PROGRAMMING - Hacking: The Art of Exploitation - page 105

return -1;
else
player = entry; // Copy the read entry into the player struct.
return 1; // Return a success.

}

// This is the new user registration function.
// It will create a new player account and append it to the file.
void register_new_player() {
int fd;

printf("-=-={ New Player Registration }=-=-\n");
printf("Enter your name: ");
input_name();

player.uid = getuid();
player.highscore = player.credits = 100;

fd = open(DATAFILE, O_WRONLY|O_CREAT|O_APPEND, S_IRUSR|S_IWUSR);
if(fd == -1)
fatal("in register_new_player() while opening file");
write(fd, &player, sizeof(struct user));
close(fd);

printf("\nWelcome to the Game of Chance %s.\n", player.name);
printf("You have been given %u credits.\n", player.credits);
}

// This function writes the current player data to the file.
// It is used primarily for updating the credits after games.
void update_player_data() {
int fd, i, read_uid;
char burned_byte;

fd = open(DATAFILE, O_RDWR);
if(fd == -1) // If open fails here, something is really wrong.
fatal("in update_player_data() while opening file");
read(fd, &read_uid, 4); // Read the uid from the first struct.
while(read_uid != player.uid) { // Loop until correct uid is found.
for(i=0; i < sizeof(struct user) - 4; i++) // Read through the
read(fd, &burned_byte, 1); // rest of that struct.
read(fd, &read_uid, 4); // Read the uid from the next struct.
}
write(fd, &(player.credits), 4); // Update credits.
write(fd, &(player.highscore), 4); // Update highscore.
write(fd, &(player.name), 100); // Update name.
close(fd);
}

// This function will display the current high score and
// the name of the person who set that high score.
void show_highscore() {
unsigned int top_score = 0;
char top_name[100];
struct user entry;