Question

My Question is very simple, how is getline(istream, string) implemented?
How can you solve the problem of having fixed size char arrays like with getline (char* s, streamsize n ) ?
Are they using temporary buffers and many calls to new char[length] or another neat structure?

Answer 1

getline(istream&, string&) is implemented in a way that it reads a line. There is no definitive implementation for it; each library probably differs from one another.

Possible implementation:

istream& getline(istream& stream, string& str)
{
  char ch;
  str.clear();
  while (stream.get(ch) && ch != '\n')
    str.push_back(ch);
  return stream;
}