Code notes

Using Array Value (AV) functions, it's possible to access Perl arrays in C. The following code snippet copies integer values from Perl into a typical C int array.

    void
    set_site_divider(site_divider)
                    AV* site_divider
            CODE:
                    I32 l = av_len(site_divider) + 1;
                    unsigned int *cpy = malloc(sizeof(*cpy) * l);
  
                    int i = 0;
                    for (; i < l; i++) {
                            SV *site = av_shift(site_divider);
                            cpy[i] = SvIV(site);
                    }
                    set_site_divider(cpy);

av_shift pops the first scalar value (SV) from the array, and SvIV returns the int value stored in the scalar.

The document perlguts contains more functions to manipulate SV's and AV's.

For referance, the C function:

   void set_site_divider(unsigned int *s) {
            site_divider = s;
   }

And the function call from perl:

   DocInfo::Store::set_site_divider([5, 6, 7, 8, 9]);

:o

ABC = ABC
PRINT ABC

PPCODE allows us to modify the return stack of the function call, like following:

    void
    docinfo_get(doc_id)
                    unsigned int doc_id
            INIT:
                    static docinfo *nfo;
           PPCODE:
                   docinfo_get(&nfo, doc_id);
                   XPUSHs(sv_2mortal(newSVnv(nfo->word_count)));
                   XPUSHs(sv_2mortal(newSViv(nfo->score)));
                   XPUSHs(sv_2mortal(newSViv(nfo->site_id)));
                   XPUSHs(sv_2mortal(newSVnv(nfo->rating)));
                   XPUSHs(sv_2mortal(newSVnv(nfo->img_size)));

docinfo_get loads values into the struct docinfo, then these values are pushed as a list out to perl. newSViv is a scalar integer value and newSVnv is a numeric value.

For referance, docinfo_get just loads a value from a glib hash table:

  void docinfo_get(docinfo **dst, guint doc_id) {
           *dst = g_hash_table_lookup(doc_hash, &doc_id);
   }

The function call from perl:

  my ($wc, $score, $site_id, $rating, $img_size) = DocInfo::Store::docinfo_get($docid);