001 /*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements. See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership. The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the "License");
007 * you may not use this file except in compliance with the License.
008 * You may obtain a copy of the License at
009 *
010 * http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018 /*
019 * $Id: Variable.java 468650 2006-10-28 07:03:30Z minchau $
020 */
021
022 package org.apache.xalan.xsltc.compiler;
023
024 import org.apache.bcel.classfile.Field;
025 import org.apache.bcel.generic.ACONST_NULL;
026 import org.apache.bcel.generic.ConstantPoolGen;
027 import org.apache.bcel.generic.DCONST;
028 import org.apache.bcel.generic.ICONST;
029 import org.apache.bcel.generic.InstructionHandle;
030 import org.apache.bcel.generic.InstructionList;
031 import org.apache.bcel.generic.PUTFIELD;
032 import org.apache.xalan.xsltc.compiler.util.BooleanType;
033 import org.apache.xalan.xsltc.compiler.util.ClassGenerator;
034 import org.apache.xalan.xsltc.compiler.util.ErrorMsg;
035 import org.apache.xalan.xsltc.compiler.util.IntType;
036 import org.apache.xalan.xsltc.compiler.util.MethodGenerator;
037 import org.apache.xalan.xsltc.compiler.util.NodeType;
038 import org.apache.xalan.xsltc.compiler.util.RealType;
039 import org.apache.xalan.xsltc.compiler.util.Type;
040 import org.apache.xalan.xsltc.compiler.util.TypeCheckError;
041
042 final class Variable extends VariableBase {
043
044 public int getIndex() {
045 return (_local != null) ? _local.getIndex() : -1;
046 }
047
048 /**
049 * Parse the contents of the variable
050 */
051 public void parseContents(Parser parser) {
052 // Parse 'name' and 'select' attributes plus parameter contents
053 super.parseContents(parser);
054
055 // Add a ref to this var to its enclosing construct
056 SyntaxTreeNode parent = getParent();
057 if (parent instanceof Stylesheet) {
058 // Mark this as a global variable
059 _isLocal = false;
060 // Check if a global variable with this name already exists...
061 Variable var = parser.getSymbolTable().lookupVariable(_name);
062 // ...and if it does we need to check import precedence
063 if (var != null) {
064 final int us = this.getImportPrecedence();
065 final int them = var.getImportPrecedence();
066 // It is an error if the two have the same import precedence
067 if (us == them) {
068 final String name = _name.toString();
069 reportError(this, parser, ErrorMsg.VARIABLE_REDEF_ERR,name);
070 }
071 // Ignore this if previous definition has higher precedence
072 else if (them > us) {
073 _ignore = true;
074 return;
075 }
076 else {
077 var.disable();
078 }
079 // Add this variable if we have higher precedence
080 }
081 ((Stylesheet)parent).addVariable(this);
082 parser.getSymbolTable().addVariable(this);
083 }
084 else {
085 _isLocal = true;
086 }
087 }
088
089 /**
090 * Runs a type check on either the variable element body or the
091 * expression in the 'select' attribute
092 */
093 public Type typeCheck(SymbolTable stable) throws TypeCheckError {
094
095 // Type check the 'select' expression if present
096 if (_select != null) {
097 _type = _select.typeCheck(stable);
098 }
099 // Type check the element contents otherwise
100 else if (hasContents()) {
101 typeCheckContents(stable);
102 _type = Type.ResultTree;
103 }
104 else {
105 _type = Type.Reference;
106 }
107 // The return type is void as the variable element does not leave
108 // anything on the JVM's stack. The '_type' global will be returned
109 // by the references to this variable, and not by the variable itself.
110 return Type.Void;
111 }
112
113 /**
114 * This method is part of a little trick that is needed to use local
115 * variables inside nested for-each loops. See the initializeVariables()
116 * method in the ForEach class for an explanation
117 */
118 public void initialize(ClassGenerator classGen, MethodGenerator methodGen) {
119 final ConstantPoolGen cpg = classGen.getConstantPool();
120 final InstructionList il = methodGen.getInstructionList();
121
122 // This is only done for local variables that are actually used
123 if (isLocal() && !_refs.isEmpty()) {
124 // Create a variable slot if none is allocated
125 if (_local == null) {
126 _local = methodGen.addLocalVariable2(getEscapedName(),
127 _type.toJCType(),
128 null);
129 }
130 // Push the default value on the JVM's stack
131 if ((_type instanceof IntType) ||
132 (_type instanceof NodeType) ||
133 (_type instanceof BooleanType))
134 il.append(new ICONST(0)); // 0 for node-id, integer and boolean
135 else if (_type instanceof RealType)
136 il.append(new DCONST(0)); // 0.0 for floating point numbers
137 else
138 il.append(new ACONST_NULL()); // and 'null' for anything else
139
140 // Mark the store as the start of the live range of the variable
141 _local.setStart(il.append(_type.STORE(_local.getIndex())));
142 }
143 }
144
145 public void translate(ClassGenerator classGen, MethodGenerator methodGen) {
146 final ConstantPoolGen cpg = classGen.getConstantPool();
147 final InstructionList il = methodGen.getInstructionList();
148
149 // Don't generate code for unreferenced variables
150 if (_refs.isEmpty()) {
151 _ignore = true;
152 }
153
154 // Make sure that a variable instance is only compiled once
155 if (_ignore) return;
156 _ignore = true;
157
158 final String name = getEscapedName();
159
160 if (isLocal()) {
161 // Compile variable value computation
162 translateValue(classGen, methodGen);
163
164 // Add a new local variable and store value
165 boolean createLocal = _local == null;
166 if (createLocal) {
167 mapRegister(methodGen);
168 }
169 InstructionHandle storeInst =
170 il.append(_type.STORE(_local.getIndex()));
171
172 // If the local is just being created, mark the store as the start
173 // of its live range. Note that it might have been created by
174 // initializeVariables already, which would have set the start of
175 // the live range already.
176 if (createLocal) {
177 _local.setStart(storeInst);
178 }
179 }
180 else {
181 String signature = _type.toSignature();
182
183 // Global variables are store in class fields
184 if (classGen.containsField(name) == null) {
185 classGen.addField(new Field(ACC_PUBLIC,
186 cpg.addUtf8(name),
187 cpg.addUtf8(signature),
188 null, cpg.getConstantPool()));
189
190 // Push a reference to "this" for putfield
191 il.append(classGen.loadTranslet());
192 // Compile variable value computation
193 translateValue(classGen, methodGen);
194 // Store the variable in the allocated field
195 il.append(new PUTFIELD(cpg.addFieldref(classGen.getClassName(),
196 name, signature)));
197 }
198 }
199 }
200 }