Debugging analog parsing.

chapter10/analog.py

@@ -35,20 +35,53 @@ class AnalogF1(packet.Packet):
 
     """
 
+    # u4 factor
+    # u1 same
+    # p3
+
+    # u6 length
+    # u2 mode
+
+    # u8 subchannel_count
+
+    # u8 subchannel
     csdw_format = BitFormat('''
-        u6 length
-        u2 mode
-        u8 subchannel
-        u8 subchannel_count
-        p3
-        u1 same
-        u4< factor
+        u8 one
+        u8 two
+        u8 three
+        u8 four
     ''')
 
     class Message(packet.Message):
         def __repr__(self):
             return '<Analog Sample %s bytes>' % len(self.data)
 
+        @classmethod
+        def from_packet(cls, packet):
+            subchannel = packet._subchannel
+            if packet.same:
+                csdw = packet.subchannels[0]
+            else:
+                csdw = packet.subchannels[subchannel]
+
+            # Find the sample size in bytes (16 bit aligned).
+            length = csdw['length'] or 64  # Length 0 = 64 bits
+            length = length // 8 + (length % 16 and 1 or 0)
+
+            data = packet.buffer.read(length)
+            if len(data) < length:
+                raise EOFError
+
+            # Account for filler byte when length is odd.
+            if length % 2:
+                packet.buffer.seek(1, 1)
+
+            packet._subchannel += 1
+            if packet._subchannel >= len(packet.subchannels):
+                packet._subchannel = 0
+
+            return packet.Message(data, parent=packet, **csdw)
+
     def __init__(self, *args, **kwargs):
         packet.Packet.__init__(self, *args, **kwargs)
 
@@ -66,31 +99,20 @@ def __init__(self, *args, **kwargs):
             'same')
         self.subchannels = [{k: getattr(self, k) for k in keys}]
 
-        # Read CSDWs for subchannels if applicable.
+        # Read CSDWs for additional subchannels if applicable.
         if not self.same:
             for i in range(self.subchannel_count):
+                raw = self.buffer.read(4)
+                print('parse: ', raw)
+                # assert 0
                 self.subchannels.append(
-                    self.csdw_format.unpack(self.buffer.read(4)))
-
-    def __next__(self):
-        subchannel = self._subchannel
-        if self.same:
-            csdw = self.subchannels[0]
-        else:
-            csdw = self.subchannels[subchannel]
-
-        # Find the sample size in bytes (16 bit aligned).
-        length = csdw['length'] or 64  # Length 0 = 64 bits
-        length = length // 8 + (length % 16 and 1 or 0)
-
-        data = self.buffer.read(length)
-        if len(data) < length:
-            raise StopIteration
-
-        # Account for filler byte when length is odd.
-        if length % 2:
-            self.packet.file.seek(1, 1)
-
-        self._subchannel += 1
-
-        return self.Message(data, parent=self, **csdw)
+                    self.csdw_format.unpack(raw))
+
+    def _raw_body(self):
+        raw = bytes()
+        for channel in self.subchannels:
+            print(channel)
+            csdw = self.csdw_format.pack(channel)
+            raw += csdw
+        raw += b''.join([bytes(msg) for msg in list(self)])
+        return raw

chapter10/packet.py

@@ -131,7 +131,9 @@ def __init__(self, file=None, parent=None, **kwargs):
         self.validate()
 
         # Read channel specific data word (CSDW)
-        self.__dict__.update(self.csdw_format.unpack(self.buffer.read(4)))
+        csdw = self.csdw_format.unpack(self.buffer.read(4))
+        print(csdw)
+        self.__dict__.update(csdw)
 
     def get_time(self):
         """Return a timestamp for this packet. Depends on parent C10 object."""

tests/unit/test_analog.py

@@ -29,3 +29,7 @@ def test_next(packet):
         assert sample.data == b'\xfc\xfc'
         if i >= 2:
             break
+
+
+def test_bytes(packet):
+    assert packet.buffer.getvalue() == bytes(packet)