1 files changed, 63 insertions, 0 deletions
diff --git a/src/main/java/com/google/devtools/build/skyframe/InterruptibleSupplier.java b/src/main/java/com/google/devtools/build/skyframe/InterruptibleSupplier.java
new file mode 100644
index 0000000000..5f4ab55749
--- /dev/null
+++ b/src/main/java/com/google/devtools/build/skyframe/InterruptibleSupplier.java
@@ -0,0 +1,63 @@
+// Copyright 2016 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.skyframe;
+
+import javax.annotation.Nullable;
+
+/** Supplier that may throw {@link InterruptedException} when value is retrieved. */
+public interface InterruptibleSupplier<T> {
+  T get() throws InterruptedException;
+
+  class Instance<T> implements InterruptibleSupplier<T> {
+    private final T instance;
+
+    public Instance(T instance) {
+      this.instance = instance;
+    }
+
+    @Override
+    public T get() {
+      return instance;
+    }
+  }
+
+  class Memoize<T> implements InterruptibleSupplier<T> {
+    private final InterruptibleSupplier<T> delegate;
+    private @Nullable T value = null;
+
+    private Memoize(InterruptibleSupplier<T> delegate) {
+      this.delegate = delegate;
+    }
+
+    public static <S> InterruptibleSupplier<S> of(InterruptibleSupplier<S> delegate) {
+      if (delegate instanceof Memoize) {
+        return delegate;
+      }
+      return new Memoize<>(delegate);
+    }
+
+    @Override
+    public T get() throws InterruptedException {
+      if (value != null) {
+        return value;
+      }
+      synchronized (this) {
+        if (value == null) {
+          value = delegate.get();
+        }
+      }
+      return value;
+    }
+  }
+}