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/*
* This file is available under and governed by the GNU General Public
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* However, the following notice accompanied the original version of this
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/*
Copyright 2009-2013 Attila Szegedi
Licensed under both the Apache License, Version 2.0 (the "Apache License")
and the BSD License (the "BSD License"), with licensee being free to
choose either of the two at their discretion.
You may not use this file except in compliance with either the Apache
License or the BSD License.
If you choose to use this file in compliance with the Apache License, the
following notice applies to you:
You may obtain a copy of the Apache 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.
If you choose to use this file in compliance with the BSD License, the
following notice applies to you:
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:
* Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in the
documentation and/or other materials provided with the distribution.
* Neither the name of the copyright holder nor the names of
contributors may be used to endorse or promote products derived from
this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL COPYRIGHT HOLDER
BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package jdk.dynalink.linker.support;
import java.util.Collections;
import java.util.LinkedList;
import java.util.List;
import java.util.Objects;
import jdk.dynalink.linker.GuardedInvocation;
import jdk.dynalink.linker.GuardingDynamicLinker;
import jdk.dynalink.linker.LinkRequest;
import jdk.dynalink.linker.LinkerServices;
import jdk.dynalink.linker.TypeBasedGuardingDynamicLinker;
/**
* A composite type-based guarding dynamic linker. When a receiver of a not yet
* seen class is encountered, all linkers are queried sequentially on their
* {@link TypeBasedGuardingDynamicLinker#canLinkType(Class)} method. The linkers
* returning true are then bound to the class, and next time a receiver of same
* type is encountered, the linking is delegated to those linkers only, speeding
* up dispatch.
*/
public class CompositeTypeBasedGuardingDynamicLinker implements TypeBasedGuardingDynamicLinker {
// Using a separate static class instance so there's no strong reference from the class value back to the composite
// linker.
private static class ClassToLinker extends ClassValue<List<TypeBasedGuardingDynamicLinker>> {
private static final List<TypeBasedGuardingDynamicLinker> NO_LINKER = Collections.emptyList();
private final TypeBasedGuardingDynamicLinker[] linkers;
private final List<TypeBasedGuardingDynamicLinker>[] singletonLinkers;
@SuppressWarnings({"unchecked", "rawtypes"})
ClassToLinker(final TypeBasedGuardingDynamicLinker[] linkers) {
this.linkers = linkers;
singletonLinkers = new List[linkers.length];
for(int i = 0; i < linkers.length; ++i) {
singletonLinkers[i] = Collections.singletonList(linkers[i]);
}
}
@SuppressWarnings("fallthrough")
@Override
protected List<TypeBasedGuardingDynamicLinker> computeValue(final Class<?> clazz) {
List<TypeBasedGuardingDynamicLinker> list = NO_LINKER;
for(int i = 0; i < linkers.length; ++i) {
final TypeBasedGuardingDynamicLinker linker = linkers[i];
if(linker.canLinkType(clazz)) {
switch(list.size()) {
case 0: {
list = singletonLinkers[i];
break;
}
case 1: {
list = new LinkedList<>(list);
}
default: {
list.add(linker);
}
}
}
}
return list;
}
}
private final ClassValue<List<TypeBasedGuardingDynamicLinker>> classToLinker;
/**
* Creates a new composite type-based linker.
*
* @param linkers the component linkers
* @throws NullPointerException if {@code linkers} or any of its elements
* are null.
*/
public CompositeTypeBasedGuardingDynamicLinker(final Iterable<? extends TypeBasedGuardingDynamicLinker> linkers) {
final List<TypeBasedGuardingDynamicLinker> l = new LinkedList<>();
for(final TypeBasedGuardingDynamicLinker linker: linkers) {
l.add(Objects.requireNonNull(linker));
}
this.classToLinker = new ClassToLinker(l.toArray(new TypeBasedGuardingDynamicLinker[0]));
}
/**
* Returns true if at least one of the composite linkers returns true from
* {@link TypeBasedGuardingDynamicLinker#canLinkType(Class)} for the type.
* @param type the type to link
* @return true true if at least one of the composite linkers returns true
* from {@link TypeBasedGuardingDynamicLinker#canLinkType(Class)}, false
* otherwise.
*/
@Override
public boolean canLinkType(final Class<?> type) {
return !classToLinker.get(type).isEmpty();
}
@Override
public GuardedInvocation getGuardedInvocation(final LinkRequest linkRequest, final LinkerServices linkerServices)
throws Exception {
final Object obj = linkRequest.getReceiver();
if(obj == null) {
return null;
}
for(final TypeBasedGuardingDynamicLinker linker: classToLinker.get(obj.getClass())) {
final GuardedInvocation invocation = linker.getGuardedInvocation(linkRequest, linkerServices);
if(invocation != null) {
return invocation;
}
}
return null;
}
/**
* Optimizes a list of type-based linkers. If a group of adjacent linkers in
* the list all implement {@link TypeBasedGuardingDynamicLinker}, they will
* be replaced with a single instance of
* {@link CompositeTypeBasedGuardingDynamicLinker} that contains them.
*
* @param linkers the list of linkers to optimize
* @return the optimized list
* @throws NullPointerException if {@code linkers} or any of its elements
* are null.
*/
public static List<GuardingDynamicLinker> optimize(final Iterable<? extends GuardingDynamicLinker> linkers) {
final List<GuardingDynamicLinker> llinkers = new LinkedList<>();
final List<TypeBasedGuardingDynamicLinker> tblinkers = new LinkedList<>();
for(final GuardingDynamicLinker linker: linkers) {
Objects.requireNonNull(linker);
if(linker instanceof TypeBasedGuardingDynamicLinker) {
tblinkers.add((TypeBasedGuardingDynamicLinker)linker);
} else {
addTypeBased(llinkers, tblinkers);
llinkers.add(linker);
}
}
addTypeBased(llinkers, tblinkers);
return llinkers;
}
private static void addTypeBased(final List<GuardingDynamicLinker> llinkers,
final List<TypeBasedGuardingDynamicLinker> tblinkers) {
switch(tblinkers.size()) {
case 0: {
break;
}
case 1: {
llinkers.addAll(tblinkers);
tblinkers.clear();
break;
}
default: {
llinkers.add(new CompositeTypeBasedGuardingDynamicLinker(tblinkers));
tblinkers.clear();
break;
}
}
}
}