strlen - how to limit input

[rzgar]

Hi
when I use code without if..else terminal window closes and "send error rapport" window pops up (WinXP). how can I limit the input to only 10 char without using if..else? I'm looking for some sort of flow control or stopping keyboard input.
thanks in advance
Here is my exercise code:

#include <iostream>
#include <cstring> 
using namespace std;
int main()
{
int size = 0; 
char UserType[10]; 

StartAgain:
cout << "Enter some char" << endl;
cin >> UserType;

size = strlen(UserType);
if(size >=11)
{
cout << "max allowed size is 10 char" <<endl;
goto StartAgain;
}else
{
cout << "Value of UserType: " << UserType << endl;
cout << "Size of :\t" << size << endl; 
}
return 0;
}

[Wazzak]

strlen() is easy to implement. That said, it's easy to write your own with your own restrictions. For example:

size_t StringLength(const char *, const size_t);

int main()
{
}

size_t StringLength(const char *String, const size_t MaxLen)
{
    if(!String)
        return(0);

    size_t Len(0);

    // Here, we'll iterate through the string until we
    // encounter the null-character. Since the null--
    // -character is zero, the loop will be false; thus
    // terminating the loop.
    while(*(String++))
    {
        // If the current amount of characters in the
        // string is not equal to the maximum length,
        // count it.
        if((Len + 1) <= MaxLen)
             ++Len;

        else break;
    }
    
    return(Len + 1);
    // The extra 1 is the null-character.
}

Since you cannot control the amount of characters entered by the user (your OS's API might yield something) with a console, you'll have to truncate the trailing characters by discarding them from the input buffer.

_Wazzak

[Moschops]

To simplify m'learned Chum Os'Frame's words, this:

char UserType[10]; 
StartAgain:
cout << "Enter some char" << endl;
cin >> UserType;

is very problematic. You make enough space for the user to enter 9 characters, and then have a trailing zero as C-strings must. You then get some input from you user, which you put into that array, and you then check that input to ensure it didn't overflow the buffer - but it's too late! You already put it into the buffer, so you will have already overflowed and trashed data.

[Galik]

For your example you probably want std::cin.getline()

	char UserType[11]; // need one more than 10 for the end marker

	std::cout << "Enter some char" << '\n';

	std::cin.getline(UserType, 11); // limit input to 10

	std::cout << UserType << '\n';

http://cplusplus.com/reference/iostream/istream/getline/

[rzgar]

thank you guys. appreciate your help.
@Galik getline() solved the issue.

Currently I'm learning about Data types, Variables, Operators and sometimes searching around for reading codes to recognize what I learned.
I even learned to include C headers and run printf() instead of cout <<. I'm not sure why even should someone run C code inside C++ source.

@Moschops: True so I need to use cin first then extract 10 char of whole input and at last put them into my array. hope i got the logic correct.

@OsiumFramework thanks already copied & saved it. looks to advance for me. I don't know what const and * is. but I'm good student I'll learn it quick :)
---------------
But there is one more issue I couldn't understand why. when I use "cin" alone without "getline()" after hitting the space-bar, program doesn't save the rest of characters e.g " well, this is a test" print out only "well," part.
why it's happening?

and what is different between cin.getline() & cin.read()? all i know is getline sorts data in c-string and cin.read doesn't sort data in c-string.
std::cin.getline(UserType, 11); and std::cin.read(UserType, 11); does the same job right?