750ed32771
File checksums are used in projects like glance and glance_store to verify image uploads and so on, so a generic oslo utility method could be useful. Change-Id: I1b76ee1876771e7965fd5704ab6281318f36e810
127 lines
3.7 KiB
Python
127 lines
3.7 KiB
Python
# Copyright 2011 OpenStack Foundation.
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# All Rights Reserved.
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#
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# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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"""
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File utilities.
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.. versionadded:: 1.8
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"""
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import contextlib
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import errno
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import hashlib
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import os
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import stat
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import tempfile
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from oslo_utils import excutils
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_DEFAULT_MODE = stat.S_IRWXU | stat.S_IRWXG | stat.S_IRWXO
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def ensure_tree(path, mode=_DEFAULT_MODE):
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"""Create a directory (and any ancestor directories required)
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:param path: Directory to create
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:param mode: Directory creation permissions
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"""
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try:
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os.makedirs(path, mode)
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except OSError as exc:
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if exc.errno == errno.EEXIST:
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if not os.path.isdir(path):
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raise
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else:
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raise
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def delete_if_exists(path, remove=os.unlink):
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"""Delete a file, but ignore file not found error.
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:param path: File to delete
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:param remove: Optional function to remove passed path
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"""
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try:
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remove(path)
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except OSError as e:
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if e.errno != errno.ENOENT:
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raise
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@contextlib.contextmanager
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def remove_path_on_error(path, remove=delete_if_exists):
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"""Protect code that wants to operate on PATH atomically.
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Any exception will cause PATH to be removed.
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:param path: File to work with
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:param remove: Optional function to remove passed path
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"""
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try:
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yield
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except Exception:
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with excutils.save_and_reraise_exception():
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remove(path)
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def write_to_tempfile(content, path=None, suffix='', prefix='tmp'):
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"""Create a temporary file containing data.
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Create a temporary file containing specified content, with a specified
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filename suffix and prefix. The tempfile will be created in a default
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location, or in the directory `path`, if it is not None. `path` and its
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parent directories will be created if they don't exist.
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:param content: bytestring to write to the file
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:param path: same as parameter 'dir' for mkstemp
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:param suffix: same as parameter 'suffix' for mkstemp
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:param prefix: same as parameter 'prefix' for mkstemp
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For example: it can be used in database tests for creating
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configuration files.
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.. versionadded:: 1.9
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"""
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if path:
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ensure_tree(path)
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(fd, path) = tempfile.mkstemp(suffix=suffix, dir=path, prefix=prefix)
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try:
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os.write(fd, content)
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finally:
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os.close(fd)
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return path
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def compute_file_checksum(path, read_chunksize=65536, algorithm='sha256'):
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"""Compute checksum of a file's contents.
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:param path: Path to the file
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:param read_chunksize: Maximum number of bytes to be read from the file
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at once. Default is 65536 bytes or 64KB
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:param algorithm: The hash algorithm name to use. For example, 'md5',
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'sha256', 'sha512' and so on. Default is 'sha256'. Refer to
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hashlib.algorithms_available for available algorithms
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:return: Hex digest string of the checksum
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.. versionadded:: 3.31.0
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"""
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checksum = hashlib.new(algorithm) # Raises appropriate exceptions.
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with open(path, 'rb') as f:
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for chunk in iter(lambda: f.read(read_chunksize), b''):
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checksum.update(chunk)
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return checksum.hexdigest()
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