Small bit of XS to retrieve the headers from a tabix indexed file such as a VCF file. Method returns an array reference.

TabixHeaders.xs

SV*
tabix_headers(t)
	tabix_t *t
  PREINIT:
  ti_iter_t iter;
  const char *s;
  int len;
  CODE:
  if (ti_lazy_index_load(t) < 0) {
    fprintf(stderr,"[tabix] failed to load the index file.\n");
    return;
  }
  const ti_conf_t *idxconf = ti_get_conf(t->idx);
  iter = ti_query(t, 0, 0, 0);
  AV *av = newAV();
  while ((s = ti_read(t, iter, &len)) != 0) {
    if ((int)(*s) != idxconf->meta_char) break;
    av_push(av, newSVpv(s,0));
  }
  ti_iter_destroy(iter);
  RETVAL=newRV_noinc(av);
  OUTPUT:
  RETVAL