review request for 6798511/6860431: Include functionality of Surrogate in Character

[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
>>>>         
>>>       
>>