prebuilts_fetcher.py revision 1320f92c476a1ad9d19dba2a48c72b75566198e9
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. 4 5"""This module fetches and syncs prebuilts from Google Cloud Storage (GCS). 6 7See prebuilts/README for a description of the respository <> GCS sync mechanism. 8""" 9 10import hashlib 11import logging 12import os 13import urllib 14 15from memory_inspector import constants 16 17 18# Bypass the GCS download logic in unittests and use the *_ForTests mock. 19in_test_harness = False 20 21 22def GetIfChanged(local_file_path): 23 """Downloads the file from GCS, only if the local one is outdated.""" 24 is_changed = _IsChanged(local_file_path) 25 26 # In test harness mode we are only interested in checking that the proper 27 # .sha1 files have been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). 28 if in_test_harness: 29 return _GetIfChanged_ForTests(local_file_path) 30 31 if not is_changed: 32 return 33 obj_name = _GetRemoteFileID(local_file_path) 34 url = constants.PREBUILTS_BASE_URL + 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 for %s failed.' % 38 local_file_path) 39 40 41def _IsChanged(local_file_path): 42 """Checks whether the local_file_path exists and matches the expected hash.""" 43 is_changed = True 44 expected_hash = _GetRemoteFileID(local_file_path) 45 if os.path.exists(local_file_path): 46 with open(local_file_path, 'rb') as f: 47 local_hash = hashlib.sha1(f.read()).hexdigest() 48 is_changed = (local_hash != expected_hash) 49 return is_changed 50 51 52def _GetRemoteFileID(local_file_path): 53 """Returns the checked-in hash which identifies the name of file in GCS.""" 54 hash_path = local_file_path + '.sha1' 55 with open(hash_path, 'rb') as f: 56 return f.read(1024).rstrip() 57 58 59def _GetIfChanged_ForTests(local_file_path): 60 """This is the mock version of |GetIfChanged| used only in unittests.""" 61 # Just truncate / create an empty file. 62 open(local_file_path, 'wb').close() 63