| # Copyright (c) 2012 The Chromium Authors. All rights reserved. |
| # Use of this source code is governed by a BSD-style license that can be |
| # found in the LICENSE file. |
| |
| import sys |
| |
| _no_value = object() |
| |
| class Future(object): |
| '''Stores a value, error, or delegate to be used later. |
| ''' |
| def __init__(self, value=_no_value, delegate=None): |
| self._value = value |
| self._delegate = delegate |
| self._exc_info = None |
| if (self._value is _no_value and self._delegate is None): |
| raise ValueError('Must have either a value or delegate.') |
| |
| def Get(self): |
| '''Gets the stored value, error, or delegate contents. |
| ''' |
| if self._value is not _no_value: |
| return self._value |
| if self._exc_info is not None: |
| self._Raise() |
| try: |
| self._value = self._delegate.Get() |
| return self._value |
| except: |
| self._exc_info = sys.exc_info() |
| self._Raise() |
| |
| def _Raise(self): |
| exc_info = self._exc_info |
| raise exc_info[0], exc_info[1], exc_info[2] |
