edu.umd.cs.findbugs.ba

Class FrameDataflowAnalysis<ValueType,FrameType extends Frame<ValueType>>

java.lang.Object

edu.umd.cs.findbugs.ba.BasicAbstractDataflowAnalysis<Fact>

edu.umd.cs.findbugs.ba.AbstractDataflowAnalysis<Fact>

edu.umd.cs.findbugs.ba.ForwardDataflowAnalysis<FrameType>

edu.umd.cs.findbugs.ba.FrameDataflowAnalysis<ValueType,FrameType>

All Implemented Interfaces:

DataflowAnalysis<FrameType>

Direct Known Subclasses:

ConstantAnalysis, IsNullValueAnalysis, ResourceValueAnalysis, TypeAnalysis, ValueNumberAnalysis

public abstract class FrameDataflowAnalysis<ValueType,FrameType extends Frame<ValueType>>
extends ForwardDataflowAnalysis<FrameType>

A convenient base class for dataflow analysis classes which use Frames as values.

Author:

David Hovemeyer

See Also:

Frame, DataflowAnalysis

Constructor Summary

Constructors

Constructor and Description
FrameDataflowAnalysis(DepthFirstSearch dfs)

Method Summary

Modifier and Type	Method and Description
void	copy(FrameType source, FrameType dest) Copy dataflow facts.
FrameType	getFactAtPC(CFG cfg, int pc) Get the dataflow fact representing the point just before given Location.
FrameType	getFactBeforeExceptionCheck(CFG cfg, int pc) Get the dataflow fact representing the point just before given Location.
int	getLastUpdateTimestamp(FrameType fact)
boolean	isFactValid(FrameType fact) Determine whether the given fact is valid (neither top nor bottom).
boolean	isTop(FrameType fact) Is the given fact the top value.
void	makeFactTop(FrameType fact) Make given fact the top value.
protected void	mergeInto(FrameType other, FrameType result) Merge one frame into another.
protected abstract void	mergeValues(FrameType otherFrame, FrameType resultFrame, int slot) Merge the values contained in a given slot of two Frames.
protected FrameType	modifyFrame(FrameType orig, FrameType copy) Create a modifiable copy of a frame.
boolean	same(FrameType fact1, FrameType fact2) Are given dataflow facts the same?
void	setLastUpdateTimestamp(FrameType fact, int lastTimestamp)

Methods inherited from class edu.umd.cs.findbugs.ba.ForwardDataflowAnalysis

getBlockOrder, getDepthFirstSearch, isForwards

Methods inherited from class edu.umd.cs.findbugs.ba.AbstractDataflowAnalysis

getFactAfterLocation, getFactAtLocation, transfer, transferInstruction

Methods inherited from class edu.umd.cs.findbugs.ba.BasicAbstractDataflowAnalysis

edgeTransfer, factToString, finishIteration, getFactOnEdge, getResultFact, getStartFact, resultFactIterator, startIteration

Methods inherited from class java.lang.Object

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

Methods inherited from interface edu.umd.cs.findbugs.ba.DataflowAnalysis

createFact, initEntryFact, meetInto

Constructor Detail

FrameDataflowAnalysis

public FrameDataflowAnalysis(DepthFirstSearch dfs)

Method Detail

copy

public void copy(FrameType source,
                 FrameType dest)

Description copied from interface: DataflowAnalysis

Copy dataflow facts.

makeFactTop

public void makeFactTop(FrameType fact)

Description copied from interface: DataflowAnalysis

Make given fact the top value.

isTop

public boolean isTop(FrameType fact)

Description copied from interface: DataflowAnalysis

Is the given fact the top value.

same

public boolean same(FrameType fact1,
                    FrameType fact2)

Description copied from interface: DataflowAnalysis

Are given dataflow facts the same?

getFactAtPC

public FrameType getFactAtPC(CFG cfg,
                             int pc)
                      throws DataflowAnalysisException

Get the dataflow fact representing the point just before given Location. Note "before" is meant in the logical sense, so for backward analyses, before means after the location in the control flow sense.

Returns:

the fact at the point just before the location

Throws:

DataflowAnalysisException

getFactBeforeExceptionCheck

public FrameType getFactBeforeExceptionCheck(CFG cfg,
                                             int pc)
                                      throws DataflowAnalysisException

Get the dataflow fact representing the point just before given Location. Note "before" is meant in the logical sense, so for backward analyses, before means after the location in the control flow sense.

Returns:

the fact at the point just before the location

Throws:

DataflowAnalysisException

isFactValid

public boolean isFactValid(FrameType fact)

Description copied from class: AbstractDataflowAnalysis

Determine whether the given fact is valid (neither top nor bottom).

Specified by:

isFactValid in class AbstractDataflowAnalysis<FrameType extends Frame<ValueType>>

getLastUpdateTimestamp

public int getLastUpdateTimestamp(FrameType fact)

Specified by:

getLastUpdateTimestamp in interface DataflowAnalysis<FrameType extends Frame<ValueType>>

Overrides:

getLastUpdateTimestamp in class BasicAbstractDataflowAnalysis<FrameType extends Frame<ValueType>>

setLastUpdateTimestamp

public void setLastUpdateTimestamp(FrameType fact,
                                   int lastTimestamp)

Specified by:

setLastUpdateTimestamp in interface DataflowAnalysis<FrameType extends Frame<ValueType>>

Overrides:

setLastUpdateTimestamp in class BasicAbstractDataflowAnalysis<FrameType extends Frame<ValueType>>

modifyFrame

protected final FrameType modifyFrame(FrameType orig,
                                      @CheckForNull
                                      FrameType copy)

Create a modifiable copy of a frame. This is useful for meetInto(), if the frame needs to be modified in a path-sensitive fashion. A typical usage pattern is:

 FrameType copy = null;
 if (someCondition()) {
     copy = modifyFrame(fact, copy);
     // modify copy
 }
 if (someOtherCondition()) {
     copy = modifyFrame(fact, copy);
     // modify copy
 }
 if (copy != null)
     fact = copy;
 mergeInto(fact, result);
 

The advantage of using modifyFrame() is that new code can be added before or after other places where the frame is modified, and the code will remain correct.

Parameters:

orig - the original frame

copy - the modifiable copy (returned by a previous call to modifyFrame()), or null if this is the first time modifyFrame() is being called

Returns:

a modifiable copy of fact

mergeInto

protected void mergeInto(FrameType other,
                         FrameType result)
                  throws DataflowAnalysisException

Merge one frame into another.

Parameters:

other - the frame to merge with the result

result - the result frame, which is modified to be the merge of the two frames

Throws:

DataflowAnalysisException

mergeValues

protected abstract void mergeValues(FrameType otherFrame,
                                    FrameType resultFrame,
                                    int slot)
                             throws DataflowAnalysisException

Merge the values contained in a given slot of two Frames.

Parameters:

otherFrame - a Frame

resultFrame - a Frame which will contain the resulting merged value

slot - a slot in both frames

Throws:

DataflowAnalysisException