1 files changed, 88 insertions, 0 deletions
diff --git a/src/main/java/com/google/devtools/build/lib/collect/nestedset/ImmutableListDirectsNestedSet.java b/src/main/java/com/google/devtools/build/lib/collect/nestedset/ImmutableListDirectsNestedSet.java
new file mode 100644
index 0000000000..12bf222be5
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/lib/collect/nestedset/ImmutableListDirectsNestedSet.java
@@ -0,0 +1,88 @@
+// 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.collect.nestedset;
+
+import com.google.common.collect.ImmutableList;
+import com.google.common.collect.ImmutableSet;
+
+import java.util.List;
+import java.util.Set;
+
+import javax.annotation.Nullable;
+
+/**
+ * Memory-optimized NestedSet implementation for NestedSets without transitive dependencies that
+ * allows us to share an ImmutableList.
+ */
+abstract class ImmutableListDirectsNestedSet<E> extends NestedSet<E> {
+
+  private static final NestedSet[] EMPTY = new NestedSet[0];
+  private final ImmutableList<E> directDeps;
+
+  public ImmutableListDirectsNestedSet(ImmutableList<E> directDeps) {
+    this.directDeps = directDeps;
+  }
+
+  @Override
+  public abstract Order getOrder();
+
+  @Override
+  Object[] directMembers() {
+    return directDeps.toArray();
+  }
+
+  @Override
+  NestedSet[] transitiveSets() {
+    return EMPTY;
+  }
+
+  @Override
+  public boolean isEmpty() {
+    return directDeps.isEmpty();
+  }
+
+  /**
+   * Currently all the Order implementations return the direct elements in the same order if they do
+   * not have transitive elements. So we skip calling order.getExpander().
+   */
+  @SuppressWarnings("unchecked")
+  @Override
+  public List<E> toList() {
+    return directDeps;
+  }
+
+  @SuppressWarnings("unchecked")
+  @Override
+  public Set<E> toSet() {
+    return ImmutableSet.copyOf(directDeps);
+  }
+
+  @Override
+  public boolean shallowEquals(@Nullable NestedSet<? extends E> other) {
+    if (this == other) {
+      return true;
+    }
+    if (other == null) {
+      return false;
+    }
+    return getOrder().equals(other.getOrder())
+        && other instanceof ImmutableListDirectsNestedSet
+        && directDeps.equals(((ImmutableListDirectsNestedSet) other).directDeps);
+  }
+
+  @Override
+  public int shallowHashCode() {
+    return directDeps.hashCode();
+  }
+}