topic_helpers.py

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# Copyright (c) 2011, Dorian Scholz, TU Darmstadt
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import roslib
import roslib.msgs
import roslib.message
from rostopic import get_topic_type
from python_qt_binding.QtCore import qDebug


def get_type_class(type_name):
    if roslib.msgs.is_valid_constant_type(type_name):
        if type_name == 'string':
            return str
        elif type_name == 'bool':
            return bool
        else:
            return type(roslib.msgs._convert_val(type_name, 0))
    else:
        return roslib.message.get_message_class(type_name)


def get_field_type(topic_name):
    """
    Get the Python type of a specific field in the given registered topic.
    If the field is an array, the type of the array's values are returned and the is_array flag is set to True.
    This is a static type check, so it works for unpublished topics and with empty arrays.

    :param topic_name: name of field of a registered topic, ``str``, i.e. '/rosout/file'
    :returns: field_type, is_array
    """
    # get topic_type and message_evaluator
    topic_type, real_topic_name, _ = get_topic_type(topic_name)
    if topic_type is None:
        #qDebug('topic_helpers.get_field_type(%s): get_topic_type failed' % (topic_name))
        return None, False

    message_class = roslib.message.get_message_class(topic_type)
    if message_class is None:
        qDebug('topic_helpers.get_field_type(%s): get_message_class(%s) failed' % (topic_name, topic_type))
        return None, False

    slot_path = topic_name[len(real_topic_name):]
    return get_slot_type(message_class, slot_path)


def get_slot_type(message_class, slot_path):
    """
    Get the Python type of a specific slot in the given message class.
    If the field is an array, the type of the array's values are returned and the is_array flag is set to True.
    This is a static type check, so it works for unpublished topics and with empty arrays.

    :param message_class: message class type, ``type``, usually inherits from genpy.message.Message
    :param slot_path: path to the slot inside the message class, ``str``, i.e. 'header/seq'
    :returns: field_type, is_array
    """
    is_array = False
    fields = [f for f in slot_path.split('/') if f]
    for field_name in fields:
        try:
            field_name, _, field_index = roslib.msgs.parse_type(field_name)
        except roslib.msgs.MsgSpecException:
            return None, False
        if field_name not in getattr(message_class, '__slots__', []):
            #qDebug('topic_helpers.get_slot_type(%s, %s): field not found: %s' % (message_class, slot_path, field_name))
            return None, False
        slot_type = message_class._slot_types[message_class.__slots__.index(field_name)]
        slot_type, slot_is_array, _ = roslib.msgs.parse_type(slot_type)
        is_array = slot_is_array and field_index is None

        message_class = get_type_class(slot_type)
    return message_class, is_array


def is_slot_numeric(topic_name):
    """
    Check is a slot in the given topic is numeric, or an array of numeric values.
    This is a static type check, so it works for unpublished topics and with empty arrays.

    :param topic_name: name of field of a registered topic, ``str``, i.e. '/rosout/file'
    :returns: is_numeric, is_array, description
    """
    field_type, is_array = get_field_type(topic_name)
    if field_type in (int, float):
        if is_array:
            message = 'topic "%s" is numeric array: %s[]' % (topic_name, field_type)
        else:
            message = 'topic "%s" is numeric: %s' % (topic_name, field_type)
        return True, is_array, message

    return False, is_array, 'topic "%s" is NOT numeric: %s' % (topic_name, field_type)


def find_slots_by_type_dfs(msg_class, slot_type):
    """
    Search inside msg_class for all slots of type slot_type and return their paths.
    Uses a depth first search.

    :param msg_class: The class to search in.
    :param slot_type: The type name or class to search for (e.g. 'float64' or Quaternion).
    :return: List of paths to slots of type slot_type inside msg_class (e.g. ['header/frame_id']).
    """

    def _find_slots(msg_class, slot_type):
        paths = []
        if msg_class == slot_type:
            paths.append([])
            return paths

        for slot_name, slot_type_name in zip(msg_class.__slots__, msg_class._slot_types):
            slot_type_name, is_array, _ = roslib.msgs.parse_type(slot_type_name)
            if is_array:
                slot_name += '[]'
            if roslib.msgs.is_valid_constant_type(slot_type_name):
                if slot_type_name == slot_type:
                    paths.append([slot_name])
                continue

            slot_class = roslib.message.get_message_class(slot_type_name)
            if slot_class is not None:
                inner_paths = _find_slots(slot_class, slot_type)
                paths.extend([[slot_name] + path for path in inner_paths])

        return paths

    return ['/'.join(path) for path in _find_slots(msg_class, slot_type)]


def find_slots_by_type_bfs(msg_class, slot_type):
    """
    Search inside msg_class for all slots of type slot_type and return their paths.
    Uses a breadth first search, so it will find the most shallow matches first.

    :param msg_class: The class to search in.
    :param slot_type: The type name or class to search for (e.g. 'float64' or Quaternion).
    :return: List of paths to slots of type slot_type inside msg_class (e.g. ['header/frame_id']).
    """
    paths = []
    queue = [(msg_class, [])]
    while queue:
        msg_class, path = queue.pop(0)
        if msg_class == slot_type:
            paths.append(path)
            continue

        for slot_name, slot_type_name in zip(msg_class.__slots__, msg_class._slot_types):
            slot_type_name, is_array, _ = roslib.msgs.parse_type(slot_type_name)
            if is_array:
                slot_name += '[]'
            if roslib.msgs.is_valid_constant_type(slot_type_name):
                if slot_type_name == slot_type:
                    paths.append(path + [slot_name])
                continue

            slot_class = roslib.message.get_message_class(slot_type_name)
            if slot_class is not None:
                queue.append((slot_class, path + [slot_name]))

    return ['/'.join(path) for path in paths]