EXPLOITATION - Hacking: The Art of Exploitation - page 157

if((choice < 1) || (choice > 7))
printf("\n[!!] The number %d is an invalid selection.\n\n", choice);
else if (choice < 4) { // Otherwise, choice was a game of some sort.
if(choice != last_game) { // If the function ptr isn't set,
if(choice == 1) // then point it at the selected game
player.current_game = pick_a_number;
else if(choice == 2)
player.current_game = dealer_no_match;
else
player.current_game = find_the_ace;
last_game = choice; // and set last_game.
}
play_the_game(); // Play the game.
}
If last_game isn't the same as the current choice, the function pointer of
current_game is changed to the appropriate game. This means that in order to
get the program to call the function pointer without overwriting it, a game
must be played first to set the last_game variable.
reader@hacking:~/booksrc $ ./game_of_chance
-=[ Game of Chance Menu ]=-
1 - Play the Pick a Number game
2 - Play the No Match Dealer game
3 - Play the Find the Ace game
4 - View current high score
5 - Change your user name
6 - Reset your account at 100 credits
7 - Quit
[Name: Jon Erickson]
[You have 70 credits] -> 1
[DEBUG] current_game pointer @ 0x08048fde
####### Pick a Number ######
This game costs 10 credits to play. Simply pick a number
between 1 and 20, and if you pick the winning number, you
will win the jackpot of 100 credits!
10 credits have been deducted from your account.
Pick a number between 1 and 20: 5
The winning number is 17
Sorry, you didn't win.
You now have 60 credits
Would you like to play again? (y/n) n
-=[ Game of Chance Menu ]=-
1 - Play the Pick a Number game
2 - Play the No Match Dealer game
3 - Play the Find the Ace game
4 - View current high score
5 - Change your user name
6 - Reset your account at 100 credits