Method resolve_array_index

core/src/vm/context.rs:301–329

Resolves array subscripts and computes the flat index for `arr_reg` with subscripts read from registers starting at `first_sub_reg`. Returns `Some((heap_idx, flat_idx))` on success, or `None` if an exception was set.

(
        &mut self,
        arr_reg: Register,
        first_sub_reg: Register,
        heap: &Heap,
    )

    ///
    /// Returns `Some((heap_idx, flat_idx))` on success, or `None` if an exception was set.
    fn resolve_array_index(
        &mut self,
        arr_reg: Register,
        first_sub_reg: Register,
        heap: &Heap,
    ) -> Option<(usize, usize)> {
        let arr_ptr = DatumPtr::from(self.get_reg(arr_reg));
        let heap_idx = arr_ptr.heap_index();
        let array = match heap.get(heap_idx) {
            HeapDatum::Array(a) => a,
            _ => unreachable!("Register must point to an array"),
        };

        let ndims = array.dimensions.len();
        let (_, first_idx) = first_sub_reg.to_parts();
        let mut subscripts = Vec::with_capacity(ndims);
        for i in 0..unchecked_usize_as_u8(ndims) {
            let sub_reg = Register::local(first_idx + i).unwrap();
            subscripts.push(self.get_reg(sub_reg) as i32);
        }

        match array.flat_index(&subscripts) {
            Ok(flat_idx) => Some((heap_idx, flat_idx)),
            Err(e) => {
                self.set_exception(e);
                None
            }
        }
    }

    /// Registers that the instruction being processed threw an exception `message`.
    ///