1 files changed, 96 insertions, 0 deletions
diff --git a/src/main/java/com/google/devtools/build/lib/query2/engine/AllRdepsFunction.java b/src/main/java/com/google/devtools/build/lib/query2/engine/AllRdepsFunction.java
new file mode 100644
index 0000000000..5f1493e54b
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/query2/engine/AllRdepsFunction.java
@@ -0,0 +1,96 @@
+// Copyright 2015 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.query2.engine;
+
+import com.google.common.base.Predicate;
+import com.google.common.base.Predicates;
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.Iterables;
+import com.google.devtools.build.lib.query2.engine.QueryEnvironment.Argument;
+import com.google.devtools.build.lib.query2.engine.QueryEnvironment.ArgumentType;
+import com.google.devtools.build.lib.query2.engine.QueryEnvironment.QueryFunction;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.LinkedHashSet;
+import java.util.List;
+import java.util.Set;
+
+/**
+ * An "allrdeps" query expression, which computes the reverse dependencies of the argument within
+ * the currently known universe. An optional integer-literal second argument may be specified; its
+ * value bounds the search from the arguments.
+ *
+ * <pre>expr ::= ALLRDEPS '(' expr ')'</pre>
+ * <pre>       | ALLRDEPS '(' expr ',' WORD ')'</pre>
+ */
+// Public because SkyQueryEnvironment needs to refer to it directly.
+public class AllRdepsFunction implements QueryFunction {
+  public AllRdepsFunction() {}
+
+  @Override
+  public String getName() {
+    return "allrdeps";
+  }
+
+  @Override
+  public int getMandatoryArguments() {
+    return 1;  // last argument is optional
+  }
+
+  @Override
+  public List<ArgumentType> getArgumentTypes() {
+    return ImmutableList.of(ArgumentType.EXPRESSION, ArgumentType.INTEGER);
+  }
+
+  /**
+   * Breadth-first search from the argument while sticking to nodes satisfying the {@param universe}
+   * predicate.
+   */
+  protected <T> Set<T> eval(QueryEnvironment<T> env, List<Argument> args, Predicate<T> universe)
+      throws QueryException {
+    Set<T> argumentValue = args.get(0).getExpression().eval(env);
+    int depthBound = args.size() > 1 ? args.get(1).getInteger() : Integer.MAX_VALUE;
+    Set<T> visited = new LinkedHashSet<>();
+    Collection<T> current = argumentValue;
+
+    // We need to iterate depthBound + 1 times.
+    for (int i = 0; i <= depthBound; i++) {
+      List<T> next = new ArrayList<>();
+      // Restrict to nodes satisfying the universe predicate.
+      Iterable<T> currentInUniverse = Iterables.filter(current, universe);
+      // Filter already visited nodes: if we see a node in a later round, then we don't need to
+      // visit it again, because the depth at which we see it must be greater than or equal to
+      // the last visit.
+      next.addAll(env.getReverseDeps(Iterables.filter(currentInUniverse,
+          Predicates.not(Predicates.in(visited)))));
+      Iterables.addAll(visited, currentInUniverse);
+      if (next.isEmpty()) {
+        // Exit when there are no more nodes to visit.
+        break;
+      }
+      current = next;
+    }
+
+    return visited;
+
+  }
+
+  /** Breadth-first search from the argument. */
+  @Override
+  public <T> Set<T> eval(QueryEnvironment<T> env, QueryExpression expression, List<Argument> args)
+      throws QueryException {
+    return eval(env, args, Predicates.<T>alwaysTrue());
+  }
+}