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Diffstat (limited to 'src/java/org/apache/bcel/generic/Instruction.java')
| -rw-r--r-- | src/java/org/apache/bcel/generic/Instruction.java | 276 |
1 files changed, 276 insertions, 0 deletions
diff --git a/src/java/org/apache/bcel/generic/Instruction.java b/src/java/org/apache/bcel/generic/Instruction.java new file mode 100644 index 00000000..1dc84b8f --- /dev/null +++ b/src/java/org/apache/bcel/generic/Instruction.java @@ -0,0 +1,276 @@ +package org.apache.bcel.generic; + +/* ==================================================================== + * The Apache Software License, Version 1.1 + * + * Copyright (c) 2001 The Apache Software Foundation. All rights + * reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in + * the documentation and/or other materials provided with the + * distribution. + * + * 3. The end-user documentation included with the redistribution, + * if any, must include the following acknowledgment: + * "This product includes software developed by the + * Apache Software Foundation (http://www.apache.org/)." + * Alternately, this acknowledgment may appear in the software itself, + * if and wherever such third-party acknowledgments normally appear. + * + * 4. The names "Apache" and "Apache Software Foundation" and + * "Apache BCEL" must not be used to endorse or promote products + * derived from this software without prior written permission. For + * written permission, please contact apache@apache.org. + * + * 5. Products derived from this software may not be called "Apache", + * "Apache BCEL", nor may "Apache" appear in their name, without + * prior written permission of the Apache Software Foundation. + * + * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED + * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES + * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE + * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR + * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, + * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT + * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF + * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND + * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, + * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT + * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + * ==================================================================== + * + * This software consists of voluntary contributions made by many + * individuals on behalf of the Apache Software Foundation. For more + * information on the Apache Software Foundation, please see + * <http://www.apache.org/>. + */ + +import org.apache.bcel.Constants; +import org.apache.bcel.classfile.Utility; +import org.apache.bcel.classfile.ConstantPool; +import java.io.*; +import org.apache.bcel.util.ByteSequence; + +/** + * Abstract super class for all Java byte codes. + * + * @version $Id$ + * @author <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A> + */ +public abstract class Instruction implements Cloneable, Serializable { + protected short length = 1; // Length of instruction in bytes + protected short opcode = -1; // Opcode number + + /** + * Empty constructor needed for the Class.newInstance() statement in + * Instruction.readInstruction(). Not to be used otherwise. + */ + Instruction() {} + + public Instruction(short opcode, short length) { + this.length = length; + this.opcode = opcode; + } + + /** + * Dump instruction as byte code to stream out. + * @param out Output stream + */ + public void dump(DataOutputStream out) throws IOException { + out.writeByte(opcode); // Common for all instructions + } + + /** + * Long output format: + * + * <name of opcode> "["<opcode number>"]" + * "("<length of instruction>")" + * + * @param verbose long/short format switch + * @return mnemonic for instruction + */ + public String toString(boolean verbose) { + if(verbose) + return Constants.OPCODE_NAMES[opcode] + "[" + opcode + "](" + length + ")"; + else + return Constants.OPCODE_NAMES[opcode]; + } + + /** + * @return mnemonic for instruction in verbose format + */ + public String toString() { + return toString(true); + } + + /** + * @return mnemonic for instruction with sumbolic references resolved + */ + public String toString(ConstantPool cp) { + return toString(false); + } + + /** + * Use with caution, since `BranchInstruction's have a `target' reference which + * is not copied correctly (only basic types are). This also applies for + * `Select' instructions with their multiple branch targets. + * + * @see BranchInstruction + * @return (shallow) copy of an instruction + */ + public Instruction copy() { + Instruction i = null; + + // "Constant" instruction, no need to duplicate + if(InstructionConstants.INSTRUCTIONS[this.getOpcode()] != null) + i = this; + else { + try { + i = (Instruction)clone(); + } catch(CloneNotSupportedException e) { + System.err.println(e); + } + } + + return i; + } + + /** + * Read needed data (e.g. index) from file. + * + * @param bytes byte sequence to read from + * @param wide "wide" instruction flag + */ + protected void initFromFile(ByteSequence bytes, boolean wide) + throws IOException + {} + + /** + * Read an instruction from (byte code) input stream and return the + * appropiate object. + * + * @param file file to read from + * @return instruction object being read + */ + public static final Instruction readInstruction(ByteSequence bytes) + throws IOException + { + boolean wide = false; + short opcode = (short)bytes.readUnsignedByte(); + Instruction obj = null; + + if(opcode == Constants.WIDE) { // Read next opcode after wide byte + wide = true; + opcode = (short)bytes.readUnsignedByte(); + } + + if(InstructionConstants.INSTRUCTIONS[opcode] != null) + return InstructionConstants.INSTRUCTIONS[opcode]; // Used predefined immutable object, if available + + /* Find appropiate class, instantiate an (empty) instruction object + * and initialize it by hand. + */ + Class clazz; + try { + clazz = Class.forName(className(opcode)); + } + catch (ClassNotFoundException cnfe){ + // If a class by that name does not exist, the opcode is illegal. + // Note that IMPDEP1, IMPDEP2, BREAKPOINT are also illegal in a sense. + throw new ClassGenException("Illegal opcode detected."); + } + try { + obj = (Instruction)clazz.newInstance(); + + if(wide && !((obj instanceof LocalVariableInstruction) || (obj instanceof IINC) || + (obj instanceof RET))) + throw new Exception("Illegal opcode after wide: " + opcode); + + obj.setOpcode(opcode); + obj.initFromFile(bytes, wide); // Do further initializations, if any + // Byte code offset set in InstructionList + } catch(Exception e) { throw new ClassGenException(e.toString()); } + + return obj; + } + + private static final String className(short opcode) { + String name = Constants.OPCODE_NAMES[opcode].toUpperCase(); + + /* ICONST_0, etc. will be shortened to ICONST, etc., since ICONST_0 and the like + * are not implemented (directly). + */ + try { + int len = name.length(); + char ch1 = name.charAt(len - 2), ch2 = name.charAt(len - 1); + + if((ch1 == '_') && (ch2 >= '0') && (ch2 <= '5')) + name = name.substring(0, len - 2); + + if(name.equals("ICONST_M1")) // Special case + name = "ICONST"; + } catch(StringIndexOutOfBoundsException e) { System.err.println(e); } + + return "org.apache.bcel.generic." + name; + } + + /** + * This method also gives right results for instructions whose + * effect on the stack depends on the constant pool entry they + * reference. + * @return Number of words consumed from stack by this instruction, + * or Constants.UNPREDICTABLE, if this can not be computed statically + */ + public int consumeStack(ConstantPoolGen cpg) { + return Constants.CONSUME_STACK[opcode]; + } + + /** + * This method also gives right results for instructions whose + * effect on the stack depends on the constant pool entry they + * reference. + * @return Number of words produced onto stack by this instruction, + * or Constants.UNPREDICTABLE, if this can not be computed statically + */ + public int produceStack(ConstantPoolGen cpg) { + return Constants.PRODUCE_STACK[opcode]; + } + + /** + * @return this instructions opcode + */ + public short getOpcode() { return opcode; } + + /** + * @return length (in bytes) of instruction + */ + public int getLength() { return length; } + + /** + * Needed in readInstruction. + */ + private void setOpcode(short opcode) { this.opcode = opcode; } + + /** Some instructions may be reused, so don't do anything by default. + */ + void dispose() { } + + /** + * Call corresponding visitor method(s). The order is: + * Call visitor methods of implemented interfaces first, then + * call methods according to the class hierarchy in descending order, + * i.e., the most specific visitXXX() call comes last. + * + * @param v Visitor object + */ + public abstract void accept(Visitor v); +} |