c++ help

[Belgarath The Sorcerer]

I have a program, protected by a password. It's pretty simple, in that it all it does is ask the user to input a password, which is compared to the correct password, which is just an interger.

Now we have to modify the program such that the user enters a password in the format 'xx11', we have to validate that the the user is entering two letters and two numbers, and then compare it to the password.

As you may have guessed by me posting here, I'm a little stuck, here's the code I have:


const char INITIALS[2]="xx";
const int NUMBER[2]={11};

for(PasswordAttempts=MAX_PWORD_ATTEMPTS; PasswordAttempts>0 && !PasswordValid; PasswordAttempts--)
  {
   cout << "Please enter password... ";
   cin >> Password;

  // this is the bit i'm a bit stuck on
   Initials[0]=Password[0,1];
   Number[0]=Password[2,3];
  
   strcmp(Initials,INITIALS)==0;


    if(isalpha(Password[0]) && isalpha(Password[1]) && isdigit(Password[2]) && isdigit(Password[3]) == (Initials && Number)
    {
     PasswordValid=true;
    }
    else
    {
    cout << "\nPassword invalid, you have " << PasswordAttempts - 1 << " attempts left." << endl;
    }
  }
    if(PasswordValid==true)
    {
      do
      {
        rest of program, etc...

Can anyone shed any light, or at least point me in the right direction?

[queball]

Wouldn't it be easier to validate and then just do a string compare to "xx11"?

Initials[0]=Password[0,1]; is not what you want. You could copy each character seperately , but I don't see what you're achieving. I'm guessing Password is a string (istream<< into a char* is dangerous - use get instead if you can't use C++ strings). After validating the password you could use atoi to get the number part if you need it.

Other things: INITIALS isn't null terminated (it holds two characters and is only 2 chars big), so don't use strcmp, but you could use strncmp. You should check the size of the password somewhere.

[djbass]

const char Pass[4] = {'x', 'x', '1', '1', 0};

if(isalpha(Password[0]) && isalpha(Password[1]) && isdigit(Password[2]) && isdigit(Password[3]) && (strcmp(Password, Pass)==0))

Would do the trick I suspect, and queball is right there's a lot of redundant code in there that doesn't actually do anything useful.

You could get rid of:

const char INITIALS[2]="xx";
const int NUMBER[2]={11};

Initials[0]=Password[0,1];
Number[0]=Password[2,3];

strcmp(Initials,INITIALS)==0;

=[DJ Bass]=

[Belgarath The Sorcerer]

queball's reply helped immensely as it happens. I now I have:

if(isalpha(Password[0]) && isalpha(Password[1]) && isdigit(Password[2]) && isdigit(Password[3]) && (strncmp(Password,FIXED_PASSWORD,4) == false))

where FIXED_PASSWORD is obviously the correct password

Everything works as it should, and does exactly what the question asked me to do, although I'm not sure that this is the exact way that she wants us to do it, but it works, heh.

thanks guys.

[queball]

But what if someone enters xx11bb?

[Flavius]

then just check that first 4 chars are the same, and then check that size of stored password <= size of input password

edit: <= in case its the same

[JetLinus]

Originally Posted by queball

But what if someone enters xx11bb?

needs a length-check as well then, i'd guess...

Edit: Ah well, been a bit late with that idea ^^

[Belgarath The Sorcerer]

I'll have a go at that tomorrow, I need to put some more validation in anyway, so I can get it all done at the same time.

Thanks for the help lads.

[Entium]

Originally Posted by JetLinus

needs a length-check as well then, i'd guess...

int len(string) ==4 (?)

And/Or you could try something like

char charAT(string, pos) == char charAT(initials, pos)

[Cyp]

#define a PasswordAttempts
#define b PasswordValid
#define e long
#define f MAX_PWORD_ATTEMPTS
#define g goto h
const char INITIALS[2]="xx";
const int NUMBER[2]={1,1};
for(a=f;a>0&&!b;--a){
char d[8224];
cout<<"Please enter password... ";
cin>>d;
e i;b=1;
e c=8224|(i=*(e*)d);
if(2155905152u&c)g;
c-=808477025;
if(2155905152u&c)g;
c-=151591194;
if(2155905152u&~c)g;
if(d[4])g;
++b;h:
if(!(b&&i==((e)INITIALS[0]|((e)INITIALS[1]<<8)|(((e)NUMBER[0]+48)<<16)|(((e)NUMBER[1]+48)<<24)))){
if(b)cout<<"\nPassword invalid, you have "<<PasswordAttempts-1<<" attempts left."<<endl;else cout<<"\nInvalid password format, you have "<<PasswordAttempts-1<<" attempts left."<<endl;
b=0;}

    if(PasswordValid==true)
    {
      do
      {
        rest of program, etc...

This checks some things in parallel...