Package org.apache.bcel.generic

Class InstructionHandle

java.lang.Object
org.apache.bcel.generic.InstructionHandle
Direct Known Subclasses:
BranchHandle
public class InstructionHandle extends Object
Instances of this class give users a handle to the instructions contained in an InstructionList. Instruction objects may be used more than once within a list, this is useful because it saves memory and may be much faster. Within an InstructionList an InstructionHandle object is wrapped around all instructions, i.e., it implements a cell in a doubly-linked list. From the outside only the next and the previous instruction (handle) are accessible. One can traverse the list via an Enumeration returned by InstructionList.elements().
See Also:

  • Field Details

    • i_position

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

  • Constructor Details

    • InstructionHandle

      protected InstructionHandle(Instruction i)

  • Method Details

    • addHandle

      @Deprecated protected void addHandle()
      Deprecated.
      Does nothing as of 6.3.1.
      Does nothing.

    • getNext

      public final InstructionHandle getNext()

    • getPrev

      public final InstructionHandle getPrev()

    • getInstruction

      public final Instruction getInstruction()

    • setInstruction

      public void setInstruction(Instruction i)
      Replace current instruction contained in this handle. Old instruction is disposed using Instruction.dispose().

    • swapInstruction

      public Instruction swapInstruction(Instruction i)
      Temporarily swap the current instruction, without disturbing anything. Meant to be used by a debugger, implementing breakpoints. Current instruction is returned.

      Warning: if this is used on a BranchHandle then some methods such as getPosition() will still refer to the original cached instruction, whereas other BH methods may affect the cache and the replacement instruction.

    • updatePosition

      protected int updatePosition(int offset, int max_offset)
      Called by InstructionList.setPositions when setting the position for every instruction. In the presence of variable length instructions `setPositions()' performs multiple passes over the instruction list to calculate the correct (byte) positions and offsets by calling this function.
      Parameters:
      offset - additional offset caused by preceding (variable length) instructions
      max_offset - the maximum offset that may be caused by these instructions
      Returns:
      additional offset caused by possible change of this instruction's length

    • getPosition

      public int getPosition()
      Returns:
      the position, i.e., the byte code offset of the contained instruction. This is accurate only after InstructionList.setPositions() has been called.

    • removeAllTargeters

      public void removeAllTargeters()
      Remove all targeters, if any.

    • removeTargeter

      public void removeTargeter(InstructionTargeter t)
      Denote this handle isn't referenced anymore by t.

    • addTargeter

      public void addTargeter(InstructionTargeter t)
      Denote this handle is being referenced by t.

    • hasTargeters

      public boolean hasTargeters()

    • getTargeters

      public InstructionTargeter[] getTargeters()
      Returns:
      null, if there are no targeters

    • toString

      public String toString(boolean verbose)
      Returns:
      a (verbose) string representation of the contained instruction.

    • toString

      public String toString()
      Overrides:
      toString in class Object
      Returns:
      a string representation of the contained instruction.

    • addAttribute

      public void addAttribute(Object key, Object attr)
      Add an attribute to an instruction handle.
      Parameters:
      key - the key object to store/retrieve the attribute
      attr - the attribute to associate with this handle

    • removeAttribute

      public void removeAttribute(Object key)
      Delete an attribute of an instruction handle.
      Parameters:
      key - the key object to retrieve the attribute

    • getAttribute

      public Object getAttribute(Object key)
      Get attribute of an instruction handle.
      Parameters:
      key - the key object to store/retrieve the attribute

    • getAttributes

      public Collection<Object> getAttributes()
      Returns:
      all attributes associated with this handle

    • accept

      public void accept(Visitor v)
      Convenience method, simply calls accept() on the contained instruction.
      Parameters:
      v - Visitor object