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# Copyright 2015 The Bazel Authors. All rights reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""This package contains various functions used when building containers."""
import json
import tarfile
from six import raise_from
def ExtractValue(value):
"""Return the contents of a file point to by value if it starts with an @.
Args:
value: The possible filename to extract or a string.
Returns:
The content of the file if value starts with an @, or the passed value.
"""
if value.startswith('@'):
with open(value[1:], 'r') as f:
value = f.read()
return value
def GetTarFile(f, name):
"""Returns the content of a file inside a tar file.
This method looks for ./f, /f and f file entry in a tar file and if found,
return its content. This allows to read file with various path prefix.
Args:
f: The tar file to read.
name: The name of the file inside the tar file.
Returns:
The content of the file, or None if not found.
"""
with open(f, 'rb') as fobj:
try:
with tarfile.open(fileobj=fobj) as tar:
members = [tarinfo.name for tarinfo in tar.getmembers()]
for i in ['', './', '/']:
if i + name in members:
return tar.extractfile(i + name).read()
except tarfile.ReadError as error:
raise_from(IOError('Error when reading %s' % f), error)
return None
def GetManifestFromTar(f=None):
"""Returns the manifest array from a tar file.
Args:
f: The tar file to read.
Returns:
The content of the manifest file or an empty array if not found.
"""
if f:
raw_manifest_data = GetTarFile(f, 'manifest.json')
if raw_manifest_data:
return json.loads(raw_manifest_data)
return []
def GetLatestManifestFromTar(f=None):
"""Returns the latest manifest entry from a tar file.
The latest manifest entry is the one at the bottom.
Args:
f: The tar file to read.
Returns:
The latest manifest entry object, or None if not found.
"""
manifest_data = GetManifestFromTar(f)
return manifest_data[-1] if manifest_data else None
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