DBM#[]=

static VALUE
fdbm_store(VALUE obj, VALUE keystr, VALUE valstr)
{
    datum key, val;
    struct dbmdata *dbmp;
    DBM *dbm;

    fdbm_modify(obj);
    keystr = rb_obj_as_string(keystr);
    valstr = rb_obj_as_string(valstr);

    key.dptr = RSTRING_PTR(keystr);
    key.dsize = RSTRING_DSIZE(keystr);

    val.dptr = RSTRING_PTR(valstr);
    val.dsize = RSTRING_DSIZE(valstr);

    GetDBM2(obj, dbmp, dbm);
    dbmp->di_size = -1;
    if (dbm_store(dbm, key, val, DBM_REPLACE)) {
        dbm_clearerr(dbm);
        if (errno == EPERM) rb_sys_fail(0);
        rb_raise(rb_eDBMError, "dbm_store failed");
    }

    return valstr;
}