def readline(self, size=-1):
        """Read one entire line from the file. If size is present
           and non-negative, return a string with at most that
           size, which may be an incomplete line.
        """
        if self.closed:
            raise ValueError("I/O operation on closed file")

        pos = self.buffer.find(b"\n") + 1
        if pos == 0:
            # no newline found.
            while True:
                buf = self.fileobj.read(self.blocksize)
                self.buffer += buf
                if not buf or b"\n" in buf:
                    pos = self.buffer.find(b"\n") + 1
                    if pos == 0:
                        # no newline found.
                        pos = len(self.buffer)
                    break

        if size != -1:
            pos = min(size, pos)

        buf = self.buffer[:pos]
        self.buffer = self.buffer[pos:]
        self.position += len(buf)
        return buf
Read one entire line from the file. If size is present
           and non-negative, return a string with at most that
           size, which may be an incomplete line.
        
product/gradle-plugin/src/main/python/pip/_vendor/distlib/_backport/tarfile.py