IO::Buffer.size_of

static VALUE
io_buffer_size_of(VALUE klass, VALUE buffer_type)
{
    if (RB_TYPE_P(buffer_type, T_ARRAY)) {
        size_t total = 0;
        for (long i = 0; i < RARRAY_LEN(buffer_type); i++) {
            total += io_buffer_buffer_type_size(RB_SYM2ID(RARRAY_AREF(buffer_type, i)));
        }
        return SIZET2NUM(total);
    }
    else {
        return SIZET2NUM(io_buffer_buffer_type_size(RB_SYM2ID(buffer_type)));
    }
}