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/*
* Copyright (C) 2014 The Project Lombok Authors.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package lombok.core;
import java.lang.ref.WeakReference;
import java.util.Map;
import java.util.WeakHashMap;
public abstract class ReferenceFieldAugment<T, F> {
/**
* Augments a instance of a type with a reference field.
* <p>
* If the type already declares an instance field with the given name and field type, that field might be used. Otherwise the field will be augmented.
* <p>
* This code assumes that for any combination of {@code type} and {@code name} this method is only called once.
* Otherwise, whether state is shared is undefined.
*
* @param type to augment
* @param fieldType type of the field
* @param name of the field
* @throws NullPointerException if {@code type}, {@code fieldType} or {@code name} is {@code null}
*/
public static <T, F> ReferenceFieldAugment<T, F> augment(Class<T> type, Class<? super F> fieldType, String name) {
return new MapFieldAugment<T, F>();
}
/**
* Augments a instance of a type with a weak reference field.
* <p>
* If the type already declares an instance field with the given name and field type, that field might be used. Otherwise the field will be augmented.
* <p>
* This code assumes that for any combination of {@code type} and {@code name} this method is only called once.
* Otherwise, whether state is shared is undefined.
*
* @param type to augment
* @param fieldType type of the field
* @param name of the field
* @throws NullPointerException if {@code type}, {@code fieldType} or {@code name} is {@code null}
*/
public static <T, F> ReferenceFieldAugment<T, F> augmentWeakField(Class<T> type, Class<? super F> fieldType, String name) {
return new MapWeakFieldAugment<T, F>();
}
private ReferenceFieldAugment() {
// prevent external instantiation
}
/**
* @throws NullPointerException if {@code object} is {@code null}
*/
public abstract F get(T object);
/**
* @throws NullPointerException if {@code object} or {@code expected} is {@code null}
*/
public final void set(T object, F value) {
getAndSet(object, value);
}
/**
* @return the value of the field <strong>before</strong> the operation.
* @throws NullPointerException if {@code object} or {@code expected} is {@code null}
*/
public abstract F getAndSet(T object, F value);
/**
* @return the value of the field <strong>before</strong> the operation.
* @throws NullPointerException if {@code object} is {@code null}
*/
public abstract F clear(T object);
/**
* @return the value of the field <strong>after</strong> the operation. If the value was equal to {@code expected} or already cleared {@code null}, otherwise the current value.
* @throws NullPointerException if {@code object} or {@code expected} is {@code null}
*/
public abstract F compareAndClear(T object, F expected);
/**
* @return the value of the field <strong>after</strong> the operation.
* @throws NullPointerException if {@code object} or {@code value} is {@code null}
*/
public abstract F setIfAbsent(T object, F value);
/**
* @return the value of the field <strong>after</strong> the operation.
* @throws NullPointerException if {@code object}, {@code expected} or {@code value} is {@code null}
*/
public abstract F compareAndSet(T object, F expected, F value);
private static class MapFieldAugment<T, F> extends ReferenceFieldAugment<T, F> {
final Map<T, Object> values = new WeakHashMap<T, Object>();
@Override
public F get(T object) {
checkNotNull(object, "object");
synchronized (values) {
return read(object);
}
}
@Override
public F getAndSet(T object, F value) {
checkNotNull(object, "object");
checkNotNull(value, "value");
synchronized (values) {
F result = read(object);
write(object, value);
return result;
}
}
@Override
public F clear(T object) {
checkNotNull(object, "object");
synchronized (values) {
F result = read(object);
values.remove(object);
return result;
}
}
@Override
public F compareAndClear(T object, F expected) {
checkNotNull(object, "object");
checkNotNull(expected, "expected");
synchronized (values) {
F result = read(object);
if (result == null) {
return null;
}
if (!expected.equals(result)) {
return result;
}
values.remove(object);
return null;
}
}
@Override
public F setIfAbsent(T object, F value) {
checkNotNull(object, "object");
checkNotNull(value, "value");
synchronized (values) {
F result = read(object);
if (result != null) {
return result;
}
write(object, value);
return value;
}
}
@Override
public F compareAndSet(T object, F expected, F value) {
checkNotNull(object, "object");
checkNotNull(expected, "expected");
checkNotNull(value, "value");
synchronized (values) {
F result = read(object);
if (!expected.equals(result)) {
return result;
}
write(object, value);
return value;
}
}
@SuppressWarnings("unchecked")
F read(T object) {
return (F)values.get(object);
}
void write(T object, F value) {
values.put(object, value);
}
}
static class MapWeakFieldAugment<T, F> extends MapFieldAugment<T, F> {
@SuppressWarnings("unchecked")
F read(T object) {
WeakReference<F> read = (WeakReference<F>)values.get(object);
if (read == null) return null;
F result = read.get();
if (result == null) values.remove(object);
return result;
}
void write(T object, F value) {
values.put(object, new WeakReference<F>(value));
}
}
private static <T> T checkNotNull(T object, String name) {
if (object == null) throw new NullPointerException(name);
return object;
}
}
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