Method cast

crates/vm/src/builtins/memory.rs:833–909

(&self, args: CastArgs, vm: &VirtualMachine)

    #[pymethod]
    fn cast(&self, args: CastArgs, vm: &VirtualMachine) -> PyResult<PyRef<Self>> {
        self.try_not_released(vm)?;
        if !self.desc.is_contiguous() {
            return Err(vm.new_type_error("memoryview: casts are restricted to C-contiguous views"));
        }

        let CastArgs { format, shape } = args;

        if let OptionalArg::Present(shape) = shape {
            if self.desc.is_zero_in_shape() {
                return Err(vm.new_type_error(
                    "memoryview: cannot cast view with zeros in shape or strides",
                ));
            }

            let tup;
            let list;
            let list_borrow;
            let shape = match shape {
                Either::A(shape) => {
                    tup = shape;
                    tup.as_slice()
                }
                Either::B(shape) => {
                    list = shape;
                    list_borrow = list.borrow_vec();
                    &list_borrow
                }
            };

            let shape_ndim = shape.len();
            // TODO: MAX_NDIM
            if self.desc.ndim() != 1 && shape_ndim != 1 {
                return Err(vm.new_type_error("memoryview: cast must be 1D -> ND or ND -> 1D"));
            }

            let mut other = self.cast_to_1d(format, vm)?;
            let itemsize = other.desc.itemsize;

            // 0 ndim is single item
            if shape_ndim == 0 {
                other.desc.dim_desc = vec![];
                other.desc.len = itemsize;
                return Ok(other.into_ref(&vm.ctx));
            }

            let mut product_shape = itemsize;
            let mut dim_descriptor = Vec::with_capacity(shape_ndim);

            for x in shape {
                let x = usize::try_from_borrowed_object(vm, x)?;

                if x > isize::MAX as usize / product_shape {
                    return Err(vm.new_value_error("memoryview.cast(): product(shape) > SSIZE_MAX"));
                }
                product_shape *= x;
                dim_descriptor.push((x, 0, 0));
            }