status.py 文件源码

def _reverse_read_lines(fp, buf_size=8192):  # pylint: disable=invalid-name
        """
        Async generator that returns the lines of a file in reverse order.

        ref: https://stackoverflow.com/a/23646049/8776239
        and: https://stackoverflow.com/questions/2301789/read-a-file-in-reverse-order-using-python
        """
        segment = None  # holds possible incomplete segment at the beginning of the buffer
        offset = 0
        await fp.seek(0, io.SEEK_END)
        file_size = remaining_size = await fp.tell()
        while remaining_size > 0:
            offset = min(file_size, offset + buf_size)
            await fp.seek(file_size - offset)
            buffer = await fp.read(min(remaining_size, buf_size))
            remaining_size -= buf_size
            lines = buffer.splitlines(True)
            # the first line of the buffer is probably not a complete line so
            # we'll save it and append it to the last line of the next buffer
            # we read
            if segment is not None:
                # if the previous chunk starts right from the beginning of line
                # do not concat the segment to the last line of new chunk
                # instead, yield the segment first
                if buffer[-1] == '\n':
                    # print 'buffer ends with newline'
                    yield segment
                else:
                    lines[-1] += segment
                    # print 'enlarged last line to >{}<, len {}'.format(lines[-1], len(lines))
            segment = lines[0]
            for index in range(len(lines) - 1, 0, -1):
                l = lines[index]
                if l:
                    yield l
        # Don't yield None if the file was empty
        if segment is not None:
            yield segment