PERL Miscellaneous - Nww Data types

Author

Nww Data types

Guenther Sohler

2005-04-27, 8:57 am

Hallo Group,

Due to your great Help in the last Days I was able to
use embedded perl in c for my program. I was also able to
register my own c functions with my perl interpreter useing newXS.
Now I am wondering if its even possible to integrate my own
data type. At the moment I am calculating with integers and floats and
strings. and it works very well.
But due to the graphical nature of my prg it would be nice, if I could
add a new data type eg Point, which contains two floats(x and y)
or a list of Points, (or maybe a list of strings).
Is it possible ?
Maybe I would finally write

$pt=convert_point($x,$y);

How can I implement new data tyes ?

Tassilo v. Parseval

2005-04-27, 8:57 am

Also sprach Guenther Sohler:
> Hallo Group,
>
> Due to your great Help in the last Days I was able to
> use embedded perl in c for my program. I was also able to
> register my own c functions with my perl interpreter useing newXS.
> Now I am wondering if its even possible to integrate my own
> data type. At the moment I am calculating with integers and floats and
> strings. and it works very well.
> But due to the graphical nature of my prg it would be nice, if I could
> add a new data type eg Point, which contains two floats(x and y)
> or a list of Points, (or maybe a list of strings).
> Is it possible ?
> Maybe I would finally write
>
> $pt=convert_point($x,$y);
>
> How can I implement new data tyes ?

At this point you will probably need a class other than main to bless
the point object into. I'd suggest writing a class in XS for a point:

typedef struct {
float x, y;
} Point;

MODULE = Point PACKAGE = Point

Point*
new (char *CLASS, float x, float y)
CODE:
{
New(0, RETVAL, Point, 1);
RETVAL->x = x;
RETVAL->y = y;
}
OUTPUT:
RETVAL

float
x (Point *pt)
CODE:
{
RETVAL = pt->x;
}
OUTPUT:
RETVAL

# likewise for y and other methods

Plus, you will need a typemap file:

Point* POINT

OUTPUT
POINT
sv_setref_pv( $arg, CLASS, (void*)$var );

INPUT
POINT
if( sv_isobject($arg) && (SvTYPE(SvRV($arg)) == SVt_PVMG) )
$var = ($type)SvIV((SV*)SvRV( $arg ));
else{
warn( \"${Package}::$func_name() -- $var is not a blessed SV reference\" );
XSRETURN_UNDEF;
}

As always, do a

xsubpp -typemap typemap_file Point.xs

and copy the generated functions into your C program and give it a name
of your choice with newXS. If you insist on main::convert_point($x, $y)
being the constructor, change the XSUB for Point::new to:

Point*
convert_point(float x, float y)
PREINIT:
char *CLASS = "Point";
CODE:
/* rest is unchanged */

The point object itself will still be blessed into the class 'Point',
though. But the programmer writing scripts for your program will usually
not notice this because all he will do is things like this:

my $pt = convert_point(1.0, 0.5);
print $pt->x;

Note that instance methods, such as x(), need to live in the Point::
namespace, so your newXS lines now should read:

newXS("main::convert_point", XS_Point__new, file);
newXS("Point::x", XS_Point__x, file);
...

Tassilo
--
use bigint;
$n=7142335034377028016139702633033737113
9054411854220053437565440;
$m=-8,;;$_=$n&(0xff)<<$m,,$_>>=$m,,print+chr,,while(($m+=8)<=200);

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