Java tutorial
// Copyright 2014 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; import com.google.common.collect.ImmutableList; import com.google.common.collect.ImmutableSet; import com.google.devtools.build.lib.cmdline.Label; import com.google.devtools.build.lib.concurrent.ThreadSafety.Immutable; import com.google.devtools.build.lib.concurrent.ThreadSafety.ThreadSafe; import com.google.devtools.build.lib.packages.Rule; import com.google.devtools.build.lib.packages.RuleClass; import com.google.devtools.build.lib.packages.Target; import com.google.devtools.build.lib.util.Preconditions; import com.google.devtools.build.lib.util.StringCanonicalizer; import com.google.devtools.build.skyframe.SkyKey; import com.google.devtools.build.skyframe.SkyValue; import java.util.ArrayList; import java.util.Collection; import java.util.List; import java.util.Objects; import java.util.Set; import java.util.concurrent.ConcurrentHashMap; import java.util.concurrent.ConcurrentMap; import javax.annotation.Nullable; /** * A <i>transitive</i> target reference that, when built in skyframe, loads the entire transitive * closure of a target. Retains the first error message found during the transitive traversal, and a * set of names of providers if the target is a {@link Rule}. * * <p>Interns values for error-free traversal nodes that correspond to built-in rules. */ @Immutable @ThreadSafe public class TransitiveTraversalValue implements SkyValue { private static final TransitiveTraversalValue EMPTY_VALUE = new TransitiveTraversalValue(false, ImmutableSet.<String>of(), null); // A quick-lookup cache that allows us to get the value for a given RuleClass, assuming no error // messages for the target. Only stores built-in RuleClass objects to avoid memory bloat. private static final ConcurrentMap<RuleClass, TransitiveTraversalValue> VALUES_BY_RULE_CLASS = new ConcurrentHashMap<>(); /** * A strong interner of TransitiveTargetValue objects. Because we only wish to intern values for * built-in rules, we need an interner with an additional method to return the canonical * representative if it is present without interning our sample. This is only mutated in {@link * #forTarget}, and read in {@link #forTarget} and {@link #create}. */ private static final InternerWithPresenceCheck<TransitiveTraversalValue> VALUE_INTERNER = new InternerWithPresenceCheck<>(); static { VALUE_INTERNER.intern(EMPTY_VALUE); } private final boolean canHaveAnyProvider; private final ImmutableSet<String> providers; @Nullable private final String firstErrorMessage; private TransitiveTraversalValue(boolean canHaveAnyProvider, ImmutableSet<String> providers, @Nullable String firstErrorMessage) { this.canHaveAnyProvider = canHaveAnyProvider; this.providers = Preconditions.checkNotNull(providers); this.firstErrorMessage = (firstErrorMessage == null) ? null : StringCanonicalizer.intern(firstErrorMessage); } static TransitiveTraversalValue unsuccessfulTransitiveTraversal(String firstErrorMessage) { return new TransitiveTraversalValue(false, ImmutableSet.<String>of(), Preconditions.checkNotNull(firstErrorMessage)); } static TransitiveTraversalValue forTarget(Target target, @Nullable String firstErrorMessage) { if (target instanceof Rule) { Rule rule = (Rule) target; RuleClass ruleClass = rule.getRuleClassObject(); if (firstErrorMessage == null && !ruleClass.isSkylark()) { TransitiveTraversalValue value = VALUES_BY_RULE_CLASS.get(ruleClass); if (value != null) { return value; } ImmutableSet<String> providers = canonicalSet(toList(ruleClass.getAdvertisedProviders())); value = new TransitiveTraversalValue(ruleClass.canHaveAnyProvider(), providers, null); // May already be there from another RuleClass or a concurrent put. value = VALUE_INTERNER.intern(value); // May already be there from a concurrent put. VALUES_BY_RULE_CLASS.putIfAbsent(ruleClass, value); return value; } else { // If this is a Skylark rule, we may still get a cache hit from another RuleClass with the // same providers. return TransitiveTraversalValue.create(ruleClass.canHaveAnyProvider(), toList(rule.getRuleClassObject().getAdvertisedProviders()), firstErrorMessage); } } if (firstErrorMessage == null) { return EMPTY_VALUE; } else { return new TransitiveTraversalValue(false, ImmutableSet.<String>of(), firstErrorMessage); } } public static TransitiveTraversalValue create(boolean canHaveAnyProvider, Collection<String> providers, @Nullable String firstErrorMessage) { TransitiveTraversalValue value = new TransitiveTraversalValue(canHaveAnyProvider, canonicalSet(providers), firstErrorMessage); if (firstErrorMessage == null) { TransitiveTraversalValue oldValue = VALUE_INTERNER.getCanonical(value); return oldValue == null ? value : oldValue; } return value; } private static ImmutableSet<String> canonicalSet(Iterable<String> strIterable) { ImmutableSet.Builder<String> builder = new ImmutableSet.Builder<>(); for (String str : strIterable) { builder.add(StringCanonicalizer.intern(str)); } return builder.build(); } private static List<String> toList(Collection<Class<?>> providers) { if (providers == null) { return ImmutableList.of(); } List<String> strings = new ArrayList<>(providers.size()); for (Class<?> clazz : providers) { strings.add(clazz.getName()); } return strings; } /** * Returns if the associated target can have any provider. True for "alias" rules. */ public boolean canHaveAnyProvider() { return canHaveAnyProvider; } /** * Returns the set of provider names from the target, if the target is a {@link Rule}. Otherwise * returns the empty set. */ public Set<String> getProviders() { return providers; } /** * Returns the first error message, if any, from loading the target and its transitive * dependencies. */ @Nullable public String getFirstErrorMessage() { return firstErrorMessage; } @Override public boolean equals(Object o) { if (this == o) { return true; } if (!(o instanceof TransitiveTraversalValue)) { return false; } TransitiveTraversalValue that = (TransitiveTraversalValue) o; return this.canHaveAnyProvider == that.canHaveAnyProvider && Objects.equals(this.firstErrorMessage, that.firstErrorMessage) && this.providers.equals(that.providers); } @Override public int hashCode() { return Objects.hash(firstErrorMessage, providers, canHaveAnyProvider); } @ThreadSafe public static SkyKey key(Label label) { Preconditions.checkArgument(!label.getPackageIdentifier().getRepository().isDefault()); return SkyKey.create(SkyFunctions.TRANSITIVE_TRAVERSAL, label); } }