use of Unsafe for ASCII detection

Andrew Haley aph at
Thu Jan 7 10:04:43 UTC 2016

On 06/01/16 23:21, Martin Buchholz wrote:

> That is, the Unsafe code is 3x faster than the simple code.  The
> ByteBuffer code used to be 2x slower and is now 2x faster - well
> done - crowd goes wild!

Why, thank you.

> I see it uses new and well-hidden Unsafe.getLongUnaligned ... all
> the performance fanatics want to use that, but y'all don't want to
> give it to us.  And we don't want to allocate a temp ByteBuffer
> object.  What to do?

If you allocate a temp ByteBuffer object carefully so that it does not
escape, it will be removed and you should get the same code as
directly using Unsafe.  I certainly tested it during the work on
Unsafe.getXXUnaligned and it was the same.  I'll have a look at your


More information about the core-libs-dev mailing list