Escape sequences

[Null]

Hello,
I'm writing a function that masks password input but I can't figure out how to handle escape sequences properly. Here's my code:

#include <termios.h>
#include <unistd.h>

#include <stdexcept>
#include <iostream>
#include <string>
#include <stdio.h>

using namespace std;


string getpass(const char *prompt, bool show_asterisk=true)

{

  const char BACKSPACE=127;
  const char RETURN='\n';


  string password;
  unsigned int ch=0;

  cout <<prompt<<endl;

  struct termios tty_attr;

  if (tcgetattr(STDIN_FILENO, &tty_attr) < 0)
      throw runtime_error("tcgetattr error");


  tcflag_t c_lflag = tty_attr.c_lflag; 
  tty_attr.c_lflag &= ~ICANON;
  tty_attr.c_lflag &= ~ECHO;


  if (tcsetattr(STDIN_FILENO, 0, &tty_attr) < 0)
      throw runtime_error("tcsetattr error");

  while((ch=getchar())!=RETURN)
    {
       if(ch==BACKSPACE)
         {
            if(password.length()!=0)
              {
                 if(show_asterisk)
                     cout <<"\b \b";

                 password.resize(password.length()-1);

              }

         }
       else if(ch==27)
         {
            // ?
         }
       else
         {
             password+=ch;

             if(show_asterisk)
                 cout <<'*';

         }
    }

  tty_attr.c_lflag = c_lflag;
  if (tcsetattr(STDIN_FILENO, 0, &tty_attr) < 0)
      throw runtime_error("tcsetattr error");

  cout <<endl;
  return password;
}




int main()
{

  const char *correct_password="null";
   

  string password=getpass("Please enter the password: ",true); 
 // For debugging
  for(int i=0;i<password.length();i++)
      cout <<(int)password[i]<<' ';

  cout <<endl;
  if(password==correct_password)
      cout <<"Correct password"<<endl;
  else
      cout <<"Incorrect password. Try again"<<endl;

  return 0;

}

I know that the first character in a sequence will be 27(Esc). The problem is that I don't know how many non-printable character will follow it, eg. if I press
Esc - I get 27
Right Arrow: 27 91 67
F1..F12: 27 79 x
Delete: 27 91 51 126
So the number of characters returned is not the same.

Maybe there's another way around this?

Thanks for help.

[kooth]

The best answer I ever saw about this subject is in a book written by Marc Rochkind entitled "Advanced C Programming for Displays." The ISBN is 0-13-010240-7 025. I don't know if it still in print, but this book has a great solution for handling the keyboard and its escape sequences.