001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 *  Unless required by applicable law or agreed to in writing, software
012 *  distributed under the License is distributed on an "AS IS" BASIS,
013 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 *  See the License for the specific language governing permissions and
015 *  limitations under the License.
016 *
017 */
018package org.apache.bcel.classfile;
019
020import java.io.DataInput;
021import java.io.IOException;
022import java.util.Objects;
023
024import org.apache.bcel.Const;
025import org.apache.bcel.generic.Type;
026import org.apache.bcel.util.BCELComparator;
027
028/**
029 * This class represents the field info structure, i.e., the representation
030 * for a variable in the class. See JVM specification for details.
031 *
032 */
033public final class Field extends FieldOrMethod {
034
035    private static BCELComparator bcelComparator = new BCELComparator() {
036
037        @Override
038        public boolean equals( final Object o1, final Object o2 ) {
039            final Field THIS = (Field) o1;
040            final Field THAT = (Field) o2;
041            return Objects.equals(THIS.getName(), THAT.getName())
042                    && Objects.equals(THIS.getSignature(), THAT.getSignature());
043        }
044
045
046        @Override
047        public int hashCode( final Object o ) {
048            final Field THIS = (Field) o;
049            return THIS.getSignature().hashCode() ^ THIS.getName().hashCode();
050        }
051    };
052
053
054    /**
055     * Initialize from another object. Note that both objects use the same
056     * references (shallow copy). Use clone() for a physical copy.
057     */
058    public Field(final Field c) {
059        super(c);
060    }
061
062
063    /**
064     * Construct object from file stream.
065     * @param file Input stream
066     */
067    Field(final DataInput file, final ConstantPool constant_pool) throws IOException,
068            ClassFormatException {
069        super(file, constant_pool);
070    }
071
072
073    /**
074     * @param access_flags Access rights of field
075     * @param name_index Points to field name in constant pool
076     * @param signature_index Points to encoded signature
077     * @param attributes Collection of attributes
078     * @param constant_pool Array of constants
079     */
080    public Field(final int access_flags, final int name_index, final int signature_index, final Attribute[] attributes,
081            final ConstantPool constant_pool) {
082        super(access_flags, name_index, signature_index, attributes, constant_pool);
083    }
084
085
086    /**
087     * Called by objects that are traversing the nodes of the tree implicitely
088     * defined by the contents of a Java class. I.e., the hierarchy of methods,
089     * fields, attributes, etc. spawns a tree of objects.
090     *
091     * @param v Visitor object
092     */
093    @Override
094    public void accept( final Visitor v ) {
095        v.visitField(this);
096    }
097
098
099    /**
100     * @return constant value associated with this field (may be null)
101     */
102    public ConstantValue getConstantValue() {
103        for (final Attribute attribute : super.getAttributes()) {
104            if (attribute.getTag() == Const.ATTR_CONSTANT_VALUE) {
105                return (ConstantValue) attribute;
106            }
107        }
108        return null;
109    }
110
111
112    /**
113     * Return string representation close to declaration format,
114     * `public static final short MAX = 100', e.g..
115     *
116     * @return String representation of field, including the signature.
117     */
118    @Override
119    public String toString() {
120        String name;
121        String signature;
122        String access; // Short cuts to constant pool
123
124        // Get names from constant pool
125        access = Utility.accessToString(super.getAccessFlags());
126        access = access.isEmpty() ? "" : (access + " ");
127        signature = Utility.signatureToString(getSignature());
128        name = getName();
129        final StringBuilder buf = new StringBuilder(64); // CHECKSTYLE IGNORE MagicNumber
130        buf.append(access).append(signature).append(" ").append(name);
131        final ConstantValue cv = getConstantValue();
132        if (cv != null) {
133            buf.append(" = ").append(cv);
134        }
135        for (final Attribute attribute : super.getAttributes()) {
136            if (!(attribute instanceof ConstantValue)) {
137                buf.append(" [").append(attribute).append("]");
138            }
139        }
140        return buf.toString();
141    }
142
143
144    /**
145     * @return deep copy of this field
146     */
147    public Field copy( final ConstantPool _constant_pool ) {
148        return (Field) copy_(_constant_pool);
149    }
150
151
152    /**
153     * @return type of field
154     */
155    public Type getType() {
156        return Type.getReturnType(getSignature());
157    }
158
159
160    /**
161     * @return Comparison strategy object
162     */
163    public static BCELComparator getComparator() {
164        return bcelComparator;
165    }
166
167
168    /**
169     * @param comparator Comparison strategy object
170     */
171    public static void setComparator( final BCELComparator comparator ) {
172        bcelComparator = comparator;
173    }
174
175
176    /**
177     * Return value as defined by given BCELComparator strategy.
178     * By default two Field objects are said to be equal when
179     * their names and signatures are equal.
180     *
181     * @see java.lang.Object#equals(java.lang.Object)
182     */
183    @Override
184    public boolean equals( final Object obj ) {
185        return bcelComparator.equals(this, obj);
186    }
187
188
189    /**
190     * Return value as defined by given BCELComparator strategy.
191     * By default return the hashcode of the field's name XOR signature.
192     *
193     * @see java.lang.Object#hashCode()
194     */
195    @Override
196    public int hashCode() {
197        return bcelComparator.hashCode(this);
198    }
199}