cli/lib/core/timer.py

#
# Copyright (C) 2016 The Android Open Source Project
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#      http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#

"""A general-purpose timer."""


import time


class Timer(object):
    """A simple object to time various things.

    Attributes:
        name: The name of what is being timed.
        label: (optional) An additional text label for the timing. Default None.
    """

    _all_timers = []
    _group_paused_timers = []

    @classmethod
    def MassPauseRunningTimers(cls):
        """Pauses all running timers."""
        timers_to_pause = [t for t in cls._all_timers if t.IsRunning()]
        for t in timers_to_pause:
            t.Stop()
        cls._group_paused_timers += timers_to_pause

    @classmethod
    def ResumeMassPausedTimers(cls):
        """Resumes all timers that were paused using
        cls.MassPauseRunningTimers()
        """
        for t in cls._group_paused_timers:
            t.Start()
        cls._group_paused_timers = []

    def __init__(self, name, label=None):
        self._all_timers.append(self)
        self.name = name
        self.label = label
        self._start_time = None
        self.Reset()

    def Reset(self):
        """Resets the timer, stopping it and setting it to 0."""
        self._time = 0
        self._start_time = None

    def Start(self):
        """Starts the timer continuing from whatever time is showing.

        Does nothing to a timer that is already running.
        """
        if self._start_time is None:
            self._start_time = time.time()

    def Stop(self):
        """Stops the timer, leaving its current amount of time showing."""
        if self._start_time is not None:
            self._time += time.time() - self._start_time
            self._start_time = None

    def IsRunning(self):
        return self._start_time is not None

    def Read(self):
        """Read the current time of the timer in seconds with float precision.

        Works while running, but best practice would be to Stop first.
        """
        # Amount of time previously timed.
        result = self._time
        # If currently running, look at the time elapsed since last stop.
        if self._start_time is not None:
            result += time.time() - self._start_time

        return result