def read(self):
"""read data blocks"""
self.data_blks = []
want_seq_num = 1
total_size = 0
is_ffs = self.volume.is_ffs
byte_size = self.block.byte_size
data = ""
for blk in self.data_blk_nums:
if is_ffs:
# ffs has raw data blocks
dat_blk = self.volume.blkdev.read_block(blk)
total_size += len(dat_blk)
# shrink last read id necessary
if total_size > byte_size:
shrink = total_size - byte_size
dat_blk = dat_blk[:-shrink-1]
total_size = byte_size
data += dat_blk
else:
# ofs
dat_blk = FileDataBlock(self.block.blkdev, blk)
dat_blk.read()
if not dat_blk.valid:
raise FSError(INVALID_FILE_DATA_BLOCK, block=dat_blk)
# check sequence number
if dat_blk.seq_num != want_seq_num:
raise FSError(INVALID_SEQ_NUM, block=dat_blk, extra="got=%d wanted=%d" % (dat_blk.seq_num, want_seq_num))
# store data blocks
self.data_blks.append(dat_blk)
total_size += dat_blk.data_size
data += dat_blk.get_block_data()
want_seq_num += 1
# store full contents of file
self.data = data
def write(self):
self.data_blks = []
off = 0
left = self.data_size
blk_idx = 0
bs = self.get_data_block_contents_bytes()
is_ffs = self.volume.is_ffs
while off < self.data_size:
# number of data block
blk_num = self.data_blk_nums[blk_idx]
# extract file data
size = left
if size > bs:
size = bs
d = self.data[off:off+size]
if is_ffs:
# pad block
if size < bs:
d += '\0' * (bs-size)
# write raw block data in FFS
self.blkdev.write_block(blk_num, d)
else:
# old FS: create and write data block
fdb = FileDataBlock(self.blkdev, blk_num)
if blk_idx == self.num_data_blks - 1:
next_data = 0
else:
next_data = self.data_blk_nums[blk_idx+1]
fdb.create(self.block.blk_num, blk_idx+1, d, next_data)
fdb.write()
self.data_blks.append(fdb)
blk_idx += 1
off += bs
left -= bs