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	/*
	* Copyright (c) 2013, 2014, 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.ArrayList;
	import java.util.Arrays;
	import static java.lang.invoke.LambdaForm.*;
	import static java.lang.invoke.LambdaForm.BasicType.*;

	/** Working storage for an LF that is being transformed.
	* Similarly to a StringBuffer, the editing can take place in multiple steps.
	*/
	final class LambdaFormBuffer {
	private int arity, length;
	private Name[] names;
	private Name[] originalNames; // snapshot of pre-transaction names
	private byte flags;
	private int firstChange;
	private Name resultName;
	private String debugName;
	private ArrayList<Name> dups;

	private static final int F_TRANS = 0x10, F_OWNED = 0x03;

	LambdaFormBuffer(LambdaForm lf) {
	this.arity = lf.arity;
	setNames(lf.names);
	int result = lf.result;
	if (result == LAST_RESULT) result = length - 1;
	if (result >= 0 && lf.names[result].type != V_TYPE)
	resultName = lf.names[result];
	debugName = lf.debugName;
	assert(lf.nameRefsAreLegal());
	}

	private LambdaForm lambdaForm() {
	assert(!inTrans()); // need endEdit call to tidy things up
	return new LambdaForm(debugName, arity, nameArray(), resultIndex());
	}

	Name name(int i) {
	assert(i < length);
	return names[i];
	}

	Name[] nameArray() {
	return Arrays.copyOf(names, length);
	}

	int resultIndex() {
	if (resultName == null) return VOID_RESULT;
	int index = indexOf(resultName, names);
	assert(index >= 0);
	return index;
	}

	void setNames(Name[] names2) {
	names = originalNames = names2; // keep a record of where everything was to start with
	length = names2.length;
	flags = 0;
	}

	private boolean verifyArity() {
	for (int i = 0; i < arity && i < firstChange; i++) {
	assert(names[i].isParam()) : "#" + i + "=" + names[i];
	}
	for (int i = arity; i < length; i++) {
	assert(!names[i].isParam()) : "#" + i + "=" + names[i];
	}
	for (int i = length; i < names.length; i++) {
	assert(names[i] == null) : "#" + i + "=" + names[i];
	}
	// check resultName also
	if (resultName != null) {
	int resultIndex = indexOf(resultName, names);
	assert(resultIndex >= 0) : "not found: " + resultName.exprString() + Arrays.asList(names);
	assert(names[resultIndex] == resultName);
	}
	return true;
	}

	private boolean verifyFirstChange() {
	assert(inTrans());
	for (int i = 0; i < length; i++) {
	if (names[i] != originalNames[i]) {
	assert(firstChange == i) : Arrays.asList(firstChange, i, originalNames[i].exprString(), Arrays.asList(names));
	return true;
	}
	}
	assert(firstChange == length) : Arrays.asList(firstChange, Arrays.asList(names));
	return true;
	}

	private static int indexOf(NamedFunction fn, NamedFunction[] fns) {
	for (int i = 0; i < fns.length; i++) {
	if (fns[i] == fn) return i;
	}
	return -1;
	}

	private static int indexOf(Name n, Name[] ns) {
	for (int i = 0; i < ns.length; i++) {
	if (ns[i] == n) return i;
	}
	return -1;
	}

	boolean inTrans() {
	return (flags & F_TRANS) != 0;
	}

	int ownedCount() {
	return flags & F_OWNED;
	}

	void growNames(int insertPos, int growLength) {
	int oldLength = length;
	int newLength = oldLength + growLength;
	int oc = ownedCount();
	if (oc == 0 \|\| newLength > names.length) {
	names = Arrays.copyOf(names, (names.length + growLength) * 5 / 4);
	if (oc == 0) {
	flags++;
	oc++;
	assert(ownedCount() == oc);
	}
	}
	if (originalNames != null && originalNames.length < names.length) {
	originalNames = Arrays.copyOf(originalNames, names.length);
	if (oc == 1) {
	flags++;
	oc++;
	assert(ownedCount() == oc);
	}
	}
	if (growLength == 0) return;
	int insertEnd = insertPos + growLength;
	int tailLength = oldLength - insertPos;
	System.arraycopy(names, insertPos, names, insertEnd, tailLength);
	Arrays.fill(names, insertPos, insertEnd, null);
	if (originalNames != null) {
	System.arraycopy(originalNames, insertPos, originalNames, insertEnd, tailLength);
	Arrays.fill(originalNames, insertPos, insertEnd, null);
	}
	length = newLength;
	if (firstChange >= insertPos) {
	firstChange += growLength;
	}
	}

	int lastIndexOf(Name n) {
	int result = -1;
	for (int i = 0; i < length; i++) {
	if (names[i] == n) result = i;
	}
	return result;
	}

	/** We have just overwritten the name at pos1 with the name at pos2.
	* This means that there are two copies of the name, which we will have to fix later.
	*/
	private void noteDuplicate(int pos1, int pos2) {
	Name n = names[pos1];
	assert(n == names[pos2]);
	assert(originalNames[pos1] != null); // something was replaced at pos1
	assert(originalNames[pos2] == null \|\| originalNames[pos2] == n);
	if (dups == null) {
	dups = new ArrayList<>();
	}
	dups.add(n);
	}

	/** Replace duplicate names by nulls, and remove all nulls. */
	private void clearDuplicatesAndNulls() {
	if (dups != null) {
	// Remove duplicates.
	assert(ownedCount() >= 1);
	for (Name dup : dups) {
	for (int i = firstChange; i < length; i++) {
	if (names[i] == dup && originalNames[i] != dup) {
	names[i] = null;
	assert(Arrays.asList(names).contains(dup));
	break; // kill only one dup
	}
	}
	}
	dups.clear();
	}
	// Now that we are done with originalNames, remove "killed" names.
	int oldLength = length;
	for (int i = firstChange; i < length; i++) {
	if (names[i] == null) {
	System.arraycopy(names, i + 1, names, i, (--length - i));
	--i; // restart loop at this position
	}
	}
	if (length < oldLength) {
	Arrays.fill(names, length, oldLength, null);
	}
	assert(!Arrays.asList(names).subList(0, length).contains(null));
	}

	/** Create a private, writable copy of names.
	* Preserve the original copy, for reference.
	*/
	void startEdit() {
	assert(verifyArity());
	int oc = ownedCount();
	assert(!inTrans()); // no nested transactions
	flags \|= F_TRANS;
	Name[] oldNames = names;
	Name[] ownBuffer = (oc == 2 ? originalNames : null);
	assert(ownBuffer != oldNames);
	if (ownBuffer != null && ownBuffer.length >= length) {
	names = copyNamesInto(ownBuffer);
	} else {
	// make a new buffer to hold the names
	final int SLOP = 2;
	names = Arrays.copyOf(oldNames, Math.max(length + SLOP, oldNames.length));
	if (oc < 2) ++flags;
	assert(ownedCount() == oc + 1);
	}
	originalNames = oldNames;
	assert(originalNames != names);
	firstChange = length;
	assert(inTrans());
	}

	private void changeName(int i, Name name) {
	assert(inTrans());
	assert(i < length);
	Name oldName = names[i];
	assert(oldName == originalNames[i]); // no multiple changes
	assert(verifyFirstChange());
	if (ownedCount() == 0)
	growNames(0, 0);
	names[i] = name;
	if (firstChange > i) {
	firstChange = i;
	}
	if (resultName != null && resultName == oldName) {
	resultName = name;
	}
	}

	/** Change the result name. Null means a void result. */
	void setResult(Name name) {
	assert(name == null \|\| lastIndexOf(name) >= 0);
	resultName = name;
	}

	/** Finish a transaction. */
	LambdaForm endEdit() {
	assert(verifyFirstChange());
	// Assuming names have been changed pairwise from originalNames[i] to names[i],
	// update arguments to ensure referential integrity.
	for (int i = Math.max(firstChange, arity); i < length; i++) {
	Name name = names[i];
	if (name == null) continue; // space for removed duplicate
	Name newName = name.replaceNames(originalNames, names, firstChange, i);
	if (newName != name) {
	names[i] = newName;
	if (resultName == name) {
	resultName = newName;
	}
	}
	}
	assert(inTrans());
	flags &= ~F_TRANS;
	clearDuplicatesAndNulls();
	originalNames = null;
	// If any parameters have been changed, then reorder them as needed.
	// This is a "sheep-and-goats" stable sort, pushing all non-parameters
	// to the right of all parameters.
	if (firstChange < arity) {
	Name[] exprs = new Name[arity - firstChange];
	int argp = firstChange, exprp = 0;
	for (int i = firstChange; i < arity; i++) {
	Name name = names[i];
	if (name.isParam()) {
	names[argp++] = name;
	} else {
	exprs[exprp++] = name;
	}
	}
	assert(exprp == (arity - argp));
	// copy the exprs just after the last remaining param
	System.arraycopy(exprs, 0, names, argp, exprp);
	// adjust arity
	arity -= exprp;
	}
	assert(verifyArity());
	return lambdaForm();
	}

	private Name[] copyNamesInto(Name[] buffer) {
	System.arraycopy(names, 0, buffer, 0, length);
	Arrays.fill(buffer, length, buffer.length, null);
	return buffer;
	}

	/** Replace any Name whose function is in oldFns with a copy
	* whose function is in the corresponding position in newFns.
	* Only do this if the arguments are exactly equal to the given.
	*/
	LambdaFormBuffer replaceFunctions(NamedFunction[] oldFns, NamedFunction[] newFns,
	Object... forArguments) {
	assert(inTrans());
	if (oldFns.length == 0) return this;
	for (int i = arity; i < length; i++) {
	Name n = names[i];
	int nfi = indexOf(n.function, oldFns);
	if (nfi >= 0 && Arrays.equals(n.arguments, forArguments)) {
	changeName(i, new Name(newFns[nfi], n.arguments));
	}
	}
	return this;
	}

	private void replaceName(int pos, Name binding) {
	assert(inTrans());
	assert(verifyArity());
	assert(pos < arity);
	Name param = names[pos];
	assert(param.isParam());
	assert(param.type == binding.type);
	changeName(pos, binding);
	}

	/** Replace a parameter by a fresh parameter. */
	LambdaFormBuffer renameParameter(int pos, Name newParam) {
	assert(newParam.isParam());
	replaceName(pos, newParam);
	return this;
	}

	/** Replace a parameter by a fresh expression. */
	LambdaFormBuffer replaceParameterByNewExpression(int pos, Name binding) {
	assert(!binding.isParam());
	assert(lastIndexOf(binding) < 0); // else use replaceParameterByCopy
	replaceName(pos, binding);
	return this;
	}

	/** Replace a parameter by another parameter or expression already in the form. */
	LambdaFormBuffer replaceParameterByCopy(int pos, int valuePos) {
	assert(pos != valuePos);
	replaceName(pos, names[valuePos]);
	noteDuplicate(pos, valuePos); // temporarily, will occur twice in the names array
	return this;
	}

	private void insertName(int pos, Name expr, boolean isParameter) {
	assert(inTrans());
	assert(verifyArity());
	assert(isParameter ? pos <= arity : pos >= arity);
	growNames(pos, 1);
	if (isParameter) arity += 1;
	changeName(pos, expr);
	}

	/** Insert a fresh expression. */
	LambdaFormBuffer insertExpression(int pos, Name expr) {
	assert(!expr.isParam());
	insertName(pos, expr, false);
	return this;
	}

	/** Insert a fresh parameter. */
	LambdaFormBuffer insertParameter(int pos, Name param) {
	assert(param.isParam());
	insertName(pos, param, true);
	return this;
	}
	}

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