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#!/usr/bin/env python3
#
# checksum.py
"""
Utilities for creating and checking file sha256 checksums.
.. versionadded:: 0.6.0
"""
#
# Copyright © 2020 Dominic Davis-Foster <dominic@davis-foster.co.uk>
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in all
# copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
# IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
# DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
# OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE
# OR OTHER DEALINGS IN THE SOFTWARE.
#
# stdlib
import io
from base64 import urlsafe_b64encode
from hashlib import md5, sha256
from typing import IO, TYPE_CHECKING, Callable, Optional, Union, cast
# 3rd party
from domdf_python_tools.paths import PathPlus
from domdf_python_tools.typing import PathLike
if TYPE_CHECKING:
# stdlib
from hashlib import _Hash
else:
try:
# stdlib
from _hashlib import HASH as _Hash
except ImportError: # pragma: no cover
try:
# stdlib
from _hashlib import Hash as _Hash
except ImportError:
pass
__all__ = ["get_sha256_hash", "check_sha256_hash", "get_md5_hash", "get_record_entry"]
_HashType = type(sha256())
def _get_hash(fp: IO[bytes], hash_type: Callable, blocksize: int = 1 << 20) -> "_Hash":
"""
Returns the SHA256 hash object for the given file object.
:param fp:
:param hash_type:
:param blocksize: The blocksize to read the file with.
:rtype: :mod:`hashlib.sha256() <hashlib>`
"""
hash_obj = hash_type()
fb = fp.read(blocksize)
while len(fb): # pylint: disable=len-as-condition
hash_obj.update(fb)
fb = fp.read(blocksize)
return hash_obj
def get_sha256_hash(
filename: Union[PathLike, IO[bytes]],
blocksize: int = 1 << 20,
) -> "_Hash":
"""
Returns the SHA256 hash object for the given file.
.. versionadded:: 0.6.0
:param filename:
:param blocksize: The blocksize to read the file with.
:rtype: :mod:`hashlib.sha256() <hashlib>`
.. versionchanged:: 0.16.0 Added support for already open file objects.
"""
if isinstance(filename, io.BufferedIOBase):
return _get_hash(filename, sha256, blocksize)
with open(cast(PathLike, filename), "rb") as f:
return _get_hash(f, sha256, blocksize)
def get_md5_hash(
filename: Union[PathLike, IO[bytes]],
blocksize: int = 1 << 20,
) -> "_Hash":
"""
Returns the md5 hash object for the given file.
.. versionadded:: 0.15.0
:param filename:
:param blocksize: The blocksize to read the file with.
:rtype: :mod:`hashlib.md5() <hashlib>`
.. versionchanged:: 0.16.0 Added support for already open file objects.
"""
if isinstance(filename, io.BufferedIOBase):
return _get_hash(filename, md5, blocksize)
with open(cast(PathLike, filename), "rb") as f:
return _get_hash(f, md5, blocksize)
def check_sha256_hash(
filename: Union[PathLike, IO[bytes]],
hash: Union["_Hash", str], # noqa: A002 # pylint: disable=redefined-builtin
blocksize: int = 1 << 20,
) -> bool:
r"""
Returns whether the SHA256 hash for the file matches ``hash``.
.. versionadded:: 0.6.0
:param filename:
:param hash: If a string, the hexdigest of the hash.
:type hash: :py:obj:`~typing.Union`\[:mod:`hashlib.sha256() <hashlib>`, :class:`str`\]
:param blocksize: The blocksize to read the file with.
:rtype:
.. versionchanged:: 0.16.0 Added support for already open file objects.
.. latex:clearpage::
"""
if isinstance(hash, _HashType):
hash = hash.hexdigest() # noqa: A001 # pylint: disable=redefined-builtin
return hash == get_sha256_hash(filename, blocksize).hexdigest()
def get_record_entry(filename: PathLike, blocksize: int = 1 << 20, relative_to: Optional[PathLike] = None) -> str:
"""
Constructs a :pep:`376` ``RECORD`` entry for the file.
.. versionadded:: 0.6.0
:param filename:
:param blocksize: The blocksize to read the file with.
:param relative_to:
"""
sha256_hash = get_sha256_hash(filename, blocksize).digest()
digest = "sha256=" + urlsafe_b64encode(sha256_hash).decode("latin1").rstrip('=')
filename = PathPlus(filename)
length = filename.stat().st_size
if relative_to:
filename = filename.relative_to(relative_to)
return ','.join([filename.as_posix(), digest, str(length)])
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