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() 59
