1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
|
"""A file-like interface to NMEA parsing.
>>> import ais
>>> import json
>>> with ais.open('test/data/typeexamples.nmea') as src:
... msg = next(src)
... print(json.dumps(next(msg), indent=4, sort_keys=True))
{
"decoded": {
"day": 0,
"fix_type": 1,
"hour": 24,
"id": 4,
"md5": "7ecb187e7edc1789de436b0c2ccf2963",
"minute": 60,
"mmsi": 3669713,
"month": 0,
"position_accuracy": 0,
"raim": false,
"repeat_indicator": 0,
"second": 60,
"slot_number": 2105,
"slot_timeout": 2,
"spare": 0,
"sync_state": 1,
"transmission_ctl": 0,
"x": 181.0,
"y": 91.0,
"year": 0
},
"line_nums": [
1
],
"line_type": "USCG",
"lines": [
"!AIVDM,1,1,,A,403Ovl@000Htt<tSF0l4Q@100`Pq,0*28,d-109,S2105,t050056.00,T56.13718694,r003669946,1325394060,1325394001"
],
"matches": [
{
"body": "403Ovl@000Htt<tSF0l4Q@100`Pq",
"chan": "A",
"checksum": "28",
"counter": null,
"fill_bits": 0,
"hour": 5,
"minute": 0,
"payload": "!AIVDM,1,1,,A,403Ovl@000Htt<tSF0l4Q@100`Pq,0*28",
"receiver_time": 50056.0,
"rssi": null,
"second": 56.0,
"sen_num": 1,
"sen_tot": 1,
"seq_id": null,
"signal_strength": -109,
"slot": 2105,
"station": "r003669946",
"station_type": "r",
"talker": "AI",
"time": 1325394060,
"time_of_arrival": 56.13718694,
"uscg_metadata": ",d-109,S2105,t050056.00,T56.13718694,r003669946,1325394060",
"vdm": "!AIVDM,1,1,,A,403Ovl@000Htt<tSF0l4Q@100`Pq,0*28",
"vdm_type": "VDM"
}
]
}
"""
import codecs
import sys
import six
import ais.nmea_queue
def open(name, mode='r', **kwargs):
"""Open a file containing NMEA and instantiate an instance of `NmeaFile()`.
Lke Python's `open()`, set the `mode` parameter to 'r' for normal reading or
or 'rU' for opening the file in universal newline mode.
Args:
name: A file path, file-like object, or '-' for stdin.
mode: I/O mode for opening the input file. r, rU, or U
Raises:
TypeError: Invalid object for name parameter.
ValueError: Invalid value for mode parameter.
Returns:
An instance of NmeaFile that is ready for reading.
"""
io_modes = ('r', 'rU', 'U')
if mode not in io_modes:
raise ValueError("Mode '{m}' is unsupported. Must be one of: {ms}".format(
m=mode, ms=', '.join(io_modes)))
if name == '-':
fobj = sys.stdin
elif isinstance(name, six.string_types):
fobj = codecs.open(name, **kwargs)
elif hasattr(name, 'close') and \
(hasattr(name, 'next') or hasattr(name, '__next__')):
fobj = name
else:
raise TypeError("'name' must be a file path, file-like object, "
"or '-' for stdin.")
return NmeaFile(fobj)
class NmeaFile(object):
"""Provides a file-like object interface to the `ais.nmea_queue` module."""
def __init__(self, fobj):
"""Construct a parsing stream.
Args:
fobj: File-like object.
"""
self._fobj = fobj
self._queue = ais.nmea_queue.NmeaQueue()
@property
def closed(self):
"""Is the file-like object from which we are reading open for reading?"""
return self._fobj.closed
@property
def name(self):
"""Name of the file-like object from which we are reading."""
return self._fobj.name
def close(self):
"""Close the file-like object from which we are reading and dump whats left
in the queue."""
return self._fobj.close()
def __iter__(self):
return self
def __enter__(self):
return self
def __exit__(self, exc_type, exc_val, exc_tb):
# Destroy the queue, which could be a large in-memory object.
self._queue = None
return self.close()
def __next__(self):
"""Return the next decoded AIS message."""
msg = None
while not msg:
self._queue.put(next(self._fobj))
msg = self._queue.GetOrNone()
return msg
next = __next__
|
