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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.rules.config;
import com.google.common.base.Optional;
import com.google.common.collect.ImmutableSet;
import com.google.common.collect.ImmutableSortedMap;
import com.google.common.hash.Hasher;
import com.google.common.hash.Hashing;
import com.google.devtools.build.lib.actions.ArtifactOwner;
import com.google.devtools.build.lib.analysis.config.BuildConfiguration;
import com.google.devtools.build.lib.analysis.config.BuildOptions;
import com.google.devtools.build.lib.analysis.config.ConfigurationEnvironment;
import com.google.devtools.build.lib.analysis.config.ConfigurationFragmentFactory;
import com.google.devtools.build.lib.analysis.config.FragmentOptions;
import com.google.devtools.build.lib.cmdline.Label;
import com.google.devtools.common.options.Converter;
import com.google.devtools.common.options.Option;
import com.google.devtools.common.options.OptionDocumentationCategory;
import com.google.devtools.common.options.OptionEffectTag;
import com.google.devtools.common.options.OptionMetadataTag;
import java.util.Map;
import java.util.SortedMap;
import javax.annotation.Nullable;
/**
* Configuration fragment for Android's config_feature_flag, flags which can be defined in BUILD
* files.
*/
public final class ConfigFeatureFlagConfiguration extends BuildConfiguration.Fragment {
/** A converter used by the flag options which always returns an empty map, ignoring input. */
public static final class EmptyImmutableSortedMapConverter
implements Converter<ImmutableSortedMap<Label, String>> {
@Override
public ImmutableSortedMap<Label, String> convert(String input) {
return ImmutableSortedMap.<Label, String>of();
}
@Override
public String getTypeDescription() {
return "n/a (do not set this on the command line)";
}
}
/** The options fragment which defines {@link ConfigFeatureFlagConfiguration}. */
public static final class Options extends FragmentOptions {
/** The mapping from config_feature_flag rules to their values. */
@Option(
name = "config_feature_flag values (private)",
documentationCategory = OptionDocumentationCategory.UNDOCUMENTED,
effectTags = {OptionEffectTag.UNKNOWN},
metadataTags = {OptionMetadataTag.INTERNAL},
converter = EmptyImmutableSortedMapConverter.class,
defaultValue = "{}"
)
public ImmutableSortedMap<Label, String> flagValues = ImmutableSortedMap.of();
/** Retrieves the set of flag-value pairs. */
public ImmutableSortedMap<Label, String> getFlagValues() {
return this.flagValues;
}
/**
* Replaces the set of flag-value pairs with the given mapping of flag-value pairs.
*
* <p>Flags not present in the new {@code flagValues} will return to being unset! To set flags
* while still retaining the values already set, call {@link #getFlagValues()} and build a map
* containing both the old values and the new ones.
*/
public void replaceFlagValues(Map<Label, String> flagValues) {
this.flagValues = ImmutableSortedMap.copyOf(flagValues);
}
}
/**
* A configuration fragment loader able to create instances of {@link
* ConfigFeatureFlagConfiguration} from {@link ConfigFeatureFlagConfiguration.Options}.
*/
public static final class Loader implements ConfigurationFragmentFactory {
@Override
public BuildConfiguration.Fragment create(
ConfigurationEnvironment env, BuildOptions buildOptions) {
return new ConfigFeatureFlagConfiguration(buildOptions.get(Options.class));
}
@Override
public Class<? extends BuildConfiguration.Fragment> creates() {
return ConfigFeatureFlagConfiguration.class;
}
@Override
public ImmutableSet<Class<? extends FragmentOptions>> requiredOptions() {
return ImmutableSet.<Class<? extends FragmentOptions>>of(Options.class);
}
}
private final ImmutableSortedMap<Label, String> flagValues;
@Nullable private final String flagHash;
/** Creates a new configuration fragment from the given {@link Options} fragment. */
public ConfigFeatureFlagConfiguration(Options options) {
this.flagValues = options.getFlagValues();
this.flagHash = this.flagValues.isEmpty() ? null : hashFlags(this.flagValues);
}
/** Converts the given flag values into a string hash for use as an output directory fragment. */
private static String hashFlags(SortedMap<Label, String> flagValues) {
// This hash function is relatively fast and stable between JVM invocations.
Hasher hasher = Hashing.murmur3_128().newHasher();
for (Map.Entry<Label, String> flag : flagValues.entrySet()) {
hasher.putUnencodedChars(flag.getKey().toString());
hasher.putByte((byte) 0);
hasher.putUnencodedChars(flag.getValue());
hasher.putByte((byte) 0);
}
return hasher.hash().toString();
}
/**
* Retrieves the value of a configuration flag.
*
* <p>If the flag is not set in the current configuration, then the returned value will be absent.
*
* <p>This method should only be used by the rule whose label is passed here. Other rules should
* depend on that rule and read a provider exported by it. To encourage callers of this method to
* do the right thing, this class takes {@link ArtifactOwner} instead of {@link Label}; to get the
* ArtifactOwner for a rule, call {@code ruleContext.getOwner()}.
*/
public Optional<String> getFeatureFlagValue(ArtifactOwner owner) {
return Optional.fromNullable(flagValues.get(owner.getLabel()));
}
/**
* Returns a fragment of the output directory name for this configuration, based on the set of
* flags and their values. It will be {@code null} if no flags are set.
*/
@Nullable
@Override
public String getOutputDirectoryName() {
return flagHash;
}
}
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