Rewrite of IBM doublebyte charsets (original) (raw)

Ulf Zibis Ulf.Zibis at gmx.de
Thu May 14 22:45:43 UTC 2009

Am 15.05.2009 00:03, Xueming Shen schrieb:

What is the "XOR approach"? I might have miss it. I'm happy to try it out. OK, the "3 times computing" and "compare <0" are the good hint to improve, the latest one looks like

I'm afraid, you really missed it. See my post from 12.05.2009 20:25 CEST ;-) I mean:

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

or maybe (to force LoadUB (Bug ID 6797305), 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 byte cnsPlane = (byte)((sa[sp +1] && 0xff) ^ (0xa0 && 0xff)); // don't know if this make a difference

But anyway, I think, static final byte[] cnspToIndex = new byte[0x100]; ...

would be the fastest.

180 int cnsPlane = sa[sp +1];

I guess this is worse, but definitely not better, than int cnsPlane = sa[sp +1] & 0xff;

Reason: http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6797305

181 if ((cnsPlane & 0xf0) != 0xa0 || 182 (cnsPlane = cnspToIndex[cnsPlane&0x0f]) < 0) 183 return CoderResult.malformedForLength(2);

And it definitely is better than the previous one, thanks! :-) Now maybe you might want to eye the IBM db webrev, any change would benefit several charsets:-)

... I'm doing that since 2 hours. :-)

-Ulf

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