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: VoidType.java 468649 2006-10-28 07:00:55Z minchau $
020     */
021    
022    package org.apache.xalan.xsltc.compiler.util;
023    
024    import org.apache.bcel.generic.Instruction;
025    import org.apache.bcel.generic.InstructionList;
026    import org.apache.bcel.generic.PUSH;
027    import org.apache.xalan.xsltc.compiler.Constants;
028    
029    /**
030     * @author Jacek Ambroziak
031     * @author Santiago Pericas-Geertsen
032     */
033    public final class VoidType extends Type {
034        protected VoidType() {}
035    
036        public String toString() {
037            return "void";
038        }
039    
040        public boolean identicalTo(Type other) {
041            return this == other;
042        }
043    
044        public String toSignature() {
045            return "V";
046        }
047    
048        public org.apache.bcel.generic.Type toJCType() {
049            return null;    // should never be called
050        }
051    
052        public Instruction POP() {
053            return NOP;
054        }
055    
056        /**
057         * Translates a void into an object of internal type <code>type</code>.
058         * This translation is needed when calling external functions
059         * that return void.
060         *
061         * @see     org.apache.xalan.xsltc.compiler.util.Type#translateTo
062         */
063        public void translateTo(ClassGenerator classGen, MethodGenerator methodGen,
064                                Type type) {
065            if (type == Type.String) {
066                translateTo(classGen, methodGen, (StringType) type);
067            }
068            else {
069                ErrorMsg err = new ErrorMsg(ErrorMsg.DATA_CONVERSION_ERR,
070                                            toString(), type.toString());
071                classGen.getParser().reportError(Constants.FATAL, err);
072            }
073        }
074    
075        /**
076         * Translates a void into a string by pushing the empty string ''.
077         *
078         * @see     org.apache.xalan.xsltc.compiler.util.Type#translateTo
079         */
080        public void translateTo(ClassGenerator classGen, MethodGenerator methodGen,
081                                StringType type) {
082            final InstructionList il = methodGen.getInstructionList();
083            il.append(new PUSH(classGen.getConstantPool(), ""));
084        }
085    
086        /**
087         * Translates an external (primitive) Java type into a void.
088         * Only an external "void" can be converted to this class.
089         */
090        public void translateFrom(ClassGenerator classGen, MethodGenerator methodGen,
091                                  Class clazz) {
092            if (!clazz.getName().equals("void")) {
093                ErrorMsg err = new ErrorMsg(ErrorMsg.DATA_CONVERSION_ERR,
094                                            toString(), clazz.getName());
095                classGen.getParser().reportError(Constants.FATAL, err);
096            }
097        }
098    }