Extracting complete current line from std::istream

Question

I am scanning text coming from a std::istream. The scanning is already under way, and I would like to extract the line that is currently being read (from beginning to end). This getCurrentLine() function must not modify the std::istream position.

I wrote this piece of code, which I find rather messy. Is there a better way to do this? (charStream_ is the std::istream)

std::string Scanner::getCurrentLine() const {
  auto pos = charStream_.tellg();

  // rewind until beginning of the line or stream
  while (charStream_.peek() != '\n' && charStream_.tellg() != 0)
    charStream_.unget();

  // consume endline character
  if (charStream_.peek() == '\n')
    charStream_.get();

  std::stringstream lineStream;
  char c;
  do {
    c = static_cast<char>(charStream_.get());
    lineStream << c;
  } while (c != '\n' && c != EOF);

  charStream_.seekg(pos);

  return lineStream.str();
}

Something wrong with using `getline` instead of that do-while loop? — ChrisMM, Apr 14 '20 at 16:37

score 0 · Answer 1 · answered Apr 14 '20 at 16:38

0

use the function std::getline(std::cin, std::string)

answered Apr 14 '20 at 16:38

Niklas Klausberger

7
4

will getline return the line from the beginning or starting at the current `std::istream` position? – Touloudou Apr 14 '20 at 17:01

Extracting complete current line from std::istream

1 Answers1