call_service.py

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from functools import partial
from rosbridge_library.capability import Capability
from rosbridge_library.internal.services import ServiceCaller


class CallService(Capability):

    call_service_msg_fields = [(True, "service", (str, unicode)),
           (False, "fragment_size", (int, type(None))), (False, "compression", (str, unicode))]

    def __init__(self, protocol):
        # Call superclas constructor
        Capability.__init__(self, protocol)

        # Register the operations that this capability provides
        protocol.register_operation("call_service", self.call_service)

    def call_service(self, message):
        # Pull out the ID
        cid = message.get("id", None)
        
        # Typecheck the args
        self.basic_type_check(message, self.call_service_msg_fields)

        # Extract the args
        service = message["service"]
        fragment_size = message.get("fragment_size", None)
        compression = message.get("compression", "none")
        args = message.get("args", [])
        
        # Check for deprecated service ID, eg. /rosbridge/topics#33
        cid = extract_id(service, cid)

        # Create the callbacks
        s_cb = partial(self._success, cid, service, fragment_size, compression)
        e_cb = partial(self._failure, cid, service)

        # Kick off the service caller thread
        ServiceCaller(trim_servicename(service), args, s_cb, e_cb).start()

    def _success(self, cid, service, fragment_size, compression, message):
        outgoing_message = {
            "op": "service_response",
            "service": service,
            "values": message,
            "result": True
        }
        if cid is not None:
            outgoing_message["id"] = cid
        # TODO: fragmentation, compression
        self.protocol.send(outgoing_message)

    def _failure(self, cid, service, exc):
        self.protocol.log("error", "call_service %s: %s" %
            (type(exc).__name__, str(exc)), cid)
        # send response with result: false
        outgoing_message = {
            "op": "service_response",
            "service": service,
            "values": str(exc),
            "result": False
        }
        if cid is not None:
            outgoing_message["id"] = cid
        self.protocol.send(outgoing_message)


def trim_servicename(service):
    if '#' in service:
        return service[:service.find('#')]
    return service


def extract_id(service, cid):
    if cid is not None:
        return cid
    elif '#' in service:
        return service[service.find('#') + 1:]