org.apache.bcel.verifier.structurals

Class ControlFlowGraph.InstructionContextImpl

java.lang.Object

org.apache.bcel.verifier.structurals.ControlFlowGraph.InstructionContextImpl

All Implemented Interfaces:

InstructionContext

Enclosing class:

ControlFlowGraph

private class ControlFlowGraph.InstructionContextImpl
extends Object
implements InstructionContext

Objects of this class represent a node in a ControlFlowGraph. These nodes are instructions, not basic blocks.

Field Summary

Fields

Modifier and Type	Field and Description
private ArrayList	executionPredecessors The 'execution predecessors' - a list of type InstructionContext of those instances that have been execute()d before in that order.
private Map	inFrames The 'incoming' execution Frames.
private InstructionHandle	instruction The InstructionHandle this InstructionContext is wrapped around.
private Map	outFrames The 'outgoing' execution Frames.
private int	TAG The TAG field is here for external temporary flagging, such as graph colouring.

Constructor Summary

Constructors

Constructor and Description
ControlFlowGraph.InstructionContextImpl(InstructionHandle inst) Creates an InstructionHandleImpl object from an InstructionHandle.

Method Summary

Methods

Modifier and Type	Method and Description
private InstructionHandle[]	_getSuccessors() A utility method that calculates the successors of a given InstructionHandle That means, a RET does have successors as defined here.
boolean	execute(Frame inFrame, ArrayList execPreds, InstConstraintVisitor icv, ExecutionVisitor ev) "Merges in" (vmspec2, page 146) the "incoming" frame situation; executes the instructions symbolically and therefore calculates the "outgoing" frame situation.
private void	extendMessageWithFlow(StructuralCodeConstraintException e) Extends the StructuralCodeConstraintException ("e") object with an at-the-end-extended message.
ExceptionHandler[]	getExceptionHandlers() Returns the exception handlers of this instruction.
private String	getExecutionChain() Returns the control flow execution chain.
Frame	getInFrame()
InstructionHandle	getInstruction() Returns the InstructionHandle this InstructionContext is wrapped around.
Frame	getOutFrame(ArrayList execChain) Returns a clone of the "outgoing" frame situation with respect to the given ExecutionChain.
InstructionContext[]	getSuccessors() Returns the usual control flow successors.
int	getTag() The getTag and setTag methods may be used for temporary flagging, such as graph colouring.
private ControlFlowGraph.InstructionContextImpl	lastExecutionJSR() Returns the InstructionContextImpl with an JSR/JSR_W that was last in the ExecutionChain, without a corresponding RET, i.e.
private boolean	mergeInFrames(Frame inFrame) Does the actual merging (vmspec2, page 146).
void	setTag(int tag) The getTag and setTag methods may be used for temporary flagging, such as graph colouring.
String	toString() Returns a simple String representation of this InstructionContext.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

TAG

private int TAG

The TAG field is here for external temporary flagging, such as graph colouring.

See Also:

getTag(), setTag(int)

instruction

private InstructionHandle instruction

The InstructionHandle this InstructionContext is wrapped around.

inFrames

private Map inFrames

The 'incoming' execution Frames.

outFrames

private Map outFrames

The 'outgoing' execution Frames.

executionPredecessors

private ArrayList executionPredecessors

The 'execution predecessors' - a list of type InstructionContext of those instances that have been execute()d before in that order.

Constructor Detail

ControlFlowGraph.InstructionContextImpl

public ControlFlowGraph.InstructionContextImpl(InstructionHandle inst)

Creates an InstructionHandleImpl object from an InstructionHandle. Creation of one per InstructionHandle suffices. Don't create more.

Method Detail

getTag

public int getTag()

Description copied from interface: InstructionContext

The getTag and setTag methods may be used for temporary flagging, such as graph colouring. Nothing in the InstructionContext object depends on the value of the tag. JustIce does not use it.

Specified by:

getTag in interface InstructionContext

See Also:

InstructionContext.setTag(int tag)

setTag

public void setTag(int tag)

Description copied from interface: InstructionContext

The getTag and setTag methods may be used for temporary flagging, such as graph colouring. Nothing in the InstructionContext object depends on the value of the tag. JustIce does not use it.

Specified by:

setTag in interface InstructionContext

See Also:

InstructionContext.getTag()

getExceptionHandlers

public ExceptionHandler[] getExceptionHandlers()

Returns the exception handlers of this instruction.

Specified by:

getExceptionHandlers in interface InstructionContext

getOutFrame

public Frame getOutFrame(ArrayList execChain)

Returns a clone of the "outgoing" frame situation with respect to the given ExecutionChain.

Specified by:

getOutFrame in interface InstructionContext

See Also:

InstructionContext.execute(Frame, ArrayList, InstConstraintVisitor, ExecutionVisitor)

getInFrame

public Frame getInFrame()

Specified by:

getInFrame in interface InstructionContext

execute

public boolean execute(Frame inFrame,
              ArrayList execPreds,
              InstConstraintVisitor icv,
              ExecutionVisitor ev)

"Merges in" (vmspec2, page 146) the "incoming" frame situation; executes the instructions symbolically and therefore calculates the "outgoing" frame situation. Returns: True iff the "incoming" frame situation changed after merging with "inFrame". The execPreds ArrayList must contain the InstructionContext objects executed so far in the correct order. This is just one execution path [out of many]. This is needed to correctly "merge" in the special case of a RET's successor. The InstConstraintVisitor and ExecutionVisitor instances must be set up correctly.

Specified by:

execute in interface InstructionContext

Returns:

true - if and only if the "outgoing" frame situation changed from the one before execute()ing.

See Also:

ControlFlowGraph, ExecutionVisitor, InstructionContext.getOutFrame(ArrayList)

toString

public String toString()

Returns a simple String representation of this InstructionContext.

Overrides:

toString in class Object

mergeInFrames

private boolean mergeInFrames(Frame inFrame)

Does the actual merging (vmspec2, page 146). Returns true IFF this.inFrame was changed in course of merging with inFrame.

getExecutionChain

private String getExecutionChain()

Returns the control flow execution chain. This is built while execute(Frame, ArrayList)-ing the code represented by the surrounding ControlFlowGraph.

extendMessageWithFlow

private void extendMessageWithFlow(StructuralCodeConstraintException e)

Extends the StructuralCodeConstraintException ("e") object with an at-the-end-extended message. This extended message will then reflect the execution flow needed to get to the constraint violation that triggered the throwing of the "e" object.

getInstruction

public InstructionHandle getInstruction()

Description copied from interface: InstructionContext

Returns the InstructionHandle this InstructionContext is wrapped around.

Specified by:

getInstruction in interface InstructionContext

Returns:

The InstructionHandle this InstructionContext is wrapped around.

lastExecutionJSR

private ControlFlowGraph.InstructionContextImpl lastExecutionJSR()

Returns the InstructionContextImpl with an JSR/JSR_W that was last in the ExecutionChain, without a corresponding RET, i.e. we were called by this one. Returns null if we were called from the top level.

getSuccessors

public InstructionContext[] getSuccessors()

Description copied from interface: InstructionContext

Returns the usual control flow successors.

Specified by:

getSuccessors in interface InstructionContext

See Also:

InstructionContext.getExceptionHandlers()

_getSuccessors

private InstructionHandle[] _getSuccessors()

A utility method that calculates the successors of a given InstructionHandle That means, a RET does have successors as defined here. A JsrInstruction has its target as its successor (opposed to its physical successor) as defined here.