| // 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. |
| |
| package com.google.gerrit.server.git; |
| |
| import com.google.common.base.Optional; |
| |
| import org.eclipse.jgit.lib.ObjectId; |
| |
| import java.io.IOException; |
| |
| /** |
| * Simple short-lived cache of individual refs read from a repo. |
| * <p> |
| * Within a single request that is known to read a small bounded number of refs, |
| * this class can be used to ensure a consistent view of one ref, and avoid |
| * multiple system calls to read refs multiple times. |
| * <p> |
| * <strong>Note:</strong> Implementations of this class are only appropriate |
| * for short-term caching, and do not support invalidation. It is also not |
| * threadsafe. |
| */ |
| public interface RefCache { |
| /** |
| * Get the possibly-cached value of a ref. |
| * |
| * @param refName name of the ref. |
| * @return value of the ref; absent if the ref does not exist in the repo. |
| * Never null, and never present with a value of {@link |
| * ObjectId#zeroId()}. |
| */ |
| Optional<ObjectId> get(String refName) throws IOException; |
| } |