org.apache.bcel.verifier.structurals

Class ControlFlowGraph.InstructionContextImpl

Enclosing Class:
ControlFlowGraph
Implemented Interfaces:
InstructionContext

private class ControlFlowGraph.InstructionContextImpl
extends java.lang.Object
implements InstructionContext

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

Field Summary

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

Constructor Summary

InstructionContextImpl(InstructionHandle inst)
Creates an InstructionHandleImpl object from an InstructionHandle.

Method Summary

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.

Field Details

TAG

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

executionPredecessors

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

inFrames

private Map inFrames
The 'incoming' execution Frames.

instruction

private InstructionHandle instruction
The InstructionHandle this InstructionContext is wrapped around.

outFrames

private Map outFrames
The 'outgoing' execution Frames.

Constructor Details

InstructionContextImpl

public InstructionContextImpl(InstructionHandle inst)
Creates an InstructionHandleImpl object from an InstructionHandle. Creation of one per InstructionHandle suffices. Don't create more.

Method Details

_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.

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.

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.

getExceptionHandlers

public ExceptionHandler[] getExceptionHandlers()
Returns the exception handlers of this instruction.
Specified by:
getExceptionHandlers in interface InstructionContext

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.

getInFrame

public Frame getInFrame()
Specified by:
getInFrame in interface InstructionContext

getInstruction

public InstructionHandle getInstruction()
Returns the InstructionHandle this InstructionContext is wrapped around.
Specified by:
getInstruction in interface InstructionContext
Returns:
The InstructionHandle this InstructionContext is wrapped around.

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

getSuccessors

public InstructionContext[] getSuccessors()
Returns the usual control flow successors.
Specified by:
getSuccessors in interface InstructionContext

getTag

public int getTag()
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:
setTag(int tag)

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.

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.

setTag

public void setTag(int tag)
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

toString

public String toString()
Returns a simple String representation of this InstructionContext.