Is it possible to get an address of a struct in the Library or Contract without using mapping?

Question

[Q] I was wondering is it possible to get an address of a struct on the memory space? Inside initialise() function after the Node object creation, I want to get is address if it is possible. Since between contracts I can only transfer its address value.

Thank you for your valuable time and help.

library LinkedList {
    uint80 constant None = uint80(0); /// NULL value.                                                           

    struct data {
        Node head;
        Node[] node_array;
    }

    struct Node {
        string data;
        uint80 prev;
        uint80 next;
    }

    function initialize(data storage self){
        self.head = Node({prev: None, next: None, data: "",});
        self.head.next = /// self.head's address.        
    }        
}

Inside initialize() following code piece works:

Node s = self.node_array[index];
uint addr;
assembly {
    addr := s
}

Inside initialize() the following code piece does not work:

Error: Expected elementary inline assembly operation.

self.head = Node({prev: None, next: None, data: 10,});

uint addr;
assembly {
    addr := self.head   
}

or

Node new_node;
new_node.data = d;
new_node.next = h.next;
new_node.prev = h.own;

uint newnode_addr;
assembly {
   newnode_addr := new_node
}

newnode_addr returns 0 instead of a valid address.

I am not able to do following assignment also:

Error: Type struct Node memory is not implicitly convertible to expected type struct Node storage pointer.

Node newnode = Node({prev: None, next: None, data: 10,});

Answer 1

Why are you trying to get a pointer to the struct? Are you trying to get a copy of that struct into another contract? Is this what you're meaning by between contracts I can only transfer its address value?

You can write constant functions which can query the state of a given contract, and will easily allow you to expose the node memory to other contracts. For example getDataForNode(i) which can return the data field of a given node at index i.