def write_share_data(self, offset, data):
length = len(data)
precondition(offset >= 0, offset)
if self._max_size is not None and offset + length > self._max_size:
raise DataTooLargeError(self._max_size, offset, length)
with open(self.home, 'rb+') as f:
real_offset = self._data_offset + offset
f.seek(real_offset)
assert f.tell() == real_offset
f.write(data)
def _change_container_size(self, f, new_container_size):
if new_container_size > self.MAX_SIZE:
raise DataTooLargeError()
old_extra_lease_offset = self._read_extra_lease_offset(f)
new_extra_lease_offset = self.DATA_OFFSET + new_container_size
if new_extra_lease_offset < old_extra_lease_offset:
# TODO: allow containers to shrink. For now they remain large.
return
num_extra_leases = self._read_num_extra_leases(f)
f.seek(old_extra_lease_offset)
extra_lease_data = f.read(4 + num_extra_leases * self.LEASE_SIZE)
f.seek(new_extra_lease_offset)
f.write(extra_lease_data)
# an interrupt here will corrupt the leases, iff the move caused the
# extra leases to overlap.
self._write_extra_lease_offset(f, new_extra_lease_offset)
def _change_container_size(self, f, new_container_size):
if new_container_size > self.MAX_SIZE:
raise DataTooLargeError()
old_extra_lease_offset = self._read_extra_lease_offset(f)
new_extra_lease_offset = self.DATA_OFFSET + new_container_size
if new_extra_lease_offset < old_extra_lease_offset:
# TODO: allow containers to shrink. For now they remain large.
return
num_extra_leases = self._read_num_extra_leases(f)
f.seek(old_extra_lease_offset)
leases_size = 4 + num_extra_leases * self.LEASE_SIZE
extra_lease_data = f.read(leases_size)
# Zero out the old lease info (in order to minimize the chance that
# it could accidentally be exposed to a reader later, re #1528).
f.seek(old_extra_lease_offset)
f.write('\x00' * leases_size)
f.flush()
# An interrupt here will corrupt the leases.
f.seek(new_extra_lease_offset)
f.write(extra_lease_data)
self._write_extra_lease_offset(f, new_extra_lease_offset)
