1 # Copyright 2014 The Chromium Authors. All rights reserved.
2 # Use of this source code is governed by a BSD-style license that can be
3 # found in the LICENSE file.
5 """This module fetches and syncs prebuilts from Google Cloud Storage (GCS).
7 See prebuilts/README for a description of the respository <> GCS sync mechanism.
16 _PREBUILTS_BUCKET = 'chromium-telemetry'
18 # Bypass the GCS download logic in unittests and use the *_ForTests mock.
19 in_test_harness = False
22 def GetIfChanged(local_file_path):
23 """Downloads the file from GCS, only if the local one is outdated."""
24 is_changed = _IsChanged(local_file_path)
26 # In test harness mode we are only interested in checking that the proper
27 # .sha1 files have been checked in (hence the call to _IsChanged() above).
29 return _GetIfChanged_ForTests(local_file_path)
33 obj_name = _GetRemoteFileID(local_file_path)
34 url = 'https://storage.googleapis.com/%s/%s' % (_PREBUILTS_BUCKET, obj_name)
35 logging.info('Downloading %s prebuilt from %s.' % (local_file_path, url))
36 urllib.urlretrieve(url, local_file_path)
37 assert(not _IsChanged(local_file_path)), 'GCS download failed.'
40 def _IsChanged(local_file_path):
41 """Checks whether the local_file_path exists and matches the expected hash."""
43 expected_hash = _GetRemoteFileID(local_file_path)
44 if os.path.exists(local_file_path):
45 with open(local_file_path, 'rb') as f:
46 local_hash = hashlib.sha1(f.read()).hexdigest()
47 is_changed = (local_hash != expected_hash)
51 def _GetRemoteFileID(local_file_path):
52 """Returns the checked-in hash which identifies the name of file in GCS."""
53 hash_path = local_file_path + '.sha1'
54 with open(hash_path, 'rb') as f:
55 return f.read(1024).rstrip()
58 def _GetIfChanged_ForTests(local_file_path):
59 """This is the mock version of |GetIfChanged| used only in unittests."""
60 # Just truncate / create an empty file.
61 open(local_file_path, 'wb').close()