C-style strings in C++

Hello,
I would like to ask a thing that I can't figure out on my own.

In before; I know that in C++ we have really nice library(string) that we can include to use strings without caring about their size, etc.

But yet i want to work on library from C. Except the fact that C looks a bit different, everything's ok.

Yet when I write code, and I want to ask about string, i have to create string(array of char) long enough to hold text that would be any long.

For example, I want to ask you for your name. I would create char[100], since there aren't many names(if any) that would exceed this number.

Yet if there is, I have a problem; my array wasn't long enough.

Also, if your name consist of only 3-12 letters, or even few more, I wasted a bit of memory.

So, here's my question: Is there any way, that I can create string long enough, not bigger, not less?

Thanks in advance.

Lowest0ne (1536)

Yes, you have to dynamically allocate space for your array. Space allocated in this way must be deleted afterward, so to properly create/delete a c-string, you would do this:

char* str;  // make a char pointer
int i;
cout << "How big do you want: ";
cin >> i;

// Allocate space
str = new char[i];  // notice that i isn't a constant

// Use the array as needed

delete [] str;  // Delete the string when done

Of course you don't want to ask someone how long their name is. The trick here is to provide a c-string much longer than necessary (1000 rather than 100), and then remove it from scope:

#include <iostream>
using namespace std;

const char* getName();

int main(void)
{
  const char* name = getName();
  cout << "Hi " << name;

  delete [] name;
  cin.get();
  return 0;
}

// While oldName is very long, a newName is made to be just the right length.
// newName is returned and oldName goes out of scope.
const char* getName()
{
  char oldName[1000];  // very long
  cout << "What is your name: ";
  cin.getline(oldName, 999);

  char * newName = new char[strlen(oldName) + 1];
  strcpy(newName, oldName);
  return newName;
}

Last edited on

Catfish2 (666)

The "C way" of doing what LowestOne posted is by using malloc() / calloc() and free() instead of new[] and delete[].

Otherwise, remember that std::string has the c_str() member function which returns the C-compatible pointer to an array of characters, '\0'-terminated.

MatthewRock (481)

Well, some ideas might be useful. Thank you for responding.
:)

Topic archived. No new replies allowed.

C++

Forum

C-style strings in C++