[Android] Add LogcatMonitor.

build/android/pylib/device/logcat_monitor.py

Index: build/android/pylib/device/logcat_monitor.py
diff --git a/build/android/pylib/device/logcat_monitor.py b/build/android/pylib/device/logcat_monitor.py
new file mode 100644
index 0000000000000000000000000000000000000000..fe53f64050228a3f79cb74303a65c6f11dfc3504
--- /dev/null
+++ b/build/android/pylib/device/logcat_monitor.py
@@ -0,0 +1,131 @@
+# 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.
+
+# pylint: disable=unused-argument
+
+import collections
+import itertools
+import logging
+import subprocess
+import tempfile
+import time
+import re
+
+from pylib.device import adb_wrapper
+from pylib.device import decorators
+from pylib.device import device_errors
+
+
+class LogcatMonitor(object):
+
+  # Format: <DATE> <TIME> <PID> <TID> <LEVEL> <COMPONENT>: <MESSAGE>
+  _THREADTIME_RE_FORMAT = r'\S* +\S* +(%s) +(%s) +(%s) +(%s): +(%s)$'
+
+  def __init__(self, adb, clear=True, filters=None):
+    if isinstance(adb, adb_wrapper.AdbWrapper):
+      self._adb = adb
+    else:
+      raise ValueError('Unsupported type passed for argument "device"')
+    self._clear = clear
+    self._filters = filters
+    self._logcat_out = None
+    self._logcat_out_file = None
+    self._logcat_proc = None
+
+  @decorators.WithTimeoutAndRetriesDefaults(10, 0)
+  def WaitFor(self, success_regex, failure_regex, timeout=None, retries=None):
+    """Waits for a logcat line matching the provided regular expression.

[klundberg, 2015/02/02 20:00:40]

As discussed offline, it might be good to update the doc a bit for this to make
it clearer what the method does.

[jbudorick, 2015/02/02 21:47:38]

Clarified the docstring and added an implementation comment below.

+
+    Note that this calls re.search on each logcat line, not re.match, so the
+    provided regular expressions don't have to match an entire line.
+
+    Args:
+      success_regex: The regular expression to search for.
+      failure_regex: An optional regular expression that, if hit, causes this
+        to stop looking for a match. Can be None.
+      timeout: timeout in seconds
+      retries: number of retries
+
+    Returns:
+      A match object if |success_regex| matches a part of a logcat line, or
+      None if |failure_regex| matches a part of a logcat line.
+    Raises:
+      CommandFailedError on logcat failure (NOT on a |failure_regex| match)

[klundberg, 2015/02/02 20:00:40]

minor nit: perioad at the end of the sentence.

[jbudorick, 2015/02/02 21:47:38]

Done.

+      CommandTimeoutError if a logcat line matching |success_regex| is not
+        found in |timeout| seconds.
+      DeviceUnreachableError if the device becomes unreachable.
+    """
+    if isinstance(success_regex, basestring):
+      success_regex = re.compile(success_regex)
+    if isinstance(failure_regex, basestring):
+      failure_regex = re.compile(failure_regex)
+
+    logging.debug('Waiting %d seconds for "%s"', timeout, success_regex.pattern)
+
+    for l in self._adb.Logcat():
+      m = success_regex.search(l)
+      if m:
+        return m
+      if failure_regex and failure_regex.search(l):
+        return None
+
+  def FindAll(self, message_regex, proc_id=None, thread_id=None, log_level=None,
+              component=None):
+    """Finds all lines in the logcat that match the provided constraints.
+
+    Args:
+      message_regex: The regular expression that the <message> section must
+        match.
+      proc_id: The process ID to match. If None, matches any process ID.
+      thread_id: The thread ID to match. If None, matches any thread ID.
+      log_level: The log level to match. If None, matches any log level.
+      component: The component to match. If None, matches any component.
+
+    Returns:
+      An iterable containing objects with five attributes:
+        |proc_id|: the process ID
+        |thread_id|: the thread ID
+        |log_level|: the log level
+        |component|: the component
+        |message|: the logcat message
+    """
+    LogcatLine = collections.namedtuple(
+        'LogcatLine',
+        ['proc_id', 'thread_id', 'log_level', 'component', 'message'])
+
+    if proc_id is None:
+      proc_id = r'\d+'
+    if thread_id is None:
+      thread_id = r'\d+'
+    if log_level is None:
+      log_level = r'[VDIWEF]'
+    if component is None:
+      component = r'[^\s:]+'
+    threadtime_re = re.compile(
+        type(self)._THREADTIME_RE_FORMAT % (
+            proc_id, thread_id, log_level, component, message_regex))
+
+    regexed_lines = (
+        re.match(threadtime_re, l)
+        for l in self._adb.Logcat(dump=True, logcat_format='threadtime'))
+    only_matches = (m for m in regexed_lines if m)
+    return (LogcatLine(*m.group(1, 2, 3, 4, 5)) for m in only_matches)
+
+  def Start(self):
+    """Starts the logcat monitor."""
+    if self._clear:
+      self._adb.Logcat(clear=True)
+
+  def Stop(self):
+    """Stops the logcat monitor."""
+    pass
+
+  def __enter__(self):
+    """Starts the logcat monitor."""
+    self.Start()
+    return self
+
+  def __exit__(self, exc_type, exc_val, exc_tb):
+    """Stops the logcat monitor."""
+    self.Stop()