Variable.java revision 628:2bfaf29cc90b 
1/*
2 * reserved comment block
3 * DO NOT REMOVE OR ALTER!
4 */
5/*
6 * Copyright 2001-2004 The Apache Software Foundation.
7 *
8 * Licensed under the Apache License, Version 2.0 (the "License");
9 * you may not use this file except in compliance with the License.
10 * You may obtain a copy of the License at
11 *
12 *     http://www.apache.org/licenses/LICENSE-2.0
13 *
14 * Unless required by applicable law or agreed to in writing, software
15 * distributed under the License is distributed on an "AS IS" BASIS,
16 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
17 * See the License for the specific language governing permissions and
18 * limitations under the License.
19 */
20/*
21 * $Id: Variable.java,v 1.2.4.1 2005/09/12 11:36:46 pvedula Exp $
22 */
23
24package com.sun.org.apache.xalan.internal.xsltc.compiler;
25
26import com.sun.org.apache.bcel.internal.classfile.Field;
27import com.sun.org.apache.bcel.internal.generic.ACONST_NULL;
28import com.sun.org.apache.bcel.internal.generic.ConstantPoolGen;
29import com.sun.org.apache.bcel.internal.generic.DCONST;
30import com.sun.org.apache.bcel.internal.generic.ICONST;
31import com.sun.org.apache.bcel.internal.generic.InstructionHandle;
32import com.sun.org.apache.bcel.internal.generic.InstructionList;
33import com.sun.org.apache.bcel.internal.generic.PUTFIELD;
34import com.sun.org.apache.xalan.internal.xsltc.compiler.util.BooleanType;
35import com.sun.org.apache.xalan.internal.xsltc.compiler.util.ClassGenerator;
36import com.sun.org.apache.xalan.internal.xsltc.compiler.util.ErrorMsg;
37import com.sun.org.apache.xalan.internal.xsltc.compiler.util.IntType;
38import com.sun.org.apache.xalan.internal.xsltc.compiler.util.MethodGenerator;
39import com.sun.org.apache.xalan.internal.xsltc.compiler.util.NodeType;
40import com.sun.org.apache.xalan.internal.xsltc.compiler.util.RealType;
41import com.sun.org.apache.xalan.internal.xsltc.compiler.util.Type;
42import com.sun.org.apache.xalan.internal.xsltc.compiler.util.TypeCheckError;
43
44final class Variable extends VariableBase {
45
46    public int getIndex() {
47        return (_local != null) ? _local.getIndex() : -1;
48    }
49
50    /**
51     * Parse the contents of the variable
52     */
53    public void parseContents(Parser parser) {
54        // Parse 'name' and 'select' attributes plus parameter contents
55        super.parseContents(parser);
56
57        // Add a ref to this var to its enclosing construct
58        SyntaxTreeNode parent = getParent();
59        if (parent instanceof Stylesheet) {
60            // Mark this as a global variable
61            _isLocal = false;
62            // Check if a global variable with this name already exists...
63            Variable var = parser.getSymbolTable().lookupVariable(_name);
64            // ...and if it does we need to check import precedence
65            if (var != null) {
66                final int us = this.getImportPrecedence();
67                final int them = var.getImportPrecedence();
68                // It is an error if the two have the same import precedence
69                if (us == them) {
70                    final String name = _name.toString();
71                    reportError(this, parser, ErrorMsg.VARIABLE_REDEF_ERR,name);
72                }
73                // Ignore this if previous definition has higher precedence
74                else if (them > us) {
75                    _ignore = true;
76                    copyReferences(var);
77                    return;
78                }
79                else {
80                    var.copyReferences(this);
81                    var.disable();
82                }
83                // Add this variable if we have higher precedence
84            }
85            ((Stylesheet)parent).addVariable(this);
86            parser.getSymbolTable().addVariable(this);
87        }
88        else {
89            _isLocal = true;
90        }
91    }
92
93    /**
94     * Runs a type check on either the variable element body or the
95     * expression in the 'select' attribute
96     */
97    public Type typeCheck(SymbolTable stable) throws TypeCheckError {
98
99        // Type check the 'select' expression if present
100        if (_select != null) {
101            _type = _select.typeCheck(stable);
102        }
103        // Type check the element contents otherwise
104        else if (hasContents()) {
105            typeCheckContents(stable);
106            _type = Type.ResultTree;
107        }
108        else {
109            _type = Type.Reference;
110        }
111        // The return type is void as the variable element does not leave
112        // anything on the JVM's stack. The '_type' global will be returned
113        // by the references to this variable, and not by the variable itself.
114        return Type.Void;
115    }
116
117    /**
118     * This method is part of a little trick that is needed to use local
119     * variables inside nested for-each loops. See the initializeVariables()
120     * method in the ForEach class for an explanation
121     */
122    public void initialize(ClassGenerator classGen, MethodGenerator methodGen) {
123        final ConstantPoolGen cpg = classGen.getConstantPool();
124        final InstructionList il = methodGen.getInstructionList();
125
126        // This is only done for local variables that are actually used
127        if (isLocal() && !_refs.isEmpty()) {
128            // Create a variable slot if none is allocated
129            if (_local == null) {
130                _local = methodGen.addLocalVariable2(getEscapedName(),
131                                                     _type.toJCType(),
132                                                     null);
133            }
134            // Push the default value on the JVM's stack
135            if ((_type instanceof IntType) ||
136                (_type instanceof NodeType) ||
137                (_type instanceof BooleanType))
138                il.append(new ICONST(0)); // 0 for node-id, integer and boolean
139            else if (_type instanceof RealType)
140                il.append(new DCONST(0)); // 0.0 for floating point numbers
141            else
142                il.append(new ACONST_NULL()); // and 'null' for anything else
143
144            // Mark the store as the start of the live range of the variable
145            _local.setStart(il.append(_type.STORE(_local.getIndex())));
146
147        }
148    }
149
150    public void translate(ClassGenerator classGen, MethodGenerator methodGen) {
151        final ConstantPoolGen cpg = classGen.getConstantPool();
152        final InstructionList il = methodGen.getInstructionList();
153
154        // Don't generate code for unreferenced variables
155        if (_refs.isEmpty()) {
156            _ignore = true;
157        }
158
159        // Make sure that a variable instance is only compiled once
160        if (_ignore) return;
161        _ignore = true;
162
163        final String name = getEscapedName();
164
165        if (isLocal()) {
166            // Compile variable value computation
167            translateValue(classGen, methodGen);
168
169            // Add a new local variable and store value
170            boolean createLocal = _local == null;
171            if (createLocal) {
172                mapRegister(methodGen);
173            }
174            InstructionHandle storeInst =
175            il.append(_type.STORE(_local.getIndex()));
176
177            // If the local is just being created, mark the store as the start
178            // of its live range.  Note that it might have been created by
179            // initializeVariables already, which would have set the start of
180            // the live range already.
181            if (createLocal) {
182                _local.setStart(storeInst);
183        }
184        }
185        else {
186            String signature = _type.toSignature();
187
188            // Global variables are store in class fields
189            if (classGen.containsField(name) == null) {
190                classGen.addField(new Field(ACC_PUBLIC,
191                                            cpg.addUtf8(name),
192                                            cpg.addUtf8(signature),
193                                            null, cpg.getConstantPool()));
194
195                // Push a reference to "this" for putfield
196                il.append(classGen.loadTranslet());
197                // Compile variable value computation
198                translateValue(classGen, methodGen);
199                // Store the variable in the allocated field
200                il.append(new PUTFIELD(cpg.addFieldref(classGen.getClassName(),
201                                                       name, signature)));
202            }
203        }
204    }
205}
206