[Nestedvm] Possible to pass floats in call in NestedVM?

ehrmann at gmail.com ehrmann at gmail.com
Tue Mar 19 20:31:16 EDT 2013


Well that's...lossy.

On Mar 19, 2013, at 5:22 PM, skinhat skinhat <skinhat at hotmail.com> wrote:

> I looked at the SQLLite code and looks like they convert floats to strings and back. For example in NestedDB.java of SQLLite source its got:
> 
> 
>     synchronized int bind_double(long stmt, int pos, double v) throws SQLException {
>         return bind_text(stmt, pos, Double.toString(v)); // TODO
>     }
> 
> 
>    synchronized double value_double(Function f, int arg) throws SQLException {
>         return Double.parseDouble(value_text(f, arg)); // TODO
>     }
> 
> I might have to do the same.
> 
> > Date: Tue, 19 Mar 2013 23:11:22 +0100
> > From: fratz at inf.uni-konstanz.de
> > To: skinhat at hotmail.com
> > Subject: Re: [Nestedvm] Possible to pass floats in call in NestedVM?
> > 
> > Hi,
> > 
> > Thinking about it, it may be possible to do
> > float foo = *((float *) &integer);
> > in C to get that float back, but I never tried anything like that.
> > 
> > However, there is a sqlite java interface (sqlite jdbc) that uses nestedvm,
> > and that thing definitely has to pass floating point values to C, so it may
> > be worth having a look at the relevant code.
> > 
> > regards
> > Matthias
> > 
> 
> Date: Mon, 18 Mar 2013 14:19:36 -0700
> Subject: Re: [Nestedvm] Possible to pass floats in call in NestedVM?
> From: ehrmann at gmail.com
> To: skinhat at hotmail.com
> CC: nestedvm at lists.hcoop.net
> 
> On Mon, Mar 18, 2013 at 1:04 PM, skinhat skinhat <skinhat at hotmail.com> wrote:
> I have tried converting the float into raw int bits:
> ia[i]=Float.floatToRawIntBits(f);
> 
> in runtime.java but just comes out to a huge integer.
>  
>  That's probably correct. Floats are stored very differently than ints, and the int version of a float will always look nothing like the float. The only exception I can think of is positive zero looking like an int zero. Negative zero looks completely different.
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