C - Doubly Linked List always null - c

Question

I am writting a program on doubly linked list with the following data structure:
typedef struct telephoneBookNode {
int id;
char name[NAME_LENGTH];
char telephone[TELEPHONE_LENGTH];
struct telephoneBookNode * previousNode;
struct telephoneBookNode * nextNode;
} TelephoneBookNode;
typedef struct telephoneBookList {
TelephoneBookNode * head;
TelephoneBookNode * tail;
TelephoneBookNode * current;
} TelephoneBookList;
In the following function, I read data from a text file to the linked list, the file content look like this:
/*100, Alice, 0411112222
101, Bob, 0411112222
102, Ali, 0411112223*/
TelephoneBookList * commandLoad(char* fileName) {
TelephoneBookList *(*createList)(TelephoneBookNode*, char[]) = createTelephoneBookList;
char entry[100], *temp1, *temp2;
TelephoneBookList* aList = NULL;
TelephoneBookNode* aNode = NULL;
FILE* telephoneListFile = NULL;
int countEntry = 0;
Boolean check;
telephoneListFile = fopen(fileName, "r");
if (!telephoneListFile)
return NULL;
else {
while (fgets(entry, 100, telephoneListFile)) {
temp2 = strcpy(temp2, entry);
temp1 = strtok(entry, "\n");
check = addressBookEntryCheck(temp1);
if (!check)
return NULL;
else
//here I pass aNode pointer to the below function
aList = (*createList)(aNode, temp2);
}
fclose(telephoneListFile);
printf("printed"); //This line is reached when program complied
return aList;
}
}
This is the function to create the list, problem may be here: it doesnot add new node to the list, it just replaces the first node with the new one. Finally, the linked list only has 1 record which was the last one in text file. How can I fix the code? Thank you!
TelephoneBookList * createTelephoneBookList(TelephoneBookNode* node, char entry[]) {
TelephoneBookList* aList = malloc(sizeof *aList);
TelephoneBookNode* aNode = (TelephoneBookNode*) malloc(sizeof *aNode);
char *tokens;
tokens = strtok(entry, ", ");
aNode->id = atoi(tokens);
tokens = strtok(NULL, ", ");
strcpy(aNode->name, tokens);
tokens = strtok(NULL, ", ");
strcpy(aNode->telephone, tokens); //Just assigning values to a node
//program always go to this block, means `node` is always null
if (node == NULL) {
aNode->nextNode = NULL;
aNode->previousNode = NULL;
node = aNode;
aList->current = node;
aList->head = node;
aList->tail = node;
}
else { //This block is not reached
while (node->nextNode)
node = node->nextNode;
node->nextNode = aNode;
aNode->previousNode = node;
aList->tail = node->nextNode;
}
return aList;
}
This is the function to check entry:
Boolean addressBookEntryCheck(char entry[]) {
char *tokens;
tokens = strtok(entry, ", ");
if(!tokens || strlen(tokens) < 1 || strlen(tokens) > 3)
return FALSE;
else {
if (!isNumber(tokens))
return FALSE;
else {
tokens = strtok(NULL, ", ");
if (!tokens)
return FALSE;
else
{
tokens = strtok(NULL, ", ");
if (!tokens)
return FALSE;
else if (!isNumber(tokens) || strlen(tokens) != 10)
return FALSE;
else
return TRUE;
}
}
}
}

Answer 1

Every time you call
createTelephoneBookList
you create a new list
TelephoneBookList* aList = malloc(sizeof *aList);
You also copy to an uninitialized pointer
temp2 = strcpy(temp2, entry);
I would suggest you create one function to create the list header, one function to add new items e.g.
aList = createList()
while (fgets(entry,sizeof(entry),fp)!=NULL)
{
if (!addEntry(aList,entry))
{
fprintf(stderr, "failed additem item %s\n", entry);
}
}
...
In addEntry parse the string
int id = 0;
char name[NAME_LENGTH];
char telephone[TELEPHONE_LENGTH];
p = strtok(entry, ","); // id
if (p != NULL)
{
id = atoi(p);
p = strtok(NULL, ","); // name, store to temporary string
if (p != NULL )
{
strcpy(name,p);
p = strtok(NULL, ","); // telephone number, store to temporary string
if ( p != NULL )
{
strcpy(telephone,p);
// here you can allocate the new node
}
}
}
// disclaimer omitted checks for length etc which any good program should have. also make sure you have room for \0
if any of the strtok above fail return 0 otherwise allocate a new entry
TelephoneBookNode* aNode = malloc(sizeof(TelephoneBookNode));
aNode->id = id;
strcpy(aNode->name, name);
strcpy(aNode->telephone, telephone);
Then add to your aList

Answer 2

//program always go to this block, means `node` is always null
if (node == NULL) {
....
This is because the caller of the function passed aNode and it never changes within that loop. So it will always pass same value of aNode which is NULL.
I haven't looked at the logic of your code in details, but I think you may want to pass aList->head or rather you already pass aList so just use that.