releasetools: Handle two edge cases in FinalizeMetadata(). (3bf8c650) · Commits · e / os / android_build

tools/releasetools/ota_from_target_files.py

+57 −33

Original line number	Original line	Diff line number	Diff line
	@@ -1024,6 +1024,9 @@ class PropertyFiles(object):
	"""		"""
	return self._GetPropertyFilesString(input_zip, reserve_space=True)		return self._GetPropertyFilesString(input_zip, reserve_space=True)

			class InsufficientSpaceException(Exception):
			pass

	def Finalize(self, input_zip, reserved_length):		def Finalize(self, input_zip, reserved_length):
	"""Finalizes a property-files string with actual METADATA offset/size info.		"""Finalizes a property-files string with actual METADATA offset/size info.

	@@ -1045,13 +1048,15 @@ class PropertyFiles(object):
	"payload.bin:679:343,payload_properties.txt:378:45,metadata:69:379 ".		"payload.bin:679:343,payload_properties.txt:378:45,metadata:69:379 ".

	Raises:		Raises:
	AssertionError: If the reserved length is insufficient to hold the final		InsufficientSpaceException: If the reserved length is insufficient to hold
	string.		the final string.
	"""		"""
	result = self._GetPropertyFilesString(input_zip, reserve_space=False)		result = self._GetPropertyFilesString(input_zip, reserve_space=False)
	assert len(result) <= reserved_length, \		if len(result) > reserved_length:
			raise self.InsufficientSpaceException(
	'Insufficient reserved space: reserved={}, actual={}'.format(		'Insufficient reserved space: reserved={}, actual={}'.format(
	reserved_length, len(result))		reserved_length, len(result)))

	result += ' ' * (reserved_length - len(result))		result += ' ' * (reserved_length - len(result))
	return result		return result

	@@ -1089,11 +1094,12 @@ class PropertyFiles(object):

	# 'META-INF/com/android/metadata' is required. We don't know its actual		# 'META-INF/com/android/metadata' is required. We don't know its actual
	# offset and length (as well as the values for other entries). So we reserve		# offset and length (as well as the values for other entries). So we reserve
	# 10-byte as a placeholder, which is to cover the space for metadata entry		# 15-byte as a placeholder ('offset:length'), which is sufficient to cover
	# ('xx:xxx', since it's ZIP_STORED which should appear at the beginning of		# the space for metadata entry. Because 'offset' allows a max of 10-digit
	# the zip), as well as the possible value changes in other entries.		# (i.e. ~9 GiB), with a max of 4-digit for the length. Note that all the
			# reserved space serves the metadata entry only.
	if reserve_space:		if reserve_space:
	tokens.append('metadata:' + ' ' * 10)		tokens.append('metadata:' + ' ' * 15)
	else:		else:
	tokens.append(ComputeEntryOffsetSize(METADATA_NAME))		tokens.append(ComputeEntryOffsetSize(METADATA_NAME))

	@@ -1252,36 +1258,54 @@ def FinalizeMetadata(metadata, input_file, output_file, needed_property_files):
	output_file: The final output ZIP filename.		output_file: The final output ZIP filename.
	needed_property_files: The list of PropertyFiles' to be generated.		needed_property_files: The list of PropertyFiles' to be generated.
	"""		"""
	output_zip = zipfile.ZipFile(
	input_file, 'a', compression=zipfile.ZIP_DEFLATED)

			def ComputeAllPropertyFiles(input_file, needed_property_files):
	# Write the current metadata entry with placeholders.		# Write the current metadata entry with placeholders.
			with zipfile.ZipFile(input_file) as input_zip:
	for property_files in needed_property_files:		for property_files in needed_property_files:
	metadata[property_files.name] = property_files.Compute(output_zip)		metadata[property_files.name] = property_files.Compute(input_zip)
			namelist = input_zip.namelist()

			if METADATA_NAME in namelist:
			common.ZipDelete(input_file, METADATA_NAME)
			output_zip = zipfile.ZipFile(input_file, 'a')
	WriteMetadata(metadata, output_zip)		WriteMetadata(metadata, output_zip)
	common.ZipClose(output_zip)		common.ZipClose(output_zip)

	# SignOutput(), which in turn calls signapk.jar, will possibly reorder the
	# ZIP entries, as well as padding the entry headers. We do a preliminary
	# signing (with an incomplete metadata entry) to allow that to happen. Then
	# compute the ZIP entry offsets, write back the final metadata and do the
	# final signing.
	if OPTIONS.no_signing:		if OPTIONS.no_signing:
	prelim_signing = input_file		return input_file
	else:
	prelim_signing = common.MakeTempFile(suffix='.zip')		prelim_signing = common.MakeTempFile(suffix='.zip')
	SignOutput(input_file, prelim_signing)		SignOutput(input_file, prelim_signing)
			return prelim_signing

	# Open the signed zip. Compute the final metadata that's needed for streaming.		def FinalizeAllPropertyFiles(prelim_signing, needed_property_files):
	with zipfile.ZipFile(prelim_signing, 'r') as prelim_signing_zip:		with zipfile.ZipFile(prelim_signing) as prelim_signing_zip:
	for property_files in needed_property_files:		for property_files in needed_property_files:
	metadata[property_files.name] = property_files.Finalize(		metadata[property_files.name] = property_files.Finalize(
	prelim_signing_zip, len(metadata[property_files.name]))		prelim_signing_zip, len(metadata[property_files.name]))

			# SignOutput(), which in turn calls signapk.jar, will possibly reorder the ZIP
			# entries, as well as padding the entry headers. We do a preliminary signing
			# (with an incomplete metadata entry) to allow that to happen. Then compute
			# the ZIP entry offsets, write back the final metadata and do the final
			# signing.
			prelim_signing = ComputeAllPropertyFiles(input_file, needed_property_files)
			try:
			FinalizeAllPropertyFiles(prelim_signing, needed_property_files)
			except PropertyFiles.InsufficientSpaceException:
			# Even with the preliminary signing, the entry orders may change
			# dramatically, which leads to insufficiently reserved space during the
			# first call to ComputeAllPropertyFiles(). In that case, we redo all the
			# preliminary signing works, based on the already ordered ZIP entries, to
			# address the issue.
			prelim_signing = ComputeAllPropertyFiles(
			prelim_signing, needed_property_files)
			FinalizeAllPropertyFiles(prelim_signing, needed_property_files)

	# Replace the METADATA entry.		# Replace the METADATA entry.
	common.ZipDelete(prelim_signing, METADATA_NAME)		common.ZipDelete(prelim_signing, METADATA_NAME)
	output_zip = zipfile.ZipFile(		output_zip = zipfile.ZipFile(prelim_signing, 'a')
	prelim_signing, 'a', compression=zipfile.ZIP_DEFLATED)
	WriteMetadata(metadata, output_zip)		WriteMetadata(metadata, output_zip)
	common.ZipClose(output_zip)		common.ZipClose(output_zip)

	@@ -1292,7 +1316,7 @@ def FinalizeMetadata(metadata, input_file, output_file, needed_property_files):
	SignOutput(prelim_signing, output_file)		SignOutput(prelim_signing, output_file)

	# Reopen the final signed zip to double check the streaming metadata.		# Reopen the final signed zip to double check the streaming metadata.
	with zipfile.ZipFile(output_file, 'r') as output_zip:		with zipfile.ZipFile(output_file) as output_zip:
	for property_files in needed_property_files:		for property_files in needed_property_files:
	property_files.Verify(output_zip, metadata[property_files.name].strip())		property_files.Verify(output_zip, metadata[property_files.name].strip())

tools/releasetools/test_ota_from_target_files.py

+97 −21

Original line number	Original line	Diff line number	Diff line
	@@ -24,8 +24,8 @@ import zipfile
	import common		import common
	import test_utils		import test_utils
	from ota_from_target_files import (		from ota_from_target_files import (
	_LoadOemDicts, AbOtaPropertyFiles, BuildInfo, GetPackageMetadata,		_LoadOemDicts, AbOtaPropertyFiles, BuildInfo, FinalizeMetadata,
	GetTargetFilesZipForSecondaryImages,		GetPackageMetadata, GetTargetFilesZipForSecondaryImages,
	GetTargetFilesZipWithoutPostinstallConfig, NonAbOtaPropertyFiles,		GetTargetFilesZipWithoutPostinstallConfig, NonAbOtaPropertyFiles,
	Payload, PayloadSigner, POSTINSTALL_CONFIG, PropertyFiles,		Payload, PayloadSigner, POSTINSTALL_CONFIG, PropertyFiles,
	StreamingPropertyFiles, WriteFingerprintAssertion)		StreamingPropertyFiles, WriteFingerprintAssertion)
	@@ -373,11 +373,22 @@ class OtaFromTargetFilesTest(unittest.TestCase):
	}		}

	def setUp(self):		def setUp(self):
			self.testdata_dir = test_utils.get_testdata_dir()
			self.assertTrue(os.path.exists(self.testdata_dir))

	# Reset the global options as in ota_from_target_files.py.		# Reset the global options as in ota_from_target_files.py.
	common.OPTIONS.incremental_source = None		common.OPTIONS.incremental_source = None
	common.OPTIONS.downgrade = False		common.OPTIONS.downgrade = False
	common.OPTIONS.timestamp = False		common.OPTIONS.timestamp = False
	common.OPTIONS.wipe_user_data = False		common.OPTIONS.wipe_user_data = False
			common.OPTIONS.no_signing = False
			common.OPTIONS.package_key = os.path.join(self.testdata_dir, 'testkey')
			common.OPTIONS.key_passwords = {
			common.OPTIONS.package_key : None,
			}

			common.OPTIONS.search_path = test_utils.get_search_path()
			self.assertIsNotNone(common.OPTIONS.search_path)

	def tearDown(self):		def tearDown(self):
	common.Cleanup()		common.Cleanup()
	@@ -590,6 +601,68 @@ class OtaFromTargetFilesTest(unittest.TestCase):
	with zipfile.ZipFile(target_file) as verify_zip:		with zipfile.ZipFile(target_file) as verify_zip:
	self.assertNotIn(POSTINSTALL_CONFIG, verify_zip.namelist())		self.assertNotIn(POSTINSTALL_CONFIG, verify_zip.namelist())

			def _test_FinalizeMetadata(self, large_entry=False):
			entries = [
			'required-entry1',
			'required-entry2',
			]
			zip_file = PropertyFilesTest.construct_zip_package(entries)
			# Add a large entry of 1 GiB if requested.
			if large_entry:
			with zipfile.ZipFile(zip_file, 'a') as zip_fp:
			zip_fp.writestr(
			# Using 'zoo' so that the entry stays behind others after signing.
			'zoo',
			'A' * 1024 * 1024 * 1024,
			zipfile.ZIP_STORED)

			metadata = {}
			output_file = common.MakeTempFile(suffix='.zip')
			needed_property_files = (
			TestPropertyFiles(),
			)
			FinalizeMetadata(metadata, zip_file, output_file, needed_property_files)
			self.assertIn('ota-test-property-files', metadata)

			def test_FinalizeMetadata(self):
			self._test_FinalizeMetadata()

			def test_FinalizeMetadata_withNoSigning(self):
			common.OPTIONS.no_signing = True
			self._test_FinalizeMetadata()

			def test_FinalizeMetadata_largeEntry(self):
			self._test_FinalizeMetadata(large_entry=True)

			def test_FinalizeMetadata_largeEntry_withNoSigning(self):
			common.OPTIONS.no_signing = True
			self._test_FinalizeMetadata(large_entry=True)

			def test_FinalizeMetadata_insufficientSpace(self):
			entries = [
			'required-entry1',
			'required-entry2',
			'optional-entry1',
			'optional-entry2',
			]
			zip_file = PropertyFilesTest.construct_zip_package(entries)
			with zipfile.ZipFile(zip_file, 'a') as zip_fp:
			zip_fp.writestr(
			# 'foo-entry1' will appear ahead of all other entries (in alphabetical
			# order) after the signing, which will in turn trigger the
			# InsufficientSpaceException and an automatic retry.
			'foo-entry1',
			'A' * 1024 * 1024,
			zipfile.ZIP_STORED)

			metadata = {}
			needed_property_files = (
			TestPropertyFiles(),
			)
			output_file = common.MakeTempFile(suffix='.zip')
			FinalizeMetadata(metadata, zip_file, output_file, needed_property_files)
			self.assertIn('ota-test-property-files', metadata)


	class TestPropertyFiles(PropertyFiles):		class TestPropertyFiles(PropertyFiles):
	"""A class that extends PropertyFiles for testing purpose."""		"""A class that extends PropertyFiles for testing purpose."""
	@@ -609,11 +682,14 @@ class TestPropertyFiles(PropertyFiles):

	class PropertyFilesTest(unittest.TestCase):		class PropertyFilesTest(unittest.TestCase):

			def setUp(self):
			common.OPTIONS.no_signing = False

	def tearDown(self):		def tearDown(self):
	common.Cleanup()		common.Cleanup()

	@staticmethod		@staticmethod
	def _construct_zip_package(entries):		def construct_zip_package(entries):
	zip_file = common.MakeTempFile(suffix='.zip')		zip_file = common.MakeTempFile(suffix='.zip')
	with zipfile.ZipFile(zip_file, 'w') as zip_fp:		with zipfile.ZipFile(zip_file, 'w') as zip_fp:
	for entry in entries:		for entry in entries:
	@@ -647,7 +723,7 @@ class PropertyFilesTest(unittest.TestCase):
	'required-entry1',		'required-entry1',
	'required-entry2',		'required-entry2',
	)		)
	zip_file = self._construct_zip_package(entries)		zip_file = self.construct_zip_package(entries)
	property_files = TestPropertyFiles()		property_files = TestPropertyFiles()
	with zipfile.ZipFile(zip_file, 'r') as zip_fp:		with zipfile.ZipFile(zip_file, 'r') as zip_fp:
	property_files_string = property_files.Compute(zip_fp)		property_files_string = property_files.Compute(zip_fp)
	@@ -663,7 +739,7 @@ class PropertyFilesTest(unittest.TestCase):
	'optional-entry1',		'optional-entry1',
	'optional-entry2',		'optional-entry2',
	)		)
	zip_file = self._construct_zip_package(entries)		zip_file = self.construct_zip_package(entries)
	property_files = TestPropertyFiles()		property_files = TestPropertyFiles()
	with zipfile.ZipFile(zip_file, 'r') as zip_fp:		with zipfile.ZipFile(zip_file, 'r') as zip_fp:
	property_files_string = property_files.Compute(zip_fp)		property_files_string = property_files.Compute(zip_fp)
	@@ -676,7 +752,7 @@ class PropertyFilesTest(unittest.TestCase):
	entries = (		entries = (
	'required-entry2',		'required-entry2',
	)		)
	zip_file = self._construct_zip_package(entries)		zip_file = self.construct_zip_package(entries)
	property_files = TestPropertyFiles()		property_files = TestPropertyFiles()
	with zipfile.ZipFile(zip_file, 'r') as zip_fp:		with zipfile.ZipFile(zip_file, 'r') as zip_fp:
	self.assertRaises(KeyError, property_files.Compute, zip_fp)		self.assertRaises(KeyError, property_files.Compute, zip_fp)
	@@ -687,7 +763,7 @@ class PropertyFilesTest(unittest.TestCase):
	'required-entry2',		'required-entry2',
	'META-INF/com/android/metadata',		'META-INF/com/android/metadata',
	]		]
	zip_file = self._construct_zip_package(entries)		zip_file = self.construct_zip_package(entries)
	property_files = TestPropertyFiles()		property_files = TestPropertyFiles()
	with zipfile.ZipFile(zip_file, 'r') as zip_fp:		with zipfile.ZipFile(zip_file, 'r') as zip_fp:
	# pylint: disable=protected-access		# pylint: disable=protected-access
	@@ -710,7 +786,7 @@ class PropertyFilesTest(unittest.TestCase):
	'optional-entry2',		'optional-entry2',
	'META-INF/com/android/metadata',		'META-INF/com/android/metadata',
	)		)
	zip_file = self._construct_zip_package(entries)		zip_file = self.construct_zip_package(entries)
	property_files = TestPropertyFiles()		property_files = TestPropertyFiles()
	with zipfile.ZipFile(zip_file, 'r') as zip_fp:		with zipfile.ZipFile(zip_file, 'r') as zip_fp:
	# First get the raw metadata string (i.e. without padding space).		# First get the raw metadata string (i.e. without padding space).
	@@ -725,7 +801,7 @@ class PropertyFilesTest(unittest.TestCase):

	# Or pass in insufficient length.		# Or pass in insufficient length.
	self.assertRaises(		self.assertRaises(
	AssertionError,		PropertyFiles.InsufficientSpaceException,
	property_files.Finalize,		property_files.Finalize,
	zip_fp,		zip_fp,
	raw_length - 1)		raw_length - 1)
	@@ -745,7 +821,7 @@ class PropertyFilesTest(unittest.TestCase):
	'optional-entry2',		'optional-entry2',
	'META-INF/com/android/metadata',		'META-INF/com/android/metadata',
	)		)
	zip_file = self._construct_zip_package(entries)		zip_file = self.construct_zip_package(entries)
	property_files = TestPropertyFiles()		property_files = TestPropertyFiles()
	with zipfile.ZipFile(zip_file, 'r') as zip_fp:		with zipfile.ZipFile(zip_file, 'r') as zip_fp:
	# First get the raw metadata string (i.e. without padding space).		# First get the raw metadata string (i.e. without padding space).
	@@ -787,7 +863,7 @@ class StreamingPropertyFilesTest(PropertyFilesTest):
	'care_map.txt',		'care_map.txt',
	'compatibility.zip',		'compatibility.zip',
	)		)
	zip_file = self._construct_zip_package(entries)		zip_file = self.construct_zip_package(entries)
	property_files = StreamingPropertyFiles()		property_files = StreamingPropertyFiles()
	with zipfile.ZipFile(zip_file, 'r') as zip_fp:		with zipfile.ZipFile(zip_file, 'r') as zip_fp:
	property_files_string = property_files.Compute(zip_fp)		property_files_string = property_files.Compute(zip_fp)
	@@ -804,7 +880,7 @@ class StreamingPropertyFilesTest(PropertyFilesTest):
	'compatibility.zip',		'compatibility.zip',
	'META-INF/com/android/metadata',		'META-INF/com/android/metadata',
	]		]
	zip_file = self._construct_zip_package(entries)		zip_file = self.construct_zip_package(entries)
	property_files = StreamingPropertyFiles()		property_files = StreamingPropertyFiles()
	with zipfile.ZipFile(zip_file, 'r') as zip_fp:		with zipfile.ZipFile(zip_file, 'r') as zip_fp:
	# pylint: disable=protected-access		# pylint: disable=protected-access
	@@ -827,7 +903,7 @@ class StreamingPropertyFilesTest(PropertyFilesTest):
	'compatibility.zip',		'compatibility.zip',
	'META-INF/com/android/metadata',		'META-INF/com/android/metadata',
	)		)
	zip_file = self._construct_zip_package(entries)		zip_file = self.construct_zip_package(entries)
	property_files = StreamingPropertyFiles()		property_files = StreamingPropertyFiles()
	with zipfile.ZipFile(zip_file, 'r') as zip_fp:		with zipfile.ZipFile(zip_file, 'r') as zip_fp:
	# First get the raw metadata string (i.e. without padding space).		# First get the raw metadata string (i.e. without padding space).
	@@ -923,8 +999,8 @@ class AbOtaPropertyFilesTest(PropertyFilesTest):
	self.assertEqual(verify_fp.read(), metadata_signature)		self.assertEqual(verify_fp.read(), metadata_signature)

	@staticmethod		@staticmethod
	def _construct_zip_package_withValidPayload(with_metadata=False):		def construct_zip_package_withValidPayload(with_metadata=False):
	# Cannot use _construct_zip_package() since we need a "valid" payload.bin.		# Cannot use construct_zip_package() since we need a "valid" payload.bin.
	target_file = construct_target_files()		target_file = construct_target_files()
	payload = Payload()		payload = Payload()
	payload.Generate(target_file)		payload.Generate(target_file)
	@@ -951,7 +1027,7 @@ class AbOtaPropertyFilesTest(PropertyFilesTest):
	return zip_file		return zip_file

	def test_Compute(self):		def test_Compute(self):
	zip_file = self._construct_zip_package_withValidPayload()		zip_file = self.construct_zip_package_withValidPayload()
	property_files = AbOtaPropertyFiles()		property_files = AbOtaPropertyFiles()
	with zipfile.ZipFile(zip_file, 'r') as zip_fp:		with zipfile.ZipFile(zip_file, 'r') as zip_fp:
	property_files_string = property_files.Compute(zip_fp)		property_files_string = property_files.Compute(zip_fp)
	@@ -964,7 +1040,7 @@ class AbOtaPropertyFilesTest(PropertyFilesTest):
	zip_file, tokens, ('care_map.txt', 'compatibility.zip'))		zip_file, tokens, ('care_map.txt', 'compatibility.zip'))

	def test_Finalize(self):		def test_Finalize(self):
	zip_file = self._construct_zip_package_withValidPayload(with_metadata=True)		zip_file = self.construct_zip_package_withValidPayload(with_metadata=True)
	property_files = AbOtaPropertyFiles()		property_files = AbOtaPropertyFiles()
	with zipfile.ZipFile(zip_file, 'r') as zip_fp:		with zipfile.ZipFile(zip_file, 'r') as zip_fp:
	# pylint: disable=protected-access		# pylint: disable=protected-access
	@@ -980,7 +1056,7 @@ class AbOtaPropertyFilesTest(PropertyFilesTest):
	zip_file, tokens, ('care_map.txt', 'compatibility.zip'))		zip_file, tokens, ('care_map.txt', 'compatibility.zip'))

	def test_Verify(self):		def test_Verify(self):
	zip_file = self._construct_zip_package_withValidPayload(with_metadata=True)		zip_file = self.construct_zip_package_withValidPayload(with_metadata=True)
	property_files = AbOtaPropertyFiles()		property_files = AbOtaPropertyFiles()
	with zipfile.ZipFile(zip_file, 'r') as zip_fp:		with zipfile.ZipFile(zip_file, 'r') as zip_fp:
	# pylint: disable=protected-access		# pylint: disable=protected-access
	@@ -1001,7 +1077,7 @@ class NonAbOtaPropertyFilesTest(PropertyFilesTest):

	def test_Compute(self):		def test_Compute(self):
	entries = ()		entries = ()
	zip_file = self._construct_zip_package(entries)		zip_file = self.construct_zip_package(entries)
	property_files = NonAbOtaPropertyFiles()		property_files = NonAbOtaPropertyFiles()
	with zipfile.ZipFile(zip_file) as zip_fp:		with zipfile.ZipFile(zip_file) as zip_fp:
	property_files_string = property_files.Compute(zip_fp)		property_files_string = property_files.Compute(zip_fp)
	@@ -1014,7 +1090,7 @@ class NonAbOtaPropertyFilesTest(PropertyFilesTest):
	entries = [		entries = [
	'META-INF/com/android/metadata',		'META-INF/com/android/metadata',
	]		]
	zip_file = self._construct_zip_package(entries)		zip_file = self.construct_zip_package(entries)
	property_files = NonAbOtaPropertyFiles()		property_files = NonAbOtaPropertyFiles()
	with zipfile.ZipFile(zip_file) as zip_fp:		with zipfile.ZipFile(zip_file) as zip_fp:
	# pylint: disable=protected-access		# pylint: disable=protected-access
	@@ -1032,7 +1108,7 @@ class NonAbOtaPropertyFilesTest(PropertyFilesTest):
	entries = (		entries = (
	'META-INF/com/android/metadata',		'META-INF/com/android/metadata',
	)		)
	zip_file = self._construct_zip_package(entries)		zip_file = self.construct_zip_package(entries)
	property_files = NonAbOtaPropertyFiles()		property_files = NonAbOtaPropertyFiles()
	with zipfile.ZipFile(zip_file) as zip_fp:		with zipfile.ZipFile(zip_file) as zip_fp:
	# pylint: disable=protected-access		# pylint: disable=protected-access

tools/releasetools/test_utils.py

+16 −0

Original line number	Original line	Diff line number	Diff line
	@@ -32,6 +32,22 @@ def get_testdata_dir():
	return os.path.join(current_dir, 'testdata')		return os.path.join(current_dir, 'testdata')


			def get_search_path():
			"""Returns the search path that has 'framework/signapk.jar' under."""
			current_dir = os.path.dirname(os.path.realpath(__file__))
			for path in (
			# In relative to 'build/make/tools/releasetools' in the Android source.
			['..'] * 4 + ['out', 'host', 'linux-x86'],
			# Or running the script unpacked from otatools.zip.
			['..']):
			full_path = os.path.realpath(os.path.join(current_dir, *path))
			signapk_path = os.path.realpath(
			os.path.join(full_path, 'framework', 'signapk.jar'))
			if os.path.exists(signapk_path):
			return full_path
			return None


	def construct_sparse_image(chunks):		def construct_sparse_image(chunks):
	"""Returns a sparse image file constructed from the given chunks.		"""Returns a sparse image file constructed from the given chunks.