org.compass.core.util.asm.tree.analysis
Class Frame

java.lang.Object
  extended by org.compass.core.util.asm.tree.analysis.Frame

public class Frame
extends Object

A symbolic execution stack frame. A stack frame contains a set of local variable slots, and an operand stack. Warning: long and double values are represented by two slots in local variables, and by one slot in the operand stack.

Author:
Eric Bruneton

Constructor Summary
Frame(Frame src)
          Constructs a new frame that is identical to the given frame.
Frame(int nLocals, int nStack)
          Constructs a new frame with the given size.
 
Method Summary
 void clearStack()
          Clears the operand stack of this frame.
 void execute(AbstractInsnNode insn, Interpreter interpreter)
           
 Value getLocal(int i)
          Returns the value of the given local variable.
 int getLocals()
          Returns the maximum number of local variables of this frame.
 Value getStack(int i)
          Returns the value of the given operand stack slot.
 int getStackSize()
          Returns the number of values in the operand stack of this frame.
 Frame init(Frame src)
          Copies the state of the given frame into this frame.
 boolean merge(Frame frame, boolean[] access)
          Merges this frame with the given frame (case of a RET instruction).
 boolean merge(Frame frame, Interpreter interpreter)
          Merges this frame with the given frame.
 Value pop()
          Pops a value from the operand stack of this frame.
 void push(Value value)
          Pushes a value into the operand stack of this frame.
 void setLocal(int i, Value value)
          Sets the value of the given local variable.
 String toString()
          Returns a string representation of this frame.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
 

Constructor Detail

Frame

public Frame(int nLocals,
             int nStack)
Constructs a new frame with the given size.

Parameters:
nLocals - the maximum number of local variables of the frame.
nStack - the maximum stack size of the frame.

Frame

public Frame(Frame src)
Constructs a new frame that is identical to the given frame.

Parameters:
src - a frame.
Method Detail

init

public Frame init(Frame src)
Copies the state of the given frame into this frame.

Parameters:
src - a frame.
Returns:
this frame.

getLocals

public int getLocals()
Returns the maximum number of local variables of this frame.

Returns:
the maximum number of local variables of this frame.

getLocal

public Value getLocal(int i)
               throws IndexOutOfBoundsException
Returns the value of the given local variable.

Parameters:
i - a local variable index.
Returns:
the value of the given local variable.
Throws:
IndexOutOfBoundsException - if the variable does not exist.

setLocal

public void setLocal(int i,
                     Value value)
              throws IndexOutOfBoundsException
Sets the value of the given local variable.

Parameters:
i - a local variable index.
value - the new value of this local variable.
Throws:
IndexOutOfBoundsException - if the variable does not exist.

getStackSize

public int getStackSize()
Returns the number of values in the operand stack of this frame. Long and double values are treated as single values.

Returns:
the number of values in the operand stack of this frame.

getStack

public Value getStack(int i)
               throws IndexOutOfBoundsException
Returns the value of the given operand stack slot.

Parameters:
i - the index of an operand stack slot.
Returns:
the value of the given operand stack slot.
Throws:
IndexOutOfBoundsException - if the operand stack slot does not exist.

clearStack

public void clearStack()
Clears the operand stack of this frame.


pop

public Value pop()
          throws IndexOutOfBoundsException
Pops a value from the operand stack of this frame.

Returns:
the value that has been popped from the stack.
Throws:
IndexOutOfBoundsException - if the operand stack is empty.

push

public void push(Value value)
          throws IndexOutOfBoundsException
Pushes a value into the operand stack of this frame.

Parameters:
value - the value that must be pushed into the stack.
Throws:
IndexOutOfBoundsException - if the operand stack is full.

execute

public void execute(AbstractInsnNode insn,
                    Interpreter interpreter)
             throws AnalyzerException
Throws:
AnalyzerException

merge

public boolean merge(Frame frame,
                     Interpreter interpreter)
              throws AnalyzerException
Merges this frame with the given frame.

Parameters:
frame - a frame.
interpreter - the interpreter used to merge values.
Returns:
true if this frame has been changed as a result of the merge operation, or false otherwise.
Throws:
AnalyzerException - if the frames have incompatible sizes.

merge

public boolean merge(Frame frame,
                     boolean[] access)
Merges this frame with the given frame (case of a RET instruction).

Parameters:
frame - a frame
access - the local variables that have been accessed by the subroutine to which the RET instruction corresponds.
Returns:
true if this frame has been changed as a result of the merge operation, or false otherwise.

toString

public String toString()
Returns a string representation of this frame.

Overrides:
toString in class Object
Returns:
a string representation of this frame.


Copyright (c) 2004-2008 The Compass Project.