| # Copyright 2021, The TensorFlow Authors. |
| # |
| # 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 |
| # |
| # https://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. |
| """Builder class for ComposedDpEvent.""" |
| |
| from dp_accounting import dp_event |
| |
| |
| class DpEventBuilder(object): |
| """Constructs a `DpEvent` representing the composition of a series of events. |
| |
| Two common use cases of the `DpEventBuilder` are 1) for producing and tracking |
| a ledger of `DpEvent`s during sequential accounting using a |
| `PrivacyAccountant`, and 2) for building up a description of a composite |
| mechanism for subsequent batch accounting. |
| """ |
| |
| def __init__(self): |
| # A list of (event, count) pairs. |
| self._event_counts = [] |
| self._composed_event = None |
| |
| def compose(self, event: dp_event.DpEvent, count: int = 1): |
| """Composes new event into event represented by builder. |
| |
| Args: |
| event: The new event to compose. |
| count: The number of times to compose the event. |
| """ |
| if not isinstance(event, dp_event.DpEvent): |
| raise TypeError('`event` must be a subclass of `DpEvent`. ' |
| f'Found {type(event)}.') |
| if not isinstance(count, int): |
| raise TypeError(f'`count` must be an integer. Found {type(count)}.') |
| if count < 1: |
| raise ValueError(f'`count` must be positive. Found {count}.') |
| |
| if isinstance(event, dp_event.NoOpDpEvent): |
| return |
| elif isinstance(event, dp_event.SelfComposedDpEvent): |
| self.compose(event.event, count * event.count) |
| else: |
| if self._event_counts and self._event_counts[-1][0] == event: |
| new_event_count = (event, self._event_counts[-1][1] + count) |
| self._event_counts[-1] = new_event_count |
| else: |
| self._event_counts.append((event, count)) |
| self._composed_event = None |
| |
| def build(self) -> dp_event.DpEvent: |
| """Builds and returns the composed DpEvent represented by the builder.""" |
| if not self._composed_event: |
| events = [] |
| for event, count in self._event_counts: |
| if count == 1: |
| events.append(event) |
| else: |
| events.append(dp_event.SelfComposedDpEvent(event, count)) |
| if not events: |
| self._composed_event = dp_event.NoOpDpEvent() |
| elif len(events) == 1: |
| self._composed_event = events[0] |
| else: |
| self._composed_event = dp_event.ComposedDpEvent(events) |
| |
| return self._composed_event |