implement SECoP proxy modules

A proxy module is a module with a known structure, but
accessed over a SECoP connection.
For the configuration, a Frappy module class has to be given.
The proxy class is created from this, but does not inherit from it.
However, the class of the returned object will be subclass of the
SECoP base classes (Readable, Drivable etc.).
A possible extension might be, that instead of the Frappy class,
the JSON module description can be given, as a separate file
or directly in the config file.
Or we might offer a tool to convert the JSON description to
a python class.

Change-Id: I9212d9f3fe82ec56dfc08611d0e1efc0b0112271
Reviewed-on: https://forge.frm2.tum.de/review/c/sine2020/secop/playground/+/22386
Tested-by: JenkinsCodeReview <bjoern_pedersen@frm2.tum.de>
Reviewed-by: Markus Zolliker <markus.zolliker@psi.ch>

cfg/ppms.cfg

@@ -8,8 +8,8 @@ bindport = 5000
 
 [module tt]
 class = secop_psi.ppms.Temp
-.description = main temperature
-.iodev = ppms
+description = main temperature
+iodev = ppms
 
 [module mf]
 class = secop_psi.ppms.Field

cfg/ppms_proxy_test.cfg

@@ -0,0 +1,22 @@
+[node filtered.PPMS.psi.ch]
+description = filtered PPMS at PSI
+
+[interface tcp]
+type = tcp
+bindto = 0.0.0.0
+bindport = 5002
+
+[module secnode]
+class = secop.SecNode
+description = a SEC node
+uri = tcp://localhost:5000
+
+[module mf]
+class = secop.Proxy
+remote_class = secop_psi.ppms.Field
+description = magnetic field
+iodev = secnode
+value.min = -0.1
+value.max = 0.1
+target.min = -8
+target.max = 8

secop/__init__.py

@@ -25,8 +25,10 @@
 
 # allow to import the most important classes from 'secop'
 from secop.datatypes import *
+from secop.lib.enum import Enum
 from secop.modules import Module, Readable, Writable, Drivable, Communicator, Attached
 from secop.params import Parameter, Command, Override
 from secop.metaclass import Done
 from secop.iohandler import IOHandler, IOHandlerBase
 from secop.stringio import StringIO, HasIodev
+from secop.proxy import SecNode, Proxy, proxy_class

secop/client/__init__.py

@@ -64,8 +64,8 @@ class Logger:
     error = warning = critical = info
 
 
-class CallbackMixin:
-    """abstract mixin
+class CallbackObject:
+    """abstract definition for a target object for callbacks
 
     this is mainly for documentation, but it might be extended
     and used as a mixin for objects registered as a callback
@@ -94,33 +94,115 @@ class CallbackMixin:
         """
 
 
-class SecopClient:
+class ProxyClient:
+    """common functionality for proxy clients"""
+
+    CALLBACK_NAMES = ('updateEvent', 'descriptiveDataChange', 'nodeStateChange', 'unhandledMessage')
+    online = False  # connected or reconnecting since a short time
+    validate_data = False
+    _state = 'disconnected'  # further possible values: 'connecting', 'reconnecting', 'connected'
+
+    def __init__(self):
+        self.callbacks = {cbname: defaultdict(list) for cbname in self.CALLBACK_NAMES}
+        # caches (module, parameter) = value, timestamp, readerror (internal names!)
+        self.cache = {}
+
+    def register(self, key, obj=None, **kwds):
+        """register callback functions
+
+        - kwds each key must be a valid callback name defined in self.CALLBACK_NAMES
+        - kwds values are the callback functions
+        - if obj is not None, use its methods named from the callback name, if not given in kwds
+        - key might be either:
+            1) None: general callback (all callbacks)
+            2) <module name>: callbacks related to a module (not called for 'unhandledMessage')
+            3) (<module name>, <parameter name>): callback for specified parameter (only called for 'updateEvent')
+        """
+        for cbname in self.CALLBACK_NAMES:
+            cbfunc = kwds.pop(cbname, None)
+            if obj and cbfunc is None:
+                cbfunc = getattr(obj, cbname, None)
+            if not cbfunc:
+                continue
+            cbdict = self.callbacks[cbname]
+            cbdict[key].append(cbfunc)
+
+            # immediately call for some callback types
+            if cbname == 'updateEvent':
+                if key is None:
+                    for (mname, pname), data in self.cache.items():
+                        cbfunc(mname, pname, *data)
+                else:
+                    data = self.cache.get(key, None)
+                    if data:
+                        cbfunc(*key, *data)  # case single parameter
+                    else:  # case key = module
+                        for (mname, pname), data in self.cache.items():
+                            if mname == key:
+                                cbfunc(mname, pname, *data)
+            elif cbname == 'nodeStateChange':
+                cbfunc(self.online, self._state)
+        if kwds:
+            raise TypeError('unknown callback: %s' % (', '.join(kwds)))
+
+    def callback(self, key, cbname, *args):
+        """perform callbacks
+
+        key=None:
+        key=<module name>: callbacks for specified module
+        key=(<module name>, <parameter name): callbacks for specified parameter
+        """
+        cblist = self.callbacks[cbname].get(key, [])
+        self.callbacks[cbname][key] = [cb for cb in cblist if cb(*args) is not UNREGISTER]
+        return bool(cblist)
+
+    def updateValue(self, module, param, value, timestamp, readerror):
+        if readerror:
+            assert isinstance(readerror, Exception)
+        if self.validate_data:
+            try:
+                # try to validate, reason: make enum_members from integers
+                datatype = self.modules[module]['parameters'][param]['datatype']
+                value = datatype(value)
+            except (KeyError, ValueError):
+                pass
+        self.cache[(module, param)] = (value, timestamp, readerror)
+        self.callback(None, 'updateEvent', module, param, value, timestamp, readerror)
+        self.callback(module, 'updateEvent', module, param, value, timestamp, readerror)
+        self.callback((module, param), 'updateEvent', module, param, value, timestamp, readerror)
+
+    def getParameter(self, module, parameter, trycache=False):
+        if trycache:
+            cached = self.cache.get((module, parameter), None)
+            if cached:
+                return cached
+        if self.online:
+            self.readParameter(module, parameter)
+        return self.cache[module, parameter]
+
+    def readParameter(self, module, parameter):
+        """forced read over connection"""
+        raise NotImplementedError()
+
+
+class SecopClient(ProxyClient):
     """a general SECoP client"""
     reconnect_timeout = 10
     shutdown = False
     _rxthread = None
     _txthread = None
-    _state = 'disconnected'  # further possible values: 'connecting', 'reconnecting', 'connected'
-    online = False  # connected or reconnecting since a short time
     disconnect_time = 0  # time of last disconnect
     secop_version = ''
-    _rxbuffer = b''
     descriptive_data = {}
-    CALLBACK_NAMES = 'updateEvent', 'nodeStateChange', 'unhandledMessage', 'descriptiveDataChange', 'handleMessage'
-    callbacks = {}
     modules = {}
     _last_error = None
-    validate_data = False
 
     def __init__(self, uri, log=Logger):
-        """like __init__, but called from SecopClient.__new__"""
+        super().__init__()
         # maps expected replies to [request, Event, is_error, result] until a response came
         # there can only be one entry per thread calling 'request'
         self.active_requests = {}
-        # caches (module, parameter) = value, timestamp, readerror (internal names!)
-        self.cache = {}
         self.io = None
-        self.callbacks = {cbname: defaultdict(list) for cbname in self.CALLBACK_NAMES}
         self.txq = queue.Queue(30)   # queue for tx requests
         self.pending = queue.Queue(30)  # requests with colliding action + ident
         self.log = log
@@ -223,14 +305,14 @@ class SecopClient:
                 if module_param is not None:
                     if action.startswith(ERRORPREFIX):
                         timestamp = data[2].get('t', None)
-                        readerror = tuple(data[0:2])
+                        readerror = secop.errors.make_secop_error(*data[0:2])
                         value = None
                     else:
                         timestamp = data[1].get('t', None)
                         value = data[0]
                         readerror = None
                     module, param = module_param
-                    self._update_value(module, param, value, timestamp, readerror)
+                    self.updateValue(module, param, value, timestamp, readerror)
                     if action in (EVENTREPLY, ERRORPREFIX + EVENTREPLY):
                         continue
             try:
@@ -359,84 +441,25 @@ class SecopClient:
             self.modules[modname] = dict(accessibles=accessibles, parameters=parameters,
                                          commands=commands, properties=properties)
         if changed_modules is not None:
-            done = self.node_callback('descriptiveDataChange', None, self)
+            done = self.callback(None, 'descriptiveDataChange', None, self)
             for mname in changed_modules:
-                if not self.module_callback('descriptiveDataChange', mname, mname, self):
+                if not self.callback(mname, 'descriptiveDataChange', mname, self):
                     self.log.warning('descriptive data changed on module %r', mname)
                     done = True
             if not done:
                 self.log.warning('descriptive data of %r changed', self.nodename)
 
-    def register(self, obj=None, module=None, **kwds):
-        """register callback functions
-
-        - kwds keys must be valid callback name defined in self.CALLBACK_NAMES
-        - kwds names are the callback functions
-        - if obj is not None, use its methods named from the callback name, if not given in kwds
-        - module may be a module name. if not None and not omitted, the registered callback will
-          be called only when it is related to the given module
-        """
-        for cbname in self.CALLBACK_NAMES:
-            cbfunc = kwds.pop(cbname, None)
-            if obj and cbfunc is None:
-                cbfunc = getattr(obj, cbname, None)
-            if not cbfunc:
-                continue
-            cbdict = self.callbacks[cbname]
-            cbdict[module].append(cbfunc)
-            if cbname == 'updateEvent':
-                if module is None:
-                    for (mname, pname), data in self.cache.items():
-                        cbfunc(mname, pname, *data)
-                else:
-                    for (mname, pname), data in self.cache.items():
-                        if mname == module:
-                            cbfunc(mname, pname, *data)
-            elif cbname == 'nodeStateChange':
-                cbfunc(self.online, self._state)
-        if kwds:
-            raise TypeError('unknown callback: %s' % (', '.join(kwds)))
-
-    def node_callback(self, cbname, *args):
-        cblist = self.callbacks[cbname].get(None, [])
-        self.callbacks[cbname][None] = [cb for cb in cblist if cb(*args) is not UNREGISTER]
-        return bool(cblist)
-
-    def module_callback(self, cbname, mname, *args):
-        cblist = self.callbacks[cbname].get(mname, [])
-        self.callbacks[cbname][mname] = [cb for cb in cblist if cb(*args) is not UNREGISTER]
-        return bool(cblist)
-
-    def _update_value(self, module, param, value, timestamp, readerror):
-        if readerror:
-            assert isinstance(readerror, tuple)
-        if self.validate_data:
-            try:
-                # try to validate, reason: make enum_members from integers
-                datatype = self.modules[module]['parameters'][param]['datatype']
-                value = datatype(value)
-            except (KeyError, ValueError):
-                pass
-        self.cache[(module, param)] = (value, timestamp, readerror)
-        self.node_callback('updateEvent', module, param, value, timestamp, readerror)
-        self.module_callback('updateEvent', module, module, param, value, timestamp, readerror)
-
     def _unhandled_message(self, action, ident, data):
-        mname = None
-        if ident:
-            mname = ident.split(':')[0]
-        done = self.node_callback('unhandledMessage', action, ident, data)
-        done = self.module_callback('unhandledMessage', mname, action, ident, data) or done
-        if not done:
+        if not self.callback(None, 'unhandledMessage', action, ident, data):
             self.log.warning('unhandled message: %s %s %r' % (action, ident, data))
 
     def _set_state(self, online, state=None):
         # treat reconnecting as online!
         self._state = state or self._state
         self.online = online
-        self.node_callback('nodeStateChange', self.online, self._state)
+        self.callback(None, 'nodeStateChange', self.online, self._state)
         for mname in self.modules:
-            self.module_callback('nodeStateChange', mname, self.online, self._state)
+            self.callback(mname, 'nodeStateChange', self.online, self._state)
 
     def queue_request(self, action, ident=None, data=None):
         """make a request"""
@@ -449,7 +472,7 @@ class SecopClient:
 
     def get_reply(self, entry):
         """wait for reply and return it"""
-        if not entry[1].wait(10):  # entry
+        if not entry[1].wait(10):  # event
             raise TimeoutError('no response within 10s')
         if not entry[2]:  # reply
             raise ConnectionError('connection closed before reply')
@@ -467,18 +490,13 @@ class SecopClient:
         entry = self.queue_request(action, ident, data)
         return self.get_reply(entry)
 
-    def getParameter(self, module, parameter, trycache=False):
-        if trycache:
-            cached = self.cache.get((module, parameter), None)
-            if cached:
-                return cached
-        if self.online:
+    def readParameter(self, module, parameter):
         try:
             self.request(READREQUEST, self.identifier[module, parameter])
         except secop.errors.SECoPError:
             # error reply message is already stored as readerror in cache
             pass
-        return self.cache[module, parameter]
+        return self.cache.get((module, parameter), None)
 
     def setParameter(self, module, parameter, value):
         self.connect()  # make sure we are connected

secop/datatypes.py

@@ -26,6 +26,7 @@
 
 
 import sys
+import math
 from base64 import b64decode, b64encode
 
 from secop.errors import ProgrammingError, ProtocolError, BadValueError, ConfigError
@@ -36,8 +37,8 @@ from secop.properties import HasProperties, Property
 
 # Only export these classes for 'from secop.datatypes import *'
 __all__ = [
-    'DataType',
-    'FloatRange', 'IntRange',
+    'DataType', 'get_datatype',
+    'FloatRange', 'IntRange', 'ScaledInteger',
     'BoolType', 'EnumType',
     'BLOBType', 'StringType',
     'TupleOf', 'ArrayOf', 'StructOf',
@@ -51,6 +52,7 @@ UNLIMITED = 1 << 64  # internal limit for integers, is probably high enough for
 
 Parser = Parser()
 
+
 # base class for all DataTypes
 class DataType(HasProperties):
     IS_COMMAND = False
@@ -116,6 +118,14 @@ class DataType(HasProperties):
         # looks like the simplest way to make a deep copy
         return get_datatype(self.export_datatype())
 
+    def compatible(self, other):
+        """check other for compatibility
+
+        raise an exception if <other> is not compatible, i.e. there
+        exists a value which is valid for ourselfs, but not for <other>
+        """
+        raise NotImplementedError
+
 
 class Stub(DataType):
     """incomplete datatype, to be replaced with a proper one later during module load
@@ -182,6 +192,9 @@ class FloatRange(DataType):
             value = float(value)
         except Exception:
             raise BadValueError('Can not __call__ %r to float' % value)
+        if math.isinf(value):
+            raise BadValueError('FloatRange does not accept infinity')
+
         prec = max(abs(value * self.relative_resolution), self.absolute_resolution)
         if self.min - prec <= value <= self.max + prec:
             return min(max(value, self.min), self.max)
@@ -215,6 +228,12 @@ class FloatRange(DataType):
             return ' '.join([self.fmtstr % value, unit])
         return self.fmtstr % value
 
+    def compatible(self, other):
+        if not isinstance(other, (FloatRange, ScaledInteger)):
+            raise BadValueError('incompatible datatypes')
+        # avoid infinity
+        other(max(sys.float_info.min, self.min))
+        other(min(sys.float_info.max, self.max))
 
 
 class IntRange(DataType):
@@ -266,6 +285,15 @@ class IntRange(DataType):
     def format_value(self, value, unit=None):
         return '%d' % value
 
+    def compatible(self, other):
+        if isinstance(other, IntRange):
+            other(self.min)
+            other(self.max)
+            return
+        # this will accept some EnumType, BoolType
+        for i in range(self.min, self.max + 1):
+            other(i)
+
 
 class ScaledInteger(DataType):
     """Scaled integer int type
@@ -365,6 +393,12 @@ class ScaledInteger(DataType):
             return ' '.join([self.fmtstr % value, unit])
         return self.fmtstr % value
 
+    def compatible(self, other):
+        if not isinstance(other, (FloatRange, ScaledInteger)):
+            raise BadValueError('incompatible datatypes')
+        other(self.min)
+        other(self.max)
+
 
 class EnumType(DataType):
 
@@ -408,6 +442,10 @@ class EnumType(DataType):
     def format_value(self, value, unit=None):
         return '%s<%s>' % (self._enum[value].name, self._enum[value].value)
 
+    def compatible(self, other):
+        for m in self._enum.members:
+            other(m)
+
 
 class BLOBType(DataType):
     properties = {
@@ -438,7 +476,7 @@ class BLOBType(DataType):
     def __call__(self, value):
         """return the validated (internal) value or raise"""
         if not isinstance(value, bytes):
-            raise BadValueError('%r has the wrong type!' % value)
+            raise BadValueError('%s has the wrong type!' % repr(value))
         size = len(value)
         if size < self.minbytes:
             raise BadValueError(
@@ -464,6 +502,13 @@ class BLOBType(DataType):
     def format_value(self, value, unit=None):
         return repr(value)
 
+    def compatible(self, other):
+        try:
+            if self.minbytes < other.minbytes or self.maxbytes > other.maxbytes:
+                raise BadValueError('incompatible datatypes')
+        except AttributeError:
+            raise BadValueError('incompatible datatypes')
+
 
 class StringType(DataType):
     properties = {
@@ -494,7 +539,7 @@ class StringType(DataType):
     def __call__(self, value):
         """return the validated (internal) value or raise"""
         if not isinstance(value, str):
-            raise BadValueError('%r has the wrong type!' % value)
+            raise BadValueError('%s has the wrong type!' % repr(value))
         if not self.isUTF8:
             try:
                 value.encode('ascii')
@@ -527,6 +572,14 @@ class StringType(DataType):
     def format_value(self, value, unit=None):
         return repr(value)
 
+    def compatible(self, other):
+        try:
+            if self.minchars < other.minchars or self.maxchars > other.maxchars or \
+                    self.isUTF8 > other.isUTF8:
+                raise BadValueError('incompatible datatypes')
+        except AttributeError:
+            raise BadValueError('incompatible datatypes')
+
 
 # TextType is a special StringType intended for longer texts (i.e. embedding \n),
 # whereas StringType is supposed to not contain '\n'
@@ -578,6 +631,11 @@ class BoolType(DataType):
     def format_value(self, value, unit=None):
         return repr(bool(value))
 
+    def compatible(self, other):
+        other(False)
+        other(True)
+
+
 Stub.fix_datatypes()
 
 #
@@ -673,6 +731,14 @@ class ArrayOf(DataType):
             return ' '.join([res, unit])
         return res
 
+    def compatible(self, other):
+        try:
+            if self.minlen < other.minlen or self.maxlen > other.maxlen:
+                raise BadValueError('incompatible datatypes')
+            self.members.compatible(other.members)
+        except AttributeError:
+            raise BadValueError('incompatible datatypes')
+
 
 class TupleOf(DataType):
 
@@ -729,6 +795,15 @@ class TupleOf(DataType):
         return '(%s)' % (', '.join([sub.format_value(elem)
                                      for sub, elem in zip(self.members, value)]))
 
+    def compatible(self, other):
+        if not isinstance(other, TupleOf):
+            raise BadValueError('incompatible datatypes')
+        if len(self.members) != len(other.members) :
+            raise BadValueError('incompatible datatypes')
+        for a, b in zip(self.members, other.members):
+            a.compatible(b)
+
+
 
 class StructOf(DataType):
 
@@ -763,7 +838,7 @@ class StructOf(DataType):
         return res
 
     def __repr__(self):
-        opt = self.optional if self.optional else ''
+        opt = ', optional=%r' % self.optional if self.optional else ''
         return 'StructOf(%s%s)' % (', '.join(
             ['%s=%s' % (n, repr(st)) for n, st in list(self.members.items())]), opt)
 
@@ -808,6 +883,17 @@ class StructOf(DataType):
     def format_value(self, value, unit=None):
         return '{%s}' % (', '.join(['%s=%s' % (k, self.members[k].format_value(v)) for k, v in sorted(value.items())]))
 
+    def compatible(self, other):
+        try:
+            mandatory = set(other.members) - set(other.optional)
+            for k, m in self.members.items():
+                m.compatible(other.members[k])
+                mandatory.discard(k)
+            if mandatory:
+                raise BadValueError('incompatible datatypes')
+        except (AttributeError, TypeError, KeyError):
+            raise BadValueError('incompatible datatypes')
+
 
 class CommandType(DataType):
     IS_COMMAND = True
@@ -858,6 +944,16 @@ class CommandType(DataType):
         # actually I have no idea what to do here!
         raise NotImplementedError
 
+    def compatible(self, other):
+        try:
+            if self.argument != other.argument:  # not both are None
+                self.argument.compatible(other.argument)
+            if self.result != other.result:  # not both are None
+                other.result.compatible(self.result)
+        except AttributeError:
+            raise BadValueError('incompatible datatypes')
+
+
 
 # internally used datatypes (i.e. only for programming the SEC-node)
 class DataTypeType(DataType):

secop/errors.py

@@ -70,6 +70,11 @@ class NoSuchModuleError(SECoPError):
     name = 'NoSuchModule'
 
 
+# pylint: disable=redefined-builtin
+class NotImplementedError(NotImplementedError, SECoPError):
+    pass
+
+
 class NoSuchParameterError(SECoPError):
     pass
 
@@ -122,6 +127,16 @@ class HardwareError(SECoPError):
     pass
 
 
+def make_secop_error(name, text):
+    errcls = EXCEPTIONS.get(name, InternalError)
+    return errcls(text)
+
+
+def secop_error(exception):
+    if isinstance(exception, SECoPError):
+        return exception
+    return InternalError(repr(exception))
+
 
 EXCEPTIONS = dict(
     NoSuchModule=NoSuchModuleError,
@@ -137,8 +152,9 @@ EXCEPTIONS = dict(
     IsError=IsErrorError,
     Disabled=DisabledError,
     SyntaxError=ProtocolError,
+    NotImplementedError=NotImplementedError,
     InternalError=InternalError,
-# internal short versions (candidates for spec)
+    # internal short versions (candidates for spec)
     Protocol=ProtocolError,
     Internal=InternalError,
 )

secop/modules.py

@@ -140,6 +140,13 @@ class Module(HasProperties, metaclass=ModuleMeta):
         for aname, aobj in self.accessibles.items():
             # make a copy of the Parameter/Command object
             aobj = aobj.copy()
+            if isinstance(aobj, Parameter):
+                # fix default properties poll and needscfg
+                if aobj.poll is None:
+                    aobj.properties['poll'] = bool(aobj.handler)
+                if aobj.needscfg is None:
+                    aobj.properties['needscfg'] = not aobj.poll
+
             if aobj.export:
                 if aobj.export is True:
                     predefined_obj = PREDEFINED_ACCESSIBLES.get(aname, None)
@@ -200,7 +207,7 @@ class Module(HasProperties, metaclass=ModuleMeta):
                     self.writeDict[pname] = pobj.value
             else:
                 if pobj.default is None:
-                    if not pobj.poll:
+                    if pobj.needscfg:
                         raise ConfigError('Module %s: Parameter %r has no default '
                                           'value and was not given in config!' %
                                           (self.name, pname))
@@ -349,7 +356,7 @@ class Readable(Module):
 
     def startModule(self, started_callback):
         """start basic polling thread"""
-        if issubclass(self.pollerClass, BasicPoller):
+        if self.pollerClass and issubclass(self.pollerClass, BasicPoller):
             # use basic poller for legacy code
             mkthread(self.__pollThread, started_callback)
         else:
@@ -479,4 +486,4 @@ class Attached(Property):
         super().__init__('attached module', StringType())
 
     def __repr__(self):
-        return 'Attached(%r)' % self.description
+        return 'Attached(%s)' % (repr(self.attrname) if self.attrname else '')

secop/params.py

@@ -83,10 +83,16 @@ class Parameter(Accessible):
     from the config file if specified there
 
     poll can be:
-    - False or 0 (never poll this parameter), this is the default
-    - True or 1  (poll this parameter)
-    - for any other integer, the meaning depends on the used poller
-      meaning for the default simple poller:
+    - None: will be converted to True/False if handler is/is not None
+    - False or 0 (never poll this parameter)
+    - True or > 0  (poll this parameter)
+    - the exact meaning depends on the used poller
+      meaning for secop.poller.Poller:
+        - 1 or True (AUTO), converted to SLOW (readonly=False), DYNAMIC('status' and 'value') or REGULAR(else)
+        - 2 (SLOW), polled with lower priority and a multiple of pollperiod
+        - 3 (REGULAR), polled with pollperiod
+        - 4 (DYNAMIC), polled with pollperiod, if not BUSY, else with a fraction of pollperiod
+      meaning for the basicPoller:
         - True or 1 (poll this every pollinterval)
         - positive int  (poll every N(th) pollinterval)
         - negative int  (normally poll every N(th) pollinterval, if module is busy, poll every pollinterval)
@@ -110,7 +116,8 @@ class Parameter(Accessible):
                                  ValueType(), export=False, default=None, mandatory=False),
         'export':      Property('Is this parameter accessible via SECoP? (vs. internal parameter)',
                                  OrType(BoolType(), StringType()), export=False, default=True),
-        'poll':        Property('Polling indicator', IntRange(), export=False, default=False),
+        'poll':        Property('Polling indicator', NoneOr(IntRange()), export=False, default=None),
+        'needscfg':    Property('needs value in config', NoneOr(BoolType()), export=False, default=None),
         'optional':    Property('[Internal] is this parameter optional?', BoolType(), export=False,
                                  settable=False, default=False),
         'handler':     Property('[internal] overload the standard read and write functions',
@@ -139,9 +146,6 @@ class Parameter(Accessible):
             datatype.setProperty('unit', unit)
         super(Parameter, self).__init__(**kwds)
 
-        if self.handler and not self.poll:
-            self.properties['poll'] = True
-
         if self.readonly and self.initwrite:
             raise ProgrammingError('can not have both readonly and initwrite!')
 
@@ -182,6 +186,7 @@ class UnusedClass:
     # do not derive anything from this!
     pass
 
+
 class Parameters(OrderedDict):
     """class storage for Parameters"""
     def __init__(self, *args, **kwds):

secop/parse.py

@@ -68,7 +68,7 @@ class Parser:
     def parse_string(self, orgtext):
         # handle quoted and unquoted strings correctly
         text = orgtext.strip()
-        if text[0] in ('"', u"'"):
+        if text[0] in ('"', "'"):
             # quoted string
             quote = text[0]
             idx = 0
@@ -160,7 +160,6 @@ class Parser:
         return self.parse_string(orgtext)
 
     def parse(self, orgtext):
-        print("parsing %r" % orgtext)
         res, rem = self.parse_sub(orgtext)
         if rem and rem[0] in ',;':
             return self.parse_sub('[%s]' % orgtext)

secop/proxy.py

@@ -0,0 +1,230 @@
+#  -*- coding: utf-8 -*-
+# *****************************************************************************
+#
+# This program is free software; you can redistribute it and/or modify it under
+# the terms of the GNU General Public License as published by the Free Software
+# Foundation; either version 2 of the License, or (at your option) any later
+# version.
+#
+# This program is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+# FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
+# details.
+#
+# You should have received a copy of the GNU General Public License along with
+# this program; if not, write to the Free Software Foundation, Inc.,
+# 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+#
+# Module authors:
+#   Markus Zolliker <markus.zolliker@psi.ch>
+#
+# *****************************************************************************
+"""SECoP proxy modules"""
+
+from secop.lib import get_class
+from secop.modules import Module, Writable, Readable, Drivable, Attached
+from secop.datatypes import StringType
+from secop.protocol.dispatcher import make_update
+from secop.properties import Property
+from secop.client import SecopClient, decode_msg, encode_msg_frame
+from secop.params import Parameter, Command
+from secop.errors import ConfigError, make_secop_error, secop_error
+
+
+
+class ProxyModule(Module):
+    properties = {
+        'iodev': Attached(),
+        'module':
+            Property('remote module name', datatype=StringType(), default=''),
+    }
+
+    _consistency_check_done = False
+    _secnode = None
+
+    def updateEvent(self, module, parameter, value, timestamp, readerror):
+        pobj = self.parameters[parameter]
+        pobj.timestamp = timestamp
+        # should be done here: deal with clock differences
+        if readerror:
+            readerror = make_secop_error(*readerror)
+        if not readerror:
+            try:
+                pobj.value = value  # store the value even in case of a validation error
+                pobj.value = pobj.datatype(value)
+            except Exception as e:
+                readerror = secop_error(e)
+        pobj.readerror = readerror
+        self.DISPATCHER.broadcast_event(make_update(self.name, pobj))
+
+    def initModule(self):
+        if not self.module:
+            self.properties['module'] = self.name
+        self._secnode = self._iodev.secnode
+        self._secnode.register(self.module, self)
+        super().initModule()
+
+    def descriptiveDataChange(self, module, moddesc):
+        if module is None:
+            return  # do not care about the node for now
+        self._check_descriptive_data()
+
+    def _check_descriptive_data(self):
+        params = self.parameters.copy()
+        cmds = self.commands.copy()
+        moddesc = self._secnode.modules[self.module]
+        remoteparams = moddesc['parameters'].copy()
+        remotecmds = moddesc['commands'].copy()
+        while params:
+            pname, pobj = params.popitem()
+            props = remoteparams.get(pname, None)
+            if props is None:
+                self.log.warning('remote parameter %s:%s does not exist' % (self.module, pname))
+                continue
+            dt = props['datatype']
+            try:
+                if pobj.readonly:
+                    dt.compatible(pobj.datatype)
+                else:
+                    if props['readonly']:
+                        self.log.warning('remote parameter %s:%s is read only' % (self.module, pname))
+                    pobj.datatype.compatible(dt)
+                    try:
+                        dt.compatible(pobj.datatype)
+                    except Exception:
+                        self.log.warning('remote parameter %s:%s is not fully compatible: %r != %r'
+                                           % (self.module, pname, pobj.datatype, dt))
+            except Exception:
+                self.log.warning('remote parameter %s:%s has an incompatible datatype: %r != %r'
+                                   % (self.module, pname, pobj.datatype, dt))
+        while cmds:
+            cname, cobj = cmds.popitem()
+            props = remotecmds.get(cname)
+            if props is None:
+                self.log.warning('remote command %s:%s does not exist' % (self.module, cname))
+                continue
+            dt = props['datatype']
+            try:
+                cobj.datatype.compatible(dt)
+            except Exception:
+                self.log.warning('remote command %s:%s is not compatible: %r != %r'
+                                 % (self.module, pname, pobj.datatype, dt))
+        # what to do if descriptive data does not match?
+        # we might raise an exception, but this would lead to a reconnection,
+        # which might not help.
+        # for now, the error message must be enough
+
+    def nodeStateChange(self, online, state):
+        if online and not self._consistency_check_done:
+            self._check_descriptive_data()
+            self._consistency_check_done = True
+
+
+class ProxyReadable(ProxyModule, Readable):
+    pass
+
+
+class ProxyWritable(ProxyModule, Writable):
+    pass
+
+
+class ProxyDrivable(ProxyModule, Drivable):
+    pass
+
+
+PROXY_CLASSES = [ProxyDrivable, ProxyWritable, ProxyReadable, ProxyModule]
+
+
+class SecNode(Module):
+    properties = {
+        'uri':
+            Property('uri of a SEC node', datatype=StringType()),
+    }
+    commands = {
+        'request':
+            Command('send a request', argument=StringType(), result=StringType())
+    }
+
+    def earlyInit(self):
+        self.secnode = SecopClient(self.uri, self.log)
+        self.secnode.register(None, self)  # for nodeStateChange
+
+    def startModule(self, started_callback):
+        self.secnode.spawn_connect(started_callback)
+
+    def do_request(self, msg):
+        """for test purposes"""
+        reply = self.secnode.request(*decode_msg(msg.encode('utf-8')))
+        return encode_msg_frame(*reply).decode('utf-8')
+
+
+def proxy_class(remote_class, name=None):
+    """create a proxy class based on the definition of remote class
+
+    remote class is <import path>.<class name> of a class used on the remote node
+    if name is not given, 'Proxy' + <class name> is used
+    """
+    rcls = get_class(remote_class)
+    if name is None:
+        name = rcls.__name__
+
+    for proxycls in PROXY_CLASSES:
+        if issubclass(rcls, proxycls.__bases__[-1]):
+            # avoid 'should not be redefined' warning
+            proxycls.accessibles = {}
+            break
+    else:
+        raise ConfigError('%r is no SECoP module class' % remote_class)
+
+    parameters = {}
+    commands = {}
+    attrs = dict(parameters=parameters, commands=commands, properties=rcls.properties)
+
+    for aname, aobj in rcls.accessibles.items():
+        if isinstance(aobj, Parameter):
+            pobj = aobj.copy()
+            parameters[aname] = pobj
+            pobj.properties['poll'] = False
+            pobj.properties['handler'] = None
+            pobj.properties['needscfg'] = False
+
+            def rfunc(self, pname=aname):
+                value, _, readerror = self._secnode.getParameter(self.name, pname)
+                if readerror:
+                    raise readerror
+                return value
+
+            attrs['read_' + aname] = rfunc
+
+            if not pobj.readonly:
+
+                def wfunc(self, value, pname=aname):
+                    value, _, readerror = self._secnode.setParameter(self.name, pname, value)
+                    if readerror:
+                        raise make_secop_error(*readerror)
+                    return value
+
+                attrs['write_' + aname] = wfunc
+
+        elif isinstance(aobj, Command):
+            cobj = aobj.copy()
+            commands[aname] = cobj
+
+            def cfunc(self, arg=None, cname=aname):
+                return self._secnode.execCommand(self.name, cname, arg)
+
+            attrs['do_' + aname] = cfunc
+
+        else:
+            raise ConfigError('do not now about %r in %s.accessibles' % (aobj, remote_class))
+
+    return type(name, (proxycls,), attrs)
+
+
+def Proxy(name, logger, cfgdict, srv):
+    """create a Proxy object based on remote_class
+
+    title cased as it acts like a class
+    """
+    remote_class = cfgdict.pop('remote_class')
+    return proxy_class(remote_class)(name, logger, cfgdict, srv)

test/test_datatypes.py

@@ -609,3 +609,44 @@ def test_get_datatype():
         get_datatype({'type': 'struct', 'members': {}})
     with pytest.raises(ValueError):
         get_datatype({'type': 'struct', 'members':[1,2,3]})
+
+
+@pytest.mark.parametrize('dt, contained_in', [
+    (FloatRange(-10, 10), FloatRange()),
+    (IntRange(-10, 10), FloatRange()),
+    (IntRange(-10, 10), IntRange(-20, 10)),
+    (StringType(), StringType(isUTF8=True)),
+    (StringType(10, 10), StringType()),
+    (ArrayOf(StringType(), 3, 5), ArrayOf(StringType(), 3, 6)),
+    (TupleOf(StringType(), BoolType()), TupleOf(StringType(), IntRange())),
+    (StructOf(a=FloatRange(-1,1)), StructOf(a=FloatRange(), b=BoolType(), optional=['b'])),
+])
+def test_oneway_compatible(dt, contained_in):
+    dt.compatible(contained_in)
+    with pytest.raises(ValueError):
+        contained_in.compatible(dt)
+
+@pytest.mark.parametrize('dt1, dt2', [
+    (FloatRange(-5.5, 5.5), ScaledInteger(10, -5.5, 5.5)),
+    (IntRange(0,1), BoolType()),
+    (IntRange(-10, 10), IntRange(-10, 10)),
+])
+def test_twoway_compatible(dt1, dt2):
+    dt1.compatible(dt1)
+    dt2.compatible(dt2)
+
+@pytest.mark.parametrize('dt1, dt2', [
+    (StringType(), FloatRange()),
+    (IntRange(-10, 10), StringType()),
+    (StructOf(a=BoolType(), b=BoolType()), ArrayOf(StringType(), 2)),
+    (ArrayOf(BoolType(), 2), TupleOf(BoolType(), StringType())),
+    (TupleOf(BoolType(), BoolType()), StructOf(a=BoolType(), b=BoolType())),
+    (ArrayOf(StringType(), 3), ArrayOf(BoolType(), 3)),
+    (TupleOf(StringType(), BoolType()), TupleOf(BoolType(), BoolType())),
+    (StructOf(a=FloatRange(-1, 1), b=StringType()), StructOf(a=FloatRange(), b=BoolType())),
+])
+def test_incompatible(dt1, dt2):
+    with pytest.raises(ValueError):
+        dt1.compatible(dt2)
+    with pytest.raises(ValueError):
+        dt2.compatible(dt1)

test/test_modules.py

@@ -203,7 +203,7 @@ def test_ModuleMeta():
     assert set(cfg['value'].keys()) == {'group', 'export', 'relative_resolution',
         'visibility', 'unit', 'default', 'datatype', 'fmtstr',
         'absolute_resolution', 'poll', 'max', 'min', 'readonly', 'constant',
-        'description'}
+        'description', 'needscfg'}
 
     # check on the level of classes
     # this checks Newclass1 too, as it is inherited by Newclass2