Re: VM support for GetDirectBufferAddress

[Michael Koch]

Am Donnerstag, 6. Januar 2005 18:01 schrieb Archie Cobbs:
> Michael Koch wrote:
> >>Hmm.. since this code will be so Classpath-specific, perhaps
> >>Classpath should provide the code to handle it.
> >
> > this means putting another layer into this. The VM needs only to
> > do aa simple malloc() operation and the give the result to a
> > constructor of java.nio.DirectByteBufferImpl (that's the code
> > fore
> > NewDirectByteBuffer() in human language). Its too trivial.
>
> Agreed. I was only talking about the two GetDirectBuffer*()
> functions.
>
> > The other
> > two methods are similar trivial. Putting a special layer into
> > this is too much overhead IMO. What we can do s to provide
> > default implementations for these methods. Then was VM supporting
> > JNI can use them. Each VM not supporting JNI don't needs them
> > anyway.
>
> If they have to handle views, they don't seem "trivial" to me, but
> then again I'm unfamiliar with this stuff.

I have a patch here which makes it easy. I just don't wanna commit it 
before the release.

> What is the "trivial" algorithm I need to implement then? It
> doesn't seem obvious, and seems dependent on the particulars of
> Classpath's java.nio classes. But maybe I'm missing something.

for GetDirectBufferAddress: Return the pointer stored in 
java.nio.Buffer.address (doesn't exist yet).

for GetDirectBufferCapacity: Return the value of 
java.nio.Buffer.capacity or -1 if java.nio.Buffer.address is NULL.

> I'd be perfectly happy using the default implementation if one
> existed, at least to get an initial implementation done.

I will provide it.


Michael
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