fix missings and empty array

Author: Fedor Baart

mmi/__init__.py

@@ -6,26 +6,37 @@
 
 def send_array(socket, A, flags=0, copy=False, track=False, metadata=None):
     """send a numpy array with metadata over zmq"""
-    md = dict(
-        dtype=str(A.dtype),
-        shape=A.shape,
-        timestamp=datetime.datetime.now().isoformat()
-    )
+
+    # create a metadata dictionary for the message
+    md = {}
+    # always add a timestamp
+    md['timestamp'] = datetime.datetime.now().isoformat()
+
+    # copy extra metadata
+    if metadata:
+        md.update(metadata)
+
+    # if we don't have an array
+    if A is None:
+        # send only json
+        socket.send_json(md, flags)
+        # and we're done
+        return
+
+    # add array metadata
+    md['dtype'] = str(A.dtype)
+    md['shape'] = A.shape
     try:
+        # If an array has a fill value assume it's an array with missings
+        # store the fill_Value in the metadata and fill the array before sending.
         md['fill_value'] = A.fill_value
         A = A.filled()
     except AttributeError:
         # no masked array, nothing to do
         pass
 
-    if metadata:
-        md.update(metadata)
-    if A is None:
-        # send only json
-        socket.send_json(md, flags)
-    else:
-        # send json, followed by array
-        socket.send_json(md, flags | zmq.SNDMORE)
+    # send json, followed by array
+    socket.send_json(md, flags | zmq.SNDMORE)
     # Make a copy if required and pass along the buffer
     msg = buffer(np.ascontiguousarray(A))
     socket.send(msg, flags, copy=copy, track=track)

tests/test_simple.py

@@ -18,9 +18,18 @@ def test_sndrcv(self):
         mmi.send_array(req, A)
         B, metadata = mmi.recv_array(rep)
         numpy.testing.assert_array_equal(A, B)
-
+    def test_metadata_only(self):
+        """send a message with only metadata"""
+        req = ctx.socket(zmq.REQ)
+        req.connect('tcp://localhost:9002')
+        rep = ctx.socket(zmq.REP)
+        rep.bind('tcp://*:9002')
+        mmi.send_array(req, A=None)
+        _, metadata = mmi.recv_array(rep)
+        self.assertTrue('timestamp' in metadata)
 
     def test_missing(self):
+        """send an array with missing data"""
         A = np.array([1, 2, 3, 4])
         A = np.ma.masked_less(A, 2)
         req = ctx.socket(zmq.REQ)