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-rw-r--r--src/main/java/com/google/devtools/build/skyframe/InterruptibleSupplier.java63
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
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index 0000000000..5f4ab55749
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+++ 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;
+ }
+ }
+}