Separate MetadataHandler (XML parser) from OpenLCBNetwork.

Author: Poikilos

examples/examples_gui.py

@@ -20,8 +20,12 @@
 
 from logging import getLogger
 
+from openlcb.memoryservice import MemorySpace
 from openlcb.message import Message
+from openlcb.metadataprocessor import MetadataProcessor
 from openlcb.mti import MTI
+from openlcb.nodeid import NodeID
+from openlcb.openlcbnetwork import OpenLCBNetwork
 
 try:
     import tkinter as tk
@@ -41,7 +45,7 @@
 from openlcb import emit_cast, formatted_ex
 from openlcb.tcplink.mdnsconventions import id_from_tcp_service_name
 
-from typing import OrderedDict as TypingOrderedDict
+from typing import Callable, OrderedDict as TypingOrderedDict
 
 zeroconf_enabled = False
 try:
@@ -454,11 +458,8 @@ def _gui(self, parent):
         self.cdi_refresh_button.grid(row=self.cdi_row, column=1)
 
         self.cdi_row += 1
-        self.cdi_form = CDIForm(self.cdi_tab)  # OpenLCBNetwork() subclass
-        # ^ CDIForm has ttk.Treeview etc.
-        self.cdi_form.canLink.registerMessageReceivedListener(
-            self.handleMessage)
-        self.cdi_form.grid(row=self.cdi_row)
+        self.network = None
+        self.cdi_form = None
 
         self.example_tab = ttk.Frame(self.notebook)
         self.example_tab.columnconfigure(index=0, weight=1)
@@ -486,6 +487,15 @@ def _gui(self, parent):
         #     self.rowconfigure(row, weight=1)
         # self.rowconfigure(self.row_count-1, weight=1)  # make last row expand
 
+    def setupNetwork(self):
+        self.network = OpenLCBNetwork(self.getValue('localNodeID'))
+        self.cdi_form = CDIForm(self.network.canLink, self.cdi_tab)  # MetadataProcessor subclass
+        # ^ formerly OpenLCBNetwork() subclass
+        # ^ CDIForm has ttk.Treeview etc.
+        self.cdi_form.canLink.registerMessageReceivedListener(
+            self.handleMessage)
+        self.cdi_form.grid(row=self.cdi_row)
+
     def handleMessage(self, message: Message):
         """Off-thread message handler.
         This is called by the OpenLCB network stack which is controlled
@@ -527,6 +537,12 @@ def _handleConnect(self):
         print(ready_message)
 
     def _connect(self):
+        userNodeID = NodeID(self.getValue('localNodeID'))  # assert good NodeID
+        if self.network is None:
+            self.setupNetwork()
+        elif self.network.canLink.localNodeID != userNodeID:
+            self.network.physicalLayer.physicalLayerDown()
+            self.setupNetwork()
         host_var = self.fields.get('host')
         host = host_var.get()
         port_var = self.fields.get('port')
@@ -535,8 +551,6 @@ def _connect(self):
             port = int(port)
         else:
             raise TypeError("Expected int, got {}".format(emit_cast(port)))
-        localNodeID_var = self.fields.get('localNodeID')
-        localNodeID = localNodeID_var.get()
         # self.cdi_form.connect(host, port, localNodeID)
         self.saveSettings()
         self.cdi_connect_button.configure(state=tk.DISABLED)
@@ -553,9 +567,8 @@ def _connect(self):
             self._tcp_socket.connect(host, port)
             # self.cdi_form.setConnectHandler(self.connectStateChanged)
             # ^ See message.mti == MTI Link_Layer_Down instead.
-            result = self.cdi_form.startListening(
+            result = self.network.startListening(
                 self._tcp_socket,
-                localNodeID,
             )
             self._connect_thread = None
         except Exception as ex:
@@ -587,12 +600,19 @@ def cdiRefreshClicked(self):
         print("Querying farNodeID={}".format(repr(farNodeID)))
         self.setStatus("Downloading CDI...")
         threading.Thread(
-            target=self.cdi_form.downloadCDI,
-            args=(farNodeID,),
+            target=self.downloadCDI,
+            args=(farNodeID, MemorySpace.CDI),
             kwargs={'callback': self.cdi_form.on_cdi_element},
             daemon=True,
         ).start()
 
+    def downloadCDI(self, farNodeID: str, space: MemorySpace,
+                    callback: Callable[[dict], None] = None):
+        self.setStatus("Downloading CDI...")
+        self.cdi_form.onStartDownload()
+        assert isinstance(space, MemorySpace)
+        self.network.download(farNodeID, self.cdi_form, callback=callback)
+
     def getValue(self, key):
         field = self.fields.get(key)
         if not field:
@@ -728,7 +748,12 @@ def fillDefaultPort(self):
     def fillDefault(self, key):
         self.fields[key].set(self.settings.getDefault(key))
 
+    def getStatus(self):
+        # See also CDIForm
+        return self.statusLabel.get()
+
     def setStatus(self, msg):
+        # See also CDIForm
         self.statusLabel.configure(text=msg)
 
     def setTooltip(self, key, msg):

examples/tkexamples/cdiform.py

@@ -17,9 +17,12 @@
 from collections import deque
 from logging import getLogger
 from typing import Callable
+
+from openlcb.linklayer import LinkLayer
+from openlcb.memoryservice import MemorySpace
+from openlcb.metadataprocessor import element_to_dict
 # from xml.etree import ElementTree as ET
 
-from openlcb.openlcbnetwork import element_to_dict
 
 if __name__ == "__main__":
     logger = getLogger(__file__)
@@ -37,7 +40,7 @@
         " since test running from repo but could not find openlcb in {}."
         .format(repr(REPO_DIR)))
 try:
-    from openlcb.openlcbnetwork import OpenLCBNetwork
+    from openlcb.metadataprocessor import MetadataProcessor
 except ImportError as ex:
     print("{}: {}".format(type(ex).__name__, ex), file=sys.stderr)
     print("* You must run this from a venv that has openlcb installed"
@@ -46,15 +49,19 @@
     raise  # sys.exit(1)
 
 
-class CDIForm(ttk.Frame, OpenLCBNetwork):
+class CDIForm(ttk.Frame, MetadataProcessor):
     """A GUI frame to represent the CDI visually as a tree.
 
     Args:
         parent (TkWidget): Typically a ttk.Frame or tk.Frame with "root"
             attribute set.
     """
     def __init__(self, *args, **kwargs):
-        OpenLCBNetwork.__init__(self, *args, **kwargs)
+        assert isinstance(args[0], LinkLayer), \
+            "Expected LinkLayer/subclass got {}".format(type(args[0]).__name__)
+        linkLayer = args[0]
+        args = args[1:]  # remove first argument (only for GUI)
+        MetadataProcessor.__init__(self, linkLayer, MemorySpace.CDI)
         ttk.Frame.__init__(self, *args, **kwargs)
         self._top_widgets = []
         if len(args) < 1:
@@ -97,20 +104,25 @@ def clear(self):
     #     return OpenLCBNetwork.connect(self, new_socket, localNodeID,
     #                                   callback=callback)
 
-    def downloadCDI(self, farNodeID: str,
-                    callback: Callable[[dict], None] = None):
-        self.setStatus("Downloading CDI...")
-        self.ignore_non_gui_tags = deque()
-        self._populating_stack = deque()
-        super().downloadCDI(farNodeID, callback=callback)
-
     def setStatus(self, message: str):
+        # See also MainForm
         self._status_var.set(message)
 
+    def getStatus(self):
+        # See also MainForm
+        return self._status_var.get()
+
+    def onStartDownload(self):
+        """Initialize variables used by element handler(s)."""
+        self.onStart()
+        self._resetTree()
+        self.ignore_non_gui_tags = deque()
+        self._populating_stack = deque()
+
     def on_cdi_element(self, event_d: dict):
         """Handler for incoming CDI tag
-        (Use this for callback in downloadCDI, which sets parser's
-        _onElement)
+        Use this for callback in downloadCDI, which sets parser
+        (_dataListener)'s _onElement.
 
         Args:
             event_d (dict): Document parsing state info:

openlcb/memoryservice.py

@@ -21,6 +21,7 @@
 - Wait for either dataReply or rejectedReply call back.
 '''
 
+from enum import Enum
 import logging
 
 from typing import (
@@ -36,6 +37,23 @@
 )
 
 
+class MemorySpace(Enum):
+    """The memory space to read.
+    In practice, MetadataProcessor (or a non-XML parser if necessary)
+    uses this to track what data type and format is to be assumed in a
+    received Message. It is assumed to have the same space as the
+    request (MemoryReadMemo).
+
+    Attributes:
+        Uninitialized: No data (memory read request response) is expected.
+        CDI: The data expected from the memory read is CDI XML.
+        FDI: The data expected from the memory read is FDI XML.
+    """
+    Uninitialized = -1
+    CDI = 0xFF  # decodes to 0x03
+    FDI = 0xFA
+
+
 class MemoryReadMemo:
     """Memo carries request and reply.
 
@@ -45,7 +63,9 @@ class MemoryReadMemo:
         space (int): Encoded memory space identifier, where values:
             - 0xFF to 0xFD are special spaces, and only the least significant
               2 bits are relevant.
+              - 0xFF is CDI (decodes to 0x03)
             - 0x00 to 0xFC represent standard memory spaces directly.
+              - 0xFA is FDI
         address (int): The address in memory where the read operation
             should be performed.
         rejectedReply (Callable[MemoryReadMemo]): Callback function to handle