def peek(self, size=1):
        """
        Looks C{size} bytes ahead in the stream, returning what it finds,
        returning the stream pointer to its initial position.

        @param size: Default is 1.
        @type size: C{int}
        @raise ValueError: Trying to peek backwards.

        @return: Bytes.
        """
        if size == -1:
            return self.peek(len(self) - self.tell())

        if size < -1:
            raise ValueError("Cannot peek backwards")

        bytes = ''
        pos = self.tell()

        while not self.at_eof() and len(bytes) != size:
            bytes += self.read(1)

        self.seek(pos)

        return bytes