server.py: poll LAT service, based on [MTL]'s old code

diff --git a/server.py b/server.py
index 3bbd697..25e8ff8 100755 (executable)
--- a/server.py
+++ b/server.py
@@ -2,12 +2,45 @@
 # UCC Door Server - hardware interface server
 # reads status of reed switches and provides a D-BUS interface to read them
 # David Adam <[email protected]>
+# LAT interface based on work by Mark Tearle <[email protected]>
 # Released under an MIT-style license; see COPYING for details.
 
 # statuses: 1 means open circuit, 0 means closed circuit, -1 means error
 
 import dbus, dbus.service
 import gobject
+from LATClient import LATClient
+from select import select
+
+def check_LAT_service(servicename, retries=3):
+    latclient = LATClient(service=servicename.upper())
+    rfh, wfh = latclient.get_fh()
+    results = {'error': retries, 'closed': retries, 'open': retries}
+    test_string = "got wombles?"
+    
+    # Only return after n(retries) consistent results, although not necessarily
+    # in order. This means we poll at least (retries) and up to (retries ** 2) times.
+    # This is mtearle's original code. No idea if it's the Right Thing.
+    while True:
+        try:
+            wfh.write(test_string)
+            wfh.flush()
+        except:
+            results['error'] -= 1
+            if results['error'] == 0: return -1
+            continue
+        rr, wr, er = select([rfh], [], [], 3.0)
+        if rfh not in rr:
+            results['open'] -= 1
+            if results['open'] == 0: return 1
+            continue
+        recv = rfh.read(len(test_string))
+        if recv <> test_string:
+            results['error'] -= 1
+            if results['error'] == 0: return -1
+            continue
+        results['closed'] -= 1
+        if results['closed'] == 0: return 0
 
 class Door(dbus.service.Object):
     
@@ -15,6 +48,9 @@ class Door(dbus.service.Object):
         self.interval = 10 # seconds
         self.service = doorname
         self.status = -1
+        self.retries = 3
+        if 'pir' in self.service:
+            self.retries = 1
         
         # set up D-BUS service name
         object_path = '/au/asn/ucc/doors/%s' % doorname
@@ -24,10 +60,11 @@ class Door(dbus.service.Object):
         self.poll()
     
     def poll(self):
-        # check LAT
-        # XXX to be added
+        try:
+            newstatus = check_LAT_service(self.service, self.retries)
+        except:
+            newstatus = -1
         
-        newstatus = -1
         if newstatus != self.status:
             self.status = newstatus
             # emit signal