How to write a character-by-character input function that returns the entered string?

Question

C++ / C#

Please help me implement a function that reads the input character by character until it reaches the end of the input or a newline character is encountered. The function should return a C-style string with the characters read.

Tried like this:

char* getline()
{
    char in;
    int i=0;
    
    char* pOld = new char[1]; 
    char* pNew = new char[1];  

    while(cin.get(in) && (in != '\n'))
    {
          i++;
          pOld[i]=in;
    }  
     
    delete [] pNew;
    pOld[i] = '\0'; 
    
    return pOld; 
}

But this causes a segmentation fault.

Answer 1

With outside help and my own efforts, I decided this:

char *getline()
{
    char in;
    int i=0;
    char* pOld = new char[1];  
    
    while(cin.get(in) && (in != '\n')){ 
        ++i;
        pOld[i-1] = in;
        char* pNew = new char[i+1]; 
        
        for (int j=0;j<i;++j){ 
                pNew[j] = pOld[j];
        }   

        delete [] pOld;
        pOld = pNew;
    }
 
pOld[i] = '\0';
return pOld; 
}

Буду рад комментариям и замечаниям!

Answer 2

That's right, segfault. You allocate an array old of size 1, and access it with an index greater than the one you allocated.