/* id-key for ext magic */
#define ALT_EXT_ALTER 6693

MODULE = Alter          PACKAGE = Alter

SV*
ego(...)
PROTOTYPE: $@
CODE:
    SV* obj = ST(0);
    SV* given = items > 1 ? ST(1) : NULL;
    HV* alt_tab;
    SV** alt_ptr;
    if (SvROK(obj)) {
        char* class = CopSTASHPV(PL_curcop);
        SV* self = SvRV(obj);
        MAGIC* mg;
        if (SvTYPE(self) < SVt_PVMG)
            SvUPGRADE(self, SVt_PVMG);
        for (mg = SvMAGIC(self); mg; mg = mg->mg_moremagic) {
            if ((mg->mg_type == PERL_MAGIC_ext) &&
                (mg->mg_private == ALT_EXT_ALTER)
           ) break;
        }
        if (!mg) {
            alt_tab = newHV();
            mg = sv_magicext(self, (SV*)alt_tab, PERL_MAGIC_ext, NULL, NULL, 0);
            mg->mg_private = ALT_EXT_ALTER;
        } else {
            alt_tab = (HV*)mg->mg_obj;
        }
        if (alt_ptr = hv_fetch(alt_tab, class, strlen(class), 0)) {
            RETVAL = newRV_inc(SvRV( *alt_ptr));
        } else {
            if (!given) { /* should probably croak, but we decree a hash */
                given = newRV_inc((SV*)newHV());
            } else {
                /* need a non-mortal ref */
                given = newRV_inc(SvRV(given));
            }
            hv_store(alt_tab, class, strlen(class), SvREFCNT_inc(given), 0);
            RETVAL = given;
        }
    } else {
        RETVAL = NULL;
    }
OUTPUT: RETVAL