#include “friends.h”
#include
#include
#include
* Create a new user with the given name. Insert it at the tail of the list
* of users whose head is pointed to by *user_ptr_add.
* – 0 on success.
* – 1 if a user by this name already exists in this list.
* – 2 if the given name cannot fit in the ‘name’ array
* (don’t forget about the null terminator).
int create_user(const char *name, User **user_ptr_add) {
if (strlen(name) >= MAX_NAME) {
User *new_user = malloc(sizeof(User));
if (new_user == NULL) {
perror(“malloc”);
strncpy(new_user->name, name, MAX_NAME); // name has max length MAX_NAME – 1
for (int i = 0; i < MAX_NAME; i++) { new_user->profile_pic[i] = ‘\0’;
new_user->first_post = NULL;
new_user->next = NULL;
for (int i = 0; i < MAX_FRIENDS; i++) {
new_user->friends[i] = NULL;
// Add user to list
User *prev = NULL;
User *curr = *user_ptr_add;
while (curr != NULL && strcmp(curr->name, name) != 0) {
prev = curr;
curr = curr->next;
if (*user_ptr_add == NULL) {
*user_ptr_add = new_user;
} else if (curr != NULL) {
free(new_user);
prev->next = new_user;
* Return a pointer to the user with this name in
* the list starting with head. Return NULL if no such user exists.
* NOTE: You’ll likely need to cast a (const User *) to a (User *)
* to satisfy the prototype without warnings.
User *find_user(const char *name, const User *head) {
while (head != NULL && strcmp(name, head->name) != 0) {
head = head->next;
return (User *)head;
* Print the usernames of all users in the list starting at curr.
* Names should be printed to standard output, one per line.
void list_users(const User *curr) {
printf(“User List\n”);
while (curr != NULL) {
printf(“\t%s\n”,curr->name);
curr = curr->next;
* Make two users friends with each other. This is symmetric – a pointer to
* each user must be stored in the ‘friends’ array of the other.
* New friends must be added in the first empty spot in the ‘friends’ array.
* – 0 on success.
* – 1 if the two users are already friends.
* – 2 if the users are not already friends, but at least one already has
* MAX_FRIENDS friends.
* – 3 if the same user is passed in twice.
* – 4 if at least one user does not exist.
* Do not modify either user if the result is a failure.
* NOTE: If multiple errors apply, return the *largest* error code that applies.
int make_friends(const char *name1, const char *name2, User *head) {
User *user1 = find_user(name1, head);
User *user2 = find_user(name2, head);
if (user1 == NULL || user2 == NULL) {
} else if (user1 == user2) { // Same user
for (i = 0; i < MAX_FRIENDS; i++) {
if (user1->friends[i] == NULL) { // Empty spot
} else if (user1->friends[i] == user2) { // Already friends.
for (j = 0; j < MAX_FRIENDS; j++) { if (user2->friends[j] == NULL) { // Empty spot
if (i == MAX_FRIENDS || j == MAX_FRIENDS) { // Too many friends.
user1->friends[i] = user2;
user2->friends[j] = user1;
* Print a post.
* Use localtime to print the time and date.
int print_post(const Post *post) {
if (post == NULL) {
// Print author
printf(“From: %s\n”, post->author);
// Print date
printf(“Date: %s\n”, asctime(localtime(post->date)));
// Print message
printf(“%s\n”, post->contents);
* Print a user profile.
* For an example of the required output format, see the example output
* linked from the handout.
* – 0 on success.
* – 1 if the user is NULL.
int print_user(const User *user) {
if (user == NULL) {
// Print name
printf(“Name: %s\n\n”, user->name);
printf(“——————————————\n”);
// Print friend list.
printf(“Friends:\n”);
for (int i = 0; i < MAX_FRIENDS && user->friends[i] != NULL; i++) {
printf(“%s\n”, user->friends[i]->name);
printf(“——————————————\n”);
// Print post list.
printf(“Posts:\n”);
const Post *curr = user->first_post;
while (curr != NULL) {
print_post(curr);
curr = curr->next;
if (curr != NULL) {
printf(“\n===\n\n”);
printf(“——————————————\n”);
* Make a new post from ‘author’ to the ‘target’ user,
* containing the given contents, IF the users are friends.
* Insert the new post at the *front* of the user’s list of posts.
* Use the ‘time’ function to store the current time.
* ‘contents’ is a pointer to heap-allocated memory – you do not need
* to allocate more memory to store the contents of the post.
* – 0 on success
* – 1 if users exist but are not friends
* – 2 if either User pointer is NULL
int make_post(const User *author, User *target, char *contents) {
if (target == NULL || author == NULL) {
int friends = 0;
for (int i = 0; i < MAX_FRIENDS && target->friends[i] != NULL; i++) {
if (strcmp(target->friends[i]->name, author->name) == 0) {
friends = 1;
if (friends == 0) {
// Create post
Post *new_post = malloc(sizeof(Post));
if (new_post == NULL) {
perror(“malloc”);
strncpy(new_post->author, author->name, MAX_NAME);
new_post->contents = contents;
new_post->date = malloc(sizeof(time_t));
if (new_post->date == NULL) {
perror(“malloc”);
time(new_post->date);
new_post->next = target->first_post;
target->first_post = new_post;