Sponsor for 6666666: A better implementation of Character.isSupplementaryCodePoint

[Ulf Zibis]

Sherman,

I know, your time ...

... but maybe someone is needed for sponsor here: 
https://bugs.openjdk.java.net/show_bug.cgi?id=100132

Could you do this?

Much thanks,

-Ulf


Am 10.03.2010 19:23, schrieb Xueming Shen:
> approved.
>
> I don't have a spare ws right now.so please just push, it's almost 
> there:-)
>
> sherman
>
> Martin Buchholz wrote:
>> Here's the proposed fix for
>> 6931812: A better implementation of sun.nio.cs.Surrogate.isBMP(int)
>>
>> http://cr.openjdk.java.net/~martin/webrevs/openjdk7/isBMPCodePoint/
>>
>> I changed the name to isBMPCodePoint in preparation for moving
>> it to Character.java.
>> (Sherman, perhaps you would like to take on that followon task?)
>>
>> Sherman, please approve.
>>
>> Martin
>>
>> On Sat, Mar 6, 2010 at 13:00, Ulf Zibis <Ulf.Zibis at gmx.de> wrote:
>>> Very fast Sherman, much thanks.
>>>
>>> Could you set the bug to accepted and evaluated, so my patch will 
>>> have a
>>> chance to get into the code base?
>>>
>>> -Ulf
>>>
>>>
>>> Am 03.03.2010 20:11, schrieb Xueming Shen:
>>>> #6931812
>>>>
>>>> Martin Buchholz wrote:
>>>>> Sherman, would you like to file bugs for Ulf's improvements?
>>>>>
>>>>> On Wed, Mar 3, 2010 at 02:44, Ulf Zibis <Ulf.Zibis at gmx.de> wrote:
>>>>>> Am 03.03.2010 09:00, schrieb Martin Buchholz:
>>>>>>> Keep in mind that supplementary characters are extremely rare.
>>>>>>>
>>>>>> Yes, but many API's in the JDK are used rarely.
>>>>>> Why should they waste memory footprint / perform bad, 
>>>>>> particularly if it
>>>>>> doesn't cost anything.
>>>>> I admire your perfectionism.
>>>>>
>>>>>>> Therefore the existing implementation
>>>>>>>
>>>>>>>  return codePoint>= MIN_SUPPLEMENTARY_CODE_POINT
>>>>>>> &&  codePoint<= MAX_CODE_POINT;
>>>>>>>
>>>>>>> will almost always perform just one comparison against a constant,
>>>>>>> which is hard to beat.
>>>>>>>
>>>>>> 1. Wondering: I think there are TWO comparisons.
>>>>>> 2. Those comparisons need to load 32 bit values from machine code,
>>>>>> against
>>>>>> only 8 bit values in my case.
>>>>> It's a good point.  In the machine code, shifts are likely to use
>>>>> immediate values, and so will be a small win.
>>>>>
>>>>> int x = codePoint >>> 16;
>>>>> return x != 0 && x < 0x11;
>>>>>
>>>>> (On modern hardware, these optimizations
>>>>> are less valuable than they used to be;
>>>>> ordinary integer arithmetic is almost free)
>>>>>
>>>>> Martin
>
>