Re: [Swig-user] C# calling a function with an array as a parameter

[David P. <dpi...@me...>]

> I am attempting to call a function like
>=20
> int sum(int inArray[], unsigned int length)
> {
>     int retval =3D 0;
>     unsigned int i =3D 0;
>     for ( i =3D 0; i<length; ++i)
>     {
>         retval +=3D inArray[i];
>     }
>     return retval;
> }
>=20
> Swig generates
>=20
>   public static int sum(SWIGTYPE_p_int inArray, int length) {
>     int ret =3D examplePINVOKE.sum(SWIGTYPE_p_int.getCPtr(inArray),
length);
>     return ret;
>   }
>=20
> but I am a bit confused about what to do with a SWIGTYPE_p_int
>=20
> I was expecting to call it with something like this:
>=20
>         int[] addArray =3D { 1, 2, 3 };
>         Console.WriteLine("Sum =3D " + sum(addArray, add.Length));
>=20
> Here is my interface file:
>=20
> /* File : example.i */
> %module example
>=20
> %inline %{
> extern int    gcd(int x, int y);
> extern double Foo;
> extern int sum(int inArray[], int length);
>=20
> %}
>=20
> Thanks

I don't know whether SWIG has any specific feature for doing this, but
in my project I cooked up a macro that will let you call sum() just as
you suggest. However, in my experience so far, it looks like the .NET
framework creates a copy of the array before passing it to the C code,
so you might want to look for a more efficient method (perhaps involving
a call to GCHandle.AddrOfPinnedObject... but I'm not sure how to
integrate such a technique into SWIG.)

%define %cs_marshal_array(TYPE, CSTYPE)
	%typemap(ctype)  TYPE[] "void*"
	%typemap(imtype,
inattributes=3D"[MarshalAs(UnmanagedType.LPArray)]") TYPE[] "CSTYPE[]"
	%typemap(cstype) TYPE[] "CSTYPE[]"
	%typemap(in)     TYPE[] %{ $1 =3D (TYPE*)$input; %}
	%typemap(csin)   TYPE[] "$csinput"
%enddef

%cs_marshal_array(bool, bool)
%cs_marshal_array(short, short)
%cs_marshal_array(unsigned short, ushort)
%cs_marshal_array(int, int)
%cs_marshal_array(unsigned int, uint)
%cs_marshal_array(long, int)
%cs_marshal_array(unsigned long, uint)
%cs_marshal_array(long long, long)
%cs_marshal_array(unsigned long long, ulong)
%cs_marshal_array(float, float)
%cs_marshal_array(double, double)