Rewrite of IBM doublebyte charsets (original) (raw)

Ulf Zibis Ulf.Zibis at gmx.de
Tue May 12 18:25:15 UTC 2009

Sherman, thanks for verifying my suggestions.

(1) simplify the "plane number" byte check by adding a new static array of cnspToIndex[16] for decoder What you think about:

        int cnsPlane = sa[sp +1] ^ 0xa0;
        if (cnsPlane > 0xf ||
                       (cnsPlane = cnspToIndex[cnsPlane]) < 0)
            return CoderResult.malformedForLength(2);

or maybe (to force LoadUB, which may be faster than sign extension to int): int cnsPlane = (sa[sp +1] ^ 0xa0) && 0xff;

or maybe use byte[] (to force LoadUB, which may be faster than sign extension to int): byte cnsPlane = (byte)(sa[sp +1] ^ 0xa0);

or simply:

   static final byte[] cnspToIndex = new byte[0x100];
   static {
       Arrays.fill(cnspToIndex, -1);
       cnspToIndex[0xa2] = 1; cnspToIndex[0xa3] = 2;

cnspToIndex[0xa4] = 3; cnspToIndex[0xa5] = 4; cnspToIndex[0xa6] = 5; cnspToIndex[0xa7] = 6; cnspToIndex[0xaf] = 7; }

        if ((cnsPlane = cnspToIndex[sa[sp + 1] && 0xff]) < 0)
            return CoderResult.malformedForLength(2);

*** Question: Why you code:

               } else if ((byte1 & MSB) == 0) {  // ASCII  G0

instead of:

               } else if (byte1 >= 0) {  // ASCII  G0

???

-Ulf

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