[Swig-devel] [PATCH] SWIG_AsCharPtrAndSize, Perl and binary data Was: %cstring_output_allocate_size and perl

[Rene R. <re...@ex...>]

Hi,

One of this patches would be nice to have upstream in a upcomming SWIG
release. The one I prefer:

=2D-- Lib/perl5/perlstrings.swg	2006-09-04 11:53:14.000000000 +0200
+++ new2	2006-09-04 11:52:43.000000000 +0200
@@ -44,15 +44,7 @@
 {
   SV *obj =3D sv_newmortal();
   if (size && carray) {
=2D    if (carray[size - 1] =3D=3D 0) {
=2D      sv_setpv(obj, carray);
=2D    } else {
=2D      char *tmp =3D %new_array(size + 1, char);
=2D      memcpy(tmp, carray, size);
=2D      tmp[size] =3D 0;
=2D      sv_setpv(obj, tmp);
=2D      %delete_array(tmp);
=2D    }
+    sv_setpvn(obj, carray, size);
   } else {
     sv_setsv(obj, &PL_sv_undef);
   }

An alternative that would also be "acceptable", though it would mess binary
data by adding a superflous and potentially irritating terminating zero ...

=2D-- Lib/perl5/perlstrings.swg	2006-09-04 11:53:14.000000000 +0200
+++ new1	2006-09-04 11:53:48.000000000 +0200
@@ -45,12 +45,12 @@
   SV *obj =3D sv_newmortal();
   if (size && carray) {
     if (carray[size - 1] =3D=3D 0) {
=2D      sv_setpv(obj, carray);
+      sv_setpvn(obj, carray, size);
     } else {
       char *tmp =3D %new_array(size + 1, char);
       memcpy(tmp, carray, size);
       tmp[size] =3D 0;
=2D      sv_setpv(obj, tmp);
+      sv_setpvn(obj, tmp, size+1);
       %delete_array(tmp);
     }
   } else {

See also:

On Monday 04 September 2006 09:24, Rene Rebe wrote:
> Hello again,
>
> On Sunday 03 September 2006 22:03, Rene Rebe wrote:
> > Hi all,
> >
> > while using SWIG to bridge a C++ (imaging) library with e.g. Perl I run
> > into a problem with &cstring_output_allocate_size.
> >
> > Among the functions I export is one to store the encoded image in
> > the system memory.
> >
> > According the SWIG documentation %cstring_output_allocate_size
> > should be what I need "This macro is used to return strings that are
> > allocated within the program and ... the returned string may contain
> > binary data.".
> >
> > However in my case the Perl scalar I get is terminated at the first
> > embedded binary 0.
> >
> > I use Perl-5.8.8 and SWIG-1.3.29.
> >
> > Fragments of my code so far (simplified for the list):
> >
> > #ifdef SWIG
> > %cstring_output_allocate_size( char ** s, int *slen, free(*$1))
> > #endif
> > void encodeImage (char **s, int *slen,
> > 		  Image* image, const char* codec, int quality,
> > 		  const char* compression);
> >
> > ...
> >
> > void encodeImage (char **s, int *slen,
> > 		  Image* image, const char* codec, int quality,
> > 		  const char* compression)
> > {
> >   // just for testing ...
> >   std::ostringstream stream (""); // empty string to start with
> >
> >   stream << '1'; <<  '2' << '\0' << '3' << '4';
> >   stream.flush();
> >
> >   std::cerr << "c++> size: " << stream.str().size() << std::endl;
> >
> >   char* payload =3D (char*) malloc (stream.str().size());
> >   memcpy (payload, stream.str().c_str(), stream.str().size());
> >
> >   *s =3D payload;
> >   *slen =3D stream.str().size();
> > }
> >
> > and when I call it from Perl:
> >
> > $image_bits =3D ExactImage::encodeImage ($image, "jpeg", 80, "");
> > print "perl> size: " . length($image_bits) . "\n";
> >
> > I get:
> >
> > c++> size: 5
> > perl> size: 2
> >
> > When I look at the code generated from SWIG I noticed:
> >
> >       if (argvi >=3D items) EXTEND(sp,1);  ST(argvi) =3D
> > SWIG_FromCharPtrAndSize(*arg1,*arg2); argvi++  ;
> >
> > and wonder if that function is the right thing to call there as
> > it only sets the pointer and no size in the target object.
> >
> > Can someone confirm I hit a SWIG bug to be fixed or is there
> > some other function that I should use instead?
> >
> > Thanks in advance,
>
> Now, when I go on and tweak the SWIG generated file to use sv_setpvn
> instead of just svn_setpv:
>
> --- api-perl-wrap.cc    2006-09-04 09:21:11.000000000 +0200
> +++ api-perl-wrap.cc.fixed      2006-09-04 09:21:05.000000000 +0200
> @@ -1630,12 +1630,12 @@
>    SV *obj =3D sv_newmortal();
>    if (size && carray) {
>      if (carray[size - 1] =3D=3D 0) {
> -      sv_setpv(obj, carray);
> +      sv_setpvn(obj, carray, size);
>      } else {
>        char *tmp =3D (new char[size + 1]);
>        memcpy(tmp, carray, size);
>        tmp[size] =3D 0;
> -      sv_setpv(obj, tmp);
> +      sv_setpvn(obj, carray, size);
>        delete[] tmp;
>      }
>    } else {
>
> I get my data back into Perl as intended.
>
> Again, do I misuse the SWIG typemaps or is this a SWIG bug that
> should be addressed properly?
>
> Yours,

=2D-=20
  Ren=E9 Rebe - ExactCODE - Berlin (Europe / Germany)
  http://exactcode.de | http://t2-project.org | http://rene.rebe.name
  +49 (0)30 / 255 897 45