private function getValueFromField()
    {
        $position = $this->readUntil($this->boundary);

        # there is always a newline after the value and before the boundary
        # exclude that newline from the value
        $value = substr($this->buffer, 0, $position - 2);

        # update the buffer to exclude the value and the pre boundary newline
        $this->buffer = substr($this->buffer, $position);

        return $value;
    }