code: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements. See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership. The ASF licenses this file
   * to you under the Apache License, Version 2.0 (the  "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  /*
   * $Id$
   */
  
  package org.apache.xalan.xsltc.compiler;
  
  import org.apache.bcel.classfile.Field;
  import org.apache.bcel.generic.ACONST_NULL;
  import org.apache.bcel.generic.ConstantPoolGen;
  import org.apache.bcel.generic.DCONST;
  import org.apache.bcel.generic.ICONST;
  import org.apache.bcel.generic.InstructionHandle;
  import org.apache.bcel.generic.InstructionList;
  import org.apache.bcel.generic.PUTFIELD;
  import org.apache.xalan.xsltc.compiler.util.BooleanType;
  import org.apache.xalan.xsltc.compiler.util.ClassGenerator;
  import org.apache.xalan.xsltc.compiler.util.ErrorMsg;
  import org.apache.xalan.xsltc.compiler.util.IntType;
  import org.apache.xalan.xsltc.compiler.util.MethodGenerator;
  import org.apache.xalan.xsltc.compiler.util.NodeType;
  import org.apache.xalan.xsltc.compiler.util.RealType;
  import org.apache.xalan.xsltc.compiler.util.Type;
  import org.apache.xalan.xsltc.compiler.util.TypeCheckError;
  
  final class Variable extends VariableBase {
  
      public int getIndex() {
  	return (_local != null) ? _local.getIndex() : -1;
      }
  
      /**
       * Parse the contents of the variable
       */
      public void parseContents(Parser parser) {
  	// Parse 'name' and 'select' attributes plus parameter contents
  	super.parseContents(parser);
  
  	// Add a ref to this var to its enclosing construct
  	SyntaxTreeNode parent = getParent();
  	if (parent instanceof Stylesheet) {
  	    // Mark this as a global variable
  	    _isLocal = false;
  	    // Check if a global variable with this name already exists...
  	    Variable var = parser.getSymbolTable().lookupVariable(_name);
  	    // ...and if it does we need to check import precedence
  	    if (var != null) {
  		final int us = this.getImportPrecedence();
  		final int them = var.getImportPrecedence();
  		// It is an error if the two have the same import precedence
  		if (us == them) {
  		    final String name = _name.toString();
  		    reportError(this, parser, ErrorMsg.VARIABLE_REDEF_ERR,name);
  		}
  		// Ignore this if previous definition has higher precedence
  		else if (them > us) {
  		    _ignore = true;
  		    return;
  		}
  		else {
  		    var.disable();
  		}
  		// Add this variable if we have higher precedence
  	    }
  	    ((Stylesheet)parent).addVariable(this);
  	    parser.getSymbolTable().addVariable(this);
  	}
  	else {
  	    _isLocal = true;
  	}
      }
  
      /**
       * Runs a type check on either the variable element body or the
       * expression in the 'select' attribute
       */
      public Type typeCheck(SymbolTable stable) throws TypeCheckError {
  
  	// Type check the 'select' expression if present
  	if (_select != null) {
  	    _type = _select.typeCheck(stable);
  	}
  	// Type check the element contents otherwise
  	else if (hasContents()) {
  	    typeCheckContents(stable);
  	    _type = Type.ResultTree;
  	}
  	else {
  	    _type = Type.Reference;
  	}
  	// The return type is void as the variable element does not leave
  	// anything on the JVM's stack. The '_type' global will be returned
  	// by the references to this variable, and not by the variable itself.
  	return Type.Void;
      }
  
      /**
       * This method is part of a little trick that is needed to use local
       * variables inside nested for-each loops. See the initializeVariables()
       * method in the ForEach class for an explanation
       */
      public void initialize(ClassGenerator classGen, MethodGenerator methodGen) {
  	final ConstantPoolGen cpg = classGen.getConstantPool();
  	final InstructionList il = methodGen.getInstructionList();
  
  	// This is only done for local variables that are actually used
  	if (isLocal() && !_refs.isEmpty()) {
  	    // Create a variable slot if none is allocated
  	    if (_local == null) {
  		_local = methodGen.addLocalVariable2(getEscapedName(),
  						     _type.toJCType(),
  						     null);
  	    }
  	    // Push the default value on the JVM's stack
  	    if ((_type instanceof IntType) ||
  		(_type instanceof NodeType) ||
  		(_type instanceof BooleanType))
  		il.append(new ICONST(0)); // 0 for node-id, integer and boolean
  	    else if (_type instanceof RealType)
  		il.append(new DCONST(0)); // 0.0 for floating point numbers
  	    else
  		il.append(new ACONST_NULL()); // and 'null' for anything else
  
              // Mark the store as the start of the live range of the variable
              _local.setStart(il.append(_type.STORE(_local.getIndex())));
  	}
      }
  
      public void translate(ClassGenerator classGen, MethodGenerator methodGen) {
  	final ConstantPoolGen cpg = classGen.getConstantPool();
  	final InstructionList il = methodGen.getInstructionList();
  
          // Don't generate code for unreferenced variables
          if (_refs.isEmpty()) {
              _ignore = true;
          }
  
  	// Make sure that a variable instance is only compiled once
  	if (_ignore) return;
  	_ignore = true;
  
  	final String name = getEscapedName();
  
  	if (isLocal()) {
  	    // Compile variable value computation
  	    translateValue(classGen, methodGen);
  
  	    // Add a new local variable and store value
              boolean createLocal = _local == null;
  	    if (createLocal) {
                  mapRegister(methodGen);
              }
  	    InstructionHandle storeInst =
                                    il.append(_type.STORE(_local.getIndex()));
  
              // If the local is just being created, mark the store as the start
              // of its live range.  Note that it might have been created by
              // initializeVariables already, which would have set the start of
              // the live range already.
              if (createLocal) {
                  _local.setStart(storeInst);
              }
  	}
  	else {
  	    String signature = _type.toSignature();
  
  	    // Global variables are store in class fields
  	    if (classGen.containsField(name) == null) {
  		classGen.addField(new Field(ACC_PUBLIC, 
  					    cpg.addUtf8(name),
  					    cpg.addUtf8(signature),
  					    null, cpg.getConstantPool()));
  
  		// Push a reference to "this" for putfield
  		il.append(classGen.loadTranslet());
  		// Compile variable value computation
  		translateValue(classGen, methodGen);
  		// Store the variable in the allocated field
  		il.append(new PUTFIELD(cpg.addFieldref(classGen.getClassName(),
  						       name, signature)));
  	    }
  	}
      }
  }
  