org.apache.bcel.generic

Class Instruction

java.lang.Object

org.apache.bcel.generic.Instruction

All Implemented Interfaces:

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

Abstract super class for all Java byte codes.

Field Summary

Fields

Modifier and Type	Field and Description
protected short	length Deprecated. (since 6.0) will be made private; do not access directly, use getter/setter
protected short	opcode Deprecated. (since 6.0) will be made private; do not access directly, use getter/setter

Constructor Summary

Constructors

Constructor and Description
Instruction(short opcode, short length)

Method Summary

Modifier and Type	Method and Description
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() Deprecated. (6.0) use the built in comparator, or wrap this class in another object that implements these methods
int	getLength()
String	getName()
short	getOpcode()
int	hashCode() calculate the hashCode of this object
protected void	initFromFile(ByteSequence bytes, boolean wide) Read needed data (e.g.
static boolean	isValidByte(int value) Check if the value can fit in a byte (signed)
static boolean	isValidShort(int value) Check if the value can fit in a short (signed)
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) Deprecated. (6.0) use the built in comparator, or wrap this class in another object that implements these methods
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, notify, notifyAll, wait, wait, wait

Field Detail

length

@Deprecated
protected short length

Deprecated. (since 6.0) will be made private; do not access directly, use getter/setter

opcode

@Deprecated
protected short opcode

Deprecated. (since 6.0) will be made private; do not access directly, use getter/setter

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 - may be thrown if the implementation needs to read data from the file

readInstruction

public static Instruction readInstruction(ByteSequence bytes)
                                   throws IOException

Read an instruction from (byte code) input stream and return the appropiate object.

If the Instruction is defined in InstructionConst, then the singleton instance is returned.

Parameters:

bytes - input stream bytes

Returns:

instruction object being read

Throws:

IOException

See Also:

InstructionConst.getInstruction(int)

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

@Deprecated
public static InstructionComparator getComparator()

Deprecated. (6.0) use the built in comparator, or wrap this class in another object that implements these methods

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

Returns:

currently used comparator for equals()

setComparator

@Deprecated
public static void setComparator(InstructionComparator c)

Deprecated. (6.0) use the built in comparator, or wrap this class in another object that implements these methods

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

hashCode

public int hashCode()

calculate the hashCode of this object

Overrides:

hashCode in class Object

Returns:

the hashCode

Since:

6.0

isValidByte

public static boolean isValidByte(int value)

Check if the value can fit in a byte (signed)

Parameters:

value - the value to check

Returns:

true if the value is in range

Since:

6.0

isValidShort

public static boolean isValidShort(int value)

Check if the value can fit in a short (signed)

Parameters:

value - the value to check

Returns:

true if the value is in range

Since:

6.0