epro: velib_python/vedbus.py comparison

comparison velib_python/vedbus.py @ 8:9c0435a617db

Import velib_python

author	Daniel O'Connor <darius@dons.net.au>
date	Sun, 05 Dec 2021 14:35:36 +1030
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+:9c0435a617db
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+import dbus.service
+import logging
+import traceback
+import os
+import weakref
+from collections import defaultdict
+from ve_utils import wrap_dbus_value, unwrap_dbus_value
+# vedbus contains three classes:
+# VeDbusItemImport -> use this to read data from the dbus, ie import
+# VeDbusItemExport -> use this to export data to the dbus (one value)
+# VeDbusService -> use that to create a service and export several values to the dbus
+# Code for VeDbusItemImport is copied from busitem.py and thereafter modified.
+# All projects that used busitem.py need to migrate to this package. And some
+# projects used to define there own equivalent of VeDbusItemExport. Better to
+# use VeDbusItemExport, or even better the VeDbusService class that does it all for you.
+# TODOS
+# 1 check for datatypes, it works now, but not sure if all is compliant with
+#	com.victronenergy.BusItem interface definition. See also the files in
+#	tests_and_examples. And see 'if type(v) == dbus.Byte:' on line 102. Perhaps
+#	something similar should also be done in VeDbusBusItemExport?
+# 2 Shouldn't VeDbusBusItemExport inherit dbus.service.Object?
+# 7 Make hard rules for services exporting data to the D-Bus, in order to make tracking
+#   changes possible. Does everybody first invalidate its data before leaving the bus?
+#   And what about before taking one object away from the bus, instead of taking the
+#   whole service offline?
+#   They should! And after taking one value away, do we need to know that someone left
+#   the bus? Or we just keep that value in invalidated for ever? Result is that we can't
+#   see the difference anymore between an invalidated value and a value that was first on
+#   the bus and later not anymore. See comments above VeDbusItemImport as well.
+# 9 there are probably more todos in the code below.
+# Some thoughts with regards to the data types:
+#
+#   Text from: http://dbus.freedesktop.org/doc/dbus-python/doc/tutorial.html#data-types
+#   ---
+#   Variants are represented by setting the variant_level keyword argument in the
+#   constructor of any D-Bus data type to a value greater than 0 (variant_level 1
+#   means a variant containing some other data type, variant_level 2 means a variant
+#   containing a variant containing some other data type, and so on). If a non-variant
+#   is passed as an argument but introspection indicates that a variant is expected,
+#   it'll automatically be wrapped in a variant.
+#   ---
+#
+#   Also the different dbus datatypes, such as dbus.Int32, and dbus.UInt32 are a subclass
+#   of Python int. dbus.String is a subclass of Python standard class unicode, etcetera
+#
+#   So all together that explains why we don't need to explicitly convert back and forth
+#   between the dbus datatypes and the standard python datatypes. Note that all datatypes
+#   in python are objects. Even an int is an object.
+#   The signature of a variant is 'v'.
+# Export ourselves as a D-Bus service.
+class VeDbusService(object):
+	def __init__(self, servicename, bus=None):
+		# dict containing the VeDbusItemExport objects, with their path as the key.
+		self._dbusobjects = {}
+		self._dbusnodes = {}
+		self._ratelimiters = []
+		self._dbusname = None
+		# dict containing the onchange callbacks, for each object. Object path is the key
+		self._onchangecallbacks = {}
+		# Connect to session bus whenever present, else use the system bus
+		self._dbusconn = bus or (dbus.SessionBus() if 'DBUS_SESSION_BUS_ADDRESS' in os.environ else dbus.SystemBus())
+		# make the dbus connection available to outside, could make this a true property instead, but ach..
+		self.dbusconn = self._dbusconn
+		# Register ourselves on the dbus, trigger an error if already in use (do_not_queue)
+		self._dbusname = dbus.service.BusName(servicename, self._dbusconn, do_not_queue=True)
+		# Add the root item that will return all items as a tree
+		self._dbusnodes['/'] = VeDbusRootExport(self._dbusconn, '/', self)
+		logging.info("registered ourselves on D-Bus as %s" % servicename)
+	# To force immediate deregistering of this dbus service and all its object paths, explicitly
+	# call __del__().
+	def __del__(self):
+		for node in list(self._dbusnodes.values()):
+			node.__del__()
+		self._dbusnodes.clear()
+		for item in list(self._dbusobjects.values()):
+			item.__del__()
+		self._dbusobjects.clear()
+		if self._dbusname:
+			self._dbusname.__del__()  # Forces call to self._bus.release_name(self._name), see source code
+		self._dbusname = None
+	# @param callbackonchange	function that will be called when this value is changed. First parameter will
+	#							be the path of the object, second the new value. This callback should return
+	#							True to accept the change, False to reject it.
+	def add_path(self, path, value, description="", writeable=False,
+					onchangecallback=None, gettextcallback=None):
+		if onchangecallback is not None:
+			self._onchangecallbacks[path] = onchangecallback
+		item = VeDbusItemExport(
+				self._dbusconn, path, value, description, writeable,
+				self._value_changed, gettextcallback, deletecallback=self._item_deleted)
+		spl = path.split('/')
+		for i in range(2, len(spl)):
+			subPath = '/'.join(spl[:i])
+			if subPath not in self._dbusnodes and subPath not in self._dbusobjects:
+				self._dbusnodes[subPath] = VeDbusTreeExport(self._dbusconn, subPath, self)
+		self._dbusobjects[path] = item
+		logging.debug('added %s with start value %s. Writeable is %s' % (path, value, writeable))
+	# Add the mandatory paths, as per victron dbus api doc
+	def add_mandatory_paths(self, processname, processversion, connection,
+			deviceinstance, productid, productname, firmwareversion, hardwareversion, connected):
+		self.add_path('/Mgmt/ProcessName', processname)
+		self.add_path('/Mgmt/ProcessVersion', processversion)
+		self.add_path('/Mgmt/Connection', connection)
+		# Create rest of the mandatory objects
+		self.add_path('/DeviceInstance', deviceinstance)
+		self.add_path('/ProductId', productid)
+		self.add_path('/ProductName', productname)
+		self.add_path('/FirmwareVersion', firmwareversion)
+		self.add_path('/HardwareVersion', hardwareversion)
+		self.add_path('/Connected', connected)
+	# Callback function that is called from the VeDbusItemExport objects when a value changes. This function
+	# maps the change-request to the onchangecallback given to us for this specific path.
+	def _value_changed(self, path, newvalue):
+		if path not in self._onchangecallbacks:
+			return True
+		return self._onchangecallbacks[path](path, newvalue)
+	def _item_deleted(self, path):
+		self._dbusobjects.pop(path)
+		for np in list(self._dbusnodes.keys()):
+			if np != '/':
+				for ip in self._dbusobjects:
+					if ip.startswith(np + '/'):
+						break
+				else:
+					self._dbusnodes[np].__del__()
+					self._dbusnodes.pop(np)
+	def __getitem__(self, path):
+		return self._dbusobjects[path].local_get_value()
+	def __setitem__(self, path, newvalue):
+		self._dbusobjects[path].local_set_value(newvalue)
+	def __delitem__(self, path):
+		self._dbusobjects[path].__del__()  # Invalidates and then removes the object path
+		assert path not in self._dbusobjects
+	def __contains__(self, path):
+		return path in self._dbusobjects
+	def __enter__(self):
+		l = ServiceContext(self)
+		self._ratelimiters.append(l)
+		return l
+	def __exit__(self, *exc):
+		# pop off the top one and flush it. If with statements are nested
+		# then each exit flushes its own part.
+		if self._ratelimiters:
+			self._ratelimiters.pop().flush()
+class ServiceContext(object):
+	def __init__(self, parent):
+		self.parent = parent
+		self.changes = {}
+	def __getitem__(self, path):
+		return self.parent[path]
+	def __setitem__(self, path, newvalue):
+		c = self.parent._dbusobjects[path]._local_set_value(newvalue)
+		if c is not None:
+			self.changes[path] = c
+	def flush(self):
+		if self.changes:
+			self.parent._dbusnodes['/'].ItemsChanged(self.changes)
+class TrackerDict(defaultdict):
+	""" Same as defaultdict, but passes the key to default_factory. """
+	def __missing__(self, key):
+		self[key] = x = self.default_factory(key)
+		return x
+class VeDbusRootTracker(object):
+	""" This tracks the root of a dbus path and listens for PropertiesChanged
+	    signals. When a signal arrives, parse it and unpack the key/value changes
+	    into traditional events, then pass it to the original eventCallback
+	    method. """
+	def __init__(self, bus, serviceName):
+		self.importers = defaultdict(weakref.WeakSet)
+		self.serviceName = serviceName
+		self._match = bus.get_object(serviceName, '/', introspect=False).connect_to_signal(
+			"ItemsChanged", weak_functor(self._items_changed_handler))
+	def __del__(self):
+		self._match.remove()
+		self._match = None
+	def add(self, i):
+		self.importers[i.path].add(i)
+	def _items_changed_handler(self, items):
+		if not isinstance(items, dict):
+			return
+		for path, changes in items.items():
+			try:
+				v = changes['Value']
+			except KeyError:
+				continue
+			try:
+				t = changes['Text']
+			except KeyError:
+				t = str(unwrap_dbus_value(v))
+			for i in self.importers.get(path, ()):
+				i._properties_changed_handler({'Value': v, 'Text': t})
+"""
+Importing basics:
+	- If when we power up, the D-Bus service does not exist, or it does exist and the path does not
+	  yet exist, still subscribe to a signal: as soon as it comes online it will send a signal with its
+	  initial value, which VeDbusItemImport will receive and use to update local cache. And, when set,
+	  call the eventCallback.
+	- If when we power up, save it
+	- When using get_value, know that there is no difference between services (or object paths) that don't
+	  exist and paths that are invalid (= empty array, see above). Both will return None. In case you do
+	  really want to know ifa path exists or not, use the exists property.
+	- When a D-Bus service leaves the D-Bus, it will first invalidate all its values, and send signals
+	  with that update, and only then leave the D-Bus. (or do we need to subscribe to the NameOwnerChanged-
+	  signal!?!) To be discussed and make sure. Not really urgent, since all existing code that uses this
+	  class already subscribes to the NameOwnerChanged signal, and subsequently removes instances of this
+	  class.
+Read when using this class:
+Note that when a service leaves that D-Bus without invalidating all its exported objects first, for
+example because it is killed, VeDbusItemImport doesn't have a clue. So when using VeDbusItemImport,
+make sure to also subscribe to the NamerOwnerChanged signal on bus-level. Or just use dbusmonitor,
+because that takes care of all of that for you.
+"""
+class VeDbusItemImport(object):
+	def __new__(cls, bus, serviceName, path, eventCallback=None, createsignal=True):
+		instance = object.__new__(cls)
+		# If signal tracking should be done, also add to root tracker
+		if createsignal:
+			if "_roots" not in cls.__dict__:
+				cls._roots = TrackerDict(lambda k: VeDbusRootTracker(bus, k))
+		return instance
+	## Constructor
+	# @param bus			the bus-object (SESSION or SYSTEM).
+	# @param serviceName	the dbus-service-name (string), for example 'com.victronenergy.battery.ttyO1'
+	# @param path			the object-path, for example '/Dc/V'
+	# @param eventCallback	function that you want to be called on a value change
+	# @param createSignal   only set this to False if you use this function to one time read a value. When
+	#						leaving it to True, make sure to also subscribe to the NameOwnerChanged signal
+	#						elsewhere. See also note some 15 lines up.
+	def __init__(self, bus, serviceName, path, eventCallback=None, createsignal=True):
+		# TODO: is it necessary to store _serviceName and _path? Isn't it
+		# stored in the bus_getobjectsomewhere?
+		self._serviceName = serviceName
+		self._path = path
+		self._match = None
+		# TODO: _proxy is being used in settingsdevice.py, make a getter for that
+		self._proxy = bus.get_object(serviceName, path, introspect=False)
+		self.eventCallback = eventCallback
+		assert eventCallback is None or createsignal == True
+		if createsignal:
+			self._match = self._proxy.connect_to_signal(
+				"PropertiesChanged", weak_functor(self._properties_changed_handler))
+			self._roots[serviceName].add(self)
+		# store the current value in _cachedvalue. When it doesn't exists set _cachedvalue to
+		# None, same as when a value is invalid
+		self._cachedvalue = None
+		try:
+			v = self._proxy.GetValue()
+		except dbus.exceptions.DBusException:
+			pass
+		else:
+			self._cachedvalue = unwrap_dbus_value(v)
+	def __del__(self):
+		if self._match is not None:
+			self._match.remove()
+			self._match = None
+		self._proxy = None
+	def _refreshcachedvalue(self):
+		self._cachedvalue = unwrap_dbus_value(self._proxy.GetValue())
+	## Returns the path as a string, for example '/AC/L1/V'
+	@property
+	def path(self):
+		return self._path
+	## Returns the dbus service name as a string, for example com.victronenergy.vebus.ttyO1
+	@property
+	def serviceName(self):
+		return self._serviceName
+	## Returns the value of the dbus-item.
+	# the type will be a dbus variant, for example dbus.Int32(0, variant_level=1)
+	# this is not a property to keep the name consistant with the com.victronenergy.busitem interface
+	# returns None when the property is invalid
+	def get_value(self):
+		return self._cachedvalue
+	## Writes a new value to the dbus-item
+	def set_value(self, newvalue):
+		r = self._proxy.SetValue(wrap_dbus_value(newvalue))
+		# instead of just saving the value, go to the dbus and get it. So we have the right type etc.
+		if r == 0:
+			self._refreshcachedvalue()
+		return r
+	## Resets the item to its default value
+	def set_default(self):
+		self._proxy.SetDefault()
+		self._refreshcachedvalue()
+	## Returns the text representation of the value.
+	# For example when the value is an enum/int GetText might return the string
+	# belonging to that enum value. Another example, for a voltage, GetValue
+	# would return a float, 12.0Volt, and GetText could return 12 VDC.
+	#
+	# Note that this depends on how the dbus-producer has implemented this.
+	def get_text(self):
+		return self._proxy.GetText()
+	## Returns true of object path exists, and false if it doesn't
+	@property
+	def exists(self):
+		# TODO: do some real check instead of this crazy thing.
+		r = False
+		try:
+			r = self._proxy.GetValue()
+			r = True
+		except dbus.exceptions.DBusException:
+			pass
+		return r
+	## callback for the trigger-event.
+	# @param eventCallback the event-callback-function.
+	@property
+	def eventCallback(self):
+		return self._eventCallback
+	@eventCallback.setter
+	def eventCallback(self, eventCallback):
+		self._eventCallback = eventCallback
+	## Is called when the value of the imported bus-item changes.
+	# Stores the new value in our local cache, and calls the eventCallback, if set.
+	def _properties_changed_handler(self, changes):
+		if "Value" in changes:
+			changes['Value'] = unwrap_dbus_value(changes['Value'])
+			self._cachedvalue = changes['Value']
+			if self._eventCallback:
+				# The reason behind this try/except is to prevent errors silently ending up the an error
+				# handler in the dbus code.
+				try:
+					self._eventCallback(self._serviceName, self._path, changes)
+				except:
+					traceback.print_exc()
+					os._exit(1)  # sys.exit() is not used, since that also throws an exception
+class VeDbusTreeExport(dbus.service.Object):
+	def __init__(self, bus, objectPath, service):
+		dbus.service.Object.__init__(self, bus, objectPath)
+		self._service = service
+		logging.debug("VeDbusTreeExport %s has been created" % objectPath)
+	def __del__(self):
+		# self._get_path() will raise an exception when retrieved after the call to .remove_from_connection,
+		# so we need a copy.
+		path = self._get_path()
+		if path is None:
+			return
+		self.remove_from_connection()
+		logging.debug("VeDbusTreeExport %s has been removed" % path)
+	def _get_path(self):
+		if len(self._locations) == 0:
+			return None
+		return self._locations[0][1]
+	def _get_value_handler(self, path, get_text=False):
+		logging.debug("_get_value_handler called for %s" % path)
+		r = {}
+		px = path
+		if not px.endswith('/'):
+			px += '/'
+		for p, item in self._service._dbusobjects.items():
+			if p.startswith(px):
+				v = item.GetText() if get_text else wrap_dbus_value(item.local_get_value())
+				r[p[len(px):]] = v
+		logging.debug(r)
+		return r
+	@dbus.service.method('com.victronenergy.BusItem', out_signature='v')
+	def GetValue(self):
+		value = self._get_value_handler(self._get_path())
+		return dbus.Dictionary(value, signature=dbus.Signature('sv'), variant_level=1)
+	@dbus.service.method('com.victronenergy.BusItem', out_signature='v')
+	def GetText(self):
+		return self._get_value_handler(self._get_path(), True)
+	def local_get_value(self):
+		return self._get_value_handler(self.path)
+class VeDbusRootExport(VeDbusTreeExport):
+	@dbus.service.signal('com.victronenergy.BusItem', signature='a{sa{sv}}')
+	def ItemsChanged(self, changes):
+		pass
+	@dbus.service.method('com.victronenergy.BusItem', out_signature='a{sa{sv}}')
+	def GetItems(self):
+		return {
+			path: {
+				'Value': wrap_dbus_value(item.local_get_value()),
+				'Text': item.GetText() }
+			for path, item in self._service._dbusobjects.items()
+		}
+class VeDbusItemExport(dbus.service.Object):
+	## Constructor of VeDbusItemExport
+	#
+	# Use this object to export (publish), values on the dbus
+	# Creates the dbus-object under the given dbus-service-name.
+	# @param bus		  The dbus object.
+	# @param objectPath	  The dbus-object-path.
+	# @param value		  Value to initialize ourselves with, defaults to None which means Invalid
+	# @param description  String containing a description. Can be called over the dbus with GetDescription()
+	# @param writeable	  what would this do!? :).
+	# @param callback	  Function that will be called when someone else changes the value of this VeBusItem
+	#                     over the dbus. First parameter passed to callback will be our path, second the new
+	#					  value. This callback should return True to accept the change, False to reject it.
+	def __init__(self, bus, objectPath, value=None, description=None, writeable=False,
+					onchangecallback=None, gettextcallback=None, deletecallback=None):
+		dbus.service.Object.__init__(self, bus, objectPath)
+		self._onchangecallback = onchangecallback
+		self._gettextcallback = gettextcallback
+		self._value = value
+		self._description = description
+		self._writeable = writeable
+		self._deletecallback = deletecallback
+	# To force immediate deregistering of this dbus object, explicitly call __del__().
+	def __del__(self):
+		# self._get_path() will raise an exception when retrieved after the
+		# call to .remove_from_connection, so we need a copy.
+		path = self._get_path()
+		if path == None:
+			return
+		if self._deletecallback is not None:
+			self._deletecallback(path)
+		self.local_set_value(None)
+		self.remove_from_connection()
+		logging.debug("VeDbusItemExport %s has been removed" % path)
+	def _get_path(self):
+		if len(self._locations) == 0:
+			return None
+		return self._locations[0][1]
+	## Sets the value. And in case the value is different from what it was, a signal
+	# will be emitted to the dbus. This function is to be used in the python code that
+	# is using this class to export values to the dbus.
+	# set value to None to indicate that it is Invalid
+	def local_set_value(self, newvalue):
+		changes = self._local_set_value(newvalue)
+		if changes is not None:
+			self.PropertiesChanged(changes)
+	def _local_set_value(self, newvalue):
+		if self._value == newvalue:
+			return None
+		self._value = newvalue
+		return {
+			'Value': wrap_dbus_value(newvalue),
+			'Text': self.GetText()
+		}
+	def local_get_value(self):
+		return self._value
+	# ==== ALL FUNCTIONS BELOW THIS LINE WILL BE CALLED BY OTHER PROCESSES OVER THE DBUS ====
+	## Dbus exported method SetValue
+	# Function is called over the D-Bus by other process. It will first check (via callback) if new
+	# value is accepted. And it is, stores it and emits a changed-signal.
+	# @param value The new value.
+	# @return completion-code When successful a 0 is return, and when not a -1 is returned.
+	@dbus.service.method('com.victronenergy.BusItem', in_signature='v', out_signature='i')
+	def SetValue(self, newvalue):
+		if not self._writeable:
+			return 1  # NOT OK
+		newvalue = unwrap_dbus_value(newvalue)
+		if newvalue == self._value:
+			return 0  # OK
+		# call the callback given to us, and check if new value is OK.
+		if (self._onchangecallback is None or
+				(self._onchangecallback is not None and self._onchangecallback(self.__dbus_object_path__, newvalue))):
+			self.local_set_value(newvalue)
+			return 0  # OK
+		return 2  # NOT OK
+	## Dbus exported method GetDescription
+	#
+	# Returns the a description.
+	# @param language A language code (e.g. ISO 639-1 en-US).
+	# @param length Lenght of the language string.
+	# @return description
+	@dbus.service.method('com.victronenergy.BusItem', in_signature='si', out_signature='s')
+	def GetDescription(self, language, length):
+		return self._description if self._description is not None else 'No description given'
+	## Dbus exported method GetValue
+	# Returns the value.
+	# @return the value when valid, and otherwise an empty array
+	@dbus.service.method('com.victronenergy.BusItem', out_signature='v')
+	def GetValue(self):
+		return wrap_dbus_value(self._value)
+	## Dbus exported method GetText
+	# Returns the value as string of the dbus-object-path.
+	# @return text A text-value. '---' when local value is invalid
+	@dbus.service.method('com.victronenergy.BusItem', out_signature='s')
+	def GetText(self):
+		if self._value is None:
+			return '---'
+		# Default conversion from dbus.Byte will get you a character (so 'T' instead of '84'), so we
+		# have to convert to int first. Note that if a dbus.Byte turns up here, it must have come from
+		# the application itself, as all data from the D-Bus should have been unwrapped by now.
+		if self._gettextcallback is None and type(self._value) == dbus.Byte:
+			return str(int(self._value))
+		if self._gettextcallback is None and self.__dbus_object_path__ == '/ProductId':
+			return "0x%X" % self._value
+		if self._gettextcallback is None:
+			return str(self._value)
+		return self._gettextcallback(self.__dbus_object_path__, self._value)
+	## The signal that indicates that the value has changed.
+	# Other processes connected to this BusItem object will have subscribed to the
+	# event when they want to track our state.
+	@dbus.service.signal('com.victronenergy.BusItem', signature='a{sv}')
+	def PropertiesChanged(self, changes):
+		pass
+## This class behaves like a regular reference to a class method (eg. self.foo), but keeps a weak reference
+## to the object which method is to be called.
+## Use this object to break circular references.
+class weak_functor:
+	def __init__(self, f):
+		self._r = weakref.ref(f.__self__)
+		self._f = weakref.ref(f.__func__)
+	def __call__(self, *args, **kargs):
+		r = self._r()
+		f = self._f()
+		if r == None or f == None:
+			return
+		f(r, *args, **kargs)

Mercurial > ~darius > hgwebdir.cgi > epro

comparison velib_python/vedbus.py @ 8:9c0435a617db