|
1 from math import ldexp |
|
2 import struct |
|
3 import sys |
|
4 |
|
5 |
|
6 if sys.version_info.major < 3: |
|
7 from datetime import tzinfo, timedelta |
|
8 |
|
9 class timezone(tzinfo): |
|
10 def __init__(self, offset): |
|
11 self.offset = offset |
|
12 |
|
13 def utcoffset(self, dt): |
|
14 return self.offset |
|
15 |
|
16 def dst(self, dt): |
|
17 return timedelta(0) |
|
18 |
|
19 def tzname(self, dt): |
|
20 return 'UTC+00:00' |
|
21 |
|
22 def as_unicode(string): |
|
23 return string.decode('utf-8') |
|
24 |
|
25 def iteritems(self): |
|
26 return self.iteritems() |
|
27 |
|
28 def bytes_from_list(values): |
|
29 return bytes(bytearray(values)) |
|
30 |
|
31 byte_as_integer = ord |
|
32 timezone.utc = timezone(timedelta(0)) |
|
33 xrange = xrange # noqa: F821 |
|
34 long = long # noqa: F821 |
|
35 unicode = unicode # noqa: F821 |
|
36 else: |
|
37 from datetime import timezone |
|
38 |
|
39 def byte_as_integer(bytestr): |
|
40 return bytestr[0] |
|
41 |
|
42 def as_unicode(string): |
|
43 return string |
|
44 |
|
45 def iteritems(self): |
|
46 return self.items() |
|
47 |
|
48 xrange = range |
|
49 long = int |
|
50 unicode = str |
|
51 bytes_from_list = bytes |
|
52 |
|
53 |
|
54 if sys.version_info.major >= 3 and sys.version_info.minor >= 6: |
|
55 # Python 3.6 added 16 bit floating point to struct |
|
56 |
|
57 def pack_float16(value): |
|
58 try: |
|
59 return struct.pack('>Be', 0xf9, value) |
|
60 except OverflowError: |
|
61 return False |
|
62 |
|
63 def unpack_float16(payload): |
|
64 return struct.unpack('>e', payload)[0] |
|
65 else: |
|
66 def pack_float16(value): |
|
67 # Based on node-cbor by hildjj |
|
68 # which was based in turn on Carsten Borman's cn-cbor |
|
69 u32 = struct.pack('>f', value) |
|
70 u = struct.unpack('>I', u32)[0] |
|
71 |
|
72 if u & 0x1FFF != 0: |
|
73 return False |
|
74 |
|
75 s16 = (u >> 16) & 0x8000 |
|
76 exponent = (u >> 23) & 0xff |
|
77 mantissa = u & 0x7fffff |
|
78 |
|
79 if 113 <= exponent <= 142: |
|
80 s16 += ((exponent - 112) << 10) + (mantissa >> 13) |
|
81 elif 103 <= exponent < 113: |
|
82 if mantissa & ((1 << (126 - exponent)) - 1): |
|
83 return False |
|
84 |
|
85 s16 += ((mantissa + 0x800000) >> (126 - exponent)) |
|
86 else: |
|
87 return False |
|
88 |
|
89 return struct.pack('>BH', 0xf9, s16) |
|
90 |
|
91 def unpack_float16(payload): |
|
92 # Code adapted from RFC 7049, appendix D |
|
93 def decode_single(single): |
|
94 return struct.unpack("!f", struct.pack("!I", single))[0] |
|
95 |
|
96 payload = struct.unpack('>H', payload)[0] |
|
97 value = (payload & 0x7fff) << 13 | (payload & 0x8000) << 16 |
|
98 if payload & 0x7c00 != 0x7c00: |
|
99 return ldexp(decode_single(value), 112) |
|
100 |
|
101 return decode_single(value | 0x7f800000) |