org.apache.bcel.generic
Class Instruction

java.lang.Object
  extended by org.apache.bcel.generic.Instruction
All Implemented Interfaces:
Serializable, Cloneable
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 Object
implements Cloneable, Serializable

Abstract super class for all Java byte codes.

Version:
$Id: Instruction.java 386056 2006-03-15 11:31:56Z tcurdt $
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(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)
           
 
Methods inherited from class java.lang.Object
clone, 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(DataOutputStream out)
          throws IOException
Dump instruction as byte code to stream out.

Parameters:
out - Output stream
Throws:
IOException

getName

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

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()
Overrides:
toString in class Object
Returns:
mnemonic for instruction in verbose format

toString

public 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 IOException
Read needed data (e.g. index) from file.

Parameters:
bytes - byte sequence to read from
wide - "wide" instruction flag
Throws:
IOException

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
Throws:
IOException

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

getComparator

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

Returns:
currently used comparator for equals()

setComparator

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


equals

public boolean equals(Object that)
Check for equality, delegated to comparator

Overrides:
equals in class Object
Returns:
true if that is an Instruction and has the same opcode


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