list.h

// List data type
// You may modify this file as needed; however,
// you may *NOT* modify the function prototypes or constant names.

#ifndef _LIST_H_
#define _LIST_H_
#include <stdbool.h>

#define LIST_SUCCESS 0
#define LIST_FAIL -1

typedef struct Node_s Node;
struct Node_s {
    void* pItem;
    Node* pNext;
    Node* pPrev;
};

enum ListOutOfBounds {
    LIST_OOB_START,
    LIST_OOB_END
};

typedef struct List_s List;
struct List_s{
    Node* pFirstNode;
    Node* pLastNode;
    Node* pCurrentNode;
    int count;
    List* pNextFreeHead;
    enum ListOutOfBounds lastOutOfBoundsReason;
};

// Maximum number of unique lists the system can support
// (You may modify for your needs)
#define LIST_MAX_NUM_HEADS 100

// Maximum total number of nodes (statically allocated) to be shared across all lists
// (You may modify for your needs)
#define LIST_MAX_NUM_NODES 1000

// General Error Handling:
// Client code is assumed never to call these functions with a NULL List pointer, or 
// bad List pointer. If it does, any behaviour is permitted (such as crashing).
// HINT: Use assert(pList != NULL); just to add a nice check, but not required.

// Makes a new, empty list, and returns its reference on success. 
// Returns a NULL pointer on failure.
List* List_create();

// Returns the number of items in pList.
int List_count(List* pList);

// Returns a pointer to the first item in pList and makes the first item the current item.
// Returns NULL and sets current item to NULL if list is empty.
void* List_first(List* pList);

// Returns a pointer to the last item in pList and makes the last item the current item.
// Returns NULL and sets current item to NULL if list is empty.
void* List_last(List* pList); 

// Advances pList's current item by one, and returns a pointer to the new current item.
// If this operation advances the current item beyond the end of the pList, a NULL pointer 
// is returned and the current item is set to be beyond end of pList.
void* List_next(List* pList);

// Backs up pList's current item by one, and returns a pointer to the new current item. 
// If this operation backs up the current item beyond the start of the pList, a NULL pointer 
// is returned and the current item is set to be before the start of pList.
void* List_prev(List* pList);

// Returns a pointer to the current item in pList.
void* List_curr(List* pList);

// Adds the new item to pList directly after the current item, and makes item the current item. 
// If the current pointer is before the start of the pList, the item is added at the start. If 
// the current pointer is beyond the end of the pList, the item is added at the end. 
// Returns 0 on success, -1 on failure.
int List_insert_after(List* pList, void* pItem);

// Adds item to pList directly before the current item, and makes the new item the current one. 
// If the current pointer is before the start of the pList, the item is added at the start. 
// If the current pointer is beyond the end of the pList, the item is added at the end. 
// Returns 0 on success, -1 on failure.
int List_insert_before(List* pList, void* pItem);

// Adds item to the end of pList, and makes the new item the current one. 
// Returns 0 on success, -1 on failure.
int List_append(List* pList, void* pItem);

// Adds item to the front of pList, and makes the new item the current one. 
// Returns 0 on success, -1 on failure.
int List_prepend(List* pList, void* pItem);

// Return current item and take it out of pList. Make the next item the current one.
// If the current pointer is before the start of the pList, or beyond the end of the pList,
// then do not change the pList and return NULL.
void* List_remove(List* pList);

// Adds pList2 to the end of pList1. The current pointer is set to the current pointer of pList1. 
// pList2 no longer exists after the operation; its head is available
// for future operations.
void List_concat(List* pList1, List* pList2);

// Delete pList. pItemFreeFn is a pointer to a routine that frees an item. 
// It should be invoked (within List_free) as: (*pItemFreeFn)(itemToBeFreedFromNode);
// pList and all its nodes no longer exists after the operation; its head and nodes are 
// available for future operations.
// UPDATED: Changed function pointer type, May 19
typedef void (*FREE_FN)(void* pItem);
void List_free(List* pList, FREE_FN pItemFreeFn);

// Return last item and take it out of pList. Make the new last item the current one.
// Return NULL if pList is initially empty.
void* List_trim(List* pList);

// Search pList, starting at the current item, until the end is reached or a match is found. 
// In this context, a match is determined by the comparator parameter. This parameter is a
// pointer to a routine that takes as its first argument an item pointer, and as its second 
// argument pComparisonArg. Comparator returns 0 if the item and comparisonArg don't match, 
// or 1 if they do. Exactly what constitutes a match is up to the implementor of comparator. 
// 
// If a match is found, the current pointer is left at the matched item and the pointer to 
// that item is returned. If no match is found, the current pointer is left beyond the end of 
// the list and a NULL pointer is returned.
// 
// UPDATED: Added May 19
// If the current pointer is before the start of the pList, then start searching from
// the first node in the list (if any).
typedef bool (*COMPARATOR_FN)(void* pItem, void* pComparisonArg);
void* List_search(List* pList, COMPARATOR_FN pComparator, void* pComparisonArg);

#endif