| // Copyright 2018 The Bazel Authors. All rights reserved. |
| // |
| // 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.devtools.build.lib.skyframe.actiongraph.v2; |
| |
| import java.io.IOException; |
| import java.util.Map; |
| import java.util.concurrent.ConcurrentHashMap; |
| import java.util.concurrent.atomic.AtomicInteger; |
| |
| /** |
| * Basic class to abstract action graph cache functionality. |
| */ |
| abstract class BaseCache<K, P> { |
| private final Map<K, Integer> cache = new ConcurrentHashMap<>(); |
| protected final AqueryOutputHandler aqueryOutputHandler; |
| // protobuf interprets the value 0 as "default value" for uint64, thus treating the field as |
| // "unset". We should start from 1 instead. |
| private final AtomicInteger nextId = new AtomicInteger(1); |
| |
| BaseCache(AqueryOutputHandler aqueryOutputHandler) { |
| this.aqueryOutputHandler = aqueryOutputHandler; |
| } |
| |
| protected K transformToKey(K data) { |
| // In most cases, the data is the key but it can be overridden by subclasses. |
| return data; |
| } |
| |
| /** |
| * Store the data in the internal cache, if it's not yet present. Return the generated id. Ids are |
| * positive and unique. |
| * |
| * <p>Stream the proto to output, the first time it's generated. |
| */ |
| int dataToIdAndStreamOutputProto(K data) throws IOException, InterruptedException { |
| int id = -1; |
| K key = transformToKey(data); |
| boolean shouldOutputProto = false; |
| |
| // Double-checked locking here: |
| // Once cache.get(key) != null it won't be changed again. |
| if (cache.get(key) == null) { |
| synchronized (this) { |
| if (cache.get(key) == null) { |
| id = nextId.getAndIncrement(); |
| // Note that this cannot be replaced by computeIfAbsent since createProto is a recursive |
| // operation for the case of nested sets which will call dataToId on the same object and |
| // thus computeIfAbsent again. |
| cache.put(key, id); |
| shouldOutputProto = true; |
| } |
| } |
| } |
| if (shouldOutputProto) { |
| P proto = createProto(data, id); |
| toOutput(proto); |
| } |
| return cache.get(key); |
| } |
| |
| abstract P createProto(K key, int id) throws IOException, InterruptedException; |
| |
| abstract void toOutput(P proto) throws IOException; |
| } |