Thread: 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;
         }
      }