org.apache.bcel.generic

Class Instruction

Implemented Interfaces:
Cloneable, Serializable
Known Direct 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, ReturnInstruction, RET, SIPUSH, StackInstruction

public abstract class Instruction
extends java.lang.Object
implements Cloneable, Serializable

Abstract super class for all Java byte codes.
Version:
$Id: Instruction.java,v 1.3 2002/08/07 18:01:32 mdahm Exp $
Author:
M. Dahm

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(DataOutputStream out)
Dump instruction as byte code to stream out.
boolean
equals(Object that)
Check for equality, delegated to comparator
static InstructionComparator
getComparator()
Get Comparator object used in the equals() method to determine equality of instructions.
int
getLength()
String
getName()
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.
static void
setComparator(InstructionComparator c)
Set comparator to be used for equals().
String
toString()
String
toString(boolean verbose)
Long output format: <name of opcode> "["<opcode number>"]" "("<length of instruction>")"
String
toString(ConstantPool cp)

Field Details

length

protected short length

opcode

protected short opcode

Constructor Details

Instruction

public Instruction(short opcode,
                   short length)

Method Details

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

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

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

dump

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

equals

public boolean equals(Object that)
Check for equality, delegated to comparator
Returns:
true if that is an Instruction and has the same opcode

getComparator

public static InstructionComparator getComparator()
Get Comparator object used in the equals() method to determine equality of instructions.
Returns:
currently used comparator for equals()

getLength

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

getName

public String getName()
Returns:
name of instruction, i.e., opcode name

getOpcode

public short getOpcode()
Returns:
this instructions opcode

initFromFile

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

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

readInstruction

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

setComparator

public static void setComparator(InstructionComparator c)
Set comparator to be used for equals().

toString

public String toString()
Returns:
mnemonic for instruction in verbose format

toString

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