doubly linked lists conversion

Hey guys im trying to convert this singly linked list code into a doubly linked list could someone have a look at the code and see if its correct and maybe give some advice.

Thankyou

Code:

---

typedef struct category* CategoryTypePtr;
typedef struct item* ItemTypePtr;

/* Structure definitions. */
typedef struct price
{
  unsigned dollars;
  unsigned cents;
} PriceType;

typedef struct item
{
  char itemID[ID_LEN + 1];
  char itemName[MAX_NAME_LEN + 1];
  PriceType prices[NUM_PRICES];
  char itemDescription[MAX_DESC_LEN + 1];
  ItemTypePtr nextItem;
  ItemTypePtr prevItem;
 
} ItemType;

typedef struct category
{
  char categoryID[ID_LEN + 1];
  char categoryName[MAX_NAME_LEN + 1];
  char drinkType;      /* (H)ot or (C)peold. */
  char categoryDescription[MAX_DESC_LEN + 1];
  CategoryTypePtr nextCategory;
  CategoryTypePtr prevCategory;
  ItemTypePtr headItem;
  unsigned numItems;
} CategoryType;

typedef struct gjc
{
  CategoryTypePtr headCategory;
  unsigned numCategories;
} GJCType;

---

Code:

---

current = menu->headCategory;

        /* Find the right category for the item to be inserted */
        while(current != NULL)
        {
            /* If the right category has been found for the item to be
              inserted. */
            if(strcmp(current->categoryID,categoryIDcopy) == 0)
            {
              submenuCurrent = current->headItem;

              /* Increase the number of items when an item is added */
              current->numItems++;

              /* If nothing exists in the category, add to the head of the
                  item list. */
              if(submenuCurrent == NULL)
              {
                  submenuCurrent = submenuNode;
                  current->headItem = submenuCurrent;
                  submenuCurrent->nextItem = NULL;
              }
              else
              {
                  submenuPrevious = NULL;

                  /* Find the right position to insert the item. */
                  while((submenuCurrent != NULL) &&
                        strcmp(submenuCurrent->itemName,
                                submenuNode->itemName) < 0)
                  {
                    submenuPrevious = submenuCurrent;
                    submenuCurrent->prevItem = submenuPrevious;
                    submenuCurrent = submenuCurrent->nextItem;
                  }

                  /* If inserting at the head of the list. */
                  if(submenuCurrent == current->headItem)
                  {
                    submenuNode->nextItem = submenuCurrent;
                    submenuCurrent = submenuNode;
                    current->headItem = submenuCurrent;
                  }

                  /* If adding to the end of the list. */
                  else if(submenuCurrent == NULL)
                  {
                    submenuPrevious->nextItem = submenuNode;
                    submenuCurrent = submenuNode;
                    submenuCurrent->nextItem = NULL;
                  }

                  /* If adding somewhere in between the list. */
                  else
                  {
                    submenuPrevious->nextItem = submenuNode;
                    submenuNode->nextItem = submenuCurrent;
                  }
              }
            }
            current = current->nextCategory;
        }
      }

---

In other words, "I didn't write the single linked list code, so I have no idea how linked lists work, so I just stuck "->prev" all over the place. Can you fix it for me?" If you actually did write it yoursef, then just make some functions that print your list backwards and forewards. If it prints everything you've input, you're probably doing it right.


Quzah.