1# Copyright 2013 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
6class SystemProperties(dict):
7
8  """A dict interface to interact with device system properties.
9
10  System properties are key/value pairs as exposed by adb shell getprop/setprop.
11
12  This implementation minimizes interaction with the physical device. It is
13  valid for the lifetime of a boot.
14  """
15
16  def __init__(self, android_commands):
17    super(SystemProperties, self).__init__()
18    self._adb = android_commands
19    self._cached_static_properties = {}
20
21  def __getitem__(self, key):
22    if self._IsStatic(key):
23      if key not in self._cached_static_properties:
24        self._cached_static_properties[key] = self._GetProperty(key)
25      return self._cached_static_properties[key]
26    return self._GetProperty(key)
27
28  def __setitem__(self, key, value):
29    # TODO(tonyg): This can fail with no root. Verify that it succeeds.
30    self._adb.SendShellCommand('setprop %s "%s"' % (key, value), retry_count=3)
31
32  @staticmethod
33  def _IsStatic(key):
34    # TODO(tonyg): This list is conservative and could be expanded as needed.
35    return (key.startswith('ro.boot.') or
36            key.startswith('ro.build.') or
37            key.startswith('ro.product.'))
38
39  def _GetProperty(self, key):
40    return self._adb.SendShellCommand('getprop %s' % key, retry_count=3).strip()
41