def test_write_value_at_offset(self):
image = Image(self.img, MiB(2))
image.write_value_at_offset(801, 130031)
# Now open the path independently, seek to the given offset, and read
# 4 bytes, then interpret it as a little-endian 32-bit integer.
with open(image.path, 'rb') as fp:
fp.seek(130031)
# Unpack always returns a tuple, but there's only one item there.
value, *ignore = unpack('<I', fp.read(4))
self.assertEqual(value, 801)
def test_write_value_at_offset(self):
image = Image(self.img, MiB(2))
image.write_value_at_offset(801, 130031)
# Now open the path independently, seek to the given offset, and read
# 4 bytes, then interpret it as a little-endian 32-bit integer.
with open(image.path, 'rb') as fp:
fp.seek(130031)
# Unpack always returns a tuple, but there's only one item there.
value, *ignore = unpack('<I', fp.read(4))
self.assertEqual(value, 801)
def test_write_value_at_offsets_near_end(self):
image = Image(self.img, 10000)
# Attempt to write a bunch of values near the end of the file. Since
# the value will always be a 32-bit value, any positions farther out
# than 4 bytes before the end will fail.
results = set()
for pos in range(9995, 10002):
with suppress(ValueError):
image.write_value_at_offset(801, pos)
self.assertEqual(os.path.getsize(self.img), 10000)
results.add(pos)
self.assertEqual(results, {9995, 9996})
def test_write_value_at_offsets_near_end(self):
image = Image(self.img, 10000)
# Attempt to write a bunch of values near the end of the file. Since
# the value will always be a 32-bit value, any positions farther out
# than 4 bytes before the end will fail.
results = set()
for pos in range(9995, 10002):
with suppress(ValueError):
image.write_value_at_offset(801, pos)
self.assertEqual(os.path.getsize(self.img), 10000)
results.add(pos)
self.assertEqual(results, {9995, 9996})
def _make_one_disk(self, imgfile, name, volume):
part_id = 1
# Create the image object for the selected volume schema
image = Image(imgfile, volume.image_size, volume.schema)
offset_writes = []
part_offsets = {}
# We first create all the needed partitions.
# For regular core16 and core18 builds, this means creating all of the
# defined partitions. For core20 (the so called 'seeded images'), we
# only create all the role-less partitions and mbr + system-seed.
# The rest is created dynamically by snapd on first boot.
for part in volume.structures:
if part.name is not None:
part_offsets[part.name] = part.offset
if part.offset_write is not None:
offset_writes.append((part.offset, part.offset_write))
if (part.role is StructureRole.mbr or part.type == 'bare' or
self._should_skip_partition(part)):
continue
activate = False
if (volume.schema is VolumeSchema.mbr and
part.role is StructureRole.system_boot):
activate = True
elif (volume.schema is VolumeSchema.gpt and
part.role is StructureRole.system_data and
part.name is None):
part.name = 'writable'
image.partition(part.offset, part.size, part.name, activate)
# Now since we're done, we need to do a second pass to copy the data
# and set all the partition types. This needs to be done like this as
# libparted's commit() operation resets type GUIDs to defaults and
# clobbers things like hybrid MBR partitions.
part_id = 1
for i, part in enumerate(volume.structures):
if self._should_skip_partition(part):
continue
image.copy_blob(volume.part_images[i],
bs=image.sector_size,
seek=part.offset // image.sector_size,
count=ceil(part.size / image.sector_size),
conv='notrunc')
if part.role is StructureRole.mbr or part.type == 'bare':
continue
image.set_parition_type(part_id, part.type)
part_id += 1
for value, dest in offset_writes:
# Decipher non-numeric offset_write values.
if isinstance(dest, tuple):
dest = part_offsets[dest[0]] + dest[1]
image.write_value_at_offset(value // image.sector_size, dest)
def _make_one_disk(self, imgfile, name, volume):
part_id = 1
# Create the image object for the selected volume schema
image = Image(imgfile, volume.image_size, volume.schema)
offset_writes = []
part_offsets = {}
# We first create all the partitions.
for part in volume.structures:
if part.name is not None:
part_offsets[part.name] = part.offset
if part.offset_write is not None:
offset_writes.append((part.offset, part.offset_write))
if part.role is StructureRole.mbr or part.type == 'bare':
continue
activate = False
if (volume.schema is VolumeSchema.mbr and
part.role is StructureRole.system_boot):
activate = True
elif (volume.schema is VolumeSchema.gpt and
part.role is StructureRole.system_data and
part.name is None):
part.name = 'writable'
image.partition(part.offset, part.size, part.name, activate)
# Now since we're done, we need to do a second pass to copy the data
# and set all the partition types. This needs to be done like this as
# libparted's commit() operation resets type GUIDs to defaults and
# clobbers things like hybrid MBR partitions.
part_id = 1
for i, part in enumerate(volume.structures):
image.copy_blob(volume.part_images[i],
bs=image.sector_size,
seek=part.offset // image.sector_size,
count=ceil(part.size / image.sector_size),
conv='notrunc')
if part.role is StructureRole.mbr or part.type == 'bare':
continue
image.set_parition_type(part_id, part.type)
part_id += 1
for value, dest in offset_writes:
# Decipher non-numeric offset_write values.
if isinstance(dest, tuple):
dest = part_offsets[dest[0]] + dest[1]
image.write_value_at_offset(value // image.sector_size, dest)
