chrome/common/extensions/docs/server2/timer.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 import time
   6
   7
   8 class Timer(object):
   9   '''A simple timer which starts when constructed and stops when Stop is called.
  10   '''
  11
  12   def __init__(self):
  13     self._start = time.time()
  14     self._elapsed = None
  15
  16   def Stop(self):
  17     '''Stops the timer. Must only be called once. Returns |self|.
  18     '''
  19     assert self._elapsed is None
  20     self._elapsed = time.time() - self._start
  21     return self
  22
  23   def With(self, other):
  24     '''Returns a new stopped Timer with this Timer's elapsed time + |other|'s.
  25     Both Timers must already be stopped.
  26     '''
  27     assert self._elapsed is not None
  28     assert other._elapsed is not None
  29     self_and_other = Timer()
  30     self_and_other._start = min(self._start, other._start)
  31     self_and_other._elapsed = self._elapsed + other._elapsed
  32     return self_and_other
  33
  34   def FormatElapsed(self):
  35     '''Returns the elapsed time as a string in a pretty format; as a whole
  36     number in either seconds or milliseconds depending on which is more
  37     appropriate. Must already be Stopped.
  38     '''
  39     assert self._elapsed is not None
  40     elapsed = self._elapsed
  41     if elapsed < 1:
  42       elapsed = int(elapsed * 1000)
  43       unit = 'ms'
  44     else:
  45       elapsed = int(elapsed)
  46       unit = 'second' if elapsed == 1 else 'seconds'
  47     return '%s %s' % (elapsed, unit)
  48
  49
  50 def TimerClosure(closure, *args, **optargs):
  51   '''A shorthand for timing a single function call. Returns a tuple of
  52   (closure return value, timer).
  53   '''
  54   timer = Timer()
  55   try:
  56     return closure(*args, **optargs), timer
  57   finally:
  58     timer.Stop()