Package 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	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	Description
Instruction(short opcode, short length)

Method Summary

Modifier and Type	Method	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)	Dumps instruction as byte code to stream out.
boolean	equals(Object that)	Tests 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()	Gets the hashCode of this object.
protected void	initFromFile(ByteSequence bytes, boolean wide)	Reads needed data (e.g.
static boolean	isValidByte(int value)	Tests if the value can fit in a byte (signed)
static boolean	isValidShort(int value)	Tests 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)	Reads an instruction from (byte code) input stream and return the appropriate 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 Details

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 Details

Instruction

public Instruction(short opcode,
 short length)

Method Details

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

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

Returns:

currently used comparator for equals()

isValidByte

public static boolean isValidByte(int value)

Tests 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)

Tests 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

readInstruction

public static Instruction readInstruction(ByteSequence bytes)
                                   throws IOException

Reads an instruction from (byte code) input stream and return the appropriate 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 - Thrown when an I/O exception of some sort has occurred.

See Also:

• InstructionConst.getInstruction(int)

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

Sets comparator to be used for equals().

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

See Also:

• BranchInstruction

dump

public void dump(DataOutputStream out)
          throws IOException

Dumps instruction as byte code to stream out.

Parameters:

out - Output stream

Throws:

IOException - Thrown when an I/O exception of some sort has occurred.

equals

public boolean equals(Object that)

Tests for equality, delegated to comparator

Overrides:

equals in class Object

Returns:

true if that is an Instruction and has the same opcode

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

hashCode

public int hashCode()

Gets the hashCode of this object.

Overrides:

hashCode in class Object

Returns:

the hashCode

Since:

6.0

initFromFile

protected void initFromFile(ByteSequence bytes,
 boolean wide)
                     throws IOException

Reads 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

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

toString

public String toString()

Overrides:

toString in class Object

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