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/*
* Copyright 2017, OpenCensus Authors
*
* 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 io.opencensus.tags.unsafe;
import io.grpc.Context;
import io.opencensus.internal.Utils;
import io.opencensus.tags.Tag;
import io.opencensus.tags.TagContext;
import java.util.Collections;
import java.util.Iterator;
import javax.annotation.concurrent.Immutable;
/*>>>
import org.checkerframework.checker.nullness.qual.Nullable;
*/
/**
* Utility methods for accessing the {@link TagContext} contained in the {@link io.grpc.Context}.
*
* Most code should interact with the current context via the public APIs in {@link
* io.opencensus.tags.TagContext} and avoid accessing {@link #TAG_CONTEXT_KEY} directly.
*
* @since 0.8
*/
public final class ContextUtils {
private static final TagContext EMPTY_TAG_CONTEXT = new EmptyTagContext();
private ContextUtils() {}
/**
* The {@link io.grpc.Context.Key} used to interact with the {@code TagContext} contained in the
* {@link io.grpc.Context}.
*/
private static final Context.Key TAG_CONTEXT_KEY =
Context.keyWithDefault("opencensus-tag-context-key", EMPTY_TAG_CONTEXT);
/**
* Creates a new {@code Context} with the given value set.
*
* @param context the parent {@code Context}.
* @param tagContext the value to be set.
* @return a new context with the given value set.
* @since 0.21
*/
public static Context withValue(
Context context, @javax.annotation.Nullable TagContext tagContext) {
return Utils.checkNotNull(context, "context").withValue(TAG_CONTEXT_KEY, tagContext);
}
/**
* Returns the value from the specified {@code Context}.
*
* @param context the specified {@code Context}.
* @return the value from the specified {@code Context}.
* @since 0.21
*/
public static TagContext getValue(Context context) {
@javax.annotation.Nullable TagContext tags = TAG_CONTEXT_KEY.get(context);
return tags == null ? EMPTY_TAG_CONTEXT : tags;
}
@Immutable
private static final class EmptyTagContext extends TagContext {
@Override
protected Iterator getIterator() {
return Collections.emptySet().iterator();
}
}
}