On Sunday, 1 December 2013 at 04:11:57 UTC, Simen Kjærås wrote:
On 2013-12-01 04:46, Craig Dillabaugh wrote:
Since questions about calling C from D seem to be popular
today, I
thought I would throw this one out there.
I am trying to call a C function which takes as parameters
several
arrays of doubles. It is valid to have some arrays passed a
NULL
pointers in the C code.
To call this from D I've come up with the following, but it
seems like a
bit of a hack.
double[] x1 = [ 2.4, 3.7, 9.7, 4.5 ];
double[] y1 = [ 2.4, 9.8, 9.1, 3.4 ];
double[] empty;
SHPObject*[] shape_ptrs;
shape_ptrs ~= SHPCreateSimpleObject( SHPT_POLYGON,
to!int(x1.length),
x1.ptr, y1.ptr, empty.ptr );
It should be clear what is going on. A POLYGON is defined as
a set of
points (provided as arrays of doubles), with X,Y and optional Z
coordinates.
In this case I want a 2D polygon, so I want the final Z array
to be
empty.
I wanted to just write 0 as the final parameter, but that
didn't work, so
I tried to!(double*)(0), and that didn't make the compiler
happy either.
I guess using the empty.ptr bit makes sense, in that the final
array is
meant to be empty, so pass it a pointer to an empty array.
But it seems
a bit hackish that I need to declare an additional empty array
just to
call this function.
Is there an accepted 'proper' way of passing NULL pointers to C
functions from D?
Well, there is null.
--
Simen
Simen and Mike. Thanks!
Now I feel stupid.
