Compressing .pak resources with new option: "type=GZIPPABLE_BINDATA"

tools/grit/grit/format/gzip_string.py

+# Copyright (c) 2016 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+"""Provides gzip utilities for strings.
+"""
+import gzip
+import cStringIO
+import subprocess
+
+def GzipStringRsyncable(data):
+  # Make call to host system's gzip to get access to --rsyncable option. This
+  # option makes updates much smaller - if one line is changed in the resource,
+  # it won't have to push the entire compressed resource with the update.
+  # Instead, --rsyncable breaks the file into small chunks, so that one doesn't
+  # affect the other in compression, and then only that chunk will have to be
+  # updated.
+  gzip_proc = subprocess.Popen(['gzip', '--stdout', '--rsyncable',
+                                '--best', '--no-name'],
+                               stdin=subprocess.PIPE,
+                               stdout=subprocess.PIPE,
+                               stderr=subprocess.PIPE)
+  data, stderr = gzip_proc.communicate(data)
+  if gzip_proc.returncode != 0:
+    raise subprocess.CalledProcessError(gzip_proc.returncode, 'gzip',
+                                        stderr)
+  return data
+
+
+def GzipString(data):
+  # Allowing for option to use Python's gzip: Windows doesn't ship with gzip,
+  # and OSX's gzip does not have an --rsyncable option built in. Although this
+  # is not as good as --rsyncable, it is an option for the systems that do not
+  # have --rsyncable. This function should be avoided for release builds.
+  gzip_output = cStringIO.StringIO()
+  with gzip.GzipFile(mode='wb', compresslevel=9, fileobj=gzip_output,
+                     mtime=0) as gzip_file:
+    gzip_file.write(data)
+  data = gzip_output.getvalue()
+  gzip_output.close()
+  return data