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from math import ldexp
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import struct
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import sys
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if sys.version_info.major < 3:
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from datetime import tzinfo, timedelta
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class timezone(tzinfo):
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def __init__(self, offset):
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self.offset = offset
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def utcoffset(self, dt):
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return self.offset
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def dst(self, dt):
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return timedelta(0)
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def tzname(self, dt):
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return 'UTC+00:00'
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def as_unicode(string):
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return string.decode('utf-8')
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def iteritems(self):
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return self.iteritems()
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def bytes_from_list(values):
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return bytes(bytearray(values))
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byte_as_integer = ord
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timezone.utc = timezone(timedelta(0))
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xrange = xrange # noqa: F821
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long = long # noqa: F821
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unicode = unicode # noqa: F821
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else:
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from datetime import timezone
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def byte_as_integer(bytestr):
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return bytestr[0]
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def as_unicode(string):
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return string
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def iteritems(self):
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return self.items()
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xrange = range
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long = int
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unicode = str
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bytes_from_list = bytes
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if sys.version_info.major >= 3 and sys.version_info.minor >= 6:
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# Python 3.6 added 16 bit floating point to struct
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def pack_float16(value):
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try:
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return struct.pack('>Be', 0xf9, value)
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except OverflowError:
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return False
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def unpack_float16(payload):
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return struct.unpack('>e', payload)[0]
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else:
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def pack_float16(value):
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# Based on node-cbor by hildjj
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# which was based in turn on Carsten Borman's cn-cbor
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u32 = struct.pack('>f', value)
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u = struct.unpack('>I', u32)[0]
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if u & 0x1FFF != 0:
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return False
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s16 = (u >> 16) & 0x8000
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exponent = (u >> 23) & 0xff
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mantissa = u & 0x7fffff
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if 113 <= exponent <= 142:
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s16 += ((exponent - 112) << 10) + (mantissa >> 13)
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elif 103 <= exponent < 113:
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if mantissa & ((1 << (126 - exponent)) - 1):
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return False
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s16 += ((mantissa + 0x800000) >> (126 - exponent))
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else:
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return False
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return struct.pack('>BH', 0xf9, s16)
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def unpack_float16(payload):
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# Code adapted from RFC 7049, appendix D
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def decode_single(single):
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return struct.unpack("!f", struct.pack("!I", single))[0]
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payload = struct.unpack('>H', payload)[0]
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value = (payload & 0x7fff) << 13 | (payload & 0x8000) << 16
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if payload & 0x7c00 != 0x7c00:
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return ldexp(decode_single(value), 112)
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return decode_single(value | 0x7f800000)
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