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

[Martin Buchholz]

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
>>
>>
>
>