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"""Manage a stream of NMEA messages with optional metadata.
TODO(schwehr): Add support for decoding non-AIS NMEA messages (e.g. ZDA).
"""
from ais import nmea
from ais import tag_block
from ais import uscg
from ais import vdm
import six.moves.queue as Queue
class Error(Exception):
pass
def GetOrNone(queue):
try:
return queue.get(block=False)
except Queue.Empty:
return
class NmeaQueue(Queue.Queue):
# pylint: disable=line-too-long
r"""Process mixed text, bare NMEA or NMEA with TAG BLOCK or USCG metadata.
Raw text lines are passed through without a decode stage. "Bare"
AIS NMEA lines are decoded and passed through without a decode or
time field in resulting decodes. The USCG and TAG Block metadata
messages will get a list of times and a "decoded" field. The
decoded field contains the AIS message contents. The extra metadata is
expected to be accessed through the matches field.
Example usage:
q = nmea_queue.NmeaQueue()
q.qsize() # Returns 0
# Raw text.
q.put('Hello world')
q.qsize() # Returns 1
q.get() # Returns a dictionary with lines containing the input.
q.qsize() # Returns 0
# Bare NMEA AIS VDM.
q.put('!SAVDM,2,1,9,B,55NG9T000001L@GKCSPLDlTpV22222222222220t2PI5540Ht00`88888888,0*33')
q.put('!SAVDM,2,2,9,B,88888888880,2*34')
q.get() # Returns a dictionary with no times or extra metadata in matches.
# USCG NMEA AIS VDM.
q.put('!SAVDM,2,1,9,B,55NG9T000001L@GKCSPLDlTpV22222222222220t2PI5540Ht00`88888888,0*33,b003669709,1428944320')
q.put('!SAVDM,2,2,9,B,88888888880,2*34,b003669709,1428944320')
q.get() # Returns a dictionary with times and extra metadata.
# TAG Block NMEA AIS VDM.
q.put('\g:1-3-144865,n:325372,s:r11CSDO1,c:1428944580*6C\!AIVDM,2,1,9,A,55MkD8000001L@7?37L4AHDqAE8F0Pu8p8huLE8t28P,0*1E')
q.put('\g:2-3-144865,n:325373*2D\!AIVDM,2,2,9,A,666v<04ThC`12AAkp0hH88888880,2*7A')
q.get() # Return a dictionary with times and extra metadata.
This sample line is a single line TAG Block position report intended
for a satellite:
\n:80677,s:b003669952,c:1428884269*2A\!SAVDM,1,1,,B,K8VSqb9LdU28WP8<,0*17
A queue get() returns:
{'decoded': {
'cog': 131,
'gnss': True,
'id': 27,
'md5': '50898a3435865cf76f1b502b2821672b',
'mmsi': 577305000,
'nav_status': 5,
'position_accuracy': 1,
'raim': False,
'repeat_indicator': 0,
'sog': 0,
'spare': 0,
'x': -90.2066650390625,
'y': 29.145000457763672},
'line_nums': [9],
'line_type': ('TAGB',),
'lines': [
'\\n:80677,s:b003669952,c:1428884269*2A'
'\\!SAVDM,1,1,,B,K8VSqb9LdU28WP8<,0*17'],
'matches': [{
'dest': None,
'group': None,
'group_id': None,
'line_num': '80677',
'metadata': 'n:80677,s:b003669952,c:1428884269*2A',
'payload': '!SAVDM,1,1,,B,K8VSqb9LdU28WP8<,0*17',
'quality': None,
'rcvr': 'b003669952',
'rel_time': None,
'sentence_num': None,
'sentence_tot': None,
'tag_checksum': '2A',
'text': None,
'text_date': None,
'time': '1428884269'}],
'times': [1428884269]})
"""
def __init__(self):
self.bare_queue = vdm.BareQueue()
self.tagb_queue = tag_block.TagQueue()
self.uscg_queue = uscg.UscgQueue()
self.line_num = 0
Queue.Queue.__init__(self)
def put(self, line, line_num=None):
"""Add a line to the queue.
Args:
line: str, Text to add to the queue.
line_num: int, Optional line number override.
"""
if line_num is not None:
self.line_num = line_num
else:
self.line_num += 1
line_num = self.line_num
line = line.rstrip()
line_type = nmea.LineType(line)
msg = None
if line_type == nmea.TEXT:
msg = {'line_nums': [self.line_num], 'lines': [line]}
elif line_type == nmea.BARE:
self.bare_queue.put(line, self.line_num)
msg = GetOrNone(self.bare_queue)
elif line_type == nmea.TAGB:
self.tagb_queue.put(line, self.line_num)
msg = GetOrNone(self.tagb_queue)
elif line_type == nmea.USCG:
self.uscg_queue.put(line, self.line_num)
msg = GetOrNone(self.uscg_queue)
else:
assert False # Should never reach here.
if msg:
msg['line_type'] = line_type
Queue.Queue.put(self, msg)
def GetOrNone(self):
try:
return self.get(block=False)
except Queue.Empty:
return
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