[Fuchsia] Script for downloading the latest prebuilt dev SDK

tools/download_latest_dev_sdk.py

+#!/usr/bin/env python
+# Copyright 2016 The Dart project authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# This script downloads the latest dev SDK from
+# http://gsdview.appspot.com/dart-archive/channels/dev/raw/latest/sdk/
+# into tools/sdks/$HOST_OS/. It is intended to be invoked from Jiri hooks in
+# a Fuchsia checkout.
+
+import os
+import sys
+import zipfile
+import urllib
+import utils
+
+HOST_OS = utils.GuessOS()
+HOST_ARCH = utils.GuessArchitecture()
+SCRIPT_DIR = os.path.dirname(sys.argv[0])
+DART_ROOT = os.path.realpath(os.path.join(SCRIPT_DIR, '..'))
+
+BASE_URL = 'http://gsdview.appspot.com/dart-archive/channels/dev/raw/latest/sdk'
+
+def host_os_for_sdk(host_os):
+  if host_os.startswith('macos'):
+    return 'mac'
+  if host_os.startswith('win'):
+    return 'windows'
+  return host_os
+
+# Python's zipfile doesn't preserve file permissions during extraction, so we
+# have to do it manually.
+def extract_file(zf, info, extract_dir):
+  zf.extract( info.filename, path=extract_dir )
+  out_path = os.path.join(extract_dir, info.filename)
+  perm = info.external_attr >> 16L
+  os.chmod(out_path, perm)
+
+def main(argv):
+  host_os = host_os_for_sdk(HOST_OS)
+  zip_file = ('dartsdk-%s-x64-release.zip' % HOST_OS)
+  sha_file = zip_file + '.sha256sum'
+  sdk_path = os.path.join(DART_ROOT, 'tools', 'sdks', host_os)
+  local_sha_path = os.path.join(sdk_path, sha_file)
+  remote_sha_path = os.path.join(sdk_path, sha_file + '.remote')
+  zip_path = os.path.join(sdk_path, zip_file)
+  sha_url = BASE_URL + '/' + sha_file
+  zip_url = BASE_URL + '/' + zip_file
+
+  local_sha = ''
+  if os.path.isfile(local_sha_path):
+    with open(local_sha_path, 'r') as fp:
+      local_sha = fp.read()
+
+  remote_sha = ''
+  urllib.urlretrieve(sha_url, remote_sha_path)
+  with open(remote_sha_path, 'r') as fp:
+    remote_sha = fp.read()
+  os.remove(remote_sha_path)
+
+  if local_sha == '' or local_sha != remote_sha:
+    with open(local_sha_path, 'w') as fp:
+      fp.write(remote_sha)
+    print 'Downloading prebuilt Dart SDK from: ' + zip_url
+    urllib.urlretrieve(zip_url, zip_path)
+    with zipfile.ZipFile(zip_path, 'r') as zf:
+      for info in zf.infolist():
+        extract_file(zf, info, sdk_path)
+
+if __name__ == '__main__':
+  sys.exit(main(sys.argv))