Re: wchar_t and XS

On Mon, Feb 27, 2012 at 04:29:57PM +0000, Alberto Simões wrote:
> I googled for that, and found a typemap, but I do not understand how  
> typemaps work.

Take a look at the Foo.c file that is generated off of your Foo.xs file.  XS
"typemaps" are not very sophisticated -- they're just strings that get
inserted into a template for an XS function and then expanded.  It so happens
that some variables are available ($var, $arg), but you seem to be using those
right already.

> My typemap looks like:
>
> ------ 8< ----------
>
>
> TYPEMAP
> wchar_t
>
> INPUT
> T_WCHAR
>    {
>    // Alloc memory for wide char string. This could be a bit more
>    // then necessary.
>    Newz(0, $var, SvLEN($arg), wchar_t);
>
>    U8* src = (U8*) SvPV_nolen($arg);
>    wchar_t* dst = (wchar_t*) $var;
>
>    if (SvUTF8($arg)) {
>       // UTF8 to wide char mapping
>       STRLEN len;
>       while (*src) {
>           *dst++ = utf8_to_uvuni(src, &len);
>           src += len;
>       }
>    } else {
>        // char to wide char mapping
>        while (*src) {
>            *dst++ = (wchar_t) *src++;
>        }
>    }
>    *dst = 0;
>    SAVEFREEPV($var);
>    }
> ------ 8< -------------

Looks good to me, aside from concerns about 16-bit wchar_t systems and code
points above the BMP. 

(Although I don't know what SAVEFREEPV does, I assume it sets up the memory
you allocated to be freed once the function you are wrapping returns.)

Cheers,

Marvin Humphrey