Linked list in contract storage?

Question

I'd like to implement a linked list in contract storage

Something link this:

contract A {

  struct LinkedList {
    uint    value;
    LinkedList storage next; // What goes here? Can I reference the storage of the next struct in solidity?
  }
}

Answer 1

Within your struct you will want to keep track of the next item in the list

struct LinkedList {
    bytes32 next;
    uint value;
}

Then keep track of the lenth + head of the list and store the structs in a mapping with their ID's

uint public length;
bytes32 public head;
mapping (bytes32 => LinkedList) public listObjects;

You can add entries like this:

function addEntry(uint _number) public returns (bool) {
    LinkedList memory object = LinkedList(head,_number);
    bytes32 id = sha3(_number, length, block.timestamp);
    listObjects[id] = object;
    head = id;
    length++; 
}

Answer 2

You do not need a linked list because arrays in Solidity are automatically expanded and this would just add gas execution overhead.