GB18030 Encoding for GB18030 Character Set

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This section provides a quick introduction of the GB18030 encoding for the GB18030 character set. GB18030 is a multi-byte (1-byte, 2-byte, or 4-byte) encoding.

GB18030 encoding scheme uses one, two or four bytes to encode a character. The following table shows the ranges of valid byte sequences:

Number Of   Valid Range
Bytes       Byte 1        Byte 2        Byte 3        Byte 4

   1        0x00 - 0x7F
   2        0x81 - 0xFE   0x40 - 0x7E
   2        0x81 - 0xFE   0x80 - 0xFE
   4        0x81 - 0xFE   0x30 - 0x39   0x81 - 0xFE   0x30 - 0x39

Processing a GB18030 encoded byte stream from the beginning of the stream is easy. Here is an algorithm to divide the stream into sequences of bytes that represent valid GB18030 characters:

Input: 
   byte stream in
Algorithm: 
   while (in.hasNext())
      b1 = in.nextByte()
      if (0x00 <= b1 <= 0x7F)
         b1 is a valid byte sequence
      else if (0x81 <= b1 <= 0xFE)
         b2 = in.nextByte()
         if (0x40 <= b2 <= 0x7E || 0x80 <= b2 <= 0xFE) 
            b1, b2 is a valid byte sequence
         else if (0x30 <= b2 <= 0x39)
            b3 = in.nextByte()
            b4 = in.nextByte()
            b1, b2, b3, b4 is a valid byte sequence
         else
            stream is corrupted
         end if
      else
         stream is corrupted
      end if

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GB18030 Encoding for GB18030 Character Set