#include "rosidl_generator_c/service_type_support.h"
#include "rcl/macros.h"
#include "rcl/node.h"
#include "rcl/visibility_control.h"

Classes
struct	rcl_service_t
	Structure which encapsulates a ROS Service. More...

struct	rcl_service_options_t
	Options available for a rcl service. More...

Typedefs
typedef struct rcl_service_t	rcl_service_t
	Structure which encapsulates a ROS Service. More...

typedef struct rcl_service_options_t	rcl_service_options_t
	Options available for a rcl service. More...

Functions
rcl_service_t	rcl_get_zero_initialized_service (void)
	Return a rcl_service_t struct with members set to `NULL`. More...

rcl_ret_t	rcl_service_init (rcl_service_t service, const rcl_node_t node, const rosidl_service_type_support_t type_support, const char service_name, const rcl_service_options_t *options)
	Initialize a rcl service. More...

rcl_ret_t	rcl_service_fini (rcl_service_t service, rcl_node_t node)
	Finalize a rcl_service_t. More...

rcl_service_options_t	rcl_service_get_default_options (void)
	Return the default service options in a rcl_service_options_t. More...

rcl_ret_t	rcl_take_request (const rcl_service_t service, rmw_request_id_t request_header, void *ros_request)
	Take a pending ROS request using a rcl service. More...

rcl_ret_t	rcl_send_response (const rcl_service_t service, rmw_request_id_t response_header, void *ros_response)
	Send a ROS response to a client using a service. More...

const char *	rcl_service_get_service_name (const rcl_service_t *service)
	Get the topic name for the service. More...

const rcl_service_options_t *	rcl_service_get_options (const rcl_service_t *service)
	Return the rcl service options. More...

rmw_service_t *	rcl_service_get_rmw_handle (const rcl_service_t *service)
	Return the rmw service handle. More...

Typedef Documentation

◆ rcl_service_t

typedef struct rcl_service_t rcl_service_t

Structure which encapsulates a ROS Service.

◆ rcl_service_options_t

typedef struct rcl_service_options_t rcl_service_options_t

Options available for a rcl service.

Function Documentation

◆ rcl_get_zero_initialized_service()

rcl_service_t rcl_get_zero_initialized_service ( void )

Return a rcl_service_t struct with members set to NULL.

Should be called to get a null rcl_service_t before passing to rcl_service_init().

◆ rcl_service_init()

rcl_ret_t rcl_service_init	(	rcl_service_t *	service,
		const rcl_node_t *	node,
		const rosidl_service_type_support_t *	type_support,
		const char *	service_name,
		const rcl_service_options_t *	options
	)

Initialize a rcl service.

After calling this function on a rcl_service_t, it can be used to take requests of the given type to the given topic using rcl_take_request(). It can also send a response to a request using rcl_send_response().

The given rcl_node_t must be valid and the resulting rcl_service_t is only valid as long as the given rcl_node_t remains valid.

The rosidl_service_type_support_t is obtained on a per .srv type basis. When the user defines a ROS service, code is generated which provides the required rosidl_service_type_support_t object. This object can be obtained using a language appropriate mechanism.

Todo:: TODO(wjwwood) write these instructions once and link to it instead For C a macro can be used (for example example_interfaces/AddTwoInts):

#include <rosidl_generator_c/service_type_support.h>
#include <example_interfaces/srv/add_two_ints.h>
const rosidl_service_type_support_t * ts =
  ROSIDL_GET_SRV_TYPE_SUPPORT(example_interfaces, AddTwoInts);

For C++ a template function is used:

#include <rosidl_generator_cpp/service_type_support.hpp>
#include <example_interfaces/srv/add_two_ints.h>
using rosidl_typesupport_cpp::get_service_type_support_handle;
const rosidl_service_type_support_t * ts =
  get_service_type_support_handle<example_interfaces::srv::AddTwoInts>();

The rosidl_service_type_support_t object contains service type specific information used to send or take requests and responses.

The topic name must be a c string which follows the topic and service name format rules for unexpanded names, also known as non-fully qualified names:

See also: rcl_expand_topic_name

The options struct allows the user to set the quality of service settings as well as a custom allocator which is used when initializing/finalizing the client to allocate space for incidentals, e.g. the service name string.

Expected usage (for C services):

#include <rcl/rcl.h>
#include <rosidl_generator_c/service_type_support.h>
#include <example_interfaces/srv/add_two_ints.h>
rcl_node_t node = rcl_get_zero_initialized_node();
rcl_node_options_t node_ops = rcl_node_get_default_options();
rcl_ret_t ret = rcl_node_init(&node, "node_name", "/my_namespace", &node_ops);
// ... error handling
const rosidl_service_type_support_t * ts =
  ROSIDL_GET_SRV_TYPE_SUPPORT(example_interfaces, AddTwoInts);
rcl_service_t service = rcl_get_zero_initialized_service();
rcl_service_options_t service_ops = rcl_service_get_default_options();
ret = rcl_service_init(&service, &node, ts, "add_two_ints", &service_ops);
// ... error handling, and on shutdown do finalization:
ret = rcl_service_fini(&service, &node);
// ... error handling for rcl_service_fini()
ret = rcl_node_fini(&node);
// ... error handling for rcl_node_fini()

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

Parameters

[out]	service	preallocated service structure
[in]	node	valid rcl node handle
[in]	type_support	type support object for the service's type
[in]	service_name	the name of the service
[in]	options	service options, including quality of service settings

Returns: RCL_RET_OK if service was initialized successfully, or; RCL_RET_INVALID_ARGUMENT if any arguments are invalid, or; RCL_RET_BAD_ALLOC if allocating memory failed, or; RCL_RET_SERVICE_NAME_INVALID if the given service name is invalid, or; RCL_RET_ERROR if an unspecified error occurs.

◆ rcl_service_fini()

rcl_ret_t rcl_service_fini	(	rcl_service_t *	service,
		rcl_node_t *	node
	)

Finalize a rcl_service_t.

After calling, the node will no longer listen for requests for this service. (assuming this is the only service of this type in this node).

After calling, calls to rcl_wait(), rcl_take_request(), and rcl_send_response() will fail when using this service. Additionally rcl_wait() will be interrupted if currently blocking. However, the given node handle is still valid.

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

Parameters

[in,out]	service	handle to the service to be deinitialized
[in]	node	handle to the node used to create the service

Returns: RCL_RET_OK if service was deinitialized successfully, or; RCL_RET_INVALID_ARGUMENT if any arguments are invalid, or; RCL_RET_ERROR if an unspecified error occurs.

◆ rcl_service_get_default_options()

rcl_service_options_t rcl_service_get_default_options ( void )

Return the default service options in a rcl_service_options_t.

The defaults are:

qos = rmw_qos_profile_services_default
allocator = rcl_get_default_allocator()

◆ rcl_take_request()

rcl_ret_t rcl_take_request	(	const rcl_service_t *	service,
		rmw_request_id_t *	request_header,
		void *	ros_request
	)

Take a pending ROS request using a rcl service.

It is the job of the caller to ensure that the type of the ros_request argument and the type associate with the service, via the type support, match. Passing a different type to rcl_take produces undefined behavior and cannot be checked by this function and therefore no deliberate error will occur.

TODO(jacquelinekay) blocking of take? TODO(jacquelinekay) pre-, during-, and post-conditions for message ownership? TODO(jacquelinekay) is rcl_take_request thread-safe? TODO(jacquelinekay) Should there be an rcl_request_id_t?

The ros_request pointer should point to an already allocated ROS request message struct of the correct type, into which the taken ROS request will be copied if one is available. If taken is false after calling, then the ROS request will be unmodified.

If allocation is required when taking the request, e.g. if space needs to be allocated for a dynamically sized array in the target message, then the allocator given in the service options is used.

request_header is a pointer to pre-allocated a rmw struct containing meta-information about the request (e.g. the sequence number).

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

[1] only if required when filling the request, avoided for fixed sizes

Parameters

[in]	service	the handle to the service from which to take
[in,out]	request_header	ptr to the struct holding metadata about the request ID
[in,out]	ros_request	type-erased ptr to an allocated ROS request message

Returns: RCL_RET_OK if the request was taken, or; RCL_RET_INVALID_ARGUMENT if any arguments are invalid, or; RCL_RET_SERVICE_INVALID if the service is invalid, or; RCL_RET_BAD_ALLOC if allocating memory failed, or; RCL_RET_ERROR if an unspecified error occurs.

◆ rcl_send_response()

rcl_ret_t rcl_send_response	(	const rcl_service_t *	service,
		rmw_request_id_t *	response_header,
		void *	ros_response
	)

Send a ROS response to a client using a service.

It is the job of the caller to ensure that the type of the ros_response parameter and the type associate with the service (via the type support) match. Passing a different type to send_response produces undefined behavior and cannot be checked by this function and therefore no deliberate error will occur.

send_response() is an non-blocking call.

The ROS response message given by the ros_response void pointer is always owned by the calling code, but should remain constant during rcl_send_response().

e This function is thread safe so long as access to both the service and the ros_response is synchronized. That means that calling rcl_send_response() from multiple threads is allowed, but calling rcl_send_response() at the same time as non-thread safe service functions is not, e.g. calling rcl_send_response() and rcl_service_fini() concurrently is not allowed. Before calling rcl_send_response() the message can change and after calling rcl_send_response() the message can change, but it cannot be changed during the rcl_send_response() call. The same ros_response, however, can be passed to multiple calls of rcl_send_response() simultaneously, even if the services differ. The ros_response is unmodified by rcl_send_response().

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

[1] for unique pairs of services and responses, see above for more

Parameters

[in]	service	handle to the service which will make the response
[in,out]	response_header	ptr to the struct holding metadata about the request ID
[in]	ros_response	type-erased pointer to the ROS response message

Returns: RCL_RET_OK if the response was sent successfully, or; RCL_RET_INVALID_ARGUMENT if any arguments are invalid, or; RCL_RET_SERVICE_INVALID if the service is invalid, or; RCL_RET_ERROR if an unspecified error occurs.

◆ rcl_service_get_service_name()

const char* rcl_service_get_service_name ( const rcl_service_t * service )

Get the topic name for the service.

This function returns the service's internal topic name string. This function can fail, and therefore return NULL, if the:

service is NULL
service is invalid (never called init, called fini, or invalid)

The returned string is only valid as long as the service is valid. The value of the string may change if the topic name changes, and therefore copying the string is recommended if this is a concern.

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

Parameters

[in] service the pointer to the service

Returns: name string if successful, otherwise NULL

◆ rcl_service_get_options()

const rcl_service_options_t* rcl_service_get_options ( const rcl_service_t * service )

Return the rcl service options.

This function returns the service's internal options struct. This function can fail, and therefore return NULL, if the:

service is NULL
service is invalid (never called init, called fini, or invalid)

The returned struct is only valid as long as the service is valid. The values in the struct may change if the service's options change, and therefore copying the struct is recommended if this is a concern.

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

Parameters

[in] service pointer to the service

Returns: options struct if successful, otherwise NULL

◆ rcl_service_get_rmw_handle()

rmw_service_t* rcl_service_get_rmw_handle ( const rcl_service_t * service )

Return the rmw service handle.

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

service is NULL
service is invalid (never called init, called fini, or invalid)

The returned handle is made invalid if the service is finalized or if rcl_shutdown() is called. The returned handle is not guaranteed to be valid for the life time of the service as it may be finalized and recreated itself. Therefore it is recommended to get the handle from the service using this function each time it is needed and avoid use of the handle concurrently with functions that might change it.

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

Parameters

[in] service pointer to the rcl service

Returns: rmw service handle if successful, otherwise NULL

Classes

Typedefs

Functions

Typedef Documentation

◆ rcl_service_t

◆ rcl_service_options_t

Function Documentation

◆ rcl_get_zero_initialized_service()

◆ rcl_service_init()

◆ rcl_service_fini()

◆ rcl_service_get_default_options()

◆ rcl_take_request()

◆ rcl_send_response()

◆ rcl_service_get_service_name()

◆ rcl_service_get_options()

◆ rcl_service_get_rmw_handle()