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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
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*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
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package jdk.nashorn.internal.runtime;
import java.lang.invoke.MethodHandle;
import java.util.AbstractList;
import java.util.Deque;
import java.util.Iterator;
import java.util.ListIterator;
import java.util.NoSuchElementException;
import java.util.Objects;
import java.util.RandomAccess;
import java.util.concurrent.Callable;
import jdk.nashorn.api.scripting.JSObject;
import jdk.nashorn.api.scripting.ScriptObjectMirror;
import jdk.nashorn.internal.objects.Global;
import jdk.nashorn.internal.runtime.linker.Bootstrap;
/**
* An adapter that can wrap any ECMAScript Array-like object (that adheres to the array rules for the property
* {@code length} and having conforming {@code push}, {@code pop}, {@code shift}, {@code unshift}, and {@code splice}
* methods) and expose it as both a Java list and double-ended queue. While script arrays aren't necessarily efficient
* as dequeues, it's still slightly more efficient to be able to translate dequeue operations into pushes, pops, shifts,
* and unshifts, than to blindly translate all list's add/remove operations into splices. Also, it is conceivable that a
* custom script object that implements an Array-like API can have a background data representation that is optimized
* for dequeue-like access. Note that with ECMAScript arrays, {@code push} and {@code pop} operate at the end of the
* array, while in Java {@code Deque} they operate on the front of the queue and as such the Java dequeue
* {@link #push(Object)} and {@link #pop()} operations will translate to {@code unshift} and {@code shift} script
* operations respectively, while {@link #addLast(Object)} and {@link #removeLast()} will translate to {@code push} and
* {@code pop}.
*/
public class ListAdapter extends AbstractList<Object> implements RandomAccess, Deque<Object> {
// Invoker creator for methods that add to the start or end of the list: PUSH and UNSHIFT. Takes fn, this, and value, returns void.
private static final Callable<MethodHandle> ADD_INVOKER_CREATOR = invokerCreator(void.class, Object.class, JSObject.class, Object.class);
// PUSH adds to the start of the list
private static final Object PUSH = new Object();
// UNSHIFT adds to the end of the list
private static final Object UNSHIFT = new Object();
// Invoker creator for methods that remove from the tail or head of the list: POP and SHIFT. Takes fn, this, returns Object.
private static final Callable<MethodHandle> REMOVE_INVOKER_CREATOR = invokerCreator(Object.class, Object.class, JSObject.class);
// POP removes from the start of the list
private static final Object POP = new Object();
// SHIFT removes from the end of the list
private static final Object SHIFT = new Object();
// SPLICE can be used to add a value in the middle of the list.
private static final Object SPLICE_ADD = new Object();
private static final Callable<MethodHandle> SPLICE_ADD_INVOKER_CREATOR = invokerCreator(void.class, Object.class, JSObject.class, int.class, int.class, Object.class);
// SPLICE can also be used to remove values from the middle of the list.
private static final Object SPLICE_REMOVE = new Object();
private static final Callable<MethodHandle> SPLICE_REMOVE_INVOKER_CREATOR = invokerCreator(void.class, Object.class, JSObject.class, int.class, int.class);
/** wrapped object */
final JSObject obj;
private final Global global;
// allow subclasses only in this package
ListAdapter(final JSObject obj, final Global global) {
if (global == null) {
throw new IllegalStateException(ECMAErrors.getMessage("list.adapter.null.global"));
}
this.obj = obj;
this.global = global;
}
/**
* Factory to create a ListAdapter for a given script object.
*
* @param obj script object to wrap as a ListAdapter
* @return A ListAdapter wrapper object
*/
public static ListAdapter create(final Object obj) {
final Global global = Context.getGlobal();
return new ListAdapter(getJSObject(obj, global), global);
}
private static JSObject getJSObject(final Object obj, final Global global) {
if (obj instanceof ScriptObject) {
return (JSObject)ScriptObjectMirror.wrap(obj, global);
} else if (obj instanceof JSObject) {
return (JSObject)obj;
}
throw new IllegalArgumentException("ScriptObject or JSObject expected");
}
@Override
public final Object get(final int index) {
checkRange(index);
return getAt(index);
}
private Object getAt(final int index) {
return obj.getSlot(index);
}
@Override
public Object set(final int index, final Object element) {
checkRange(index);
final Object prevValue = getAt(index);
obj.setSlot(index, element);
return prevValue;
}
private void checkRange(final int index) {
if(index < 0 || index >= size()) {
throw invalidIndex(index);
}
}
@Override
public int size() {
return JSType.toInt32(obj.getMember("length"));
}
@Override
public final void push(final Object e) {
addFirst(e);
}
@Override
public final boolean add(final Object e) {
addLast(e);
return true;
}
@Override
public final void addFirst(final Object e) {
try {
getDynamicInvoker(UNSHIFT, ADD_INVOKER_CREATOR).invokeExact(getFunction("unshift"), obj, e);
} catch(RuntimeException | Error ex) {
throw ex;
} catch(final Throwable t) {
throw new RuntimeException(t);
}
}
@Override
public final void addLast(final Object e) {
try {
getDynamicInvoker(PUSH, ADD_INVOKER_CREATOR).invokeExact(getFunction("push"), obj, e);
} catch(RuntimeException | Error ex) {
throw ex;
} catch(final Throwable t) {
throw new RuntimeException(t);
}
}
@Override
public final void add(final int index, final Object e) {
try {
if(index < 0) {
throw invalidIndex(index);
} else if(index == 0) {
addFirst(e);
} else {
final int size = size();
if(index < size) {
getDynamicInvoker(SPLICE_ADD, SPLICE_ADD_INVOKER_CREATOR).invokeExact(obj.getMember("splice"), obj, index, 0, e);
} else if(index == size) {
addLast(e);
} else {
throw invalidIndex(index);
}
}
} catch(final RuntimeException | Error ex) {
throw ex;
} catch(final Throwable t) {
throw new RuntimeException(t);
}
}
private Object getFunction(final String name) {
final Object fn = obj.getMember(name);
if(!(Bootstrap.isCallable(fn))) {
throw new UnsupportedOperationException("The script object doesn't have a function named " + name);
}
return fn;
}
private static IndexOutOfBoundsException invalidIndex(final int index) {
return new IndexOutOfBoundsException(String.valueOf(index));
}
@Override
public final boolean offer(final Object e) {
return offerLast(e);
}
@Override
public final boolean offerFirst(final Object e) {
addFirst(e);
return true;
}
@Override
public final boolean offerLast(final Object e) {
addLast(e);
return true;
}
@Override
public final Object pop() {
return removeFirst();
}
@Override
public final Object remove() {
return removeFirst();
}
@Override
public final Object removeFirst() {
checkNonEmpty();
return invokeShift();
}
@Override
public final Object removeLast() {
checkNonEmpty();
return invokePop();
}
private void checkNonEmpty() {
if(isEmpty()) {
throw new NoSuchElementException();
}
}
@Override
public final Object remove(final int index) {
if(index < 0) {
throw invalidIndex(index);
} else if (index == 0) {
return invokeShift();
} else {
final int maxIndex = size() - 1;
if(index < maxIndex) {
final Object prevValue = get(index);
invokeSpliceRemove(index, 1);
return prevValue;
} else if(index == maxIndex) {
return invokePop();
} else {
throw invalidIndex(index);
}
}
}
private Object invokeShift() {
try {
return getDynamicInvoker(SHIFT, REMOVE_INVOKER_CREATOR).invokeExact(getFunction("shift"), obj);
} catch(RuntimeException | Error ex) {
throw ex;
} catch(final Throwable t) {
throw new RuntimeException(t);
}
}
private Object invokePop() {
try {
return getDynamicInvoker(POP, REMOVE_INVOKER_CREATOR).invokeExact(getFunction("pop"), obj);
} catch(RuntimeException | Error ex) {
throw ex;
} catch(final Throwable t) {
throw new RuntimeException(t);
}
}
@Override
protected final void removeRange(final int fromIndex, final int toIndex) {
invokeSpliceRemove(fromIndex, toIndex - fromIndex);
}
private void invokeSpliceRemove(final int fromIndex, final int count) {
try {
getDynamicInvoker(SPLICE_REMOVE, SPLICE_REMOVE_INVOKER_CREATOR).invokeExact(getFunction("splice"), obj, fromIndex, count);
} catch(RuntimeException | Error ex) {
throw ex;
} catch(final Throwable t) {
throw new RuntimeException(t);
}
}
@Override
public final Object poll() {
return pollFirst();
}
@Override
public final Object pollFirst() {
return isEmpty() ? null : invokeShift();
}
@Override
public final Object pollLast() {
return isEmpty() ? null : invokePop();
}
@Override
public final Object peek() {
return peekFirst();
}
@Override
public final Object peekFirst() {
return isEmpty() ? null : get(0);
}
@Override
public final Object peekLast() {
return isEmpty() ? null : get(size() - 1);
}
@Override
public final Object element() {
return getFirst();
}
@Override
public final Object getFirst() {
checkNonEmpty();
return get(0);
}
@Override
public final Object getLast() {
checkNonEmpty();
return get(size() - 1);
}
@Override
public final Iterator<Object> descendingIterator() {
final ListIterator<Object> it = listIterator(size());
return new Iterator<Object>() {
@Override
public boolean hasNext() {
return it.hasPrevious();
}
@Override
public Object next() {
return it.previous();
}
@Override
public void remove() {
it.remove();
}
};
}
@Override
public final boolean removeFirstOccurrence(final Object o) {
return removeOccurrence(o, iterator());
}
@Override
public final boolean removeLastOccurrence(final Object o) {
return removeOccurrence(o, descendingIterator());
}
private static boolean removeOccurrence(final Object o, final Iterator<Object> it) {
while(it.hasNext()) {
if(Objects.equals(o, it.next())) {
it.remove();
return true;
}
}
return false;
}
private static Callable<MethodHandle> invokerCreator(final Class<?> rtype, final Class<?>... ptypes) {
return new Callable<MethodHandle>() {
@Override
public MethodHandle call() {
return Bootstrap.createDynamicCallInvoker(rtype, ptypes);
}
};
}
private MethodHandle getDynamicInvoker(final Object key, final Callable<MethodHandle> creator) {
return global.getDynamicInvoker(key, creator);
}
}