Coverage for sparts/timer : 98%

# Copyright (c) 2014, Facebook, Inc.  All rights reserved. 

# 

# This source code is licensed under the BSD-style license found in the 

# LICENSE file in the root directory of this source tree. An additional grant 

# of patent rights can be found in the PATENTS file in the same directory. 

# 

"""Sparts module implementing a basic timer class""" 

import time 

from datetime import timedelta 

class Timer(object): 

    """Basic Timer class that can be used as a context manager.""" 

    def __init__(self): 

        self.start_time = self.end_time = None 

    def __enter__(self): 

        """ContextManager protocol enter to start the timer""" 

        self.start() 

        return self 

    def __exit__(self, exc_type, exc_value, traceback): 

        """ContextManager protocol exit to stop the timer""" 

        self.stop() 

    def start(self): 

        """Explicitly start/restart the timer""" 

        self.start_time = self._time() 

    def stop(self): 

        """Explicitly stop the timer""" 

        self.end_time = self._time() 

    @property 

    def elapsed(self): 

        """Return the duration that the timer was/is active""" 

        # If the timer is not started, return 0.0 

        if self.start_time is None: 

            return 0.0 

        # If the timer has not stopped, return the elapsed time until now 

        if self.end_time is None: 

            return self._time() - self.start_time 

        # If the timer has stopped, return the difference in times 

        return self.end_time - self.start_time 

    def __str__(self): 

        return str(timedelta(seconds=self.elapsed)) 

    def _time(self): 

        """Private-ish time to help with mocking/unittests""" 

        return time.time() 

def run_until_true(f, timeout): 

    """Runs function `f` until it returns True or `timeout` elapses. 

    Returns if f returns True.  Raises if timeout is exceeded.""" 

    with Timer() as t: 

        while t.elapsed < timeout: 

            if f(): 

                return 

            time.sleep(0.001) 

    raise Exception("%.1fs Timeout Exceeded waiting for %s to complete" % 

                    (timeout, f))