build/android/pylib/utils/device_temp_file.py

   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 """A temp file that automatically gets pushed and deleted from a device."""
   6
   7 # pylint: disable=W0622
   8
   9 import random
  10 import time
  11
  12 from pylib import cmd_helper
  13 from pylib.device import device_errors
  14
  15
  16 class DeviceTempFile(object):
  17   def __init__(self, adb, suffix='', prefix='temp_file', dir='/data/local/tmp'):
  18     """Find an unused temporary file path in the devices external directory.
  19
  20     When this object is closed, the file will be deleted on the device.
  21
  22     Args:
  23       adb: An instance of AdbWrapper
  24       suffix: The suffix of the name of the temp file.
  25       prefix: The prefix of the name of the temp file.
  26       dir: The directory on the device where to place the temp file.
  27     """
  28     self._adb = adb
  29     # make sure that the temp dir is writable
  30     self._adb.Shell('test -d %s' % cmd_helper.SingleQuote(dir))
  31     while True:
  32       self.name = '{dir}/{prefix}-{time:d}-{nonce:d}{suffix}'.format(
  33         dir=dir, prefix=prefix, time=int(time.time()),
  34         nonce=random.randint(0, 1000000), suffix=suffix)
  35       self.name_quoted = cmd_helper.SingleQuote(self.name)
  36       try:
  37         self._adb.Shell('test -e %s' % self.name_quoted)
  38       except device_errors.AdbCommandFailedError:
  39         break # file does not exist
  40
  41     # Immediately touch the file, so other temp files can't get the same name.
  42     self._adb.Shell('touch %s' % self.name_quoted)
  43
  44   def close(self):
  45     """Deletes the temporary file from the device."""
  46     # ignore exception if the file is already gone.
  47     try:
  48       self._adb.Shell('rm -f %s' % self.name_quoted)
  49     except device_errors.AdbCommandFailedError:
  50       # file does not exist on Android version without 'rm -f' support (ICS)
  51       pass
  52
  53   def __enter__(self):
  54     return self
  55
  56   def __exit__(self, type, value, traceback):
  57     self.close()