| # 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 |