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
5import os
6import subprocess
7
8from telemetry.core.platform import platform_backend
9from telemetry.util import support_binaries
10
11
12class DesktopPlatformBackend(platform_backend.PlatformBackend):
13
14  # This is an abstract class. It is OK to have abstract methods.
15  # pylint: disable=W0223
16
17  def FlushSystemCacheForDirectory(self, directory, ignoring=None):
18    assert directory and os.path.exists(directory), \
19        'Target directory %s must exist' % directory
20    flush_command = support_binaries.FindPath('clear_system_cache',
21                                              self.GetOSName())
22    assert flush_command, 'You must build clear_system_cache first'
23
24    args = []
25    directory_contents = os.listdir(directory)
26    for item in directory_contents:
27      if not ignoring or item not in ignoring:
28        args.append(os.path.join(directory, item))
29
30    # According to msdn:
31    # http://msdn.microsoft.com/en-us/library/ms682425%28VS.85%29.aspx
32    # there's a maximum allowable command line of 32,768 characters on windows.
33    while args:
34      # Small note about [:256] and [256:]
35      # [:N] will return a list with the first N elements, ie.
36      # with [1,2,3,4,5], [:2] -> [1,2], and [2:] -> [3,4,5]
37      # with [1,2,3,4,5], [:5] -> [1,2,3,4,5] and [5:] -> []
38      subprocess.check_call([flush_command, '--recurse'] + args[:256])
39      args = args[256:]
40