Package org.apache.bcel.generic

Class InstructionList

java.lang.Object

org.apache.bcel.generic.InstructionList

All Implemented Interfaces:

Iterable<InstructionHandle>

public class InstructionList
extends Object
implements Iterable<InstructionHandle>

This class is a container for a list of Instruction objects. Instructions can be appended, inserted, moved, deleted, etc.. Instructions are being wrapped into InstructionHandles objects that are returned upon append/insert operations. They give the user (read only) access to the list structure, such that it can be traversed and manipulated in a controlled way. A list is finally dumped to a byte code array with getByteCode.

See Also:

• Instruction
• InstructionHandle
• BranchHandle

Constructor Summary

Constructors

Constructor	Description
InstructionList()	Create (empty) instruction list.
InstructionList(byte[] code)	Initialize instruction list from byte array.
InstructionList(BranchInstruction i)	Create instruction list containing one instruction.
InstructionList(CompoundInstruction c)	Initialize list with (nonnull) compound instruction.
InstructionList(Instruction i)	Create instruction list containing one instruction.

Method Summary

Modifier and Type	Method	Description
void	addObserver(InstructionListObserver o)	Add observer for this object.
BranchHandle	append(BranchInstruction i)	Append a branch instruction to the end of this list.
InstructionHandle	append(CompoundInstruction c)	Append a compound instruction.
InstructionHandle	append(Instruction i)	Append an instruction to the end of this list.
BranchHandle	append(InstructionHandle ih, BranchInstruction i)	Append an instruction after instruction (handle) ih contained in this list.
InstructionHandle	append(InstructionHandle ih, CompoundInstruction c)	Append a compound instruction.
InstructionHandle	append(InstructionHandle ih, Instruction i)	Append an instruction after instruction (handle) ih contained in this list.
InstructionHandle	append(InstructionHandle ih, InstructionList il)	Append another list after instruction (handle) ih contained in this list.
InstructionHandle	append(InstructionList il)	Append another list to this one.
InstructionHandle	append(Instruction i, CompoundInstruction c)	Append a compound instruction, after instruction i.
InstructionHandle	append(Instruction i, Instruction j)	Append a single instruction j after another instruction i, which must be in this list of course!
InstructionHandle	append(Instruction i, InstructionList il)	Append another list after instruction i contained in this list.
boolean	contains(Instruction i)
boolean	contains(InstructionHandle i)
InstructionList	copy()
void	delete(Instruction i)	Remove instruction from this list.
void	delete(InstructionHandle ih)	Remove instruction from this list.
void	delete(InstructionHandle from, InstructionHandle to)	Remove instructions from instruction 'from' to instruction 'to' contained in this list.
void	delete(Instruction from, Instruction to)	Remove instructions from instruction 'from' to instruction 'to' contained in this list.
void	dispose()	Delete contents of list.
InstructionHandle	findHandle(int pos)	Gets instruction handle for instruction at byte code position pos.
static InstructionHandle	findHandle(InstructionHandle[] ihs, int[] pos, int count, int target)	Find the target instruction (handle) that corresponds to the given target position (byte code offset).
byte[]	getByteCode()	When everything is finished, use this method to convert the instruction list into an array of bytes.
InstructionHandle	getEnd()
InstructionHandle[]	getInstructionHandles()
int[]	getInstructionPositions()	Gets positions (offsets) of all instructions in the list.
Instruction[]	getInstructions()
int	getLength()
InstructionHandle	getStart()
BranchHandle	insert(BranchInstruction i)	Insert a branch instruction at start of this list.
InstructionHandle	insert(CompoundInstruction c)	Insert a compound instruction.
InstructionHandle	insert(Instruction i)	Insert an instruction at start of this list.
BranchHandle	insert(InstructionHandle ih, BranchInstruction i)	Insert an instruction before instruction (handle) ih contained in this list.
InstructionHandle	insert(InstructionHandle ih, CompoundInstruction c)	Insert a compound instruction.
InstructionHandle	insert(InstructionHandle ih, Instruction i)	Insert an instruction before instruction (handle) ih contained in this list.
InstructionHandle	insert(InstructionHandle ih, InstructionList il)	Insert another list before Instruction handle ih contained in this list.
InstructionHandle	insert(InstructionList il)	Insert another list.
InstructionHandle	insert(Instruction i, CompoundInstruction c)	Insert a compound instruction before instruction i.
InstructionHandle	insert(Instruction i, Instruction j)	Insert a single instruction j before another instruction i, which must be in this list of course!
InstructionHandle	insert(Instruction i, InstructionList il)	Insert another list before Instruction i contained in this list.
boolean	isEmpty()	Test for empty list.
Iterator<InstructionHandle>	iterator()
void	move(InstructionHandle ih, InstructionHandle target)	Move a single instruction (handle) to a new location.
void	move(InstructionHandle start, InstructionHandle end, InstructionHandle target)	Take all instructions (handles) from "start" to "end" and append them after the new location "target".
void	redirectBranches(InstructionHandle oldTarget, InstructionHandle newTarget)	Redirect all references from oldTarget to newTarget, i.e., update targets of branch instructions.
void	redirectExceptionHandlers(CodeExceptionGen[] exceptions, InstructionHandle oldTarget, InstructionHandle newTarget)	Redirect all references of exception handlers from oldTarget to newTarget.
void	redirectLocalVariables(LocalVariableGen[] lg, InstructionHandle oldTarget, InstructionHandle newTarget)	Redirect all references of local variables from oldTarget to newTarget.
void	removeObserver(InstructionListObserver o)	Remove observer for this object.
void	replaceConstantPool(ConstantPoolGen oldCp, ConstantPoolGen newCp)	Replace all references to the old constant pool with references to the new constant pool
void	setPositions()
void	setPositions(boolean check)	Give all instructions their position number (offset in byte stream), i.e., make the list ready to be dumped.
int	size()
String	toString()
String	toString(boolean verbose)
void	update()	Call notify() method on all observers.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface java.lang.Iterable

forEach, spliterator

Constructor Details

InstructionList

public InstructionList()

Create (empty) instruction list.

InstructionList

public InstructionList(BranchInstruction i)

Create instruction list containing one instruction.

Parameters:

i - initial instruction

InstructionList

public InstructionList(byte[] code)

Initialize instruction list from byte array.

Parameters:

code - byte array containing the instructions

InstructionList

public InstructionList(CompoundInstruction c)

Initialize list with (nonnull) compound instruction. Consumes argument list, i.e., it becomes empty.

Parameters:

c - compound instruction (list)

InstructionList

public InstructionList(Instruction i)

Create instruction list containing one instruction.

Parameters:

i - initial instruction

Method Details

findHandle

public static InstructionHandle findHandle(InstructionHandle[] ihs,
 int[] pos,
 int count,
 int target)

Find the target instruction (handle) that corresponds to the given target position (byte code offset).

Parameters:

ihs - array of instruction handles, i.e. il.getInstructionHandles()

pos - array of positions corresponding to ihs, i.e. il.getInstructionPositions()

count - length of arrays

target - target position to search for

Returns:

target position's instruction handle if available

addObserver

public void addObserver(InstructionListObserver o)

Add observer for this object.

append

public BranchHandle append(BranchInstruction i)

Append a branch instruction to the end of this list.

Parameters:

i - branch instruction to append

Returns:

branch instruction handle of the appended instruction

append

public InstructionHandle append(CompoundInstruction c)

Append a compound instruction.

Parameters:

c - The composite instruction (containing an InstructionList)

Returns:

instruction handle of the first appended instruction

append

public InstructionHandle append(Instruction i)

Append an instruction to the end of this list.

Parameters:

i - instruction to append

Returns:

instruction handle of the appended instruction

append

public InstructionHandle append(Instruction i,
 CompoundInstruction c)

Append a compound instruction, after instruction i.

Parameters:

i - Instruction in list

c - The composite instruction (containing an InstructionList)

Returns:

instruction handle of the first appended instruction

append

public InstructionHandle append(Instruction i,
 Instruction j)

Append a single instruction j after another instruction i, which must be in this list of course!

Parameters:

i - Instruction in list

j - Instruction to append after i in list

Returns:

instruction handle of the first appended instruction

append

public InstructionHandle append(Instruction i,
 InstructionList il)

Append another list after instruction i contained in this list. Consumes argument list, i.e., it becomes empty.

Parameters:

i - where to append the instruction list

il - Instruction list to append to this one

Returns:

instruction handle pointing to the first appended instruction

append

public BranchHandle append(InstructionHandle ih,
 BranchInstruction i)

Append an instruction after instruction (handle) ih contained in this list.

Parameters:

ih - where to append the instruction list

i - Instruction to append

Returns:

instruction handle pointing to the first appended instruction

append

public InstructionHandle append(InstructionHandle ih,
 CompoundInstruction c)

Append a compound instruction.

Parameters:

ih - where to append the instruction list

c - The composite instruction (containing an InstructionList)

Returns:

instruction handle of the first appended instruction

append

public InstructionHandle append(InstructionHandle ih,
 Instruction i)

Append an instruction after instruction (handle) ih contained in this list.

Parameters:

ih - where to append the instruction list

i - Instruction to append

Returns:

instruction handle pointing to the first appended instruction

append

public InstructionHandle append(InstructionHandle ih,
 InstructionList il)

Append another list after instruction (handle) ih contained in this list. Consumes argument list, i.e., it becomes empty.

Parameters:

ih - where to append the instruction list

il - Instruction list to append to this one

Returns:

instruction handle pointing to the first appended instruction

append

public InstructionHandle append(InstructionList il)

Append another list to this one. Consumes argument list, i.e., it becomes empty.

Parameters:

il - list to append to end of this list

Returns:

instruction handle of the first appended instruction

contains

public boolean contains(Instruction i)

contains

public boolean contains(InstructionHandle i)

copy

public InstructionList copy()

Returns:

complete, i.e., deep copy of this list

delete

public void delete(Instruction i)
            throws TargetLostException

Remove instruction from this list. The corresponding Instruction handles must not be reused!

Parameters:

i - instruction to remove

Throws:

TargetLostException

delete

public void delete(Instruction from,
 Instruction to)
            throws TargetLostException

Remove instructions from instruction 'from' to instruction 'to' contained in this list. The user must ensure that 'from' is an instruction before 'to', or risk havoc. The corresponding Instruction handles must not be reused!

Parameters:

from - where to start deleting (inclusive)

to - where to end deleting (inclusive)

Throws:

TargetLostException

delete

public void delete(InstructionHandle ih)
            throws TargetLostException

Remove instruction from this list. The corresponding Instruction handles must not be reused!

Parameters:

ih - instruction (handle) to remove

Throws:

TargetLostException

delete

public void delete(InstructionHandle from,
 InstructionHandle to)
            throws TargetLostException

Remove instructions from instruction 'from' to instruction 'to' contained in this list. The user must ensure that 'from' is an instruction before 'to', or risk havoc. The corresponding Instruction handles must not be reused!

Parameters:

from - where to start deleting (inclusive)

to - where to end deleting (inclusive)

Throws:

TargetLostException

dispose

public void dispose()

Delete contents of list. Provides better memory utilization, because the system then may reuse the instruction handles. This method is typically called right after MethodGen.getMethod().

findHandle

public InstructionHandle findHandle(int pos)

Gets instruction handle for instruction at byte code position pos. This only works properly, if the list is freshly initialized from a byte array or setPositions() has been called before this method.

Parameters:

pos - byte code position to search for

Returns:

target position's instruction handle if available

getByteCode

public byte[] getByteCode()

When everything is finished, use this method to convert the instruction list into an array of bytes.

Returns:

the byte code ready to be dumped

getEnd

public InstructionHandle getEnd()

Returns:

end of list

getInstructionHandles

public InstructionHandle[] getInstructionHandles()

Returns:

array containing all instructions (handles)

getInstructionPositions

public int[] getInstructionPositions()

Gets positions (offsets) of all instructions in the list. This relies on that the list has been freshly created from an byte code array, or that setPositions() has been called. Otherwise this may be inaccurate.

Returns:

array containing all instruction's offset in byte code

getInstructions

public Instruction[] getInstructions()

Returns:

an array of instructions without target information for branch instructions.

getLength

public int getLength()

Returns:

length of list (Number of instructions, not bytes)

getStart

public InstructionHandle getStart()

Returns:

start of list

insert

public BranchHandle insert(BranchInstruction i)

Insert a branch instruction at start of this list.

Parameters:

i - branch instruction to insert

Returns:

branch instruction handle of the appended instruction

insert

public InstructionHandle insert(CompoundInstruction c)

Insert a compound instruction.

Parameters:

c - The composite instruction (containing an InstructionList)

Returns:

instruction handle of the first inserted instruction

insert

public InstructionHandle insert(Instruction i)

Insert an instruction at start of this list.

Parameters:

i - instruction to insert

Returns:

instruction handle of the inserted instruction

insert

public InstructionHandle insert(Instruction i,
 CompoundInstruction c)

Insert a compound instruction before instruction i.

Parameters:

i - Instruction in list

c - The composite instruction (containing an InstructionList)

Returns:

instruction handle of the first inserted instruction

insert

public InstructionHandle insert(Instruction i,
 Instruction j)

Insert a single instruction j before another instruction i, which must be in this list of course!

Parameters:

i - Instruction in list

j - Instruction to insert before i in list

Returns:

instruction handle of the first inserted instruction

insert

public InstructionHandle insert(Instruction i,
 InstructionList il)

Insert another list before Instruction i contained in this list. Consumes argument list, i.e., it becomes empty.

Parameters:

i - where to append the instruction list

il - Instruction list to insert

Returns:

instruction handle pointing to the first inserted instruction, i.e., il.getStart()

insert

public BranchHandle insert(InstructionHandle ih,
 BranchInstruction i)

Insert an instruction before instruction (handle) ih contained in this list.

Parameters:

ih - where to insert to the instruction list

i - Instruction to insert

Returns:

instruction handle of the first inserted instruction

insert

public InstructionHandle insert(InstructionHandle ih,
 CompoundInstruction c)

Insert a compound instruction.

Parameters:

ih - where to insert the instruction list

c - The composite instruction (containing an InstructionList)

Returns:

instruction handle of the first inserted instruction

insert

public InstructionHandle insert(InstructionHandle ih,
 Instruction i)

Insert an instruction before instruction (handle) ih contained in this list.

Parameters:

ih - where to insert to the instruction list

i - Instruction to insert

Returns:

instruction handle of the first inserted instruction

insert

public InstructionHandle insert(InstructionHandle ih,
 InstructionList il)

Insert another list before Instruction handle ih contained in this list. Consumes argument list, i.e., it becomes empty.

Parameters:

ih - where to append the instruction list

il - Instruction list to insert

Returns:

instruction handle of the first inserted instruction

insert

public InstructionHandle insert(InstructionList il)

Insert another list.

Parameters:

il - list to insert before start of this list

Returns:

instruction handle of the first inserted instruction

isEmpty

public boolean isEmpty()

Test for empty list.

iterator

public Iterator<InstructionHandle> iterator()

Specified by:

iterator in interface Iterable<InstructionHandle>

Returns:

iterator that lists all instructions (handles)

move

public void move(InstructionHandle ih,
 InstructionHandle target)

Move a single instruction (handle) to a new location.

Parameters:

ih - moved instruction

target - new location of moved instruction

move

public void move(InstructionHandle start,
 InstructionHandle end,
 InstructionHandle target)

Take all instructions (handles) from "start" to "end" and append them after the new location "target". Of course, "end" must be after "start" and target must not be located withing this range. If you want to move something to the start of the list use null as value for target.

Any instruction targeters pointing to handles within the block, keep their targets.

Parameters:

start - of moved block

end - of moved block

target - of moved block

redirectBranches

public void redirectBranches(InstructionHandle oldTarget,
 InstructionHandle newTarget)

Redirect all references from oldTarget to newTarget, i.e., update targets of branch instructions.

Parameters:

oldTarget - the old target instruction handle

newTarget - the new target instruction handle

redirectExceptionHandlers

public void redirectExceptionHandlers(CodeExceptionGen[] exceptions,
 InstructionHandle oldTarget,
 InstructionHandle newTarget)

Redirect all references of exception handlers from oldTarget to newTarget.

Parameters:

exceptions - array of exception handlers

oldTarget - the old target instruction handle

newTarget - the new target instruction handle

See Also:

• MethodGen

redirectLocalVariables

public void redirectLocalVariables(LocalVariableGen[] lg,
 InstructionHandle oldTarget,
 InstructionHandle newTarget)

Redirect all references of local variables from oldTarget to newTarget.

Parameters:

lg - array of local variables

oldTarget - the old target instruction handle

newTarget - the new target instruction handle

See Also:

• MethodGen

removeObserver

public void removeObserver(InstructionListObserver o)

Remove observer for this object.

replaceConstantPool

public void replaceConstantPool(ConstantPoolGen oldCp,
 ConstantPoolGen newCp)

Replace all references to the old constant pool with references to the new constant pool

setPositions

public void setPositions()

setPositions

public void setPositions(boolean check)

Give all instructions their position number (offset in byte stream), i.e., make the list ready to be dumped.

Parameters:

check - Perform sanity checks, e.g. if all targeted instructions really belong to this list

size

public int size()

Returns:

length of list (Number of instructions, not bytes)

toString

public String toString()

Overrides:

toString in class Object

toString

public String toString(boolean verbose)

Parameters:

verbose - toggle output format

Returns:

String containing all instructions in this list.

update

public void update()

Call notify() method on all observers. This method is not called automatically whenever the state has changed, but has to be called by the user after he has finished editing the object.