Add Python util to read from a data pipe into a bytearray

mojo/python/tests/data_pipe_utils_unittest.py

+# Copyright 2015 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.
+
+import random
+
+import mojo_unittest
+from mojo_bindings import promise
+
+# pylint: disable=F0401
+import mojo_system as system
+
+# pylint: disable=F0401
+from mojo_utils import data_pipe_utils
+
+
+def _GetRandomBuffer(size):
+  random.seed(size)
+  return bytearray(''.join(chr(random.randint(0, 255)) for i in xrange(size)))
+
+
+class DataPipeCopyTest(mojo_unittest.MojoTestCase):
+  def setUp(self):
+    super(DataPipeCopyTest, self).setUp()
+    self.handles = system.DataPipe()
+    self.error = None
+
+  def tearDown(self):
+    self.handles = None
+    super(DataPipeCopyTest, self).tearDown()
+
+  def _writeDataAndClose(self, handle, data):
+    status, num_bytes_written = handle.WriteData(data)
+    handle.Close()
+    self.assertEquals(system.RESULT_OK, status)
+    self.assertEquals(len(data), num_bytes_written)
+
+  def _copyDataFromPipe(self, handle, expected_data,
+                        deadline=system.DEADLINE_INDEFINITE):
+    self._VerifyDataCopied(data_pipe_utils.CopyFromDataPipe(
+         handle, deadline), expected_data).Catch(self._CatchError)
+
+  def _CatchError(self, error):
+    if self.loop:
+      self.loop.Quit()
+    self.error = error
+
+  @promise.async
+  def _VerifyDataCopied(self, data, expected_data):
+    self.handles.consumer_handle.Close()

[qsr, 2015/03/03 17:10:37]

I think you do not need to handle this close yourself, am I wrong?

[blundell, 2015/03/04 10:28:52]

Done.

+    self.assertEquals(expected_data, data)
+    self.loop.Quit()
+
+  def _runAndCheckError(self):
+    self.loop.Run()
+    if self.error:
+      # pylint: disable=E0702
+      raise self.error
+
+  def _testEagerWrite(self, data):
+    self._writeDataAndClose(self.handles.producer_handle, data)
+    self._copyDataFromPipe(self.handles.consumer_handle, data)
+    self._runAndCheckError()
+
+  def _testDelayedWrite(self, data):
+    self._copyDataFromPipe(self.handles.consumer_handle, data)
+    self._writeDataAndClose(self.handles.producer_handle, data)
+    self._runAndCheckError()
+
+  def testTimeout(self):
+    self._copyDataFromPipe(self.handles.consumer_handle, bytearray(),
+                           deadline=100)
+    try:
+      self._runAndCheckError()

[qsr, 2015/03/03 17:10:36]

You have construction in python unittest when you expect an exception ->
https://docs.python.org/2/library/unittest.html#unittest.TestCase.assertRaises
and co.

[blundell, 2015/03/04 10:28:52]

Done.

+    except data_pipe_utils.DataPipeCopyException:
+      pass
+    else:
+      assert 0
+
+  def testCloseProducerWithoutWriting(self):
+    self._copyDataFromPipe(self.handles.consumer_handle, bytearray())
+    self.handles.producer_handle.Close()
+    self._runAndCheckError()
+
+  def testCloseConsumerWithoutWriting(self):

[qsr, 2015/03/03 17:10:37]

You should not have this test. This is kind of an undefined behavior. 

[blundell, 2015/03/04 10:28:52]

Done.

+    self._copyDataFromPipe(self.handles.consumer_handle, bytearray())
+    self.handles.consumer_handle.Close()
+    try:
+      self._runAndCheckError()
+    except data_pipe_utils.DataPipeCopyException:
+      pass
+    else:
+      assert 0
+
+  def testEagerWriteOfEmptyData(self):
+    self._testEagerWrite(bytearray())
+
+  def testDelayedWriteOfEmptyData(self):
+    self._testDelayedWrite(bytearray())
+
+  def testEagerWriteOfNonEmptyData(self):
+    self._testEagerWrite(_GetRandomBuffer(1024))
+
+  def testDelayedWriteOfNonEmptyData(self):
+    self._testDelayedWrite(_GetRandomBuffer(1024))
+
+  def testEagerWriteOfLargeBuffer(self):
+    self._testEagerWrite(_GetRandomBuffer(32 * 1024))
+
+  def testDelayedWriteOfLargeBuffer(self):
+    self._testDelayedWrite(_GetRandomBuffer(32 * 1024))