kopia lustrzana https://github.com/Yakifo/amqtt
70 wiersze
2.1 KiB
Python
70 wiersze
2.1 KiB
Python
# Copyright (c) 2015 Nicolas JOUANIN
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#
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# See the file license.txt for copying permission.
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import asyncio
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from hbmqtt.codecs.utils import (
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bytes_to_hex_str,
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bytes_to_int,
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read_or_raise,
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)
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from hbmqtt.message import FixedHeader, MessageType
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from hbmqtt.codecs.errors import CodecException
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class FixedHeaderException(CodecException):
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pass
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class FixedHeaderCodec:
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def __init__(self):
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pass
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@asyncio.coroutine
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def decode(self, reader) -> FixedHeader:
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"""
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Decode MQTT message fixed header from stream
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:param reader: Stream to read
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:return: FixedHeader instance
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"""
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b1 = yield from read_or_raise(reader, 1)
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msg_type = FixedHeaderCodec.get_message_type(b1)
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if msg_type is MessageType.RESERVED_0 or msg_type is MessageType.RESERVED_15:
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raise FixedHeaderException("Usage of control packet type %s is forbidden" % msg_type)
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flags = FixedHeaderCodec.get_flags(b1)
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remain_length = yield from self.decode_remaining_length(reader)
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return FixedHeader(msg_type, flags, remain_length)
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@staticmethod
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def get_message_type(byte):
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byte_type = (bytes_to_int(byte) & 0xf0) >> 4
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return MessageType(byte_type)
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@staticmethod
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def get_flags(data):
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byte = bytes_to_int(data)
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return byte & 0x0f
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@asyncio.coroutine
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def decode_remaining_length(self, reader):
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"""
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Decode message length according to MQTT specifications
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:param reader:
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:return:
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"""
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multiplier = 1
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value = 0
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length_bytes = b''
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while True:
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encoded_byte = yield from read_or_raise(reader, 1)
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length_bytes += encoded_byte
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int_byte = bytes_to_int(encoded_byte)
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value += (int_byte & 0x7f) * multiplier
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if (int_byte & 0x80) == 0:
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break
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else:
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multiplier *= 128
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if multiplier > 128*128*128:
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raise FixedHeaderException("Invalid remaining length bytes:%s" % bytes_to_hex_str(length_bytes))
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return value
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