third_party/pigweed/repo/pw_env_setup/py/pw_env_setup/spinner.py

   1 # Copyright 2020 The Pigweed Authors
   2 #
   3 # Licensed under the Apache License, Version 2.0 (the "License"); you may not
   4 # use this file except in compliance with the License. You may obtain a copy of
   5 # the License at
   6 #
   7 #     https://www.apache.org/licenses/LICENSE-2.0
   8 #
   9 # Unless required by applicable law or agreed to in writing, software
  10 # distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
  11 # WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
  12 # License for the specific language governing permissions and limitations under
  13 # the License.
  14 """Spinner!"""
  15
  16 import contextlib
  17 import os
  18 import sys
  19 import threading
  20 import time
  21
  22 PW_ENVSETUP_DISABLE_SPINNER = os.environ.get('PW_ENVSETUP_DISABLE_SPINNER')
  23
  24
  25 class Spinner(object):  # pylint: disable=useless-object-inheritance
  26     """Spinner!"""
  27     def __init__(self):
  28         self._done = None
  29         self._thread = None
  30
  31     def __del__(self):
  32         self._done = True
  33
  34     def _spin(self):
  35         i = 0
  36         chars = '|/-\\'
  37         while not self._done:
  38             sys.stdout.write('[{}]'.format(chars[i]))
  39             sys.stdout.flush()
  40             time.sleep(0.1)
  41             sys.stdout.write('\b\b\b')
  42             i = (i + 1) % len(chars)
  43
  44     def start(self):
  45         if PW_ENVSETUP_DISABLE_SPINNER:
  46             return
  47
  48         self._done = False
  49         self._thread = threading.Thread(target=self._spin)
  50         self._thread.start()
  51
  52     def stop(self):
  53         if PW_ENVSETUP_DISABLE_SPINNER:
  54             return
  55
  56         assert self._thread
  57         self._done = True
  58         self._thread.join()
  59         self._thread = None
  60
  61     @contextlib.contextmanager
  62     def __call__(self):
  63         try:
  64             self.start()
  65             yield self
  66         finally:
  67             self.stop()