message_converter.py

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#!/usr/bin/env python
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# Copyright (c) 2013, Willow Garage, Inc.
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from __future__ import absolute_import
 
import roslib.message
import rospy
import base64
import sys
import copy
import collections
 
from .custom_mappings import map_api2ros, map_ros2api
 
python3 = (sys.hexversion > 0x03000000)
 
python_list_types = [list, tuple]
 
if python3:
    python_string_types = [str, bytes]
    python_int_types = [int]
else:
    python_string_types = [str, unicode]
    python_int_types = [int, long]
 
python_float_types = [float]
 
ros_to_python_type_map = {
    'bool'    : [bool],
    'float32' : copy.deepcopy(python_float_types + python_int_types),
    'float64' : copy.deepcopy(python_float_types + python_int_types),
    'int8'    : copy.deepcopy(python_int_types),
    'int16'   : copy.deepcopy(python_int_types),
    'int32'   : copy.deepcopy(python_int_types),
    'int64'   : copy.deepcopy(python_int_types),
    'uint8'   : copy.deepcopy(python_int_types),
    'uint16'  : copy.deepcopy(python_int_types),
    'uint32'  : copy.deepcopy(python_int_types),
    'uint64'  : copy.deepcopy(python_int_types),
    'byte'    : copy.deepcopy(python_int_types),
    'char'    : copy.deepcopy(python_int_types),
    'string'  : copy.deepcopy(python_string_types)
}
 
try:
    import numpy as np
    _ros_to_numpy_type_map = {
        'float32' : [np.float32, np.int8, np.int16, np.uint8, np.uint16],
        # don't include int32, because conversion to float may change value: v = np.iinfo(np.int32).max; np.float32(v) != v
        'float64' : [np.float32, np.float64, np.int8, np.int16, np.int32, np.uint8, np.uint16, np.uint32],
        'int8'    : [np.int8],
        'int16'   : [np.int8, np.int16, np.uint8],
        'int32'   : [np.int8, np.int16, np.int32, np.uint8, np.uint16],
        'int64'   : [np.int8, np.int16, np.int32, np.int64, np.uint8, np.uint16, np.uint32],
        'uint8'   : [np.uint8],
        'uint16'  : [np.uint8, np.uint16],
        'uint32'  : [np.uint8, np.uint16, np.uint32],
        'uint64'  : [np.uint8, np.uint16, np.uint32, np.uint64],
        'byte'    : [np.int8],
        'char'    : [np.uint8],
    }
 
    # merge type_maps
    merged = collections.defaultdict(list, ros_to_python_type_map)
    for k, v in _ros_to_numpy_type_map.items():
        merged[k].extend(v)
    ros_to_python_type_map = dict(merged)
except ImportError:
    pass
 
 
ros_time_types = ['time', 'duration']
ros_primitive_types = ['bool', 'byte', 'char', 'int8', 'uint8', 'int16',
                       'uint16', 'int32', 'uint32', 'int64', 'uint64',
                       'float32', 'float64', 'string']
ros_header_types = ['Header', 'std_msgs/Header', 'roslib/Header']
 
def convert_dictionary_to_ros_message(message_type, dictionary, kind='message', strict_mode=True,
                                      check_missing_fields=False, check_types=True):
    """
    Takes in the message type and a Python dictionary and returns a ROS message.
 
    Example:
        >>> msg_type = "std_msgs/String"
        >>> dict_msg = { "data": "Hello, Robot" }
        >>> convert_dictionary_to_ros_message(msg_type, dict_msg)
        data: "Hello, Robot"
 
        >>> msg_type = "std_srvs/SetBool"
        >>> dict_msg = { "data": True }
        >>> kind = "request"
        >>> convert_dictionary_to_ros_message(msg_type, dict_msg, kind)
        data: True
    """
    if hasattr(message_type, '_type'):
        message = message_type
        message_type = message._type
    elif type(message_type) in python_string_types:
        if kind == 'message':
            message_class = roslib.message.get_message_class(message_type)
            message = message_class()
        elif kind == 'request':
            service_class = roslib.message.get_service_class(message_type)
            message = service_class._request_class()
        elif kind == 'response':
            service_class = roslib.message.get_service_class(message_type)
            message = service_class._response_class()
        else:
            raise ValueError('Unknown kind "%s".' % kind)
    else:
        raise ValueError('message_type is neither a ROS message instance nor type string')
 
    # do our custom mappings if required
    mapped_dict = map_api2ros(dictionary, message_type)
 
    message_fields = dict(_get_message_fields(message))
    remaining_message_fields = copy.deepcopy(message_fields)
 
    for field_name, field_value in mapped_dict.items():
        if field_name in message_fields:
            field_type = message_fields[field_name]
            field_value = _convert_to_ros_type(field_name, field_type, field_value, strict_mode, check_missing_fields,
                                               check_types)
            setattr(message, field_name, field_value)
            del remaining_message_fields[field_name]
        else:
            error_message = 'ROS message type "{0}" has no field named "{1}"'\
                .format(message_type, field_name)
            if strict_mode:
                raise ValueError(error_message)
            else:
                rospy.logerr('{}! It will be ignored.'.format(error_message))
 
    if check_missing_fields and remaining_message_fields:
        error_message = 'Missing fields "{0}"'.format(remaining_message_fields)
        raise ValueError(error_message)
 
    return message
 
def _convert_to_ros_type(field_name, field_type, field_value, strict_mode=True, check_missing_fields=False,
                         check_types=True):
    if _is_ros_binary_type(field_type):
        field_value = _convert_to_ros_binary(field_type, field_value)
    elif field_type in ros_time_types:
        field_value = _convert_to_ros_time(field_type, field_value)
    elif field_type in ros_primitive_types:
        # Note: one could also use genpy.message.check_type() here, but:
        # 1. check_type is "not designed to run fast and is meant only for error diagnosis"
        # 2. it doesn't check floats (see ros/genpy#130)
        # 3. it rejects numpy types, although they can be serialized
        if check_types and type(field_value) not in ros_to_python_type_map[field_type]:
            raise TypeError("Field '{0}' has wrong type {1} (valid types: {2})".format(field_name, type(field_value), ros_to_python_type_map[field_type]))
        field_value = _convert_to_ros_primitive(field_type, field_value)
    elif _is_field_type_a_primitive_array(field_type):
        field_value = field_value
    elif _is_field_type_an_array(field_type):
        field_value = _convert_to_ros_array(field_name, field_type, field_value, strict_mode, check_missing_fields,
                                            check_types)
    else:
        field_value = convert_dictionary_to_ros_message(field_type, field_value, strict_mode=strict_mode,
                                                        check_missing_fields=check_missing_fields,
                                                        check_types=check_types)
    return field_value
 
def _convert_to_ros_binary(field_type, field_value):
    if type(field_value) in python_string_types:
        if python3:
            # base64 in python3 added the `validate` arg:
            # If field_value is not properly base64 encoded and there are non-base64-alphabet characters in the input,
            # a binascii.Error will be raised.
            binary_value_as_string = base64.b64decode(field_value, validate=True)
        else:
            # base64 in python2 doesn't have the `validate` arg: characters that are not in the base-64 alphabet are
            # silently discarded, resulting in garbage output.
            binary_value_as_string = base64.b64decode(field_value)
    else:
        binary_value_as_string = bytes(bytearray(field_value))
    return binary_value_as_string
 
def _convert_to_ros_time(field_type, field_value):
    time = None
 
    if field_type == 'time' and field_value == 'now':
        time = rospy.get_rostime()
    else:
        if field_type == 'time':
            time = rospy.rostime.Time()
        elif field_type == 'duration':
            time = rospy.rostime.Duration()
        if 'sec' in field_value:
            setattr(time, 'secs', field_value['sec'])
        if 'nsec' in field_value:
            setattr(time, 'nsecs', field_value['nsec'])
 
    return time
 
def _convert_to_ros_primitive(field_type, field_value):
    # std_msgs/msg/_String.py always calls encode() on python3, so don't do it here
    if field_type == "string" and not python3:
        field_value = field_value.encode('utf-8')
    return field_value
 
def _convert_to_ros_array(field_name, field_type, list_value, strict_mode=True, check_missing_fields=False,
                          check_types=True):
    # use index to raise ValueError if '[' not present
    list_type = field_type[:field_type.index('[')]
    return [_convert_to_ros_type(field_name, list_type, value, strict_mode, check_missing_fields, check_types) for value
            in list_value]
 
def convert_ros_message_to_dictionary(message, binary_array_as_bytes=True):
    """
    Takes in a ROS message and returns a Python dictionary.
 
    Example:
        >>> import std_msgs.msg
        >>> ros_message = std_msgs.msg.UInt32(data=42)
        >>> convert_ros_message_to_dictionary(ros_message)
        {'data': 42}
    """
    dictionary = {}
    message_fields = _get_message_fields(message)
    for field_name, field_type in message_fields:
        field_value = getattr(message, field_name)
        dictionary[field_name] = _convert_from_ros_type(field_type, field_value, binary_array_as_bytes)
 
    # do our custom mappings if required
    mapped_dict = map_ros2api(dictionary, message._type)
    return mapped_dict
 
 
def _convert_from_ros_type(field_type, field_value, binary_array_as_bytes=True):
    if field_type in ros_primitive_types:
        field_value = _convert_from_ros_primitive(field_type, field_value)
    elif field_type in ros_time_types:
        field_value = _convert_from_ros_time(field_type, field_value)
    elif _is_ros_binary_type(field_type):
        if binary_array_as_bytes:
            field_value = _convert_from_ros_binary(field_type, field_value)
        elif isinstance(field_value, str):
            field_value = [ord(v) for v in field_value]
        else:
            field_value = list(field_value)
    elif _is_field_type_a_primitive_array(field_type):
        field_value = list(field_value)
    elif _is_field_type_an_array(field_type):
        field_value = _convert_from_ros_array(field_type, field_value, binary_array_as_bytes)
    else:
        field_value = convert_ros_message_to_dictionary(field_value, binary_array_as_bytes)
 
    return field_value
 
def _is_ros_binary_type(field_type):
    """ Checks if the field is a binary array one, fixed size or not
 
    >>> _is_ros_binary_type("uint8")
    False
    >>> _is_ros_binary_type("uint8[]")
    True
    >>> _is_ros_binary_type("uint8[3]")
    True
    >>> _is_ros_binary_type("char")
    False
    >>> _is_ros_binary_type("char[]")
    True
    >>> _is_ros_binary_type("char[3]")
    True
    """
    return field_type.startswith('uint8[') or field_type.startswith('char[')
 
def _convert_from_ros_binary(field_type, field_value):
    field_value = base64.b64encode(field_value).decode('utf-8')
    return field_value
 
def _convert_from_ros_time(field_type, field_value):
    field_value = {
        'sec'  : field_value.secs,
        'nsec' : field_value.nsecs
    }
    return field_value
 
def _convert_from_ros_primitive(field_type, field_value):
    # std_msgs/msg/_String.py always calls decode() on python3, so don't do it here
    if field_type == "string" and not python3:
        field_value = field_value.decode('utf-8')
    return field_value
 
def _convert_from_ros_array(field_type, field_value, binary_array_as_bytes=True):
    # use index to raise ValueError if '[' not present
    list_type = field_type[:field_type.index('[')]
    return [_convert_from_ros_type(list_type, value, binary_array_as_bytes) for value in field_value]
 
def _get_message_fields(message):
    return zip(message.__slots__, message._slot_types)
 
def _is_field_type_an_array(field_type):
    return field_type.find('[') >= 0
 
def _is_field_type_a_primitive_array(field_type):
    bracket_index = field_type.find('[')
    if bracket_index < 0:
        return False
    else:
        list_type = field_type[:bracket_index]
        return list_type in ros_primitive_types