Allow RunShellCommand to work even with very large commands

build/android/pylib/utils/device_temp_file.py

 # Copyright 2013 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.
 
 """A temp file that automatically gets pushed and deleted from a device."""
 
 # pylint: disable=W0622
 
 import random
 import time
 
+from pylib import cmd_helper
+from pylib.device import adb_wrapper
+from pylib.device import device_errors
+
+
 class DeviceTempFile(object):
   def __init__(self, device, prefix='temp_file', suffix=''):
     """Find an unused temporary file path in the devices external directory.
 
     When this object is closed, the file will be deleted on the device.
 
     Args:
-      device: An instance of DeviceUtils
+      device: An instance of AdbWrapper, or an object with an 'adb' property
       prefix: The prefix of the name of the temp file.
       suffix: The suffix of the name of the temp file.
     """
-    self._device = device
+    if isinstance(device, adb_wrapper.AdbWrapper):
+      self._adb = device
+    elif (hasattr(device, 'adb')
+          and isinstance(device.adb, adb_wrapper.AdbWrapper)):

[perezju, 2014/11/25 16:25:33]

I think this should be quite safe, and allows us to pass both AdbWrapper or
DeviceUtils objects.

I couldn't easily test for isinstnance(.., device_utils.DeviceUtils) because
importing device_utils causes a cyclic module dependency. (which, as we learned
yesterday, is precisely what we don't want to do!)

[jbudorick, 2014/11/25 17:05:26]

Does it make sense to pass DeviceUtils at all? DeviceUtils instances have a
public 'adb' attribute (obviously), so perhaps we should just make the clients
pass in the AdbWrapper?

+      self._adb = device.adb
+    else:
+      raise ValueError('Unsupported type passed for argument "device"')
+
+    external_storage = self._adb.Shell('echo $EXTERNAL_STORAGE').rstrip()
+    # make sure that external storage is readable
+    self._adb.Shell('test -d %s' % external_storage)
     while True:
-      i = random.randint(0, 1000000)
-      self.name = '%s/%s-%d-%010d%s' % (
-          self._device.GetExternalStoragePath(),
-          prefix, int(time.time()), i, suffix)
-      if not self._device.FileExists(self.name):
-        break
-    # Immediately create an empty file so that other temp files can't
-    # be given the same name.
-    # |as_root| must be set to False due to the implementation of |WriteFile|.
-    # Having |as_root| be True may cause infinite recursion.
-    self._device.WriteFile(self.name, '', as_root=False)
+      self.name = '{path}/{prefix}-{time:d}-{nonce:d}{suffix}'.format(
+        path=external_storage, prefix=prefix, time=int(time.time()),
+        nonce=random.randint(0, 1000000), suffix=suffix)
+      self.name_quoted = cmd_helper.SingleQuote(self.name)

[perezju, 2014/11/25 16:25:33]

we use this quite often, so thought it was a better idea to have it cached.

+      try:
+        self._adb.Shell('test -e %s' % self.name_quoted)
+      except device_errors.AdbCommandFailedError:
+        break # file does not exist
+
+    # Immediately touch the file, so other temp files can't get the same name.
+    self._adb.Shell('touch %s' % self.name_quoted)
 
   def close(self):
     """Deletes the temporary file from the device."""
-    self._device.RunShellCommand(['rm', self.name])
+    # we use -f to ignore errors if the file is already gone
+    self._adb.Shell('rm -f %s' % self.name_quoted)
 
   def __enter__(self):
     return self
 
   def __exit__(self, type, value, traceback):
     self.close()