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	/*
	* Copyright (c) 1997, 2003, 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 sun.tools.tree;

	import sun.tools.java.*;
	import sun.tools.asm.Assembler;
	import java.io.PrintStream;

	/**
	* This class encapsulates the information required to generate an update to a private
	* field referenced from another class, e.g., an inner class. An expression denoting a
	* reference to the object to which the field belongs is associated with getter and
	* setter methods.
	* <p>
	* We use this class only for assignment, increment, and decrement operators, in which
	* the old value is first retrieved and then a new value is computed and stored.
	* Simple assignment expressions in which a value is copied without modification are
	* handled by another mechanism.
	*
	* WARNING: The contents of this source file are not part of any
	* supported API. Code that depends on them does so at its own risk:
	* they are subject to change or removal without notice.
	*/

	class FieldUpdater implements Constants {

	// Location for reporting errors.
	// Errors will always indicate compiler failure, but these will be easier to diagnose
	// if the bogus error is localized to the offending assignment.
	private long where;

	// The field to which this updater applies.
	// It would be easy to eliminate the need to store the field here, but we retain it for
	// diagnostic purposes.
	private MemberDefinition field;

	// Expression denoting the object to which the getter and setter are applied.
	// If the field is static, 'base' may be null, but need not be, as a static field
	// may be selected from an object reference. Even though the value of the object
	// reference will be ignored, it may have side-effects.
	private Expression base;

	// The getter and setter methods, generated by 'getAccessMember' and 'getUpdateMember'.
	private MemberDefinition getter;
	private MemberDefinition setter;

	// The number of words occupied on the stack by the object reference.
	// For static fields, this is zero.
	private int depth;

	/**
	* Constructor.
	*/

	public FieldUpdater(long where, MemberDefinition field,
	Expression base, MemberDefinition getter, MemberDefinition setter) {
	this.where = where;
	this.field = field;
	this.base = base;
	this.getter = getter;
	this.setter = setter;
	}


	/**
	* Since the object reference expression may be captured before it has been inlined,
	* we must inline it later. A <code>FieldUpdater</code> is inlined essentially as if
	* it were a child of the assignment node to which it belongs.
	*/

	public FieldUpdater inline(Environment env, Context ctx) {
	if (base != null) {
	if (field.isStatic()) {
	base = base.inline(env, ctx);
	} else {
	base = base.inlineValue(env, ctx);
	}
	}
	return this;
	}

	public FieldUpdater copyInline(Context ctx) {
	return new FieldUpdater(where, field, base.copyInline(ctx), getter, setter);
	}

	public int costInline(int thresh, Environment env, Context ctx, boolean needGet) {
	// Size of 'invokestatic' call for access method is 3 bytes.
	int cost = needGet ? 7 : 3; // getter needs extra invokestatic + dup
	// Size of expression to compute 'this' arg if needed.
	if (!field.isStatic() && base != null) {
	cost += base.costInline(thresh, env, ctx);
	}
	// We ignore the cost of duplicating value in value-needed context.
	return cost;
	}

	/**
	* Duplicate <code>items</code> words from the top of the stack, locating them
	* below the topmost <code>depth</code> words on the stack.
	*/

	// This code was cribbed from 'Expression.java'. We cannot reuse that code here,
	// because we do not inherit from class 'Expression'.

	private void codeDup(Assembler asm, int items, int depth) {
	switch (items) {
	case 0:
	return;
	case 1:
	switch (depth) {
	case 0:
	asm.add(where, opc_dup);
	return;
	case 1:
	asm.add(where, opc_dup_x1);
	return;
	case 2:
	asm.add(where, opc_dup_x2);
	return;

	}
	break;
	case 2:
	switch (depth) {
	case 0:
	asm.add(where, opc_dup2);
	return;
	case 1:
	asm.add(where, opc_dup2_x1);
	return;
	case 2:
	asm.add(where, opc_dup2_x2);
	return;

	}
	break;
	}
	throw new CompilerError("can't dup: " + items + ", " + depth);
	}

	/**
	* Begin a field update by an assignment, increment, or decrement operator.
	* The current value of the field is left at the top of the stack.
	* If <code>valNeeded</code> is true, we arrange for the initial value to remain
	* on the stack after the update.
	*/

	public void startUpdate(Environment env, Context ctx, Assembler asm, boolean valNeeded) {
	if (!(getter.isStatic() && setter.isStatic())) {
	throw new CompilerError("startUpdate isStatic");
	}
	if (!field.isStatic()) {
	// Provide explicit 'this' argument.
	base.codeValue(env, ctx, asm);
	depth = 1;
	} else {
	// May need to evaluate 'base' for effect.
	// If 'base' was a type expression, it should have previously been inlined away.
	if (base != null) {
	base.code(env, ctx, asm);
	}
	depth = 0;
	}
	codeDup(asm, depth, 0);
	asm.add(where, opc_invokestatic, getter);
	if (valNeeded) {
	codeDup(asm, field.getType().stackSize(), depth);
	}
	}

	/**
	* Complete a field update by an assignment, increment, or decrement operator.
	* The original value of the field left on the stack by <code>startUpdate</code>
	* must have been replaced with the updated value, with no other stack alterations.
	* If <code>valNeeded</code> is true, we arrange for the updated value to remain
	* on the stack after the update. The <code>valNeeded</code> argument must not be
	* true in both <code>startUpdate</code> and <code>finishUpdate</code>.
	*/

	public void finishUpdate(Environment env, Context ctx, Assembler asm, boolean valNeeded) {
	if (valNeeded) {
	codeDup(asm, field.getType().stackSize(), depth);
	}
	asm.add(where, opc_invokestatic, setter);
	}

	/**
	* Like above, but used when assigning a new value independent of the
	* old, as in a simple assignment expression. After 'startAssign',
	* code must be emitted to leave one additional value on the stack without
	* altering any others, followed by 'finishAssign'.
	*/

	public void startAssign(Environment env, Context ctx, Assembler asm) {
	if (!setter.isStatic()) {
	throw new CompilerError("startAssign isStatic");
	}
	if (!field.isStatic()) {
	// Provide explicit 'this' argument.
	base.codeValue(env, ctx, asm);
	depth = 1;
	} else {
	// May need to evaluate 'base' for effect.
	// If 'base' was a type expression, it should have previously been inlined away.
	if (base != null) {
	base.code(env, ctx, asm);
	}
	depth = 0;
	}
	}

	public void finishAssign(Environment env, Context ctx, Assembler asm, boolean valNeeded) {
	if (valNeeded) {
	codeDup(asm, field.getType().stackSize(), depth);
	}
	asm.add(where, opc_invokestatic, setter);
	}

	}

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