image.py 文件源码

def __init__(self, path, size, schema=None):
        """Initialize an image file to a given size in bytes.

        :param path: Path to image file on the file system.
        :type path: str
        :param size: Size in bytes to set the image file to.
        :type size: int
        :param schema: The partitioning schema of the volume.
        :type schema: VolumeSchema

        Public attributes:

        * path - Path to the image file.
        """
        self.path = path
        # Create an empty image file of a fixed size.  Unlike
        # truncate(1) --size 0, os.truncate(path, 0) doesn't touch the
        # file; i.e. it must already exist.
        with open(path, 'wb'):
            pass
        # Truncate to zero, so that extending the size in the next call
        # will cause all the bytes to read as zero.  Stevens $4.13
        os.truncate(path, 0)
        os.truncate(path, size)
        # Prepare the device and disk objects for parted to be used for all
        # future partition() calls.  Only do it if we actually care about the
        # partition table.
        if schema is None:
            self.sector_size = 512
            self.device = None
            self.disk = None
            self.schema = None
        else:
            self.device = parted.Device(self.path)
            label = 'msdos' if schema is VolumeSchema.mbr else 'gpt'
            self.schema = schema
            self.disk = parted.freshDisk(self.device, label)
            self.sector_size = self.device.sectorSize