mailbox.py 文件源码

def _generate_toc(self):
        """Generate key-to-(start, stop) table of contents."""
        starts, stops = [], []
        last_was_empty = False
        self._file.seek(0)
        while True:
            line_pos = self._file.tell()
            line = self._file.readline()
            if line.startswith('From '):
                if len(stops) < len(starts):
                    if last_was_empty:
                        stops.append(line_pos - len(os.linesep))
                    else:
                        # The last line before the "From " line wasn't
                        # blank, but we consider it a start of a
                        # message anyway.
                        stops.append(line_pos)
                starts.append(line_pos)
                last_was_empty = False
            elif not line:
                if last_was_empty:
                    stops.append(line_pos - len(os.linesep))
                else:
                    stops.append(line_pos)
                break
            elif line == os.linesep:
                last_was_empty = True
            else:
                last_was_empty = False
        self._toc = dict(enumerate(zip(starts, stops)))
        self._next_key = len(self._toc)
        self._file_length = self._file.tell()