def test_popleft(self):
desired_queue_size = 3
queue = CircularQueue(desired_queue_size)
assert queue.popleft() is None
for i in range(desired_queue_size):
queue.append(i)
for i in range(desired_queue_size):
assert queue.popleft() == i
assert queue.popleft() is None
def test__iter__(self):
data = [1, 2, 3, 4, 5]
queue = CircularQueue(5)
for x in queue:
# nothing is in queue, should not be reached
assert 0
queue.extend(data)
for ind, x in enumerate(queue):
assert x == data[ind]
# test for circularity
poped_item = queue.popleft()
queue.append(poped_item)
poped_item = queue.popleft()
queue.append(poped_item)
new_data = [3, 4, 5, 1, 2]
for ind, x in enumerate(queue):
assert x == new_data[ind]
class SerialPacketQueue(PacketQueue):
""" SerialPacketQueue enables extraction of well formed, crc-verified packets from its circular byte queue
It is a specialized circular queue which takes in raw bytes and returns the packet's message.
The packet's message is a byte array consisting of a type byte followed by payload bytes.
General Packet Format:
| 0x55 | length | type | ---payload--- | crcL | crcH |
'length' is the (uint8) number of bytes in 'data'
'type' is the (uint8) message type
'payload' is a series of (uint8) bytes, serialized Little-Endian
'crc' is the (uint16) CRC value for 'length'+'type'+'data', Little-Endian
"""
# Don't forget to change the __init__ descriptiton
_MAX_BYTE_QUEUE_SIZE = (255 + 5) * 2 # size of max packet * 2
def __init__(self):
""" Create an empty SerialPacketQueue of constant size 512
"""
self._byte_queue = CircularQueue(maxlen=self._MAX_BYTE_QUEUE_SIZE)
self._has_a_packet = 0
def __len__(self):
return len(self._byte_queue)
@property
def is_empty(self):
""" Check if queue is empty
Returns:
true: if the queue is empty
false: if the queue has some bytes in it
"""
return self._byte_queue.is_empty
@property
def free_space(self):
current_size = len(self._byte_queue)
return self._byte_queue.maxlen - current_size
def put_bytes(self, new_bytes):
""" Append bytes to the queue
Args:
new_bytes: bytes you want to append.
Returns:
true: if succesful
Raise:
PacketQueueError("Byte Queue Overflow")
"""
try:
iter(new_bytes)
except TypeError:
# not iterable
if not self._byte_queue.append(new_bytes):
raise PacketQueueError("Byte Queue Overflow")
else:
# iterable
if not self._byte_queue.extend(new_bytes):
raise PacketQueueError("Byte Queue Overflow")
return 1
def peek(self):
""" Peeks for the first available packet in the queue and extract its message
Returns:
bytearray: The first available message
None: There was no well form packet in the queue
Raise:
When the queue is empty
PacketQueueError("Serial packet queue is empty")
"""
if self._byte_queue.is_empty:
raise PacketQueueError("Serial packet queue is empty")
return self._parse_bytes()
def _parse_bytes(self):
packet_state = SerialStartState(self._byte_queue)
packet_parser = PacketParser(packet_state)
packet_parser.parse()
if not packet_parser.succesful:
self._has_a_packet = 0
return None
self._has_a_packet = 1
return packet_parser.message
def clear(self):
""" Clears the queue """
self._byte_queue.clear()
def drop_packet(self):
""" Drops the first packet available in the queue
Returns:
True: a packet was droped
False: no packet was droped
"""
# no need to parse if you know there is a packet
if self._has_a_packet:
self._pop_packet_bytes()
self._has_a_packet = 0
return True
self._parse_bytes()
if self._has_a_packet:
self._pop_packet_bytes()
self._has_a_packet = 0
return True
return False
def _pop_packet_bytes(self):
msg_len = self._byte_queue[1]
# + start byte, len, type, crch, crcl
packet_len = msg_len + 5
for _ in range(packet_len):
self._byte_queue.popleft()