Corrected an issue where Ethernet format 0 messages over a certain si…

…ze would have an incorrect length.

chapter10/ethernet.py

@@ -60,14 +60,25 @@ def __repr__(self):
         # order.
         FORMAT = BitFormat('''
             u64 ipts
-            u14 length
-            u1 data_length_error
-            u1 data_crc_error
+
+            u16 length
+
             u8 network_id
             u1 crc_error
             u1 frame_error
             u2 content
-            u4 ethernet_speed''')
+            u4 ethernet_speed
+        ''')
+
+        def __init__(self, *args, **kwargs):
+            packet.Message.__init__(self, *args, **kwargs)
+            self.length_error = self.length >> 14 & 0b1
+            self.data_error = self.length >> 15
+            self.length &= 0b11111111111111
+
+        def __bytes__(self):
+            self.length |= (self.length_error << 14) | (self.data_error << 15)
+            return packet.Message.__bytes__(self)
 
 
 class EthernetF1(packet.Packet):

tests/unit/test_ethernet.py

@@ -22,3 +22,10 @@ def test_format_1_count():
             break
     assert i+1 == len(packet)
     assert len(packet) == 2
+
+
+def test_bytes():
+    for packet in C10(ETHERNET):
+        if packet.data_type == 0x68:
+            break
+    assert packet.buffer.getvalue() == bytes(packet)