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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.analysis;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.Interner;
import com.google.devtools.build.lib.concurrent.BlazeInterners;
import java.util.Arrays;
import java.util.Map.Entry;
import javax.annotation.Nullable;
import javax.annotation.concurrent.Immutable;
/**
* Provides a mapping between a TransitiveInfoProvider class and an instance.
*
* <p>This class implements a map where it is expected that a lot of the key sets will be the same.
* These key sets are shared and an offset table of indices is computed. Each provider map instance
* thus contains only a reference to the shared offset table, and a plain array of providers.
*/
@Immutable
final class TransitiveInfoProviderMapOffsetBased implements TransitiveInfoProviderMap {
private static final Interner<OffsetTable> offsetTables = BlazeInterners.newWeakInterner();
private final OffsetTable offsetTable;
private final TransitiveInfoProvider[] providers;
private static final class OffsetTable {
private final Class<? extends TransitiveInfoProvider>[] providerClasses;
// Keep a map around to speed up get lookups for larger maps.
// We make this value lazy to avoid computing for values that end up being thrown away
// during interning anyway (the majority).
private volatile ImmutableMap<Class<? extends TransitiveInfoProvider>, Integer> indexMap;
OffsetTable(Class<? extends TransitiveInfoProvider>[] providerClasses) {
this.providerClasses = providerClasses;
}
private ImmutableMap<Class<? extends TransitiveInfoProvider>, Integer> getIndexMap() {
if (indexMap == null) {
synchronized (this) {
if (indexMap == null) {
ImmutableMap.Builder<Class<? extends TransitiveInfoProvider>, Integer> builder =
ImmutableMap.builder();
for (int i = 0; i < providerClasses.length; ++i) {
builder.put(providerClasses[i], i);
}
this.indexMap = builder.build();
}
}
}
return indexMap;
}
int getOffsetForClass(Class effectiveClass) {
return getIndexMap().getOrDefault(effectiveClass, -1);
}
@Override
public boolean equals(Object o) {
if (this == o) {
return true;
}
if (!(o instanceof OffsetTable)) {
return false;
}
OffsetTable that = (OffsetTable) o;
return Arrays.equals(this.providerClasses, that.providerClasses);
}
@Override
public int hashCode() {
return Arrays.hashCode(providerClasses);
}
}
TransitiveInfoProviderMapOffsetBased(
ImmutableMap<Class<? extends TransitiveInfoProvider>, TransitiveInfoProvider> map) {
int count = map.size();
Class<? extends TransitiveInfoProvider>[] providerClasses = new Class[count];
this.providers = new TransitiveInfoProvider[count];
int i = 0;
for (Entry<Class<? extends TransitiveInfoProvider>, TransitiveInfoProvider> entry :
map.entrySet()) {
providerClasses[i] = entry.getKey();
providers[i] = entry.getValue();
++i;
}
OffsetTable offsetTable = new OffsetTable(providerClasses);
this.offsetTable = offsetTables.intern(offsetTable);
}
/** Returns the instance for the provided providerClass, or <tt>null</tt> if not present. */
@Override
@Nullable
public <P extends TransitiveInfoProvider> P getProvider(Class<P> providerClass) {
Class effectiveClass = TransitiveInfoProviderEffectiveClassHelper.get(providerClass);
int offset = offsetTable.getOffsetForClass(effectiveClass);
return offset >= 0 ? (P) providers[offset] : null;
}
@Override
public int getProviderCount() {
return providers.length;
}
@Override
public Class<? extends TransitiveInfoProvider> getProviderClassAt(int i) {
return offsetTable.providerClasses[i];
}
@Override
public TransitiveInfoProvider getProviderAt(int i) {
return providers[i];
}
}
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