org.gradle.internal.model.CalculatedModelValue Maven / Gradle / Ivy
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/*
* Copyright 2020 the original author or authors.
*
* 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 org.gradle.internal.model;
import javax.annotation.Nullable;
import javax.annotation.concurrent.ThreadSafe;
import java.util.function.Function;
/**
* Represents a value that is calculated from some mutable state managed by a {@link ModelContainer}, where the calculated value may
* be used by multiple threads.
*/
@ThreadSafe
public interface CalculatedModelValue {
/**
* Returns the current value, failing if not present.
*
* May be called by any thread. This method returns immediately and does not block to wait for any currently running or pending calls to {@link #update(Function)} to complete.
*/
T get() throws IllegalStateException;
/**
* Returns the current value, returning {@code null} if not present.
*
*
May be called by any thread. This method returns immediately and does not block to wait for any currently running or pending calls to {@link #update(Function)} to complete.
*/
@Nullable
T getOrNull();
/**
* Updates the current value. The function is passed the current value or {@code null} if there is no value, and the function's return value is
* used as the new value.
*
*
The calling thread must own the mutable state from which the value is calculated (via {@link ModelContainer#fromMutableState(Function)}). At most a single thread
* will run the update function at a given time. This additional guarantee is because the mutable state lock may be released
* while the function is running or while waiting to access the value.
*/
T update(Function updateFunction);
/**
* Sets the current value.
*
* The calling thread< must own the mutable state from which the value is calculated.
*/
void set(T newValue);
}