Package com.android.dx.cf.code

Class Frame

java.lang.Object
com.android.dx.cf.code.Frame
public final class Frame extends Object
Representation of a Java method execution frame. A frame consists of a set of locals and a value stack, and it can be told to act on them to load and store values between them and an "arguments / results" area.

  • Constructor Details

    • Frame

      public Frame(int maxLocals, int maxStack)
      Constructs an instance. The locals array initially consists of all-uninitialized values (represented as nulls) and the stack starts out empty.
      Parameters:
      maxLocals - >= 0; the maximum number of locals this instance can refer to
      maxStack - >= 0; the maximum size of the stack for this instance

  • Method Details

    • copy

      public Frame copy()
      Makes and returns a mutable copy of this instance. The copy contains copies of the locals and stack (that is, it doesn't share them with the original).
      Returns:
      non-null; the copy

    • setImmutable

      public void setImmutable()
      Makes this instance immutable.

    • makeInitialized

      public void makeInitialized(Type type)
      Replaces all the occurrences of the given uninitialized type in this frame with its initialized equivalent.
      Parameters:
      type - non-null; type to replace

    • getLocals

      public LocalsArray getLocals()
      Gets the locals array for this instance.
      Returns:
      non-null; the locals array

    • getStack

      public ExecutionStack getStack()
      Gets the execution stack for this instance.
      Returns:
      non-null; the execution stack

    • getSubroutines

      public IntList getSubroutines()
      Returns the largest subroutine nesting this block may be in. An empty list is returned if this block is not in any subroutine. Subroutines are identified by the label of their start block. The list is ordered such that the deepest nesting (the actual subroutine this block is in) is the last label in the list.
      Returns:
      non-null; list as noted above

    • initializeWithParameters

      public void initializeWithParameters(StdTypeList params)
      Initialize this frame with the method's parameters. Used for the first frame.
      Parameters:
      params - Type list of method parameters.

    • subFrameForLabel

      public Frame subFrameForLabel(int startLabel, int subLabel)
      Returns a Frame instance representing the frame state that should be used when returning from a subroutine. The stack state of all subroutine invocations is identical, but the locals state may differ.
      Parameters:
      startLabel - >=0; The label of the returning subroutine's start block
      subLabel - >=0; A calling label of a subroutine
      Returns:
      null-ok; an appropriatly-constructed instance, or null if label is not in the set

    • mergeWith

      public Frame mergeWith(Frame other)
      Merges two frames. If the merged result is the same as this frame, then this instance is returned.
      Parameters:
      other - non-null; another frame
      Returns:
      non-null; the result of merging the two frames

    • mergeWithSubroutineCaller

      public Frame mergeWithSubroutineCaller(Frame other, int subLabel, int predLabel)
      Merges this frame with the frame of a subroutine caller at predLabel. Only called on the frame at the first block of a subroutine.
      Parameters:
      other - non-null; another frame
      subLabel - label of subroutine start block
      predLabel - label of calling block
      Returns:
      non-null; the result of merging the two frames

    • makeNewSubroutineStartFrame

      public Frame makeNewSubroutineStartFrame(int subLabel, int callerLabel)
      Makes a frame for a subroutine start block, given that this is the ending frame of one of the subroutine's calling blocks. Subroutine calls may be nested and thus may have nested locals state, so we start with an initial state as seen by the subroutine, but keep track of the individual locals states that will be expected when the individual subroutine calls return.
      Parameters:
      subLabel - label of subroutine start block
      callerLabel - >=0; label of the caller block where this frame came from.
      Returns:
      a new instance to begin a called subroutine.

    • makeExceptionHandlerStartFrame

      public Frame makeExceptionHandlerStartFrame(CstType exceptionClass)
      Makes a new frame for an exception handler block invoked from this frame.
      Parameters:
      exceptionClass - exception that the handler block will handle
      Returns:
      new frame

    • annotate

      public void annotate(ExceptionWithContext ex)
      Annotates (adds context to) the given exception with information about this frame.
      Parameters:
      ex - non-null; the exception to annotate