1 files changed, 81 insertions, 0 deletions
diff --git a/core_impl/src/main/java/io/opencensus/implcore/tags/TagContextUtils.java b/core_impl/src/main/java/io/opencensus/implcore/tags/TagContextUtils.java
new file mode 100644
index 00000000..c46c98d7
--- /dev/null
+++ b/core_impl/src/main/java/io/opencensus/implcore/tags/TagContextUtils.java
@@ -0,0 +1,81 @@
+/*
+ * Copyright 2017, Google Inc.
+ * 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.opencensus.common.Function;
+import io.opencensus.common.Functions;
+import io.opencensus.tags.Tag;
+import io.opencensus.tags.Tag.TagBoolean;
+import io.opencensus.tags.Tag.TagLong;
+import io.opencensus.tags.Tag.TagString;
+
+final class TagContextUtils {
+  private TagContextUtils() {}
+
+  /**
+   * Add a {@code Tag} of any type to a builder.
+   *
+   * @param tag tag containing the key and value to set.
+   * @param builder the builder to update.
+   */
+  static void addTagToBuilder(Tag tag, TagContextBuilderImpl builder) {
+    tag.match(
+        new AddTagString(builder),
+        new AddTagLong(builder),
+        new AddTagBoolean(builder),
+        Functions.<Void>throwAssertionError());
+  }
+
+  private static class AddTagString implements Function<TagString, Void> {
+    private final TagContextBuilderImpl builder;
+
+    AddTagString(TagContextBuilderImpl builder) {
+      this.builder = builder;
+    }
+
+    @Override
+    public Void apply(TagString tag) {
+      builder.set(tag.getKey(), tag.getValue());
+      return null;
+    }
+  }
+
+  private static class AddTagLong implements Function<TagLong, Void> {
+    private final TagContextBuilderImpl builder;
+
+    AddTagLong(TagContextBuilderImpl builder) {
+      this.builder = builder;
+    }
+
+    @Override
+    public Void apply(TagLong tag) {
+      builder.set(tag.getKey(), tag.getValue());
+      return null;
+    }
+  }
+
+  private static class AddTagBoolean implements Function<TagBoolean, Void> {
+    private final TagContextBuilderImpl builder;
+
+    AddTagBoolean(TagContextBuilderImpl builder) {
+      this.builder = builder;
+    }
+
+    @Override
+    public Void apply(TagBoolean tag) {
+      builder.set(tag.getKey(), tag.getValue());
+      return null;
+    }
+  }
+}