python-roslib 1.13.4-2 / usr / lib / python2.7 / dist-packages / roslib / message.py

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"""
Support library for Python autogenerated message files. This defines
the Message base class used by genmsg_py as well as support
libraries for type checking and retrieving message classes by type
name.
"""

import os
import sys
import rospkg
import roslib

import genmsg
import genpy.message #for wrapping get_message_class, get_service_class

# forward a bunch of old symbols from genpy for backwards compat
from genpy import Message, DeserializationError, SerializationError, \
     Time, Duration, TVal
from genpy.message import get_printable_message_args, fill_message_args
from genpy.message import check_type, strify_message

def _get_message_or_service_class(type_str, message_type, reload_on_error=False):
    ## parse package and local type name for import
    package, base_type = genmsg.package_resource_name(message_type)
    if not package:
        if base_type == 'Header':
            package = 'std_msgs'
        else:
            raise ValueError("message type is missing package name: %s"%str(message_type))
    pypkg = val = None
    try: 
        # bootstrap our sys.path
        roslib.launcher.load_manifest(package)
        # import the package and return the class
        pypkg = __import__('%s.%s'%(package, type_str))
        val = getattr(getattr(pypkg, type_str), base_type)
    except rospkg.ResourceNotFound:
        val = None
    except ImportError:
        val = None
    except AttributeError:
        val = None

    # this logic is mainly to support rosh, so that a user doesn't
    # have to exit a shell just because a message wasn't built yet
    if val is None and reload_on_error:
        try:
            if pypkg:
                reload(pypkg)
            val = getattr(getattr(pypkg, type_str), base_type)
        except:
            val = None
    return val
        
## cache for get_message_class
_message_class_cache = {}

## cache for get_service_class
_service_class_cache = {}

def get_message_class(message_type, reload_on_error=False):
    if message_type in _message_class_cache:
        return _message_class_cache[message_type]
    # try w/o bootstrapping
    cls = genpy.message.get_message_class(message_type, reload_on_error=reload_on_error)
    if cls is None:
        # try old loader w/ bootstrapping
        cls = _get_message_or_service_class('msg', message_type, reload_on_error=reload_on_error)
    if cls:
        _message_class_cache[message_type] = cls
    return cls

def get_service_class(service_type, reload_on_error=False):
    if service_type in _service_class_cache:
        return _service_class_cache[service_type]
    cls = genpy.message.get_service_class(service_type, reload_on_error=reload_on_error)
    # try w/o bootstrapping
    if cls is None:
        # try old loader w/ bootstrapping
        cls = _get_message_or_service_class('srv', service_type, reload_on_error=reload_on_error)
    if cls:
        _service_class_cache[service_type] = cls
    return cls