1 /*
2 * reserved comment block
3 * DO NOT REMOVE OR ALTER!
4 */
5 package com.sun.org.apache.bcel.internal.generic;
6
7 /* ====================================================================
8 * The Apache Software License, Version 1.1
9 *
10 * Copyright (c) 2001 The Apache Software Foundation. All rights
11 * reserved.
12 *
13 * Redistribution and use in source and binary forms, with or without
14 * modification, are permitted provided that the following conditions
15 * are met:
16 *
17 * 1. Redistributions of source code must retain the above copyright
18 * notice, this list of conditions and the following disclaimer.
19 *
20 * 2. Redistributions in binary form must reproduce the above copyright
21 * notice, this list of conditions and the following disclaimer in
22 * the documentation and/or other materials provided with the
23 * distribution.
24 *
25 * 3. The end-user documentation included with the redistribution,
26 * if any, must include the following acknowledgment:
27 * "This product includes software developed by the
28 * Apache Software Foundation (http://www.apache.org/)."
29 * Alternately, this acknowledgment may appear in the software itself,
30 * if and wherever such third-party acknowledgments normally appear.
31 *
32 * 4. The names "Apache" and "Apache Software Foundation" and
33 * "Apache BCEL" must not be used to endorse or promote products
34 * derived from this software without prior written permission. For
35 * written permission, please contact apache@apache.org.
36 *
37 * 5. Products derived from this software may not be called "Apache",
38 * "Apache BCEL", nor may "Apache" appear in their name, without
39 * prior written permission of the Apache Software Foundation.
40 *
41 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
42 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
43 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
44 * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
45 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
46 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
47 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
48 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
49 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
50 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
51 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
52 * SUCH DAMAGE.
53 * ====================================================================
54 *
55 * This software consists of voluntary contributions made by many
56 * individuals on behalf of the Apache Software Foundation. For more
57 * information on the Apache Software Foundation, please see
58 * <http://www.apache.org/>.
59 */
60
61 import java.io.*;
62 import com.sun.org.apache.bcel.internal.util.ByteSequence;
63
64 /**
65 * Abstract super class for branching instructions like GOTO, IFEQ, etc..
66 * Branch instructions may have a variable length, namely GOTO, JSR,
67 * LOOKUPSWITCH and TABLESWITCH.
68 *
69 * @see InstructionList
70 * @author <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>
71 */
72 public abstract class BranchInstruction extends Instruction implements InstructionTargeter {
73 protected int index; // Branch target relative to this instruction
74 protected InstructionHandle target; // Target object in instruction list
75 protected int position; // Byte code offset
76
77 /**
78 * Empty constructor needed for the Class.newInstance() statement in
79 * Instruction.readInstruction(). Not to be used otherwise.
80 */
81 BranchInstruction() {}
82
83 /** Common super constructor
84 * @param opcodee Instruction opcode
85 * @param target instruction to branch to
86 */
87 protected BranchInstruction(short opcode, InstructionHandle target) {
88 super(opcode, (short)3);
89 setTarget(target);
90 }
91
92 /**
93 * Dump instruction as byte code to stream out.
94 * @param out Output stream
95 */
96 @Override
97 public void dump(DataOutputStream out) throws IOException {
98 out.writeByte(opcode);
99
100 index = getTargetOffset();
101
102 if(Math.abs(index) >= 32767) // too large for short
103 throw new ClassGenException("Branch target offset too large for short");
104
105 out.writeShort(index); // May be negative, i.e., point backwards
106 }
107
108 /**
109 * @param target branch target
110 * @return the offset to `target' relative to this instruction
111 */
112 protected int getTargetOffset(InstructionHandle target) {
113 if(target == null)
114 throw new ClassGenException("Target of " + super.toString(true) +
115 " is invalid null handle");
116
117 int t = target.getPosition();
118
119 if(t < 0)
120 throw new ClassGenException("Invalid branch target position offset for " +
121 super.toString(true) + ":" + t + ":" + target);
122
123 return t - position;
124 }
125
126 /**
127 * @return the offset to this instruction's target
128 */
129 protected int getTargetOffset() { return getTargetOffset(target); }
130
131 /**
132 * Called by InstructionList.setPositions when setting the position for every
133 * instruction. In the presence of variable length instructions `setPositions'
134 * performs multiple passes over the instruction list to calculate the
135 * correct (byte) positions and offsets by calling this function.
136 *
137 * @param offset additional offset caused by preceding (variable length) instructions
138 * @param max_offset the maximum offset that may be caused by these instructions
139 * @return additional offset caused by possible change of this instruction's length
140 */
141 protected int updatePosition(int offset, int max_offset) {
142 position += offset;
143 return 0;
144 }
145
146 /**
147 * Long output format:
148 *
149 * <position in byte code>
150 * <name of opcode> "["<opcode number>"]"
151 * "("<length of instruction>")"
152 * "<"<target instruction>">" "@"<branch target offset>
153 *
154 * @param verbose long/short format switch
155 * @return mnemonic for instruction
156 */
157 @Override
158 public String toString(boolean verbose) {
159 String s = super.toString(verbose);
160 String t = "null";
161
162 if(verbose) {
163 if(target != null) {
164 if(target.getInstruction() == this)
165 t = "<points to itself>";
166 else if(target.getInstruction() == null)
167 t = "<null instruction!!!?>";
168 else
169 t = target.getInstruction().toString(false); // Avoid circles
170 }
171 } else {
172 if(target != null) {
173 index = getTargetOffset();
174 t = "" + (index + position);
175 }
176 }
177
178 return s + " -> " + t;
179 }
180
181 /**
182 * Read needed data (e.g. index) from file. Conversion to a InstructionHandle
183 * is done in InstructionList(byte[]).
184 *
185 * @param bytes input stream
186 * @param wide wide prefix?
187 * @see InstructionList
188 */
189 @Override
190 protected void initFromFile(ByteSequence bytes, boolean wide) throws IOException
191 {
192 length = 3;
193 index = bytes.readShort();
194 }
195
196 /**
197 * @return target offset in byte code
198 */
199 public final int getIndex() { return index; }
200
201 /**
202 * @return target of branch instruction
203 */
204 public InstructionHandle getTarget() { return target; }
205
206 /**
207 * Set branch target
208 * @param target branch target
209 */
210 public final void setTarget(InstructionHandle target) {
211 notifyTargetChanging(this.target, this);
212 this.target = target;
213 notifyTargetChanged(this.target, this);
214 }
215
216 /**
217 * Used by BranchInstruction, LocalVariableGen, CodeExceptionGen.
218 * Must be called before the target is actually changed in the
219 * InstructionTargeter.
220 */
221 static void notifyTargetChanging(InstructionHandle old_ih,
222 InstructionTargeter t) {
223 if(old_ih != null) {
224 old_ih.removeTargeter(t);
225 }
226 }
227
228 /**
229 * Used by BranchInstruction, LocalVariableGen, CodeExceptionGen.
230 * Must be called after the target is actually changed in the
231 * InstructionTargeter.
232 */
233 static void notifyTargetChanged(InstructionHandle new_ih,
234 InstructionTargeter t) {
235 if(new_ih != null) {
236 new_ih.addTargeter(t);
237 }
238 }
239
240 /**
241 * @param old_ih old target
242 * @param new_ih new target
243 */
244 @Override
245 public void updateTarget(InstructionHandle old_ih, InstructionHandle new_ih) {
246 if(target == old_ih)
247 setTarget(new_ih);
248 else
249 throw new ClassGenException("Not targeting " + old_ih + ", but " + target);
250 }
251
252 /**
253 * @return true, if ih is target of this instruction
254 */
255 @Override
256 public boolean containsTarget(InstructionHandle ih) {
257 return (target == ih);
258 }
259
260 /**
261 * Inform target that it's not targeted anymore.
262 */
263 @Override
264 void dispose() {
265 setTarget(null);
266 index=-1;
267 position=-1;
268 }
269 }