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// Copyright 2017 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.collect.nestedset;
import com.google.common.annotations.VisibleForTesting;
import com.google.common.collect.HashMultiset;
import com.google.common.collect.Multiset;
import com.google.devtools.build.lib.actions.CommandLineItem;
import com.google.devtools.build.lib.actions.CommandLineItem.MapFn;
import com.google.devtools.build.lib.util.Fingerprint;
import java.util.HashSet;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
/** Computes fingerprints for nested sets, reusing sub-computations from children. */
public class NestedSetFingerprintCache {
private static final int DIGEST_SIZE = 16;
private static final int EMPTY_SET_DIGEST = 104_395_303;
/** Memoize the subresults. We have to have one cache per type of command item map function. */
private Map<CommandLineItem.MapFn<?>, DigestMap> mapFnToDigestMap = createMap();
private final Set<Class<?>> seenMapFns = new HashSet<>();
private final Multiset<Class<?>> seenParametrizedMapFns = HashMultiset.create();
public <T> void addNestedSetToFingerprint(Fingerprint fingerprint, NestedSet<T> nestedSet) {
addNestedSetToFingerprint(CommandLineItem.MapFn.DEFAULT, fingerprint, nestedSet);
}
public <T> void addNestedSetToFingerprint(
CommandLineItem.MapFn<? super T> mapFn, Fingerprint fingerprint, NestedSet<T> nestedSet) {
if (mapFn instanceof CommandLineItem.CapturingMapFn) {
addNestedSetToFingerprintSlow(mapFn, fingerprint, nestedSet);
return;
}
// Only top-level nested sets can be empty, so we can bail here
if (nestedSet.isEmpty()) {
fingerprint.addInt(EMPTY_SET_DIGEST);
return;
}
DigestMap digestMap = mapFnToDigestMap.computeIfAbsent(mapFn, this::newDigestMap);
fingerprint.addInt(nestedSet.getOrder().ordinal());
Object children = nestedSet.getChildren();
addToFingerprint(mapFn, fingerprint, digestMap, children);
}
private <T> void addNestedSetToFingerprintSlow(
MapFn<? super T> mapFn, Fingerprint fingerprint, NestedSet<T> nestedSet) {
for (T object : nestedSet) {
mapFn.expandToCommandLine(object, fingerprint);
}
}
public void clear() {
mapFnToDigestMap = createMap();
seenMapFns.clear();
seenParametrizedMapFns.clear();
}
@SuppressWarnings("unchecked")
private <T> void addToFingerprint(
CommandLineItem.MapFn<? super T> mapFn,
Fingerprint fingerprint,
DigestMap digestMap,
Object children) {
if (children instanceof Object[]) {
if (!digestMap.readDigest(children, fingerprint)) {
Fingerprint childrenFingerprint = new Fingerprint();
for (Object child : (Object[]) children) {
addToFingerprint(mapFn, childrenFingerprint, digestMap, child);
}
digestMap.insertAndReadDigest(children, childrenFingerprint, fingerprint);
}
} else {
addToFingerprint(mapFn, fingerprint, (T) children);
}
}
@VisibleForTesting
<T> void addToFingerprint(
CommandLineItem.MapFn<? super T> mapFn, Fingerprint fingerprint, T object) {
mapFn.expandToCommandLine(object, fingerprint);
}
private static Map<CommandLineItem.MapFn<?>, DigestMap> createMap() {
return new ConcurrentHashMap<>();
}
private DigestMap newDigestMap(CommandLineItem.MapFn<?> mapFn) {
Class<?> mapFnClass = mapFn.getClass();
if (mapFn instanceof CommandLineItem.ParametrizedMapFn) {
int occurrences = seenParametrizedMapFns.add(mapFnClass, 1) + 1;
if (occurrences > ((CommandLineItem.ParametrizedMapFn) mapFn).maxInstancesAllowed()) {
throw new IllegalArgumentException(
String.format(
"Too many instances of CommandLineItem.ParametrizedMapFn '%s' detected. "
+ "Please construct fewer instances or use CommandLineItem.CapturingMapFn.",
mapFnClass.getName()));
}
} else {
if (!seenMapFns.add(mapFnClass)) {
throw new IllegalArgumentException(
String.format(
"Illegal mapFn implementation: '%s'. "
+ "CommandLineItem.MapFn instances must be singletons. "
+ "Please see CommandLineItem.ParametrizedMapFn or "
+ "CommandLineItem.CapturingMapFn for alternatives.",
mapFnClass.getName()));
}
}
return new DigestMap(DIGEST_SIZE, 1024);
}
}
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