1/*
2 * Copyright (c) 1997, 2003, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.  Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26package sun.tools.tree;
27
28import sun.tools.java.*;
29import sun.tools.asm.Assembler;
30import java.io.PrintStream;
31
32/**
33 * This class encapsulates the information required to generate an update to a private
34 * field referenced from another class, e.g., an inner class.  An expression denoting a
35 * reference to the object to which the field belongs is associated with getter and
36 * setter methods.
37 * <p>
38 * We use this class only for assignment, increment, and decrement operators, in which
39 * the old value is first retrieved and then a new value is computed and stored.
40 * Simple assignment expressions in which a value is copied without modification are
41 * handled by another mechanism.
42 *
43 * WARNING: The contents of this source file are not part of any
44 * supported API.  Code that depends on them does so at its own risk:
45 * they are subject to change or removal without notice.
46 */
47
48class FieldUpdater implements Constants {
49
50    // Location for reporting errors.
51    // Errors will always indicate compiler failure, but these will be easier to diagnose
52    // if the bogus error is localized to the offending assignment.
53    private long where;
54
55    // The field to which this updater applies.
56    // It would be easy to eliminate the need to store the field here, but we retain it for
57    // diagnostic  purposes.
58    private MemberDefinition field;
59
60    // Expression denoting the object to which the getter and setter are applied.
61    // If the field is static, 'base' may be null, but need not be, as a static field
62    // may be selected from an object reference. Even though the value of the object
63    // reference will be ignored, it may have side-effects.
64    private Expression base;
65
66    // The getter and setter methods, generated by 'getAccessMember' and 'getUpdateMember'.
67    private MemberDefinition getter;
68    private MemberDefinition setter;
69
70    // The number of words occupied on the stack by the object reference.
71    // For static fields, this is zero.
72    private int depth;
73
74    /**
75     * Constructor.
76     */
77
78    public FieldUpdater(long where, MemberDefinition field,
79                        Expression base, MemberDefinition getter, MemberDefinition setter) {
80        this.where = where;
81        this.field = field;
82        this.base = base;
83        this.getter = getter;
84        this.setter = setter;
85    }
86
87
88    /**
89     * Since the object reference expression may be captured before it has been inlined,
90     * we must inline it later.  A <code>FieldUpdater</code> is inlined essentially as if
91     * it were a child of the assignment node to which it belongs.
92     */
93
94    public FieldUpdater inline(Environment env, Context ctx) {
95        if (base != null) {
96            if (field.isStatic()) {
97                base = base.inline(env, ctx);
98            } else {
99                base = base.inlineValue(env, ctx);
100            }
101        }
102        return this;
103    }
104
105    public FieldUpdater copyInline(Context ctx) {
106        return new FieldUpdater(where, field, base.copyInline(ctx), getter, setter);
107    }
108
109    public int costInline(int thresh, Environment env, Context ctx, boolean needGet) {
110        // Size of 'invokestatic' call for access method is 3 bytes.
111        int cost = needGet ? 7 : 3;  // getter needs extra invokestatic + dup
112        // Size of expression to compute 'this' arg if needed.
113        if (!field.isStatic() && base != null) {
114            cost += base.costInline(thresh, env, ctx);
115        }
116        // We ignore the cost of duplicating value in value-needed context.
117        return cost;
118    }
119
120    /**
121     * Duplicate <code>items</code> words from the top of the stack, locating them
122     * below the topmost <code>depth</code> words on the stack.
123     */
124
125    // This code was cribbed from 'Expression.java'.  We cannot reuse that code here,
126    // because we do not inherit from class 'Expression'.
127
128    private void codeDup(Assembler asm, int items, int depth) {
129        switch (items) {
130          case 0:
131            return;
132          case 1:
133            switch (depth) {
134              case 0:
135                asm.add(where, opc_dup);
136                return;
137              case 1:
138                asm.add(where, opc_dup_x1);
139                return;
140              case 2:
141                asm.add(where, opc_dup_x2);
142                return;
143
144            }
145            break;
146          case 2:
147            switch (depth) {
148              case 0:
149                asm.add(where, opc_dup2);
150                return;
151              case 1:
152                asm.add(where, opc_dup2_x1);
153                return;
154              case 2:
155                asm.add(where, opc_dup2_x2);
156                return;
157
158            }
159            break;
160        }
161        throw new CompilerError("can't dup: " + items + ", " + depth);
162    }
163
164    /**
165     * Begin a field update by an assignment, increment, or decrement operator.
166     * The current value of the field is left at the top of the stack.
167     * If <code>valNeeded</code> is true, we arrange for the initial value to remain
168     * on the stack after the update.
169     */
170
171    public void startUpdate(Environment env, Context ctx, Assembler asm, boolean valNeeded) {
172        if (!(getter.isStatic() && setter.isStatic())) {
173            throw new CompilerError("startUpdate isStatic");
174        }
175        if (!field.isStatic()) {
176            // Provide explicit 'this' argument.
177            base.codeValue(env, ctx, asm);
178            depth = 1;
179        } else {
180            // May need to evaluate 'base' for effect.
181            // If 'base' was a type expression, it should have previously been inlined away.
182            if (base != null) {
183                base.code(env, ctx, asm);
184            }
185            depth = 0;
186        }
187        codeDup(asm, depth, 0);
188        asm.add(where, opc_invokestatic, getter);
189        if (valNeeded) {
190            codeDup(asm, field.getType().stackSize(), depth);
191        }
192    }
193
194    /**
195     * Complete a field update by an assignment, increment, or decrement operator.
196     * The original value of the field left on the stack by <code>startUpdate</code>
197     * must have been replaced with the updated value, with no other stack alterations.
198     * If <code>valNeeded</code> is true, we arrange for the updated value to remain
199     * on the stack after the update.  The <code>valNeeded</code> argument must not be
200     * true in both <code>startUpdate</code> and <code>finishUpdate</code>.
201     */
202
203    public void finishUpdate(Environment env, Context ctx, Assembler asm, boolean valNeeded) {
204        if (valNeeded) {
205            codeDup(asm, field.getType().stackSize(), depth);
206        }
207        asm.add(where, opc_invokestatic, setter);
208    }
209
210    /**
211     * Like above, but used when assigning a new value independent of the
212     * old, as in a simple assignment expression.  After 'startAssign',
213     * code must be emitted to leave one additional value on the stack without
214     * altering any others, followed by 'finishAssign'.
215     */
216
217    public void startAssign(Environment env, Context ctx, Assembler asm) {
218        if (!setter.isStatic()) {
219            throw new CompilerError("startAssign isStatic");
220        }
221        if (!field.isStatic()) {
222            // Provide explicit 'this' argument.
223            base.codeValue(env, ctx, asm);
224            depth = 1;
225        } else {
226            // May need to evaluate 'base' for effect.
227            // If 'base' was a type expression, it should have previously been inlined away.
228            if (base != null) {
229                base.code(env, ctx, asm);
230            }
231            depth = 0;
232        }
233    }
234
235    public void finishAssign(Environment env, Context ctx, Assembler asm, boolean valNeeded) {
236        if (valNeeded) {
237            codeDup(asm, field.getType().stackSize(), depth);
238        }
239        asm.add(where, opc_invokestatic, setter);
240    }
241
242}
243