genmsp: created a ROS message to MSP serializer generator.
ROS messages are a simple text based format that can be converted to various native formats using text based templates. This patch adds the generator itself. Signed-off-by: Michael Hope <mlhx@google.com>
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support/genmsp/README.md
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support/genmsp/README.md
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genmsp
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======
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Converts ROS messages into the Cleanflight native encoders and
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decoders.
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See:
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* msg/ for the messages.
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* http://wiki.ros.org/msg for the message format.
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genmsp depends on the [genmsg](https://github.com/ros/genmsg).
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See http://www.ros.org/install/ for pre-built Ubuntu packages
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including `ros-jade-genmsg` which installs under
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`/opt/ros/jade/lib/python2.7/dist-packages`.
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Implementation
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--------------
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The conversion is designed to be backwards compatible and to minimise
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the size of the flight software. To do this, it has certain features
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and limitations:
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* Fixed length arrays show as `const Foo *field`.
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* Variable length arrays show as `const Foo *field` and `int nfield`
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pair.
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* Values are passed as arguments. As such, messages can't be nested
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past one level deep.
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* To reduce copying or duplication, inner messages can be aliased to
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the existing native form using `string clearflight_type=fooBar_t'.
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-- Michael Hope <mlhx@google.com> <michaelh@juju.net.nz>
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support/genmsp/genmsp.py
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support/genmsp/genmsp.py
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"""Convert ROS format messages to Clearflight format encoders."""
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import collections
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import re
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import sys
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import genmsg.msgs
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import genmsg.template_tools
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Env = collections.namedtuple('Env', 'spec msg_context search_path')
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# Details on the native version of a ROS type.
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Type = collections.namedtuple('Type', 'name size encoder')
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# All base types.
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MSG_TYPES = {
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'char': Type('char', 1, '8'),
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'bool': Type('bool', 1, '8'),
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'uint8': Type('uint8_t', 1, '8'),
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'int8': Type('int8_t', 1, '8'),
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'uint16': Type('uint16_t', 2, '16'),
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'int16': Type('int16_t', 2, '16'),
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'uint32': Type('uint32_t', 4, '32'),
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'int32': Type('int32_t', 4, '32'),
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'uint64': Type('uint64_t', 8, '64'),
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'int64': Type('int64_t', 8, '64'),
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'float32': Type('float', 4, 'Float'),
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'float64': Type('double', 8, 'Double'),
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'string': Type('const char *', None, 'String'),
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'time': Type('ros::Time', 4, '32'),
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'duration': Type('ros::Duration', 4, '32'),
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}
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def make_env(spec, msg_context, search_path):
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"""Wrap commonly used arguments up into an environment."""
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return Env(spec, msg_context, search_path)
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def load_spec(typename, spec, env):
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"""Find and load the spec of the given message type."""
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t = genmsg.msgs.resolve_type(typename, spec.package)
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assert isinstance(env.search_path, dict)
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return genmsg.msg_loader.load_msg_by_type(
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env.msg_context, t, env.search_path)
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def get_type(typename):
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"""Gets the type of a basic type.
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Returns None for other types.
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"""
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base_type, _, _ = genmsg.msgs.parse_type(typename)
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return MSG_TYPES.get(base_type, None)
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def to_caps(name):
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"""Convers a CamelCase string to CAPS_CASE."""
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return re.sub(r'([a-z])([A-Z])', r'\1_\2', name).upper()
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def _multiply(left, right):
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"""Returns a pretty string version of multiplying the arguments."""
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if left == 1:
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return right
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else:
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return '{}*{}'.format(left, right)
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def _lcfirst(name):
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"""Converts the first letter of the string to lower case."""
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return name[0].lower() + name[1:]
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def get_length(field, spec, env):
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"""Returns the byte length of a field as a string."""
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ctype = get_type(field.type)
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if ctype is not None:
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# A base type.
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if field.base_type == 'string':
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if get_count(field) != 1:
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raise RuntimeError(
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('{}: support for arrays of strings is not '
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'implemented'.format(field.name)))
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return 'strlen({})'.format(field.name)
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else:
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return _multiply(get_count(field), ctype.size)
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else:
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# Load the message and return the size of it.
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child = load_spec(field.base_type, spec, env)
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sizes = (str(get_length(x, child, env)) for x in child.parsed_fields())
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joined = '({})'.format(' + '.join(sizes))
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return _multiply(get_count(field), joined)
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def get_count(field):
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"""Returns the number of items in a field."""
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if not field.is_array:
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return 1
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if field.array_len is not None:
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return field.array_len
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# Return the name of the parameter that holds the length.
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return 'n{}'.format(field.name)
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def _msg_type_to_cpp(name, spec, env):
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base_type, is_array, _ = genmsg.msgs.parse_type(name)
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ctype = get_type(base_type)
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if ctype:
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if is_array:
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return 'const {} *'.format(ctype.name)
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else:
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return ctype.name
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else:
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if '/' in base_type:
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# Use the short type.
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base_type = base_type.split('/')[-1]
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# Check if the message overrides the native type name.
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child = load_spec(base_type, spec, env)
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constants = {x.name: x.val for x in child.constants}
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ctype = constants.get('clearflight_type', base_type)
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if ctype == 'auto':
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# Remap messages named FooBar to fooBar_t
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ctype = _lcfirst(base_type) + '_t'
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return 'const {} *'.format(ctype)
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def generate_encoder_args(spec, env):
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"""Generates the function arguments for each field."""
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for field in spec.parsed_fields():
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ctype = get_type(field.base_type)
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cname = _msg_type_to_cpp(field.base_type, spec, env)
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if ctype is None:
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yield '{}{}'.format(cname, field.name)
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if field.is_array and field.array_len is None:
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yield 'int n{}'.format(field.name)
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else:
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if field.is_array:
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yield 'const {} *{}'.format(cname, field.name)
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if field.array_len is None:
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yield 'int n{}'.format(field.name)
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else:
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yield '{} {}'.format(cname, field.name)
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def main():
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msg_template_map = {'msg.h.template': '@NAME@.h'}
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genmsg.template_tools.generate_from_command_line_options(
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sys.argv, msg_template_map, None)
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if __name__ == '__main__':
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main()
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