1 files changed, 71 insertions, 0 deletions
diff --git a/impl_core/src/main/java/io/opencensus/implcore/tags/CurrentTagContextUtils.java b/impl_core/src/main/java/io/opencensus/implcore/tags/CurrentTagContextUtils.java
new file mode 100644
index 00000000..e6bb12f5
--- /dev/null
+++ b/impl_core/src/main/java/io/opencensus/implcore/tags/CurrentTagContextUtils.java
@@ -0,0 +1,71 @@
+/*
+ * 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.implcore.tags;
+
+import io.grpc.Context;
+import io.opencensus.common.Scope;
+import io.opencensus.tags.TagContext;
+import io.opencensus.tags.unsafe.ContextUtils;
+
+/**
+ * Utility methods for accessing the {@link TagContext} contained in the {@link io.grpc.Context}.
+ */
+final class CurrentTagContextUtils {
+
+  private CurrentTagContextUtils() {}
+
+  /**
+   * Returns the {@link TagContext} from the current context.
+   *
+   * @return the {@code TagContext} from the current context.
+   */
+  static TagContext getCurrentTagContext() {
+    return ContextUtils.TAG_CONTEXT_KEY.get();
+  }
+
+  /**
+   * Enters the scope of code where the given {@link TagContext} is in the current context and
+   * returns an object that represents that scope. The scope is exited when the returned object is
+   * closed.
+   *
+   * @param tags the {@code TagContext} to be set to the current context.
+   * @return an object that defines a scope where the given {@code TagContext} is set to the current
+   *     context.
+   */
+  static Scope withTagContext(TagContext tags) {
+    return new WithTagContext(tags);
+  }
+
+  private static final class WithTagContext implements Scope {
+
+    private final Context orig;
+
+    /**
+     * Constructs a new {@link WithTagContext}.
+     *
+     * @param tags the {@code TagContext} to be added to the current {@code Context}.
+     */
+    private WithTagContext(TagContext tags) {
+      orig = Context.current().withValue(ContextUtils.TAG_CONTEXT_KEY, tags).attach();
+    }
+
+    @Override
+    public void close() {
+      Context.current().detach(orig);
+    }
+  }
+}