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// Copyright 2014 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;
/** Wrapper for a value or the typed exception thrown when trying to compute it. */
public abstract class ValueOrException<E extends Exception> extends ValueOrUntypedException {
/** Gets the stored value. Throws an exception if one was thrown when computing this value. */
@Nullable
public abstract SkyValue get() throws E;
static <E extends Exception> ValueOrException<E> fromUntypedException(
ValueOrUntypedException voe, Class<E> exceptionClass) {
SkyValue value = voe.getValue();
if (value != null) {
return ofValue(value);
}
Exception e = voe.getException();
if (e != null) {
if (exceptionClass.isInstance(e)) {
return ofExn1(exceptionClass.cast(e));
}
}
return ofNullValue();
}
private static <E extends Exception> ValueOrException<E> ofExn1(E e) {
return new ValueOrExceptionExnImpl<>(e);
}
private static <E extends Exception> ValueOrException<E> ofNullValue() {
return ValueOrExceptionValueImpl.ofNullValue();
}
private static <E extends Exception> ValueOrException<E> ofValue(SkyValue value) {
return new ValueOrExceptionValueImpl<>(value);
}
private static class ValueOrExceptionValueImpl<E extends Exception> extends ValueOrException<E> {
private static final ValueOrExceptionValueImpl<Exception> NULL =
new ValueOrExceptionValueImpl<>(null);
@Nullable private final SkyValue value;
private ValueOrExceptionValueImpl(@Nullable SkyValue value) {
this.value = value;
}
@Override
@Nullable
public SkyValue get() {
return value;
}
@Override
@Nullable
public SkyValue getValue() {
return value;
}
@Override
@Nullable
public Exception getException() {
return null;
}
@SuppressWarnings("unchecked")
static <E extends Exception> ValueOrExceptionValueImpl<E> ofNullValue() {
return (ValueOrExceptionValueImpl<E>) NULL;
}
}
private static class ValueOrExceptionExnImpl<E extends Exception> extends ValueOrException<E> {
private final E e;
private ValueOrExceptionExnImpl(E e) {
this.e = e;
}
@Override
public SkyValue get() throws E {
throw e;
}
@Override
@Nullable
public SkyValue getValue() {
return null;
}
@Override
public Exception getException() {
return e;
}
}
}
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