Save This Page
Home » asm-3.1 » org.objectweb » asm » [javadoc | source]
org.objectweb.asm
public class: Label [javadoc | source]
java.lang.Object
   org.objectweb.asm.Label
A label represents a position in the bytecode of a method. Labels are used for jump, goto, and switch instructions, and for try catch blocks.
Field Summary
static final  int DEBUG    Indicates if this label is only used for debug attributes. Such a label is not the start of a basic block, the target of a jump instruction, or an exception handler. It can be safely ignored in control flow graph analysis algorithms (for optimization purposes). 
static final  int RESOLVED    Indicates if the position of this label is known. 
static final  int RESIZED    Indicates if this label has been updated, after instruction resizing. 
static final  int PUSHED    Indicates if this basic block has been pushed in the basic block stack. See visitMaxs
static final  int TARGET    Indicates if this label is the target of a jump instruction, or the start of an exception handler. 
static final  int STORE    Indicates if a stack map frame must be stored for this label. 
static final  int REACHABLE    Indicates if this label corresponds to a reachable basic block. 
static final  int JSR    Indicates if this basic block ends with a JSR instruction. 
static final  int RET    Indicates if this basic block ends with a RET instruction. 
static final  int SUBROUTINE    Indicates if this basic block is the start of a subroutine. 
static final  int VISITED    Indicates if this subroutine basic block has been visited. 
public  Object info    Field used to associate user information to a label. Warning: this field is used by the ASM tree package. In order to use it with the ASM tree package you must override the org.objectweb.asm.tree.MethodNode#getLabelNode method. 
 int status    Flags that indicate the status of this label. 
 int line    The line number corresponding to this label, if known. 
 int position    The position of this label in the code, if known. 
 int inputStackTop    Start of the output stack relatively to the input stack. The exact semantics of this field depends on the algorithm that is used. When only the maximum stack size is computed, this field is the number of elements in the input stack. When the stack map frames are completely computed, this field is the offset of the first output stack element relatively to the top of the input stack. This offset is always negative or null. A null offset means that the output stack must be appended to the input stack. A -n offset means that the first n output stack elements must replace the top n input stack elements, and that the other elements must be appended to the input stack. 
 int outputStackMax    Maximum height reached by the output stack, relatively to the top of the input stack. This maximum is always positive or null. 
 Frame frame    Information about the input and output stack map frames of this basic block. This field is only used when ClassWriter#COMPUTE_FRAMES option is used. 
 Label successor    The successor of this label, in the order they are visited. This linked list does not include labels used for debug info only. If ClassWriter#COMPUTE_FRAMES option is used then, in addition, it does not contain successive labels that denote the same bytecode position (in this case only the first label appears in this list). 
 Edge successors    The successors of this node in the control flow graph. These successors are stored in a linked list of Edge objects, linked to each other by their Edge#next field. 
 Label next    The next basic block in the basic block stack. This stack is used in the main loop of the fix point algorithm used in the second step of the control flow analysis algorithms.
    Also see:
    MethodWriter#visitMaxs
 
Constructor:
 public Label() 
Method from org.objectweb.asm.Label Summary:
addToSubroutine,   getFirst,   getOffset,   inSameSubroutine,   inSubroutine,   put,   resolve,   toString,   visitSubroutine
Methods from java.lang.Object:
equals,   getClass,   hashCode,   notify,   notifyAll,   toString,   wait,   wait,   wait
Method from org.objectweb.asm.Label Detail:
  void addToSubroutine(long id,
    int nbSubroutines) 
    Marks this basic block as belonging to the given subroutine.
 Label getFirst() 
    Returns the first label of the series to which this label belongs. For an isolated label or for the first label in a series of successive labels, this method returns the label itself. For other labels it returns the first label of the series.
 public int getOffset() 
    Returns the offset corresponding to this label. This offset is computed from the start of the method's bytecode. This method is intended for Attribute sub classes, and is normally not needed by class generators or adapters.
 boolean inSameSubroutine(Label block) 
    Returns true if this basic block and the given one belong to a common subroutine.
 boolean inSubroutine(long id) 
    Returns true is this basic block belongs to the given subroutine.
  void put(MethodWriter owner,
    ByteVector out,
    int source,
    boolean wideOffset) 
    Puts a reference to this label in the bytecode of a method. If the position of the label is known, the offset is computed and written directly. Otherwise, a null offset is written and a new forward reference is declared for this label.
 boolean resolve(MethodWriter owner,
    int position,
    byte[] data) 
    Resolves all forward references to this label. This method must be called when this label is added to the bytecode of the method, i.e. when its position becomes known. This method fills in the blanks that where left in the bytecode by each forward reference previously added to this label.
 public String toString() 
    Returns a string representation of this label.
  void visitSubroutine(Label JSR,
    long id,
    int nbSubroutines) 
    Finds the basic blocks that belong to a given subroutine, and marks these blocks as belonging to this subroutine. This recursive method follows the control flow graph to find all the blocks that are reachable from the current block WITHOUT following any JSR target.