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.DataInputStream; 022import java.io.DataOutputStream; 023import java.io.IOException; 024import java.util.HashMap; 025import java.util.Map; 026 027import org.apache.bcel.Const; 028 029/** 030 * Abstract super class for <em>Attribute</em> objects. Currently the 031 * <em>ConstantValue</em>, <em>SourceFile</em>, <em>Code</em>, 032 * <em>Exceptiontable</em>, <em>LineNumberTable</em>, 033 * <em>LocalVariableTable</em>, <em>InnerClasses</em> and 034 * <em>Synthetic</em> attributes are supported. The <em>Unknown</em> 035 * attribute stands for non-standard-attributes. 036 * 037 * @version $Id: Attribute.java 1750029 2016-06-23 22:14:38Z sebb $ 038 * @see ConstantValue 039 * @see SourceFile 040 * @see Code 041 * @see Unknown 042 * @see ExceptionTable 043 * @see LineNumberTable 044 * @see LocalVariableTable 045 * @see InnerClasses 046 * @see Synthetic 047 * @see Deprecated 048 * @see Signature 049 */ 050public abstract class Attribute implements Cloneable, Node { 051 052 /** 053 * @deprecated (since 6.0) will be made private; do not access directly, use getter/setter 054 */ 055 @java.lang.Deprecated 056 protected int name_index; // Points to attribute name in constant pool TODO make private (has getter & setter) 057 058 /** 059 * @deprecated (since 6.0) (since 6.0) will be made private; do not access directly, use getter/setter 060 */ 061 @java.lang.Deprecated 062 protected int length; // Content length of attribute field TODO make private (has getter & setter) 063 064 /** 065 * @deprecated (since 6.0) will be made private; do not access directly, use getter/setter 066 */ 067 @java.lang.Deprecated 068 protected byte tag; // Tag to distinguish subclasses TODO make private & final; supposed to be immutable 069 070 /** 071 * @deprecated (since 6.0) will be made private; do not access directly, use getter/setter 072 */ 073 @java.lang.Deprecated 074 protected ConstantPool constant_pool; // TODO make private (has getter & setter) 075 076 protected Attribute(final byte tag, final int name_index, final int length, final ConstantPool constant_pool) 077 { 078 this.tag = tag; 079 this.name_index = name_index; 080 this.length = length; 081 this.constant_pool = constant_pool; 082 } 083 084 /** 085 * Called by objects that are traversing the nodes of the tree implicitely 086 * defined by the contents of a Java class. I.e., the hierarchy of methods, 087 * fields, attributes, etc. spawns a tree of objects. 088 * 089 * @param v 090 * Visitor object 091 */ 092 @Override 093 public abstract void accept(Visitor v); 094 095 /** 096 * Dump attribute to file stream in binary format. 097 * 098 * @param file 099 * Output file stream 100 * @throws IOException 101 */ 102 public void dump(final DataOutputStream file) throws IOException 103 { 104 file.writeShort(name_index); 105 file.writeInt(length); 106 } 107 108 private static final Map<String, Object> readers = new HashMap<>(); 109 110 /** 111 * Add an Attribute reader capable of parsing (user-defined) attributes 112 * named "name". You should not add readers for the standard attributes such 113 * as "LineNumberTable", because those are handled internally. 114 * 115 * @param name the name of the attribute as stored in the class file 116 * @param r the reader object 117 * @deprecated (6.0) Use {@link #addAttributeReader(String, UnknownAttributeReader)} instead 118 */ 119 @java.lang.Deprecated 120 public static void addAttributeReader(final String name, final AttributeReader r) 121 { 122 readers.put(name, r); 123 } 124 125 /** 126 * Add an Attribute reader capable of parsing (user-defined) attributes 127 * named "name". You should not add readers for the standard attributes such 128 * as "LineNumberTable", because those are handled internally. 129 * 130 * @param name the name of the attribute as stored in the class file 131 * @param r the reader object 132 */ 133 public static void addAttributeReader(final String name, final UnknownAttributeReader r) 134 { 135 readers.put(name, r); 136 } 137 138 /** 139 * Remove attribute reader 140 * 141 * @param name the name of the attribute as stored in the class file 142 */ 143 public static void removeAttributeReader(final String name) 144 { 145 readers.remove(name); 146 } 147 148 /** 149 * Class method reads one attribute from the input data stream. This method 150 * must not be accessible from the outside. It is called by the Field and 151 * Method constructor methods. 152 * 153 * @see Field 154 * @see Method 155 * 156 * @param file Input stream 157 * @param constant_pool Array of constants 158 * @return Attribute 159 * @throws IOException 160 * @throws ClassFormatException 161 */ 162 public static Attribute readAttribute(final DataInputStream file, final ConstantPool constant_pool) 163 throws IOException, ClassFormatException 164 { 165 return readAttribute((DataInput) file, constant_pool); 166 } 167 168 /** 169 * Class method reads one attribute from the input data stream. This method 170 * must not be accessible from the outside. It is called by the Field and 171 * Method constructor methods. 172 * 173 * @see Field 174 * @see Method 175 * 176 * @param file Input stream 177 * @param constant_pool Array of constants 178 * @return Attribute 179 * @throws IOException 180 * @throws ClassFormatException 181 * @since 6.0 182 */ 183 public static Attribute readAttribute(final DataInput file, final ConstantPool constant_pool) 184 throws IOException, ClassFormatException 185 { 186 byte tag = Const.ATTR_UNKNOWN; // Unknown attribute 187 // Get class name from constant pool via `name_index' indirection 188 final int name_index = file.readUnsignedShort(); 189 final ConstantUtf8 c = (ConstantUtf8) constant_pool.getConstant(name_index, Const.CONSTANT_Utf8); 190 final String name = c.getBytes(); 191 192 // Length of data in bytes 193 final int length = file.readInt(); 194 195 // Compare strings to find known attribute 196 for (byte i = 0; i < Const.KNOWN_ATTRIBUTES; i++) 197 { 198 if (name.equals(Const.getAttributeName(i))) 199 { 200 tag = i; // found! 201 break; 202 } 203 } 204 205 // Call proper constructor, depending on `tag' 206 switch (tag) 207 { 208 case Const.ATTR_UNKNOWN: 209 final Object r = readers.get(name); 210 if (r instanceof UnknownAttributeReader) 211 { 212 return ((UnknownAttributeReader) r).createAttribute(name_index, length, file, constant_pool); 213 } 214 return new Unknown(name_index, length, file, constant_pool); 215 case Const.ATTR_CONSTANT_VALUE: 216 return new ConstantValue(name_index, length, file, constant_pool); 217 case Const.ATTR_SOURCE_FILE: 218 return new SourceFile(name_index, length, file, constant_pool); 219 case Const.ATTR_CODE: 220 return new Code(name_index, length, file, constant_pool); 221 case Const.ATTR_EXCEPTIONS: 222 return new ExceptionTable(name_index, length, file, constant_pool); 223 case Const.ATTR_LINE_NUMBER_TABLE: 224 return new LineNumberTable(name_index, length, file, constant_pool); 225 case Const.ATTR_LOCAL_VARIABLE_TABLE: 226 return new LocalVariableTable(name_index, length, file, constant_pool); 227 case Const.ATTR_INNER_CLASSES: 228 return new InnerClasses(name_index, length, file, constant_pool); 229 case Const.ATTR_SYNTHETIC: 230 return new Synthetic(name_index, length, file, constant_pool); 231 case Const.ATTR_DEPRECATED: 232 return new Deprecated(name_index, length, file, constant_pool); 233 case Const.ATTR_PMG: 234 return new PMGClass(name_index, length, file, constant_pool); 235 case Const.ATTR_SIGNATURE: 236 return new Signature(name_index, length, file, constant_pool); 237 case Const.ATTR_STACK_MAP: 238 return new StackMap(name_index, length, file, constant_pool); 239 case Const.ATTR_RUNTIME_VISIBLE_ANNOTATIONS: 240 return new RuntimeVisibleAnnotations(name_index, length, file, constant_pool); 241 case Const.ATTR_RUNTIME_INVISIBLE_ANNOTATIONS: 242 return new RuntimeInvisibleAnnotations(name_index, length, file, constant_pool); 243 case Const.ATTR_RUNTIME_VISIBLE_PARAMETER_ANNOTATIONS: 244 return new RuntimeVisibleParameterAnnotations(name_index, length, file, constant_pool); 245 case Const.ATTR_RUNTIME_INVISIBLE_PARAMETER_ANNOTATIONS: 246 return new RuntimeInvisibleParameterAnnotations(name_index, length, file, constant_pool); 247 case Const.ATTR_ANNOTATION_DEFAULT: 248 return new AnnotationDefault(name_index, length, file, constant_pool); 249 case Const.ATTR_LOCAL_VARIABLE_TYPE_TABLE: 250 return new LocalVariableTypeTable(name_index, length, file, constant_pool); 251 case Const.ATTR_ENCLOSING_METHOD: 252 return new EnclosingMethod(name_index, length, file, constant_pool); 253 case Const.ATTR_STACK_MAP_TABLE: 254 return new StackMap(name_index, length, file, constant_pool); 255 case Const.ATTR_BOOTSTRAP_METHODS: 256 return new BootstrapMethods(name_index, length, file, constant_pool); 257 case Const.ATTR_METHOD_PARAMETERS: 258 return new MethodParameters(name_index, length, file, constant_pool); 259 default: 260 // Never reached 261 throw new IllegalStateException("Unrecognized attribute type tag parsed: " + tag); 262 } 263 } 264 265 /** 266 * @return Name of attribute 267 * @since 6.0 268 */ 269 public String getName() 270 { 271 final ConstantUtf8 c = (ConstantUtf8) constant_pool.getConstant(name_index, Const.CONSTANT_Utf8); 272 return c.getBytes(); 273 } 274 275 /** 276 * @return Length of attribute field in bytes. 277 */ 278 public final int getLength() 279 { 280 return length; 281 } 282 283 /** 284 * @param length length in bytes. 285 */ 286 public final void setLength(final int length) 287 { 288 this.length = length; 289 } 290 291 /** 292 * @param name_index of attribute. 293 */ 294 public final void setNameIndex(final int name_index) 295 { 296 this.name_index = name_index; 297 } 298 299 /** 300 * @return Name index in constant pool of attribute name. 301 */ 302 public final int getNameIndex() 303 { 304 return name_index; 305 } 306 307 /** 308 * @return Tag of attribute, i.e., its type. Value may not be altered, thus there is no setTag() method. 309 */ 310 public final byte getTag() 311 { 312 return tag; 313 } 314 315 /** 316 * @return Constant pool used by this object. 317 * @see ConstantPool 318 */ 319 public final ConstantPool getConstantPool() 320 { 321 return constant_pool; 322 } 323 324 /** 325 * @param constant_pool Constant pool to be used for this object. 326 * @see ConstantPool 327 */ 328 public final void setConstantPool(final ConstantPool constant_pool) 329 { 330 this.constant_pool = constant_pool; 331 } 332 333 /** 334 * Use copy() if you want to have a deep copy(), i.e., with all references 335 * copied correctly. 336 * 337 * @return shallow copy of this attribute 338 */ 339 @Override 340 public Object clone() 341 { 342 Attribute attr = null; 343 try 344 { 345 attr = (Attribute) super.clone(); 346 } 347 catch (final CloneNotSupportedException e) 348 { 349 throw new Error("Clone Not Supported"); // never happens 350 } 351 return attr; 352 } 353 354 /** 355 * @return deep copy of this attribute 356 */ 357 public abstract Attribute copy(ConstantPool _constant_pool); 358 359 /** 360 * @return attribute name. 361 */ 362 @Override 363 public String toString() 364 { 365 return Const.getAttributeName(tag); 366 } 367}