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Diffstat (limited to 'src/main/java/com/google/devtools/build/skyframe/InterruptibleSupplier.java')
-rw-r--r-- | src/main/java/com/google/devtools/build/skyframe/InterruptibleSupplier.java | 63 |
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; + } + } +} |