org.eclipse.persistence.internal.libraries.asm.tree.analysis

Class Frame<V extends Value>

java.lang.Object

org.eclipse.persistence.internal.libraries.asm.tree.analysis.Frame<V>

Type Parameters:

V - type of the Value used for the analysis.

public class Frame<V extends Value>
extends java.lang.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 with two slots in local variables, and with one slot in the operand stack.

Author:

Eric Bruneton

Constructor Summary

Constructors

Constructor and Description
Frame(Frame<? extends V> frame) Constructs a copy of the given Frame.
Frame(int numLocals, int numStack) Constructs a new frame with the given size.

Method Summary

Modifier and Type	Method and Description
void	clearStack() Clears the operand stack of this frame.
void	execute(AbstractInsnNode insn, Interpreter<V> interpreter) Simulates the execution of the given instruction on this execution stack frame.
V	getLocal(int index) Returns the value of the given local variable.
int	getLocals() Returns the maximum number of local variables of this frame.
int	getMaxStackSize() Returns the maximum stack size of this frame.
V	getStack(int index) Returns the value of the given operand stack slot.
int	getStackSize() Returns the number of values in the operand stack of this frame.
Frame<V>	init(Frame<? extends V> frame) Copies the state of the given frame into this frame.
void	initJumpTarget(int opcode, LabelNode target) Initializes a frame corresponding to the target or to the successor of a jump instruction.
boolean	merge(Frame<? extends V> frame, boolean[] localsUsed) Merges the given frame into this frame (case of a subroutine).
boolean	merge(Frame<? extends V> frame, Interpreter<V> interpreter) Merges the given frame into this frame.
V	pop() Pops a value from the operand stack of this frame.
void	push(V value) Pushes a value into the operand stack of this frame.
void	setLocal(int index, V value) Sets the value of the given local variable.
void	setReturn(V v) Sets the expected return type of the analyzed method.
void	setStack(int index, V value) Sets the value of the given stack slot.
java.lang.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 numLocals,
             int numStack)

Constructs a new frame with the given size.

Parameters:

numLocals - the maximum number of local variables of the frame.

numStack - the maximum stack size of the frame.

Frame

public Frame(Frame<? extends V> frame)

Constructs a copy of the given Frame.

Parameters:

frame - a frame.

Method Detail

init

public Frame<V> init(Frame<? extends V> frame)

Copies the state of the given frame into this frame.

Parameters:

frame - a frame.

Returns:

this frame.

initJumpTarget

public void initJumpTarget(int opcode,
                           LabelNode target)

Initializes a frame corresponding to the target or to the successor of a jump instruction. This method is called by Analyzer.analyze(String, org.eclipse.persistence.internal.libraries.asm.tree.MethodNode) while interpreting jump instructions. It is called once for each possible target of the jump instruction, and once for its successor instruction (except for GOTO and JSR), before the frame is merged with the existing frame at this location. The default implementation of this method does nothing.

Overriding this method and changing the frame values allows implementing branch-sensitive analyses.

Parameters:

opcode - the opcode of the jump instruction. Can be IFEQ, IFNE, IFLT, IFGE, IFGT, IFLE, IF_ICMPEQ, IF_ICMPNE, IF_ICMPLT, IF_ICMPGE, IF_ICMPGT, IF_ICMPLE, IF_ACMPEQ, IF_ACMPNE, GOTO, JSR, IFNULL, IFNONNULL, TABLESWITCH or LOOKUPSWITCH.

target - a target of the jump instruction this frame corresponds to, or null if this frame corresponds to the successor of the jump instruction (i.e. the next instruction in the instructions sequence).

setReturn

public void setReturn(V v)

Sets the expected return type of the analyzed method.

Parameters:

v - the expected return type of the analyzed method, or null if the method returns void.

getLocals

public int getLocals()

Returns the maximum number of local variables of this frame.

Returns:

the maximum number of local variables of this frame.

getMaxStackSize

public int getMaxStackSize()

Returns the maximum stack size of this frame.

Returns:

the maximum stack size of this frame.

getLocal

public V getLocal(int index)

Returns the value of the given local variable.

Parameters:

index - a local variable index.

Returns:

the value of the given local variable.

Throws:

java.lang.IndexOutOfBoundsException - if the variable does not exist.

setLocal

public void setLocal(int index,
                     V value)

Sets the value of the given local variable.

Parameters:

index - a local variable index.

value - the new value of this local variable.

Throws:

java.lang.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 V getStack(int index)

Returns the value of the given operand stack slot.

Parameters:

index - the index of an operand stack slot.

Returns:

the value of the given operand stack slot.

Throws:

java.lang.IndexOutOfBoundsException - if the operand stack slot does not exist.

setStack

public void setStack(int index,
                     V value)

Sets the value of the given stack slot.

Parameters:

index - the index of an operand stack slot.

value - the new value of the stack slot.

Throws:

java.lang.IndexOutOfBoundsException - if the stack slot does not exist.

clearStack

public void clearStack()

Clears the operand stack of this frame.

pop

public V pop()

Pops a value from the operand stack of this frame.

Returns:

the value that has been popped from the stack.

Throws:

java.lang.IndexOutOfBoundsException - if the operand stack is empty.

push

public void push(V value)

Pushes a value into the operand stack of this frame.

Parameters:

value - the value that must be pushed into the stack.

Throws:

java.lang.IndexOutOfBoundsException - if the operand stack is full.

execute

public void execute(AbstractInsnNode insn,
                    Interpreter<V> interpreter)
             throws AnalyzerException

Simulates the execution of the given instruction on this execution stack frame.

Parameters:

insn - the instruction to execute.

interpreter - the interpreter to use to compute values from other values.

Throws:

AnalyzerException - if the instruction cannot be executed on this execution frame (e.g. a POP on an empty operand stack).

merge

public boolean merge(Frame<? extends V> frame,
                     Interpreter<V> interpreter)
              throws AnalyzerException

Merges the given frame into this frame.

Parameters:

frame - a frame. This frame is left unchanged by this method.

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<? extends V> frame,
                     boolean[] localsUsed)

Merges the given frame into this frame (case of a subroutine). The operand stacks are not merged, and only the local variables that have not been used by the subroutine are merged.

Parameters:

frame - a frame. This frame is left unchanged by this method.

localsUsed - the local variables that are read or written by the subroutine. The i-th element is true if and only if the local variable at index i is read or written by the subroutine.

Returns:

true if this frame has been changed as a result of the merge operation, or false otherwise.

toString

public java.lang.String toString()

Returns a string representation of this frame.

Overrides:

toString in class java.lang.Object

Returns:

a string representation of this frame.