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:

  • Constructor Details

    • InstructionList

      public InstructionList()
      Create (empty) instruction list.

    • InstructionList

      public InstructionList(Instruction i)
      Create instruction list containing one instruction.
      Parameters:
      i - initial instruction

    • InstructionList

      public InstructionList(BranchInstruction i)
      Create instruction list containing one instruction.
      Parameters:
      i - initial instruction

    • 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(byte[] code)
      Initialize instruction list from byte array.
      Parameters:
      code - byte array containing the instructions

  • Method Details

    • isEmpty

      public boolean isEmpty()
      Test for empty list.

    • 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

    • findHandle

      public InstructionHandle findHandle(int pos)
      Get 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

    • 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(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 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

    • 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 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(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, 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(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(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 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

    • 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

    • 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 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 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(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, 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(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(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, 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 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

    • 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

    • 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

    • 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(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(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

    • 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

    • contains

      public boolean contains(InstructionHandle i)

    • contains

      public boolean contains(Instruction i)

    • 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

    • 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

    • getInstructions

      public Instruction[] getInstructions()
      Returns:
      an array of instructions without target information for branch instructions.

    • 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.

    • iterator

      public Iterator<InstructionHandle> iterator()
      Specified by:
      iterator in interface Iterable<InstructionHandle>
      Returns:
      iterator that lists all instructions (handles)

    • getInstructionHandles

      public InstructionHandle[] getInstructionHandles()
      Returns:
      array containing all instructions (handles)

    • getInstructionPositions

      public int[] getInstructionPositions()
      Get 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

    • copy

      public InstructionList copy()
      Returns:
      complete, i.e., deep copy of this list

    • replaceConstantPool

      public void replaceConstantPool(ConstantPoolGen old_cp, ConstantPoolGen new_cp)
      Replace all references to the old constant pool with references to the new constant pool

    • 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().

    • getStart

      public InstructionHandle getStart()
      Returns:
      start of list

    • getEnd

      public InstructionHandle getEnd()
      Returns:
      end of list

    • getLength

      public int getLength()
      Returns:
      length of list (Number of instructions, not bytes)

    • size

      public int size()
      Returns:
      length of list (Number of instructions, not bytes)

    • redirectBranches

      public void redirectBranches(InstructionHandle old_target, InstructionHandle new_target)
      Redirect all references from old_target to new_target, i.e., update targets of branch instructions.
      Parameters:
      old_target - the old target instruction handle
      new_target - the new target instruction handle

    • redirectLocalVariables

      public void redirectLocalVariables(LocalVariableGen[] lg, InstructionHandle old_target, InstructionHandle new_target)
      Redirect all references of local variables from old_target to new_target.
      Parameters:
      lg - array of local variables
      old_target - the old target instruction handle
      new_target - the new target instruction handle
      See Also:

    • redirectExceptionHandlers

      public void redirectExceptionHandlers(CodeExceptionGen[] exceptions, InstructionHandle old_target, InstructionHandle new_target)
      Redirect all references of exception handlers from old_target to new_target.
      Parameters:
      exceptions - array of exception handlers
      old_target - the old target instruction handle
      new_target - the new target instruction handle
      See Also:

    • addObserver

      public void addObserver(InstructionListObserver o)
      Add observer for this object.

    • removeObserver

      public void removeObserver(InstructionListObserver o)
      Remove observer for this object.

    • 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.