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附录__设备基于CCP接入_设备端接入手册_阿里云物联网套件-阿里云

CCP协议中字段类型为可变长数值，都需要使用该算法来实现。

The algorithm for encoding a decimal number (X) into the variable length encoding scheme is as follows:

    do
      digit = X MOD 128
      X = X DIV 128
      // if there are more digits to encode, set the top bit of this digit
      if ( X > 0 )
        digit = digit OR 0x80
      endif
      'output' digit
    while ( X> 0 )

where MOD is the modulo operator (% in C), DIV is integer division (/ in C), and OR is bit-wise or (| in C).The algorithm for decoding the Number Length field is as follows:

    multiplier = 1
    value = 0
    do
      digit = 'next digit from stream'
      value += (digit AND 127) * multiplier
      multiplier *= 128
    while ((digit AND 128) != 0)

where AND is the bit-wise and operator (& in C).LS When this algorithm terminates, value contains the Remaining Length in bytes.

最后更新：2016-11-23 17:16:07

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