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# Copyright (c) 2015 SUSE Linux GmbH. All rights reserved.
#
# This file is part of kiwi.
#
# kiwi is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# kiwi is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with kiwi. If not, see <http://www.gnu.org/licenses/>
#
import os
from collections import namedtuple
import hashlib
import encodings.ascii as encoding
# project
from kiwi.api_helper import decommissioned
from kiwi.utils.compress import Compress
from kiwi.utils.primes import factors
from kiwi.exceptions import (
KiwiFileNotFound
)
class Checksum:
"""
**Manage checksum creation for files**
:param str source_filename: source file name to build checksum for
:param str checksum_filename: target file with checksum information
"""
def __init__(self, source_filename):
if not os.path.exists(source_filename):
raise KiwiFileNotFound(
f'checksum source file {source_filename} not found'
)
self.source_filename = source_filename
self.checksum_filename = None
self.ascii = encoding.getregentry().name
def matches(self, checksum, filename):
"""
Compare given checksum with reference checksum stored
in the provided filename. If the checksum matches the
method returns True, or False in case it does not match
:param str checksum: checksum string to compare
:param str filename: filename containing checksum
:return: True or False
:rtype: bool
"""
if not os.path.exists(filename):
return False
with open(filename, encoding=self.ascii) as checksum_file:
checksum_from_file = checksum_file.read()
# checksum is expected to be stored in the first field
# separated by space, other information might contain
# the filename or blocklist data which is not of interest
# for the plain checksum match
if checksum_from_file.split(' ')[0] == checksum:
return True
return False
@decommissioned
def md5(self, filename=None):
pass # pragma: no cover
def sha256(self, filename=None):
"""
Create sha256 checksum
:param str filename: filename for checksum
"""
sha256_checksum = self._calculate_hash_hexdigest(
hashlib.sha256(), self.source_filename
)
if filename:
self._create_checksum_file(
sha256_checksum, filename
)
return sha256_checksum
def _create_checksum_file(self, checksum, filename):
"""
Creates the text file that contains the checksum
:param str checksum: checksum to include into the file
:param str filename: filename of the output file
"""
compressed_blocks = None
compress = Compress(self.source_filename)
if compress.get_format():
compressed_blocks = self._block_list(
os.path.getsize(self.source_filename)
)
compress.uncompress(temporary=True)
blocks = self._block_list(
os.path.getsize(compress.uncompressed_filename)
)
checksum = self._calculate_hash_hexdigest(
hashlib.sha256(), compress.uncompressed_filename
)
else:
blocks = self._block_list(
os.path.getsize(self.source_filename)
)
with open(filename, encoding=self.ascii, mode='w') as checksum_file:
if compressed_blocks:
checksum_file.write(
'%s %s %s %s %s\n' % (
checksum, blocks.blocks, blocks.blocksize,
compressed_blocks.blocks, compressed_blocks.blocksize
)
)
else:
checksum_file.write(
f'{checksum} {blocks.blocks} {blocks.blocksize}\n'
)
def _calculate_hash_hexdigest(self, digest, filename, digest_blocks=128):
"""
Calculates the hash hexadecimal digest for a given file.
:param func digest: Digest function for hash calculation
:param str filename: File to compute
:param int digest_blocks: Number of blocks processed at a time
"""
chunk_size = digest_blocks * digest.block_size
with open(filename, 'rb') as source:
for chunk in iter(lambda: source.read(chunk_size), b''):
digest.update(chunk)
return digest.hexdigest()
def _block_list(self, file_size):
"""
Calculates the number of blocks and the block size for a given file
size in bytes.
:param int file_size: files size in bytes.
:return: int:blocksize, int:blocks
:rtype: tuple
"""
blocksize = 1
for factor in factors(file_size, 8192):
if blocksize * factor > 8192:
break
blocksize *= factor
blocks = int(file_size / blocksize)
block_list = namedtuple(
'block_list', ['blocksize', 'blocks']
)
return block_list(
blocksize=blocksize,
blocks=blocks
)
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