1 files changed, 93 insertions, 0 deletions
diff --git a/src/main/java/com/google/devtools/build/lib/query2/engine/OutputFormatterCallback.java b/src/main/java/com/google/devtools/build/lib/query2/engine/OutputFormatterCallback.java
new file mode 100644
index 0000000000..546b0d51bb
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/query2/engine/OutputFormatterCallback.java
@@ -0,0 +1,93 @@
+// Copyright 2015 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.query2.engine;
+
+import com.google.devtools.build.lib.concurrent.ThreadSafety.ThreadCompatible;
+
+import java.io.Closeable;
+import java.io.IOException;
+
+import javax.annotation.Nullable;
+
+/** A callback that can receive a finish event when there are no more partial results */
+@ThreadCompatible
+public abstract class OutputFormatterCallback<T> implements Callback<T>, Closeable {
+
+  private IOException ioException;
+
+  /**
+   * This method will be called before any partial result are available.
+   *
+   * <p>It should be used for opening resources or sending a header to the output.
+   */
+  public void start() throws IOException { }
+
+  /**
+   * Same as start but for closing resources or writting a footer.
+   *
+   * <p>Will be called even in the case of an error.
+   */
+  @Override
+  public void close() throws IOException{}
+
+  /**
+   * Note that {@link Callback} interface does not throw IOExceptions. What this implementation does
+   * instead is throw {@code InterruptedException} and store the {@code IOException} in the {@code
+   * ioException} field. Users of this class should check on InterruptedException the field to
+   * disambiguate between real interruptions or IO Exceptions.
+   */
+  @Override
+  public final void process(Iterable<T> partialResult) throws QueryException, InterruptedException {
+    try {
+      processOutput(partialResult);
+    } catch (IOException e) {
+      ioException = e;
+      throw new InterruptedException("Interrupting due to a IOException in the OutputFormatter");
+    }
+  }
+
+  protected abstract void processOutput(Iterable<T> partialResult)
+      throws IOException, InterruptedException;
+
+  @Nullable
+  public IOException getIoException() {
+    return ioException;
+  }
+
+  /**
+   * Use an {@code OutputFormatterCallback} with an already computed set of targets. Note that this
+   * does not work in stream mode, as the {@code targets} would already be computed.
+   *
+   * <p>The intended usage of this method is to use {@code StreamedFormatter} formaters in non
+   * streaming contexts.
+   */
+  public static <T> void processAllTargets(OutputFormatterCallback<T> callback,
+      Iterable<T> targets) throws IOException, InterruptedException {
+    try {
+      callback.start();
+      callback.process(targets);
+    } catch (InterruptedException e) {
+      IOException ioException = callback.getIoException();
+      if (ioException != null) {
+        throw ioException;
+      }
+      throw e;
+    } catch (QueryException e) {
+      throw new IllegalStateException("This should not happen, as we are not running any query,"
+          + " only printing the results:" + e.getMessage(), e);
+    } finally {
+      callback.close();
+    }
+  }
+}