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org.apache.bcel.generic
Class Instruction

java.lang.Object
  |
  +--org.apache.bcel.generic.Instruction
All Implemented Interfaces:
java.lang.Cloneable, java.io.Serializable
Direct Known Subclasses:
ACONST_NULL, ArithmeticInstruction, ArrayInstruction, ARRAYLENGTH, ATHROW, BIPUSH, BranchInstruction, BREAKPOINT, ConversionInstruction, CPInstruction, DCMPG, DCMPL, DCONST, FCMPG, FCMPL, FCONST, ICONST, IMPDEP1, IMPDEP2, LCMP, LCONST, LocalVariableInstruction, MONITORENTER, MONITOREXIT, NEWARRAY, NOP, RET, ReturnInstruction, SIPUSH, StackInstruction
public abstract class Instruction
extends java.lang.Object
implements java.lang.Cloneable, java.io.Serializable

Abstract super class for all Java byte codes.

Version:
$Id: Instruction.java,v 1.1.1.1 2001/10/29 20:00:18 jvanzyl Exp $
Author:
M. Dahm
See Also:
Serialized Form

Field Summary
protected  short length
           
protected  short opcode
           
 
Constructor Summary
Instruction(short opcode, short length)
           
 
Method Summary
abstract  void accept(Visitor v)
          Call corresponding visitor method(s).
 int consumeStack(ConstantPoolGen cpg)
          This method also gives right results for instructions whose effect on the stack depends on the constant pool entry they reference.
 Instruction copy()
          Use with caution, since `BranchInstruction's have a `target' reference which is not copied correctly (only basic types are).
 void dump(java.io.DataOutputStream out)
          Dump instruction as byte code to stream out.
 int getLength()
           
 short getOpcode()
           
protected  void initFromFile(ByteSequence bytes, boolean wide)
          Read needed data (e.g.
 int produceStack(ConstantPoolGen cpg)
          This method also gives right results for instructions whose effect on the stack depends on the constant pool entry they reference.
static Instruction readInstruction(ByteSequence bytes)
          Read an instruction from (byte code) input stream and return the appropiate object.
 java.lang.String toString()
           
 java.lang.String toString(boolean verbose)
          Long output format: <name of opcode> "["<opcode number>"]" "("<length of instruction>")"
 java.lang.String toString(ConstantPool cp)
           
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
 

Field Detail

length

protected short length

opcode

protected short opcode
Constructor Detail

Instruction

public Instruction(short opcode,
                   short length)
Method Detail

dump

public void dump(java.io.DataOutputStream out)
          throws java.io.IOException
Dump instruction as byte code to stream out.
Parameters:
out - Output stream

toString

public java.lang.String toString(boolean verbose)
Long output format: <name of opcode> "["<opcode number>"]" "("<length of instruction>")"
Parameters:
verbose - long/short format switch
Returns:
mnemonic for instruction

toString

public java.lang.String toString()
Overrides:
toString in class java.lang.Object
Returns:
mnemonic for instruction in verbose format

toString

public java.lang.String toString(ConstantPool cp)
Returns:
mnemonic for instruction with sumbolic references resolved

copy

public Instruction copy()
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.
Returns:
(shallow) copy of an instruction
See Also:
BranchInstruction

initFromFile

protected void initFromFile(ByteSequence bytes,
                            boolean wide)
                     throws java.io.IOException
Read needed data (e.g. index) from file.
Parameters:
bytes - byte sequence to read from
wide - "wide" instruction flag

readInstruction

public static final Instruction readInstruction(ByteSequence bytes)
                                         throws java.io.IOException
Read an instruction from (byte code) input stream and return the appropiate object.
Parameters:
file - file to read from
Returns:
instruction object being read

consumeStack

public int consumeStack(ConstantPoolGen cpg)
This method also gives right results for instructions whose effect on the stack depends on the constant pool entry they reference.
Returns:
Number of words consumed from stack by this instruction, or Constants.UNPREDICTABLE, if this can not be computed statically

produceStack

public int produceStack(ConstantPoolGen cpg)
This method also gives right results for instructions whose effect on the stack depends on the constant pool entry they reference.
Returns:
Number of words produced onto stack by this instruction, or Constants.UNPREDICTABLE, if this can not be computed statically

getOpcode

public short getOpcode()
Returns:
this instructions opcode

getLength

public int getLength()
Returns:
length (in bytes) of instruction

accept

public abstract void accept(Visitor v)
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.
Parameters:
v - Visitor object
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