Package edu.umd.cs.findbugs.ba

Class Frame<ValueType>

  • Direct Known Subclasses:
    ConstantFrame, IsNullValueFrame, ResourceValueFrame, TypeFrame, ValueNumberFrame
    public abstract class Frame<ValueType>
extends java.lang.Object

    Generic class for representing a Java stack frame as a dataflow value. A frame consists of "slots", which represent the local variables and values on the Java operand stack. Slots 0 .. getNumLocals() - 1 represent the local variables. Slots getNumLocals() .. getNumSlots() - 1 represent the Java operand stack.

    Frame is parametized by "ValueType", which is the type of value to be stored in the Frame's slots. This type must form a lattice, according to the abstract mergeValues() operation in the corresponding analysis class (which should be derived from FrameDataflowAnalysis). When a Frame is constructed, all of its slots will contain null. The analysis is responsible for initializing created Frames with default values at the appropriate time. Typically, only initEntryFact() will need to do this.

    A Frame may have the special "TOP" value. Such frames serve as the identity element for the meet operation operation.

    A Frame may have the special "BOTTOM" value. The result of merging any frame with BOTTOM is BOTTOM.

    Author:
    David Hovemeyer
    See Also:
    FrameDataflowAnalysis

    • Constructor Summary

      Constructors 
      Constructor Description
      Frame​(int numLocals)
      Constructor.

    • Method Summary

      All Methods Instance Methods Concrete Methods Deprecated Methods 
      Modifier and Type Method Description
      java.util.Collection<ValueType> allSlots()  
      void clearStack()
      Clear the Java operand stack.
      boolean contains​(ValueType value)  
      void copyFrom​(Frame<ValueType> other)
      Make this Frame exactly the same as the one given as a parameter.
      ValueType getArgument​(org.apache.bcel.generic.InvokeInstruction ins, org.apache.bcel.generic.ConstantPoolGen cpg, int i, int numArguments)
      Deprecated.
      ValueType getArgument​(org.apache.bcel.generic.InvokeInstruction ins, org.apache.bcel.generic.ConstantPoolGen cpg, int i, SignatureParser sigParser)
      Get the ith argument passed to given method invocation.
      java.util.BitSet getArgumentSet​(org.apache.bcel.generic.InvokeInstruction invokeInstruction, org.apache.bcel.generic.ConstantPoolGen cpg, DataflowValueChooser<ValueType> chooser)
      Get set of arguments passed to a method invocation which match given predicate.
      int getArgumentSlot​(int i, int numArguments)
      Get the stack slot that will contain given method argument.
      ValueType getInstance​(org.apache.bcel.generic.Instruction ins, org.apache.bcel.generic.ConstantPoolGen cpg)
      Get the value corresponding to the object instance used in the given instruction.
      int getInstanceSlot​(org.apache.bcel.generic.Instruction ins, org.apache.bcel.generic.ConstantPoolGen cpg)
      Get the slot the object instance referred to by given instruction is located in.
      int getInstanceStackLocation​(org.apache.bcel.generic.Instruction ins, org.apache.bcel.generic.ConstantPoolGen cpg)
      Get the stack location (counting down from top of stack, starting at 0) containing the object instance referred to by given instruction.
      int getLastUpdateTimestamp()  
      int getNumArguments​(org.apache.bcel.generic.InvokeInstruction ins, org.apache.bcel.generic.ConstantPoolGen cpg)
      Get the number of arguments passed to given method invocation.
      int getNumArgumentsIncludingObjectInstance​(org.apache.bcel.generic.InvokeInstruction ins, org.apache.bcel.generic.ConstantPoolGen cpg)
      Get the number of arguments passed to given method invocation, including the object instance if the call is to an instance method.
      int getNumLocals()
      Get the number of locals.
      int getNumSlots()
      Get the number of slots (locals plus stack values).
      ValueType getOperand​(org.apache.bcel.generic.StackConsumer ins, org.apache.bcel.generic.ConstantPoolGen cpg, int i)
      Get the ith operand used by given instruction.
      int getStackDepth()
      Get the depth of the Java operand stack.
      int getStackLocation​(int loc)
      Get a the location in the frame of a value on the operand stack.
      ValueType getStackValue​(int loc)
      Get a value on the operand stack.
      void getTopStackWords​(ValueType[] valueList)
      Get the values on the top of the Java operand stack.
      ValueType getTopValue()
      Get the value on the top of the Java operand stack.
      ValueType getValue​(int n)
      Get the value at the nth slot.
      boolean isBottom()
      Return whether or not this object is the special "BOTTOM" value for Frames.
      boolean isTop()
      Return whether or not this object the special "TOP" value for Frames.
      boolean isValid()
      Is the frame valid (meaning it is not TOP or BOTTOM)?
      ValueType popValue()
      Pop a value off of the Java operand stack.
      void pushValue​(ValueType value)
      Push a value onto the Java operand stack.
      boolean sameAs​(Frame<ValueType> other)
      Return true if this stack frame is the same as the one given as a parameter.
      void setBottom()
      Make this Frame the special "BOTTOM" value.
      void setLastUpdateTimestamp​(int lastUpdateTimestamp)  
      void setTop()
      Make this frame the special "TOP" value.
      void setValid()
      Set the Frame to be valid (neither TOP nor BOTTOM).
      void setValue​(int n, ValueType value)
      Set the value at the nth slot.
      java.lang.String toString()
      Convert to string.
      protected java.lang.String valueToString​(ValueType value)
      Subclasses may override this if they want to do something special to convert Value objects to Strings.

      • Methods inherited from class java.lang.Object

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

    • Constructor Detail

      • Frame

        public Frame​(int numLocals)
        Constructor. This version of the constructor is for subclasses for which it is always safe to call getDefaultValue(), even when the object is not fully initialized.
        Parameters:
        numLocals - number of local variable slots in the method

    • Method Detail

      • isTop

        public boolean isTop()
        Return whether or not this object the special "TOP" value for Frames. Such Frames are the identity element of the meet operation.

      • setTop

        public void setTop()
        Make this frame the special "TOP" value. Such Frames are the identity element of the meet operation.

      • isBottom

        public boolean isBottom()
        Return whether or not this object is the special "BOTTOM" value for Frames. Such Frames arise when merging two frames of different size.

      • setBottom

        public void setBottom()
        Make this Frame the special "BOTTOM" value. Such Frames arise when merging two frames of different size.

      • setValid

        public void setValid()
        Set the Frame to be valid (neither TOP nor BOTTOM).

      • isValid

        public boolean isValid()
        Is the frame valid (meaning it is not TOP or BOTTOM)?

      • pushValue

        public void pushValue​(ValueType value)
        Push a value onto the Java operand stack.
        Parameters:
        value - the ValueType to push

      • getTopStackWords

        public void getTopStackWords​(ValueType[] valueList)
                      throws DataflowAnalysisException
        Get the values on the top of the Java operand stack. The top stack item is placed at the end of the array, so that to restore the values to the stack, you would push them in the order they appear in the array.
        Throws:
        DataflowAnalysisException

      • getStackLocation

        public int getStackLocation​(int loc)
                     throws DataflowAnalysisException
        Get a the location in the frame of a value on the operand stack.
        Parameters:
        loc - the stack location, counting downwards from the top (location 0)
        Throws:
        DataflowAnalysisException

      • getInstance

        public ValueType getInstance​(org.apache.bcel.generic.Instruction ins,
                             org.apache.bcel.generic.ConstantPoolGen cpg)
                      throws DataflowAnalysisException
        Get the value corresponding to the object instance used in the given instruction. This relies on the observation that in instructions which use an object instance (such as getfield, invokevirtual, etc.), the object instance is the first operand used by the instruction.
        Parameters:
        ins - the instruction
        cpg - the ConstantPoolGen for the method
        Throws:
        DataflowAnalysisException

      • getInstanceStackLocation

        public int getInstanceStackLocation​(org.apache.bcel.generic.Instruction ins,
                                    org.apache.bcel.generic.ConstantPoolGen cpg)
                             throws DataflowAnalysisException
        Get the stack location (counting down from top of stack, starting at 0) containing the object instance referred to by given instruction. This relies on the observation that in instructions which use an object instance (such as getfield, invokevirtual, etc.), the object instance is the first operand used by the instruction.

        The value returned may be passed to getStackValue(int).

        Parameters:
        ins - the Instruction
        cpg - the ConstantPoolGen for the method
        Returns:
        stack location (counting down from top of stack, starting at 0) containing the object instance
        Throws:
        DataflowAnalysisException

      • getInstanceSlot

        public int getInstanceSlot​(org.apache.bcel.generic.Instruction ins,
                           org.apache.bcel.generic.ConstantPoolGen cpg)
                    throws DataflowAnalysisException
        Get the slot the object instance referred to by given instruction is located in.
        Parameters:
        ins - the Instruction
        cpg - the ConstantPoolGen for the method
        Returns:
        stack slot the object instance is in
        Throws:
        DataflowAnalysisException

      • getNumArguments

        public int getNumArguments​(org.apache.bcel.generic.InvokeInstruction ins,
                           org.apache.bcel.generic.ConstantPoolGen cpg)
        Get the number of arguments passed to given method invocation.
        Parameters:
        ins - the method invocation instruction
        cpg - the ConstantPoolGen for the class containing the method
        Returns:
        number of arguments; note that this excludes the object instance for instance methods

      • getNumArgumentsIncludingObjectInstance

        public int getNumArgumentsIncludingObjectInstance​(org.apache.bcel.generic.InvokeInstruction ins,
                                                  org.apache.bcel.generic.ConstantPoolGen cpg)
                                           throws DataflowAnalysisException
        Get the number of arguments passed to given method invocation, including the object instance if the call is to an instance method.
        Parameters:
        ins - the method invocation instruction
        cpg - the ConstantPoolGen for the class containing the method
        Returns:
        number of arguments, including object instance if appropriate
        Throws:
        DataflowAnalysisException

      • getArgument

        @Deprecated
public ValueType getArgument​(org.apache.bcel.generic.InvokeInstruction ins,
                             org.apache.bcel.generic.ConstantPoolGen cpg,
                             int i,
                             int numArguments)
                      throws DataflowAnalysisException
        Deprecated.
        Get the ith argument passed to given method invocation.
        Parameters:
        ins - the method invocation instruction
        cpg - the ConstantPoolGen for the class containing the method
        i - index of the argument; 0 for the first argument, etc.
        numArguments - total number of arguments to the method
        Returns:
        the ith argument
        Throws:
        DataflowAnalysisException

      • getArgument

        public ValueType getArgument​(org.apache.bcel.generic.InvokeInstruction ins,
                             org.apache.bcel.generic.ConstantPoolGen cpg,
                             int i,
                             SignatureParser sigParser)
                      throws DataflowAnalysisException
        Get the ith argument passed to given method invocation.
        Parameters:
        ins - the method invocation instruction
        cpg - the ConstantPoolGen for the class containing the method
        i - index of the argument; 0 for the first argument, etc.
        Returns:
        the ith argument
        Throws:
        DataflowAnalysisException

      • getArgumentSlot

        public int getArgumentSlot​(int i,
                           int numArguments)
        Get the stack slot that will contain given method argument. Assumes that this frame is at the location (just before) a method invocation instruction.
        Parameters:
        i - the argument index: 0 for first arg, etc.
        numArguments - total number of arguments to the called method
        Returns:
        slot containing the argument value

      • getOperand

        public ValueType getOperand​(org.apache.bcel.generic.StackConsumer ins,
                            org.apache.bcel.generic.ConstantPoolGen cpg,
                            int i)
                     throws DataflowAnalysisException
        Get the ith operand used by given instruction.
        Parameters:
        ins - the instruction, which must be a StackConsumer
        cpg - the ConstantPoolGen
        i - index of operand to get: 0 for the first operand, etc.
        Returns:
        the ith operand used by the given instruction
        Throws:
        DataflowAnalysisException

      • getArgumentSet

        public java.util.BitSet getArgumentSet​(org.apache.bcel.generic.InvokeInstruction invokeInstruction,
                                       org.apache.bcel.generic.ConstantPoolGen cpg,
                                       DataflowValueChooser<ValueType> chooser)
                                throws DataflowAnalysisException
        Get set of arguments passed to a method invocation which match given predicate.
        Parameters:
        invokeInstruction - the InvokeInstruction
        cpg - the ConstantPoolGen
        chooser - predicate to choose which argument values should be in the returned set
        Returns:
        BitSet specifying which arguments match the predicate, indexed by argument number (starting from 0)
        Throws:
        DataflowAnalysisException

      • clearStack

        public void clearStack()
        Clear the Java operand stack. Only local variable slots will remain in the frame.

      • getStackDepth

        public int getStackDepth()
        Get the depth of the Java operand stack.

      • getNumLocals

        public int getNumLocals()
        Get the number of locals.

      • getNumSlots

        public int getNumSlots()
        Get the number of slots (locals plus stack values).

      • contains

        public boolean contains​(ValueType value)

      • getValue

        public ValueType getValue​(int n)
        Get the value at the nth slot.
        Parameters:
        n - the slot to get the value of
        Returns:
        the value in the slot

      • setValue

        public void setValue​(int n,
                     ValueType value)
        Set the value at the nth slot.
        Parameters:
        n - the slot in which to set a new value
        value - the value to set

      • sameAs

        public boolean sameAs​(Frame<ValueType> other)
        Return true if this stack frame is the same as the one given as a parameter.
        Parameters:
        other - the other Frame
        Returns:
        true if the frames are the same, false otherwise

      • copyFrom

        public void copyFrom​(Frame<ValueType> other)
        Make this Frame exactly the same as the one given as a parameter.
        Parameters:
        other - the Frame to make this object the same as

      • toString

        public java.lang.String toString()
        Convert to string.
        Overrides:
        toString in class java.lang.Object

      • valueToString

        protected java.lang.String valueToString​(ValueType value)
        Subclasses may override this if they want to do something special to convert Value objects to Strings. By default, we just call toString() on the values.

      • allSlots

        public java.util.Collection<ValueType> allSlots()
        Returns:
        an unmodifiable Collection of the local variable and operand stack slots

      • setLastUpdateTimestamp

        public void setLastUpdateTimestamp​(int lastUpdateTimestamp)
        Parameters:
        lastUpdateTimestamp - The lastUpdateTimestamp to set.

      • getLastUpdateTimestamp

        public int getLastUpdateTimestamp()
        Returns:
        Returns the lastUpdateTimestamp.