Rewrite of IBM doublebyte charsets (original) (raw)

Ulf Zibis Ulf.Zibis at gmx.de
Tue May 12 19:00:24 UTC 2009

Am 12.05.2009 20:31, Xueming Shen schrieb:

Ulf Zibis wrote:

Sherman, thanks for verifying my suggestions.

> (1) simplify the "plane number" byte check by adding a new static array of cnspToIndex[16] for decoder 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); considered that, but ended up thinking it might not really worth the 0x100 bytes:-) at least based on my measurement.

Well, int[16] is even 64 bytes, and loop performance should be more important here than wasting 196 bytes considering ~227,000 Bytes for the mapping tables?

*** Question: Why you code: } else if ((byte1 & MSB) == 0) { // ASCII G0 instead of: } else if (byte1 >= 0) { // ASCII G0 I believe this line was written 10 years ago, so I have no idea (or forgot) why we picked this one, my guess is the code might be a little easier to read with "MSB"...you think the >=0 is better or faster/

Yes, I think it's also faster, as loading of "MSB" + AND would be saved. Not sure if HotSpot will detect the shortcut!

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