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 386056 2006-03-15 11:31:56Z tcurdt $
Author:
M. Dahm

Field Summary

private static InstructionComparator
cmp
protected short
length
protected short
opcode

Constructor Summary

Instruction()
Empty constructor needed for the Class.newInstance() statement in Instruction.readInstruction().
Instruction(short opcode, short length)

Method Summary

abstract void
accept(Visitor v)
Call corresponding visitor method(s).
private static String
className(short opcode)
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).
(package private) void
dispose()
Some instructions may be reused, so don't do anything by default.
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().
private void
setOpcode(short opcode)
Needed in readInstruction.
String
toString()
String
toString(boolean verbose)
Long output format: <name of opcode> "["<opcode number>"]" "("<length of instruction>")"
String
toString(ConstantPool cp)

Field Details

cmp

private static InstructionComparator cmp

length

protected short length

opcode

protected short opcode

Constructor Details

Instruction

(package private)  Instruction()
Empty constructor needed for the Class.newInstance() statement in Instruction.readInstruction(). Not to be used otherwise.

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

className

private static final String className(short opcode)

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

dispose

(package private)  void dispose()
Some instructions may be reused, so don't do anything by default.

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:
bytes - input stream bytes
Returns:
instruction object being read

setComparator

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

setOpcode

private void setOpcode(short opcode)
Needed in readInstruction.

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