1 files changed, 85 insertions, 0 deletions
diff --git a/src/main/java/com/google/devtools/build/lib/actions/ActionGraphVisitor.java b/src/main/java/com/google/devtools/build/lib/actions/ActionGraphVisitor.java
new file mode 100644
index 0000000000..4ddda4c027
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/actions/ActionGraphVisitor.java
@@ -0,0 +1,85 @@
+// Copyright 2014 Google Inc. 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.actions;
+
+/**
+ * An abstract visitor for the action graph.  Specializes {@link BipartiteVisitor} for artifacts and
+ * actions, and takes care of visiting the complete transitive closure.
+ */
+public abstract class ActionGraphVisitor extends BipartiteVisitor<Action, Artifact> {
+
+  private final ActionGraph actionGraph;
+
+  public ActionGraphVisitor(ActionGraph actionGraph) {
+    this.actionGraph = actionGraph;
+  }
+
+  /**
+   * Called for all artifacts in the visitation.  Hook for subclasses. 
+   *
+   * @param artifact
+   */
+  protected void visitArtifact(Artifact artifact) {}
+
+  /**
+   * Called for all actions in the visitation.  Hook for subclasses.
+   *
+   * @param action
+   */
+  protected void visitAction(Action action) {}
+
+  /**
+   * Whether the given action should be visited. If this returns false, the visitation stops here,
+   * so the dependencies of this action are also not visited.
+   *
+   * @param action  
+   */
+  protected boolean shouldVisit(Action action) {
+    return true;
+  }
+
+  /**
+   * Whether the given artifact should be visited. If this returns false, the visitation stops here,
+   * so dependencies of this artifact (if it is a generated one) are also not visited.
+   *
+   * @param artifact
+   */
+  protected boolean shouldVisit(Artifact artifact) {
+    return true;
+  }
+
+  @SuppressWarnings("unused")
+  protected final void visitArtifacts(Iterable<Artifact> artifacts) {
+    for (Artifact artifact : artifacts) {
+      visitArtifact(artifact);
+    }
+  }
+
+  @Override protected void white(Artifact artifact) {
+    Action action = actionGraph.getGeneratingAction(artifact);
+    visitArtifact(artifact);
+    if (action != null && shouldVisit(action)) {
+      visitBlackNode(action);
+    }
+  }
+
+  @Override protected void black(Action action) {
+    visitAction(action);
+    for (Artifact input : action.getInputs()) {
+      if (shouldVisit(input)) {
+        visitWhiteNode(input);
+      }
+    }
+  }
+}