

allocation

Allocation object to be destroyed.

Returns

RMW_RET_OK if successful, or

RMW_RET_INVALID_ARGUMENT if argument is null, or

RMW_RET_ERROR if an unexpected error occurs.

rmw_get_default_publisher_options()

rmw_publisher_options_t rmw_get_default_publisher_options

(

void

)

Return a rmw_publisher_options_t initialized with default values.

rmw_create_publisher()

rmw_publisher_t* rmw_create_publisher	(	const rmw_node_t *	node,
		const rosidl_message_type_support_t *	type_support,
		const char *	topic_name,
		const rmw_qos_profile_t *	qos_policies,
		const rmw_publisher_options_t *	publisher_options
	)

Create and return an rmw publisher.

(wjwwood): add detailed documentation, adding a not about one of the arguments for now.

The argument publisher_options must not be nullptr.

Parameters

[in]

publisher_options

options for configuring the publisher

rmw_destroy_publisher()

rmw_ret_t rmw_destroy_publisher	(	rmw_node_t *	node,
		rmw_publisher_t *	publisher
	)

rmw_borrow_loaned_message()

rmw_ret_t rmw_borrow_loaned_message	(	const rmw_publisher_t *	publisher,
		const rosidl_message_type_support_t *	type_support,
		void **	ros_message
	)

Borrow a loaned message.

The memory allocated for the ros message belongs to the middleware and must not be deallocated. A call to

See also

rmw_publish_loned_message as well as

rmw_return_loaned_message_from_publisher` will return ownership of the loaned message back to the middleware.

In order to react to failures, the ros message is passed by pointer as an output parameter. Therefore, the pointer to the ros message has to be null and not previously allocated or else that memory is lost.

Parameters

[in]	publisher	Publisher to which the allocated message is associated.
[in]	type_support	Typesupport to which the internal ros message is allocated.
[out]	ros_message	The pointer to be filled with a valid ros message by the middleware.

Returns

RMW_RET_OK if the ros message was correctly initialized, or

RMW_RET_INVALID_ARGUMENT if an argument other than the ros message is null, or

RMW_RET_BAD_ALLOC if the ros message could not be correctly created, or

RMW_RET_ERROR if an unexpected error occured.

rmw_return_loaned_message_from_publisher()

rmw_ret_t rmw_return_loaned_message_from_publisher	(	const rmw_publisher_t *	publisher,
		void *	loaned_message
	)

Return a loaned message previously borrow from a publisher.

The ownership of the passed in ros message will be transferred back to the middleware. The middleware might deallocate and destroy the message so that the pointer is no longer guaranteed to be valid after this call.

Parameters

[in]	publisher	Publisher to which the loaned message is associated.
[in]	loaned_message	Loaned message to be returned.

Returns

RMW_RET_OK if successful, or

RMW_RET_INVALID_ARGUMENT if an argument is null, or

RMW_RET_ERROR if an unexpected error occurs and no message can be initialized.

rmw_publish()

rmw_ret_t rmw_publish	(	const rmw_publisher_t *	publisher,
		const void *	ros_message,
		rmw_publisher_allocation_t *	allocation
	)

Publish a given ros_message.

Publish a given ROS message via a publisher.

Parameters

[in]	publisher	Publisher to be used to send message.
[in]	ros_message	Message to be sent.
[in]	allocation	Specify preallocated memory to use (may be NULL).

Returns

RMW_RET_OK if successful, or

RMW_RET_INVALID_ARGUMENT if publisher or ros_message is null, or

RMW_RET_ERROR if an unexpected error occurs.

rmw_publish_loaned_message()

rmw_ret_t rmw_publish_loaned_message	(	const rmw_publisher_t *	publisher,
		void *	ros_message,
		rmw_publisher_allocation_t *	allocation
	)

Publish a loaned ros_message.

Publish a loaned ROS message via a publisher and return ownership of the loaned message back to the middleware.

In contrast to

See also

rmw_publish the ownership of the ros message is being transferred to the middleware which might deallocate the memory for it. Similar to

rmw_return_loaned_message_from_publisher the passed in ros message might not be valid after this call and thus should only be called with messages previously loaned with a call to

rmw_borrow_loaned_message.

Parameters

[in]	publisher	Publisher to be used to send message.
[in]	ros_message	Message to be sent.
[in]	allocation	Specify preallocated memory to use (may be NULL).

Returns

RMW_RET_OK if successful, or

RMW_RET_INVALID_ARGUMENT if publisher or ros_message is null, or

RMW_RET_ERROR if an unexpected error occurs.

rmw_publisher_count_matched_subscriptions()

rmw_ret_t rmw_publisher_count_matched_subscriptions	(	const rmw_publisher_t *	publisher,
		size_t *	subscription_count
	)

Retrieve the number of matched subscriptions to a publisher.

Query the underlying middleware to determine how many subscriptions are matched to a given publisher.

Parameters

[in]	publisher	the publisher object to inspect
[out]	subscription_count	the number of subscriptions matched

Returns

RMW_RET_OK if successful, or

RMW_RET_INVALID_ARGUMENT if either argument is null, or

RMW_RET_ERROR if an unexpected error occurs.

rmw_publisher_get_actual_qos()

rmw_ret_t rmw_publisher_get_actual_qos	(	const rmw_publisher_t *	publisher,
		rmw_qos_profile_t *	qos
	)

Retrieve the actual qos settings of the publisher.

Query the underlying middleware to determine the qos settings of the publisher. The actual configuration applied when using RMW_*_SYSTEM_DEFAULT can only be resolved after the creation of the publisher, and it depends on the underlying rmw implementation. If the underlying setting in use can't be represented in ROS terms, it will be set to RMW_*_UNKNOWN. The value of avoid_ros_namespace_conventions field is not resolved with this function. The rcl function rcl_publisher_get_actual_qos resolves it.

Parameters

[in]	publisher	the publisher object to inspect
[out]	qos	the actual qos settings

Returns

RMW_RET_OK if successful, or

RMW_RET_INVALID_ARGUMENT if either argument is null, or

RMW_RET_ERROR if an unexpected error occurs.

rmw_publish_serialized_message()

rmw_ret_t rmw_publish_serialized_message	(	const rmw_publisher_t *	publisher,
		const rmw_serialized_message_t *	serialized_message,
		rmw_publisher_allocation_t *	allocation
	)

Publish an already serialized message.

The publisher must already be registered with the correct message type support so that it can send serialized data corresponding to that type. This function sends the serialized byte stream directly over the wire without having to serialize the message first. A ROS message can be serialized manually using the rmw_serialize() function.

Parameters

[in]	publisher	The publisher object registered to send the message.
[in]	serialized_message	The serialized message holding the byte stream.
[in]	allocation	Specify preallocated memory to use (may be NULL).

Returns

RMW_RET_OK if successful, or

RMW_RET_ERROR if an unexpected error occurs.

rmw_get_serialized_message_size()

rmw_ret_t rmw_get_serialized_message_size	(	const rosidl_message_type_support_t *	type_support,
		const rosidl_message_bounds_t *	message_bounds,
		size_t *	size
	)

Compute the size of a serialized message.

Given a message definition and bounds, compute the serialized size.

Parameters

[in]	type_support	The type support of the message to compute.
[in]	bounds	Artifical bounds to use on unbounded fields.
[out]	size	The computed size of the serialized message.

Returns

RMW_RET_OK if successful, or

RMW_RET_INVALID_ARGUMENT if either argument is null, or

RMW_RET_ERROR if an unexpected error occurs.

rmw_publisher_assert_liveliness()

rmw_ret_t rmw_publisher_assert_liveliness

(

const rmw_publisher_t *

publisher

)

Manually assert that this Publisher is alive (for RMW_QOS_POLICY_LIVELINESS_MANUAL_BY_TOPIC)

If the rmw Liveliness policy is set to RMW_QOS_POLICY_LIVELINESS_MANUAL_BY_TOPIC, the creator of this publisher may manually call assert_liveliness at some point in time to signal to the rest of the system that this Node is still alive.

---

Attribute	Adherence
Allocates Memory	No
Thread-Safe	Yes
Uses Atomics	No
Lock-Free	Yes

Parameters

[in]

publisher

handle to the publisher that needs liveliness to be asserted

Returns

RMW_RET_OK if the liveliness assertion was completed successfully, or

RMW_RET_ERROR if an unspecified error occurs, or

RMW_RET_UNSUPPORTED if the rmw implementation does not support asserting liveliness.

rmw_serialize()

rmw_ret_t rmw_serialize	(	const void *	ros_message,
		const rosidl_message_type_support_t *	type_support,
		rmw_serialized_message_t *	serialized_message
	)

Serialize a ROS message into a rmw_serialized_message_t.

The ROS message is serialized into a byte stream contained within the rmw_serialized_message_t structure. The serialization format depends on the underlying middleware.

Parameters

ros_message	the typed ROS message
type_support	the typesupport for the ROS message
serialized_message	the destination for the serialize ROS message

Returns

RMW_RET_OK if successful, or

RMW_RET_BAD_ALLOC if memory allocation failed, or

RMW_RET_ERROR if an unexpected error occurs.

rmw_deserialize()

rmw_ret_t rmw_deserialize	(	const rmw_serialized_message_t *	serialized_message,
		const rosidl_message_type_support_t *	type_support,
		void *	ros_message
	)

Deserialize a ROS message.

The given rmw_serialized_message_t's internal byte stream buffer is deserialized into the given ROS message. The ROS message must already be allocated and initialized, and must match the given typesupport structure. The serialization format expected in the rmw_serialized_message_t depends on the underlying middleware.

Parameters

serialized_message	the serialized message holding the byte stream
type_support	the typesupport for the typed ros message
ros_message	destination for the deserialized ROS message

Returns

RMW_RET_OK if successful, or

RMW_RET_BAD_ALLOC if memory allocation failed, or

RMW_RET_ERROR if an unexpected error occurs.

rmw_init_subscription_allocation()

rmw_ret_t rmw_init_subscription_allocation	(	const rosidl_message_type_support_t *	type_support,
		const rosidl_message_bounds_t *	message_bounds,
		rmw_subscription_allocation_t *	allocation
	)

Initialize a subscription allocation to be used with later takes.

This creates an allocation object that can be used in conjunction with the rmw_take method to perform more carefully control memory allocations.

This will allow the middleware to preallocate the correct amount of memory for a given message type and message bounds. As allocation is performed in this method, it will not be necessary to allocate in the rmw_take method.

Parameters

[in]	type_support	Type support of the message to be preallocated.
[in]	message_bounds	Bounds structure of the message to be preallocated.
[out]	allocation	Allocation structure to be passed to rmw_take.

Returns

RMW_RET_OK if successful, or

RMW_RET_INVALID_ARGUMENT if an argument is null, or

RMW_RET_ERROR if an unexpected error occurs.

rmw_fini_subscription_allocation()

rmw_ret_t rmw_fini_subscription_allocation

(

rmw_subscription_allocation_t *

allocation

)

Destroy a publisher allocation object.

This deallocates memory allocated by rmw_init_subscription_allocation.

Parameters

[in]

allocation

Allocation object to be destroyed.

Returns

RMW_RET_OK if successful, or

RMW_RET_INVALID_ARGUMENT if argument is null, or

RMW_RET_ERROR if an unexpected error occurs.

rmw_create_subscription()

rmw_subscription_t* rmw_create_subscription	(	const rmw_node_t *	node,
		const rosidl_message_type_support_t *	type_support,
		const char *	topic_name,
		const rmw_qos_profile_t *	qos_policies,
		const rmw_subscription_options_t *	subscription_options
	)

Create and return an rmw subscription.

(wjwwood): add detailed documentation, adding a not about one of the arguments for now.

The argument subscription_options must not be nullptr.

Parameters

[in]

subscription_options

options for configuring the subscription

rmw_destroy_subscription()

rmw_ret_t rmw_destroy_subscription	(	rmw_node_t *	node,
		rmw_subscription_t *	subscription
	)

rmw_subscription_count_matched_publishers()

rmw_ret_t rmw_subscription_count_matched_publishers	(	const rmw_subscription_t *	subscription,
		size_t *	publisher_count
	)

Retrieve the number of matched publishers to a subscription.

Query the underlying middleware to determine how many publishers are matched to a given subscription.

Parameters

[in]	subscription	the subscription object to inspect
[out]	publisher_count	the number of publishers matched

Returns

RMW_RET_OK if successful, or

RMW_RET_INVALID_ARGUMENT if either argument is null, or

RMW_RET_ERROR if an unexpected error occurs.

rmw_subscription_get_actual_qos()

rmw_ret_t rmw_subscription_get_actual_qos	(	const rmw_subscription_t *	subscription,
		rmw_qos_profile_t *	qos
	)

Retrieve the actual qos settings of the subscription.

Query the underlying middleware to determine the qos settings of the subscription. The actual configuration applied when using RMW_*_SYSTEM_DEFAULT can only be resolved after the creation of the subscription, and it depends on the underlying rmw implementation. If the underlying setting in use can't be represented in ROS terms, it will be set to RMW_*_UNKNOWN. The value of avoid_ros_namespace_conventions field is not resolved with this function. The rcl function rcl_subscription_get_actual_qos resolves it.

Parameters

[in]	subscription	the subscription object to inspect
[out]	qos	the actual qos settings

Returns

RMW_RET_OK if successful, or

RMW_RET_INVALID_ARGUMENT if either argument is null, or

RMW_RET_ERROR if an unexpected error occurs.

rmw_take()

rmw_ret_t rmw_take	(	const rmw_subscription_t *	subscription,
		void *	ros_message,
		bool *	taken,
		rmw_subscription_allocation_t *	allocation
	)

Take an incoming message from a subscription.

Take an incoming ROS message from a given subscription.

Parameters

[in]	subscription	The subscription object to take from.
[out]	ros_message	The ROS message data on success.
[out]	taken	Boolean flag indicating if a message was taken or not.
[in]	allocation	Preallocated buffer to use (may be NULL).

Returns

RMW_RET_OK if successful, or

RMW_RET_ERROR if an unexpected error occurs.

rmw_take_with_info()

rmw_ret_t rmw_take_with_info	(	const rmw_subscription_t *	subscription,
		void *	ros_message,
		bool *	taken,
		rmw_message_info_t *	message_info,
		rmw_subscription_allocation_t *	allocation
	)

Take an incoming message from a subscription with additional metadata.

Take an incoming ROS message from a given subscription.

Parameters

[in]	subscription	The subscription object to take from.
[out]	ros_message	The ROS message data on success.
[out]	taken	Boolean flag indicating if a message was taken or not.
[out]	message_info	Additional message metadata.
[in]	allocation	Preallocated buffer to use (may be NULL).

Returns

RMW_RET_OK if successful, or

RMW_RET_ERROR if an unexpected error occurs.

rmw_take_serialized_message()

rmw_ret_t rmw_take_serialized_message	(	const rmw_subscription_t *	subscription,
		rmw_serialized_message_t *	serialized_message,
		bool *	taken,
		rmw_subscription_allocation_t *	allocation
	)

Take a message without deserializing it.

The message is taken in its serialized form. In contrast to rmw_take, the message is not deserialized in its ROS type but rather returned as a byte stream. The subscriber has to be registered for a specific type. But instead of receiving the message as its corresponding message type, it is taken as a byte stream. If needed, this byte stream can then be deserialized in a ROS message with a call to rmw_deserialize.

Parameters

[in]	subscription	Subscription object to take from.
[out]	serialized_message	The destination in which to store the serialized message.
[out]	taken	Boolean flag indicating if a message was taken or not.
[in]	allocation	Preallocated buffer to use (may be NULL).

Returns

RMW_RET_OK if successful, or

RMW_RET_BAD_ALLOC if memory allocation failed, or

RMW_RET_ERROR if an unexpected error occurs.

rmw_take_serialized_message_with_info()

rmw_ret_t rmw_take_serialized_message_with_info	(	const rmw_subscription_t *	subscription,
		rmw_serialized_message_t *	serialized_message,
		bool *	taken,
		rmw_message_info_t *	message_info,
		rmw_subscription_allocation_t *	allocation
	)

Take a message without deserializing it and with its additional message information.

The same as rmw_take_serialized_message(), except it also includes the rmw_message_info_t.

Parameters

[in]	subscription	Subscription object to take from.
[out]	serialized_message	The destination in which to store the serialized message.
[out]	taken	Boolean flag indicating if a message was taken or not.
[out]	message_info	A structure containing meta information about the taken message.
[in]	allocation	Preallocated buffer to use (may be NULL).

Returns

RMW_RET_OK if successful, or

RMW_RET_BAD_ALLOC if memory allocation failed, or

RMW_RET_ERROR if an unexpected error occurs.

rmw_take_loaned_message()

rmw_ret_t rmw_take_loaned_message	(	const rmw_subscription_t *	subscription,
		void **	loaned_message,
		bool *	taken,
		rmw_subscription_allocation_t *	allocation
	)

Take a loaned message.

If capable, the middleware can loan messages containing incoming messages. The message is owned by the middleware and thus has to be returned with a call to

See also

rmw_return_loaned_message_from_subscription.

Parameters

[in]	subscription	Subscription object to take from.
[in,out]	loaned_message	The destination in which to store the loaned message.
[out]	taken	Boolean flag indicating if a message was taken or not.
[in]	allocation	Preallocated buffer to use (may be NULL).

Returns

RMW_RET_OK if successful, or

RMW_RET_BAD_ALLOC if memory allocation failed, or

RMW_RET_ERROR if an unexpected error occurs.

rmw_take_loaned_message_with_info()

rmw_ret_t rmw_take_loaned_message_with_info	(	const rmw_subscription_t *	subscription,
		void **	loaned_message,
		bool *	taken,
		rmw_message_info_t *	message_info,
		rmw_subscription_allocation_t *	allocation
	)

Take a loaned message and with its additional message information.

If capable, the middleware can loan messages containing incoming messages. The message is owned by the middleware and thus has to be returned with a call to

See also

rmw_release_loaned_message.

Parameters

[in]	subscription	Subscription object to take from.
[in,out]	loaned_message	The destination in which to store the loaned message.
[out]	taken	Boolean flag indicating if a message was taken or not.
[out]	message_info	A structure containing meta information about the taken message.
[in]	allocation	Preallocated buffer to use (may be NULL).

Returns

RMW_RET_OK if successful, or

RMW_RET_BAD_ALLOC if memory allocation failed, or

RMW_RET_ERROR if an unexpected error occurs.

rmw_return_loaned_message_from_subscription()

rmw_ret_t rmw_return_loaned_message_from_subscription	(	const rmw_subscription_t *	subscription,
		void *	loaned_message
	)

Return a loaned message previously taken from a subscription.

After the taking a loaned message from the middleware, the middleware has to keep the memory for the loaned message alive and valid as long as the user is working with that loan. In order to indicate that the loaned message is no longer needed, the call to

See also

rmw_return_loaned_message_from_subscription tells the middleware that memory can be deallocated/destroyed.

Parameters

[in]	subscription	The subscription instance which loaned the message.
[in]	loaned_message	The message to be released.

rmw_create_client()

rmw_client_t* rmw_create_client	(	const rmw_node_t *	node,
		const rosidl_service_type_support_t *	type_support,
		const char *	service_name,
		const rmw_qos_profile_t *	qos_policies
	)

rmw_destroy_client()

rmw_ret_t rmw_destroy_client	(	rmw_node_t *	node,
		rmw_client_t *	client
	)

rmw_send_request()

rmw_ret_t rmw_send_request	(	const rmw_client_t *	client,
		const void *	ros_request,
		int64_t *	sequence_id
	)

rmw_take_response()

rmw_ret_t rmw_take_response	(	const rmw_client_t *	client,
		rmw_request_id_t *	request_header,
		void *	ros_response,
		bool *	taken
	)

rmw_create_service()

rmw_service_t* rmw_create_service	(	const rmw_node_t *	node,
		const rosidl_service_type_support_t *	type_support,
		const char *	service_name,
		const rmw_qos_profile_t *	qos_policies
	)

rmw_destroy_service()

rmw_ret_t rmw_destroy_service	(	rmw_node_t *	node,
		rmw_service_t *	service
	)

rmw_take_request()

rmw_ret_t rmw_take_request	(	const rmw_service_t *	service,
		rmw_request_id_t *	request_header,
		void *	ros_request,
		bool *	taken
	)

rmw_send_response()

rmw_ret_t rmw_send_response	(	const rmw_service_t *	service,
		rmw_request_id_t *	request_header,
		void *	ros_response
	)

rmw_create_guard_condition()

rmw_guard_condition_t* rmw_create_guard_condition

(

rmw_context_t *

context

)

Create a guard condition and return a handle to that guard condition.

This function can fail, and therefore return NULL, if:

• context is NULL
• context is invalid
• memory allocation fails during guard condition creation
• an unspecified error occurs

The context must be non-null and valid, i.e. it has been initialized by rmw_init() and has not been finalized by rmw_shutdown().

---

Attribute	Adherence
Allocates Memory	Yes
Thread-Safe	No
Uses Atomics	No [1]
Lock-Free	No [1]

[1] rmw implementation defined, check the implementation documentation

This should be defined by the rmw implementation.

Parameters

[in]

context

init context that this node should be associated with

Returns

rmw guard condition handle or NULL if there was an error

rmw_destroy_guard_condition()

rmw_ret_t rmw_destroy_guard_condition

(

rmw_guard_condition_t *

guard_condition

)

Finalize a given guard condition handle, reclaim the resources, and deallocate the handle.

Parameters

guard_condition

the guard condition handle to be destroyed

Returns

RMW_RET_OK if successful, or

RMW_RET_INVALID_ARGUMENT if guard_condition is null, or

RMW_RET_ERROR if an unexpected error occurs.

rmw_trigger_guard_condition()

rmw_ret_t rmw_trigger_guard_condition

(

const rmw_guard_condition_t *

guard_condition

)

rmw_create_wait_set()

rmw_wait_set_t* rmw_create_wait_set	(	rmw_context_t *	context,
		size_t	max_conditions
	)

Create a wait set to store conditions that the middleware will block on.

This function can fail, and therefore return NULL, if:

• context is NULL
• context is invalid
• memory allocation fails during wait set creation
• an unspecified error occurs

If max_conditions is 0, the wait set can store an unbounded number of conditions to wait on. If max_conditions is greater than 0, the number of conditions that can be attached to the wait set is bounded at max_conditions.

Parameters

[in]	context	init context that this node should be associated with
[in]	max_conditions	The maximum number of conditions that can be attached to the wait set.

Returns

A pointer to the created wait set, NULL if an error occurred.

rmw_destroy_wait_set()

rmw_ret_t rmw_destroy_wait_set

(

rmw_wait_set_t *

wait_set

)

rmw_wait()

rmw_ret_t rmw_wait	(	rmw_subscriptions_t *	subscriptions,
		rmw_guard_conditions_t *	guard_conditions,
		rmw_services_t *	services,
		rmw_clients_t *	clients,
		rmw_events_t *	events,
		rmw_wait_set_t *	wait_set,
		const rmw_time_t *	wait_timeout
	)

Waits on sets of different waitable entities and returns when one is ready.

Add conditions to the wait set and wait until a response comes in, or until the timeout is reached. The arrays contain type-erased representations of waitable entities. This function casts the pointers to middleware-specific conditions and adds them to the wait set.

The count variables in the arrays represents the number of valid pointers in the array. NULL pointers are in the array considered invalid. If they are encountered, an error is returned.

The array structs are allocated and deallocated outside of this function. They do not have any information about how much memory is allocated for the arrays.

After the wait wakes up, the entries in each array that correspond to conditions that were not triggered are set to NULL.

Parameters

subscriptions	Array of subscriptions to wait on
guard_conditions	Array of guard conditions to wait on
services	Array of services to wait on
clients	Array of clients to wait on
wait_set	Storage for the wait set
wait_timeout	If NULL, block until a condition is ready. If zero, check only for immediately available conditions and don't block. Else, this represents the maximum time to wait for a response from the wait set.

Returns

RMW_RET_OK if success, or

RMW_RET_ERROR if error, or

RMW_RET_TIMEOUT if wait timed out.

rmw_get_node_names()

rmw_ret_t rmw_get_node_names	(	const rmw_node_t *	node,
		rcutils_string_array_t *	node_names,
		rcutils_string_array_t *	node_namespaces
	)

Return a list of node name and namespaces discovered via a node.

This function will return a list of node names and a list of node namespaces that are discovered via the middleware. The two lists represent pairs of namespace and name for each discovered node. The lists will be the same length and the same position will refer to the same node across lists.

The node parameter must not be NULL, and must point to a valid node.

The node_names parameter must not be NULL, and must point to a valid string array.

The node_namespaces parameter must not be NULL, and must point to a valid string array.

This function does manipulate heap memory. This function is not thread-safe. This function is lock-free.

Parameters

[in]	node	the handle to the node being used to query the ROS graph
[out]	node_names	a list of discovered node names
[out]	node_namespaces	a list of discovered node namespaces

Returns

RMW_RET_OK if node the query was made successfully, or

RMW_RET_ERROR if an unspecified error occurs.

rmw_count_publishers()

rmw_ret_t rmw_count_publishers	(	const rmw_node_t *	node,
		const char *	topic_name,
		size_t *	count
	)

rmw_count_subscribers()

rmw_ret_t rmw_count_subscribers	(	const rmw_node_t *	node,
		const char *	topic_name,
		size_t *	count
	)

rmw_get_gid_for_publisher()

rmw_ret_t rmw_get_gid_for_publisher	(	const rmw_publisher_t *	publisher,
		rmw_gid_t *	gid
	)

rmw_compare_gids_equal()

rmw_ret_t rmw_compare_gids_equal	(	const rmw_gid_t *	gid1,
		const rmw_gid_t *	gid2,
		bool *	result
	)

rmw_service_server_is_available()

rmw_ret_t rmw_service_server_is_available	(	const rmw_node_t *	node,
		const rmw_client_t *	client,
		bool *	is_available
	)

Check if a service server is available for the given service client.

This function will return true for is_available if there is a service server available for the given client.

The node parameter must not be NULL, and must point to a valid node.

The client parameter must not be NULL, and must point to a valid client.

The given client and node must match, i.e. the client must have been created using the given node.

The is_available parameter must not be NULL, and must point to a bool variable. The result of the check will be stored in the is_available parameter.

This function does manipulate heap memory. This function is not thread-safe. This function is lock-free.

Parameters

[in]	node	the handle to the node being used to query the ROS graph
[in]	client	the handle to the service client being queried
[out]	is_available	set to true if there is a service server available, else false

Returns

RMW_RET_OK if node the check was made successfully, or

RMW_RET_ERROR if an unspecified error occurs.

rmw_set_log_severity()

rmw_ret_t rmw_set_log_severity

(

rmw_log_severity_t

severity

)