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	/*
	* Copyright (c) 2017, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* 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).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	package java.lang.invoke;

	import java.util.*;
	import jdk.internal.vm.annotation.Stable;

	import static java.lang.invoke.MethodHandleStatics.rangeCheck1;
	import static java.lang.invoke.MethodHandleStatics.rangeCheck2;

	/** Utility class for implementing ConstantGroup. */
	/non-public/
	abstract class AbstractConstantGroup implements ConstantGroup {
	/** The size of this constant group, set permanently by the constructor. */
	protected final int size;

	/** The constructor requires the size of the constant group being represented.
	* @param size the size of this constant group, set permanently by the constructor
	*/
	AbstractConstantGroup(int size) {
	this.size = size;
	}

	@Override public final int size() {
	return size;
	}

	public abstract Object get(int index) throws LinkageError;

	public abstract Object get(int index, Object ifNotPresent);

	public abstract boolean isPresent(int index);

	// Do not override equals or hashCode, since this type is stateful.

	/**
	* Produce a string using the non-resolving list view,
	* where unresolved elements are presented as asterisks.
	* @return {@code this.asList("*").toString()}
	*/
	@Override public String toString() {
	return asList("*").toString();
	}

	static class AsIterator implements Iterator<Object> {
	private final ConstantGroup self;
	private final int end;
	private final boolean resolving;
	private final Object ifNotPresent;

	// Mutable state:
	private int index;

	private AsIterator(ConstantGroup self, int start, int end,
	boolean resolving, Object ifNotPresent) {
	this.self = self;
	this.end = end;
	this.index = start;
	this.resolving = resolving;
	this.ifNotPresent = ifNotPresent;
	}
	AsIterator(ConstantGroup self, int start, int end) {
	this(self, start, end, true, null);
	}
	AsIterator(ConstantGroup self, int start, int end,
	Object ifNotPresent) {
	this(self, start, end, false, ifNotPresent);
	}

	@Override
	public boolean hasNext() {
	return index < end;
	}

	@Override
	public Object next() {
	int i = bumpIndex();
	if (resolving)
	return self.get(i);
	else
	return self.get(i, ifNotPresent);
	}

	private int bumpIndex() {
	int i = index;
	if (i >= end) throw new NoSuchElementException();
	index = i+1;
	return i;
	}
	}

	static class SubGroup extends AbstractConstantGroup {
	private final ConstantGroup self; // the real CG
	private final int offset; // offset within myself
	SubGroup(ConstantGroup self, int start, int end) {
	super(end - start);
	this.self = self;
	this.offset = start;
	rangeCheck2(start, end, size);
	}

	private int mapIndex(int index) {
	return rangeCheck1(index, size) + offset;
	}

	@Override
	public Object get(int index) {
	return self.get(mapIndex(index));
	}

	@Override
	public Object get(int index, Object ifNotPresent) {
	return self.get(mapIndex(index), ifNotPresent);
	}

	@Override
	public boolean isPresent(int index) {
	return self.isPresent(mapIndex(index));
	}

	@Override
	public ConstantGroup subGroup(int start, int end) {
	rangeCheck2(start, end, size);
	return new SubGroup(self, offset + start, offset + end);
	}

	@Override
	public List<Object> asList() {
	return new AsList(self, offset, offset + size);
	}

	@Override
	public List<Object> asList(Object ifNotPresent) {
	return new AsList(self, offset, offset + size, ifNotPresent);
	}

	@Override
	public int copyConstants(int start, int end,
	Object[] buf, int pos) throws LinkageError {
	rangeCheck2(start, end, size);
	return self.copyConstants(offset + start, offset + end,
	buf, pos);
	}

	@Override
	public int copyConstants(int start, int end,
	Object[] buf, int pos,
	Object ifNotPresent) {
	rangeCheck2(start, end, size);
	return self.copyConstants(offset + start, offset + end,
	buf, pos, ifNotPresent);
	}
	}

	static class AsList extends AbstractList<Object> {
	private final ConstantGroup self;
	private final int size;
	private final int offset;
	private final boolean resolving;
	private final Object ifNotPresent;

	private AsList(ConstantGroup self, int start, int end,
	boolean resolving, Object ifNotPresent) {
	this.self = self;
	this.size = end - start;
	this.offset = start;
	this.resolving = resolving;
	this.ifNotPresent = ifNotPresent;
	rangeCheck2(start, end, self.size());
	}
	AsList(ConstantGroup self, int start, int end) {
	this(self, start, end, true, null);
	}
	AsList(ConstantGroup self, int start, int end,
	Object ifNotPresent) {
	this(self, start, end, false, ifNotPresent);
	}

	private int mapIndex(int index) {
	return rangeCheck1(index, size) + offset;
	}

	@Override public final int size() {
	return size;
	}

	@Override public Object get(int index) {
	if (resolving)
	return self.get(mapIndex(index));
	else
	return self.get(mapIndex(index), ifNotPresent);
	}

	@Override
	public Iterator<Object> iterator() {
	if (resolving)
	return new AsIterator(self, offset, offset + size);
	else
	return new AsIterator(self, offset, offset + size, ifNotPresent);
	}

	@Override public List<Object> subList(int start, int end) {
	rangeCheck2(start, end, size);
	return new AsList(self, offset + start, offset + end,
	resolving, ifNotPresent);
	}

	@Override public Object[] toArray() {
	return toArray(new Object[size]);
	}
	@Override public <T> T[] toArray(T[] a) {
	int pad = a.length - size;
	if (pad < 0) {
	pad = 0;
	a = Arrays.copyOf(a, size);
	}
	if (resolving)
	self.copyConstants(offset, offset + size, a, 0);
	else
	self.copyConstants(offset, offset + size, a, 0,
	ifNotPresent);
	if (pad > 0) a[size] = null;
	return a;
	}
	}

	static abstract
	class WithCache extends AbstractConstantGroup {
	@Stable final Object[] cache;

	WithCache(int size) {
	super(size);
	// It is caller's responsibility to initialize the cache.
	// Initial contents are all-null, which means nothing is present.
	cache = new Object[size];
	}

	void initializeCache(List<Object> cacheContents, Object ifNotPresent) {
	// Replace ifNotPresent with NOT_PRESENT,
	// and null with RESOLVED_TO_NULL.
	// Then forget about the user-provided ifNotPresent.
	for (int i = 0; i < cache.length; i++) {
	Object x = cacheContents.get(i);
	if (x == ifNotPresent)
	continue; // leave the null in place
	if (x == null)
	x = RESOLVED_TO_NULL;
	cache[i] = x;
	}
	}

	@Override public Object get(int i) {
	Object x = cache[i];
	// @Stable array must use null for sentinel
	if (x == null) x = fillCache(i);
	return unwrapNull(x);
	}

	@Override public Object get(int i, Object ifNotAvailable) {
	Object x = cache[i];
	// @Stable array must use null for sentinel
	if (x == null) return ifNotAvailable;
	return unwrapNull(x);
	}

	@Override
	public boolean isPresent(int i) {
	return cache[i] != null;
	}

	/** hook for local subclasses */
	Object fillCache(int i) {
	throw new NoSuchElementException("constant group does not contain element #"+i);
	}

	/// routines for mapping between null sentinel and true resolved null

	static Object wrapNull(Object x) {
	return x == null ? RESOLVED_TO_NULL : x;
	}

	static Object unwrapNull(Object x) {
	assert(x != null);
	return x == RESOLVED_TO_NULL ? null : x;
	}

	// secret sentinel for an actual null resolved value, in the cache
	static final Object RESOLVED_TO_NULL = new Object();

	// secret sentinel for a "hole" in the cache:
	static final Object NOT_PRESENT = new Object();

	}

	/** Skeleton implementation of BootstrapCallInfo. */
	static
	class BSCIWithCache<T> extends WithCache implements BootstrapCallInfo<T> {
	private final MethodHandle bsm;
	private final String name;
	private final T type;

	@Override public String toString() {
	return bsm+"/"+name+":"+type+super.toString();
	}

	BSCIWithCache(MethodHandle bsm, String name, T type, int size) {
	super(size);
	this.type = type;
	this.bsm = bsm;
	this.name = name;
	assert(type instanceof Class \|\| type instanceof MethodType);
	}

	@Override public MethodHandle bootstrapMethod() { return bsm; }
	@Override public String invocationName() { return name; }
	@Override public T invocationType() { return type; }
	}
	}

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