How to use perlapi/ XS in an XSUB for array element insertion and removal

Question

I would like to insert and remove elements into an existing Perl array passed into a XSUB.

perlapi has av_push, av_pop, av_fetch, av_store and friends for array manipulation. I was hoping for av_insert or av_splice or similar functions, but these don't seem to exist.

There is av_delete, but the documentation describes this as replacing the element with undef, not actually removing the item from the array.

Of course I could manually resize the array (av_extend) and loop moving elements (av_fetch/av_store).

Is there an existing API function I can use? If so a pointer to its documentation would be great.

Answer 1

void av_insert( pTHX_ AV * av, Size_t key, SV * sv ) {
#define av_insert( a, b, c ) av_insert( aTHX_ a, b, c )
   sv = newSVsv( sv );

   Size_t count = av_count( av );
   if ( key < count ) {
      av_extend( av, count );
      SV ** a = AvARRAY( av );
      memmove( a+key, a+key+1, sizeof( SV * ) * ( count - key ) );
      a[ key ] = sv;
   } else {
      *av_fetch( av, key, 1 ) = sv;
   }
}