Limiting Input

aaroncohn · #1 23-May-2004, 20:07

Hey, this may seem like a silly question to you all, but I guess my head isn't screwed on as tight as it should be right now, because it seems easy enough to me, yet I can't quite fix it. I want to limit user input into an array of chars to a maximum of 100 characters. Right now I'm using cin.getline() for input, but It doesn't work the way I thought it did.

CPP / C++ / C Code:

cin.getline( tempPhrase, MAX_LENGTH-1, '\n' );

That's how I was using it before... I thought the int in the middle was a delimiter on how much input to take, but apparently it isn't, because if I input more than MAX_LENGTH-1, the program crashes (because the program continues writing data outside of the array). So, anyone have a function or a quick algorithm to limit the amount of characters I receive?

Max Payne · #2 23-May-2004, 20:45

You can try using the setw() manipulator....

CPP / C++ / C Code:

#include <iostream>
#include <string>
#include <iomanip>

int main()
{
    char foo[5];
    std::cout << "Enter some text :\n";

    std::cin >> std::setw(5) >> foo;

    return 0;
}

dabigmooish · #3 23-May-2004, 22:51

have you tried it with out the character delim "/n"? Thats the only thing I can think of because getline should work the way you have it written.

aaroncohn · #4 24-May-2004, 11:25

Quote:

Originally Posted by Max Payne

You can try using the setw() manipulator....

Didn't work... entering too many characters still crashes the program.

aaroncohn · #5 24-May-2004, 14:46

Quote:

Originally Posted by dabigmooish

have you tried it with out the character delim "/n"? Thats the only thing I can think of because getline should work the way you have it written.

This didn't work either... I tried doing a loop where the user types out the phrase to be entered, then the loop reads it one character at a time from the keyboard buffer and the loop stops if it reaches MAX_LENGTH... but couldn't stop the loop if there was no more input. I have an idea now that I'm going to try. If anyone comes up with something... let me know!

aaroncohn · #6 24-May-2004, 15:15

Ok, I'm a little peeved now. This loop SHOULD work the way it was intended to work, yet the program STILL crashes when too many characters are received.

CPP / C++ / C Code:

while ( (ch = cin.get()) != '\n' && index != MAX_LENGTH-1)
  {
    tempPhrase[index] = ch;
    index++;
  }

Max Payne · #7 24-May-2004, 19:19

Quote:

Originally Posted by aaroncohn

Didn't work... entering too many characters still crashes the program.

Weird, I tried using getline() and cin>>setw(), both works fine with me!!

Max Payne · #8 24-May-2004, 19:23

Quote:

Originally Posted by aaroncohn

Ok, I'm a little peeved now. This loop SHOULD work the way it was intended to work, yet the program STILL crashes when too many characters are received.

CPP / C++ / C Code:

while ( (ch = cin.get()) != '\n' && index != MAX_LENGTH-1)
  {
    tempPhrase[index] = ch;
    index++;
  }

find out when it crashes, put a cout in your code, which statement causing the crash??

CPP / C++ / C Code:

cout<<"check 1"<<endl;
while ( (ch = cin.get()) != '\n' && index != MAX_LENGTH-1)
  {
cout<<"check 2"<<endl;
    tempPhrase[index] = ch;
cout<<"check 3"<<endl;
    index++;
  }

aaroncohn · #9 25-May-2004, 01:42

Hah, the problem wasn't even with the stupid input. It was with displaying it. When I display the input, I move it from the list to a new array of chars of size MAX_LENGTH, but I add a space after each character, effectively doubling the amount of space the string takes up. So, when I tried to add a space after each character, it would run out of room and write outside of the array causing an access violation. All I did to fix it was instead of using MAX_LENGTH for the size of the char array, I used MAX_LENGTH*2 : ) Thanks for your input, guys. I guess the limiting worked all along. Now I don't have to use that stupid loop.

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