com.ibm.wala.util.ssa

Class ParameterAccessor

java.lang.Object

com.ibm.wala.util.ssa.ParameterAccessor

public class ParameterAccessor
extends Object

Access parameters without confusion on their numbers. Depending on the representation of a method (IMethod, MethodReference) parameters are placed at a different position. Functions furthermore may have an implicit this-pointer which alters the positions again. Accessing parameters of these functions by their numbers only is error prone and leads to confusion. This class tries to leverage parameter-access. You can use this class using now numbers at all. However if you choose to use numbers this class has yet another numbering convention (jupeee): 1 is the first parameter appearing in the Selector, no matter if the Method has an implicit this. It is not zero as Java initializes new integer-arrays with zero. If you want to alter the values of the incoming parameters you may also want to use the ParameterManager which tracks the changes.

Since:

2013-10-19

Author:

Tobias Blaschke

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	ParameterAccessor.BasedOn The Constructor used to create ParameterAccessor influences the parameter-offset.
static class	ParameterAccessor.ParamerterDisposition The kind of parameter.
static class	ParameterAccessor.Parameter The representation of a Parameter handled using a ParameterAccessor.
static class	ParameterAccessor.ParameterKey This key is identified by type and parameter number.

Constructor Summary

Constructors

Constructor and Description
ParameterAccessor(IMethod method) Read the parameters from an IMethod.
ParameterAccessor(MethodReference mRef, boolean hasImplicitThis) Reads the parameters of a MethodReference CAUTION:.
ParameterAccessor(MethodReference mRef, IClassHierarchy cha) Reads the parameters of a MethodReference CAUTION:.

Method Summary

Methods

Modifier and Type	Method and Description
List<ParameterAccessor.Parameter>	all() This list _excludes_ the implicit this-pointer (if any).
List<ParameterAccessor.Parameter>	allExtend(TypeName tName, IClassHierarchy cha) All parameters in the selector that are a subclass of tName (slow).
List<ParameterAccessor.Parameter>	allExtend(TypeReference tRef, IClassHierarchy cha) All parameters in the selector that are a subclass of tRef (slow).
List<SSAValue>	connectThrough(ParameterAccessor callee, Set<? extends SSAValue> overrides, Set<? extends SSAValue> defaults, IClassHierarchy cha) Assign parameters to a call based on their type.
List<SSAValue>	connectThrough(ParameterAccessor callee, Set<? extends SSAValue> overrides, Set<? extends SSAValue> defaults, IClassHierarchy cha, IInstantiator instantiator, Object... instantiatorArgs) Connects though parameters from the calling function (overridable) - CAUTION:.
String	dump() Extensive output for debugging purposes.
ParameterAccessor.Parameter	firstExtends(TypeName tName, IClassHierarchy cha) First parameter in the selector that is a subclass of tName (slow).
ParameterAccessor.Parameter	firstExtends(TypeReference tRef, IClassHierarchy cha) First parameter in the selector that is a subclass of tRef (slow).
int	firstInSelector() The SSA-Value to acces the parameter appearing first in the Descriptor with.
ParameterAccessor.Parameter	firstOf(TypeName tName) First parameter in the selector that matches _exactly_.
ParameterAccessor.Parameter	firstOf(TypeReference tRef) First parameter in the selector that matches _exactly_.
int[]	forInvokeStatic(List<? extends ParameterAccessor.Parameter> args, MethodReference target, IClassHierarchy cha) Shorthand for forInvokeStatic(final List args, final ParameterAccessor target, final IClassHierarchy cha).
int[]	forInvokeStatic(List<? extends SSAValue> args) Generate the params-param for an InvokeIstruction w/o type checking.
int[]	forInvokeStatic(List<? extends SSAValue> args, ParameterAccessor target, IClassHierarchy cha) Generate the params-param for an InvokeIstruction with type checking.
int[]	forInvokeVirtual(int self, List<? extends ParameterAccessor.Parameter> args, MethodReference target, IClassHierarchy cha) Shorthand for forInvokeVirtual(final int self, final List args, final ParameterAccessor target, final IClassHierarchy cha).
int[]	forInvokeVirtual(int self, List<? extends SSAValue> args) Generate the params-param for an InvokeIstruction w/o type checking.
int[]	forInvokeVirtual(int self, List<? extends SSAValue> args, ParameterAccessor target, IClassHierarchy cha) Generate the params-param for an InvokeIstruction with type checking.
MethodReference	forMethod() The method this accessor reads the parameters from.
int	getFirstAfter() The first SSA-Number after the parameters.
int	getNumberOfParameters() Number of parameters _excluding_ implicit this
ParameterAccessor.Parameter	getParameter(int no) Make an Parameter Object using a Descriptor-based numbering (starting with 1).
int	getParameterNo(int no) Return the SSA-Value to access a parameter using a Descriptor-based numbering (starting with 1).
int	getParameterNo(ParameterAccessor.Parameter param) Same as Parameter.getNumber().
TypeReference	getParameterType(int no) Prefer: getParameter(int no) or all().
TypeReference	getReturnType() Handed through to the IMethod / MethodReference
ParameterAccessor.Parameter	getThis() Return the implicit this-pointer (or throw).
ParameterAccessor.Parameter	getThisAs(TypeReference asType) Return the implicit this-pointer as a supertype.
int	getThisNo() Return the SSA-Value of the implicit this-pointer (or throw).
boolean	hasImplicitThis() If the method has an implicit this parameter.
boolean	hasReturn() If the method returns a value eg is non-void.
protected boolean	isAssignable(SSAValue from, SSAValue to, IClassHierarchy cha) Does "to x := from" hold?.
static boolean	isAssignable(TypeReference from, TypeReference to, IClassHierarchy cha) Does "to x := from" hold?.
static boolean	isSubclassOf(TypeReference sub, TypeReference superC, IClassHierarchy cha) Is sub a subclass of superC (or the same).
ParameterAccessor.Parameter	makeReturn(int ssa) Create a "Parameter" containing the Return-Type w/o Type-checking.
ParameterAccessor.Parameter	makeReturn(int ssa, TypeReference type, IClassHierarchy cha) Create a "Parameter" containing the Return-Type with Type-checking.
String	toString()

Methods inherited from class java.lang.Object

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

Constructor Detail

ParameterAccessor

public ParameterAccessor(MethodReference mRef,
                 IClassHierarchy cha)

Reads the parameters of a MethodReference CAUTION:. Do _not_ use ParameterAceesor(IMethod.getReference()), but ParameterAceesor(IMehod)! Using this Constructor influences the SSA-Values returned later. The cha is needed to determine whether mRef is static. If this is already known one should prefer the faster #ParameterAccessor(ParameterAccessor, boolean).

Parameters:

mRef - The method to read the parameters from.

ParameterAccessor

public ParameterAccessor(MethodReference mRef,
                 boolean hasImplicitThis)

Reads the parameters of a MethodReference CAUTION:. Do _not_ use ParameterAceesor(IMethod.getReference()), but ParameterAceesor(IMehod)! This constructor is faster than #ParameterAccessor(MethodReference, IClassHierarchy.

Parameters:

mRef - The method to read the parameters from.

ParameterAccessor

public ParameterAccessor(IMethod method)

Read the parameters from an IMethod. Using this Constructor influences the SSA-Values returned later.

Parameters:

method - The method to read the parameters from.

Method Detail

getParameter

public ParameterAccessor.Parameter getParameter(int no)

Make an Parameter Object using a Descriptor-based numbering (starting with 1). Number 1 is the first parameter in the methods Selector. No matter if the function has an implicit this pointer. If the Function has an implicit this-pointer you can access it using getThis().

Parameters:

no - the number in the Selector

Returns:

new Parameter-Object for no

Throws:

IllegalArgumentExceptions - if the parameter is zero

ArrayIndexOutOfBoundsException - if no is not within bounds [1 to numberOfParameters]

getParameterNo

public int getParameterNo(int no)

Return the SSA-Value to access a parameter using a Descriptor-based numbering (starting with 1). Number 1 is the first parameter in the methods Selector. No matter if the function has an implicit this pointer. If the Function has an implicit this-pointer you can acess it using getThisNo().

Parameters:

no - the number in the Selector

Returns:

the offseted number for accessing the parameter

Throws:

IllegalArgumentException - if the parameter is zero

ArrayIndexOutOfBoundsException - if no is not within bounds [1 to numberOfParameters]

getParameterNo

public int getParameterNo(ParameterAccessor.Parameter param)

Same as Parameter.getNumber().

Returns:

SSA-Value to access the parameters contents.

all

public List<ParameterAccessor.Parameter> all()

This list _excludes_ the implicit this-pointer (if any). If you want the implicit this-pointer use getThis().

Returns:

All parameters appearing in the Selector.

getThis

public ParameterAccessor.Parameter getThis()

Return the implicit this-pointer (or throw). This obviously only works on non-static methods. You probably want to check if the method has such an implicit this using hasImplicitThis() as this method will throw if there is none. If you only want the number use the more lightweight getThisNo().

Returns:

Object containing all Information on the parameter.

Throws:

IllegalStateException - if the function has no implicit this

getThisAs

public ParameterAccessor.Parameter getThisAs(TypeReference asType)

Return the implicit this-pointer as a supertype.

Parameters:

asType - A type of a super-class of this

getThisNo

public int getThisNo()

Return the SSA-Value of the implicit this-pointer (or throw). This obviously only works on non-static methods. You probably want to check if the method has such an implicit this using hasImplicitThis() as this method will throw if there is none.

Returns:

Number of the this.

Throws:

IllegalStateException - if the function has no implicit this.

hasImplicitThis

public boolean hasImplicitThis()

If the method has an implicit this parameter.

makeReturn

public ParameterAccessor.Parameter makeReturn(int ssa)

Create a "Parameter" containing the Return-Type w/o Type-checking. This should be of rather theoretical use.

Throws:

IllegalStateException - if used on a void-Function

makeReturn

public ParameterAccessor.Parameter makeReturn(int ssa,
                                     TypeReference type,
                                     IClassHierarchy cha)

Create a "Parameter" containing the Return-Type with Type-checking.

Parameters:

ssa - The value to return

type - The type of ssa

cha - The ClassHierarchy to use for the assignability test

Throws:

IllegalStateException - if used on a void-Function

firstInSelector

public int firstInSelector()

The SSA-Value to acces the parameter appearing first in the Descriptor with.

Throws:

IllegalArgumentException - if the method has no parameters in its Descriptor.

getParameterType

public TypeReference getParameterType(int no)

Prefer: getParameter(int no) or all(). Get the type of the parameter (not this) using a fixed numbering. Number 1 is the first parameter in the methods Selector. No matter if the function has an implicit this pointer. Use all() if you want to get all parameter-types.

Parameters:

no - the number in the Selector

Returns:

the type of the parameter

firstOf

public ParameterAccessor.Parameter firstOf(TypeName tName)

First parameter in the selector that matches _exactly_.

Returns:

first parameter found or null if there is none

Throws:

IllegalArgumentException - if searching for void or null

firstOf

public ParameterAccessor.Parameter firstOf(TypeReference tRef)

First parameter in the selector that matches _exactly_.

Returns:

first parameter found or null if there is none

Throws:

IllegalArgumentException - if searching for void or null

allExtend

public List<ParameterAccessor.Parameter> allExtend(TypeName tName,
                                          IClassHierarchy cha)

All parameters in the selector that are a subclass of tName (slow). TypeNames have to be looked up first, do prefer the variant with the TypeReference if one is available.

Throws:

IllegalArgumentException - if searching for void or null

allExtend

public List<ParameterAccessor.Parameter> allExtend(TypeReference tRef,
                                          IClassHierarchy cha)

All parameters in the selector that are a subclass of tRef (slow).

Throws:

IllegalArgumentException - if searching for void or null

firstExtends

public ParameterAccessor.Parameter firstExtends(TypeName tName,
                                       IClassHierarchy cha)

First parameter in the selector that is a subclass of tName (slow). TypeNames have to be lloked up first, do prefer the variant with the TypeReference if one is available.

Returns:

first parameter found or null if there is none

Throws:

IllegalArgumentException - if searching for void or null

firstExtends

public ParameterAccessor.Parameter firstExtends(TypeReference tRef,
                                       IClassHierarchy cha)

First parameter in the selector that is a subclass of tRef (slow).

Returns:

first parameter found or null if there is none

Throws:

IllegalArgumentException - if searching for void or null

getFirstAfter

public int getFirstAfter()

The first SSA-Number after the parameters. This is useful for making synthetic methods.

forInvokeStatic

public int[] forInvokeStatic(List<? extends SSAValue> args)

Generate the params-param for an InvokeIstruction w/o type checking.

Parameters:

args - list to build the arguments from - without implicit this

forInvokeStatic

public int[] forInvokeStatic(List<? extends SSAValue> args,
                    ParameterAccessor target,
                    IClassHierarchy cha)

Generate the params-param for an InvokeIstruction with type checking.

Parameters:

args - list to build the arguments from - without implicit this

target - the method to be called - for type checking only

cha - if types don't match exactly needed for the assignability check (may be null if that check is not wanted)

Throws:

IllegalArgumentException - if you call this method on a target that needs an implicit this

IllegalArgumentException - if args length does not match the targets param-length

IllegalArgumentException - if a parameter is unassignable

forInvokeVirtual

public int[] forInvokeVirtual(int self,
                     List<? extends SSAValue> args)

Generate the params-param for an InvokeIstruction w/o type checking.

Parameters:

self - the this-pointer to use

args - the rest of the arguments. Be shure it does not start with a this pointer. This is _not_ checked so you can use a this-pointer as an argument. However a warning is issued.

Throws:

IllegalArgumentException - if the value of self is to small in the current method

forInvokeVirtual

public int[] forInvokeVirtual(int self,
                     List<? extends SSAValue> args,
                     ParameterAccessor target,
                     IClassHierarchy cha)

Generate the params-param for an InvokeIstruction with type checking.

Parameters:

self - the this-pointer to use

args - list to build the arguments from - without implicit this

target - the method to be called - for type checking only

cha - if types don't match exactly needed for the assignability check (may be null if that check is not wanted)

Throws:

IllegalArgumentException - if you call this method on a target that needs an implicit this

IllegalArgumentException - if args length does not match the targets param-length

IllegalArgumentException - if a parameter is unassignable

connectThrough

public List<SSAValue> connectThrough(ParameterAccessor callee,
                            Set<? extends SSAValue> overrides,
                            Set<? extends SSAValue> defaults,
                            IClassHierarchy cha,
                            IInstantiator instantiator,
                            Object... instantiatorArgs)

Connects though parameters from the calling function (overridable) - CAUTION:. This functions makes is decisions based on Type-Referes only so if a TypeReference occurs multiple times in the caller or callee it may make surprising connections. The List of Parameters is generated based on the overrides, than parameters in 'this' are searched, finally we'll fall back to defaults. A "perfect match" is searched. If a parameter was not assigned yet these three sources are considdered again but cha.isAssignableFrom is used. If the parameter was still not found a value of 'null' is used. This funktion is useful when generating wrapper-functions.

Parameters:

callee - The function to generate the parameter-list for

overrides - If a parameter occurs here, it is preferred over the ones present in this

defaults - If a parameter is not present in this or the overrides, defaults are searched. If the parameter is not present there null is assigned.

cha - Optional class hierarchy for testing assignability

Returns:

the parameter-list for the call of toMethod

isAssignable

public static boolean isAssignable(TypeReference from,
                   TypeReference to,
                   IClassHierarchy cha)

Does "to x := from" hold?.

isSubclassOf

public static boolean isSubclassOf(TypeReference sub,
                   TypeReference superC,
                   IClassHierarchy cha)
                            throws ClassLookupException

Is sub a subclass of superC (or the same).

Throws:

ClassLookupException

forMethod

public MethodReference forMethod()

The method this accessor reads the parameters from.

isAssignable

protected boolean isAssignable(SSAValue from,
                   SSAValue to,
                   IClassHierarchy cha)

Does "to x := from" hold?.

forInvokeStatic

public int[] forInvokeStatic(List<? extends ParameterAccessor.Parameter> args,
                    MethodReference target,
                    IClassHierarchy cha)

Shorthand for forInvokeStatic(final List args, final ParameterAccessor target, final IClassHierarchy cha). Generates a new ParameterAccessor for target and hands the call through.

forInvokeVirtual

public int[] forInvokeVirtual(int self,
                     List<? extends ParameterAccessor.Parameter> args,
                     MethodReference target,
                     IClassHierarchy cha)

Shorthand for forInvokeVirtual(final int self, final List args, final ParameterAccessor target, final IClassHierarchy cha). Generates a new ParameterAccessor for target and hands the call through.

hasReturn

public boolean hasReturn()

If the method returns a value eg is non-void.

connectThrough

public List<SSAValue> connectThrough(ParameterAccessor callee,
                            Set<? extends SSAValue> overrides,
                            Set<? extends SSAValue> defaults,
                            IClassHierarchy cha)

Assign parameters to a call based on their type. this variant of connectThrough cannot create new instances if needed.

Parameters:

callee - The function to generate the parameter-list for

overrides - If a parameter occurs here, it is preferred over the ones present in this

defaults - If a parameter is not present in this or the overrides, defaults are searched. If the parameter is not present there null is assigned.

cha - Optional class hierarchy for testing assignability

Returns:

the parameter-list for the call of toMethod

getReturnType

public TypeReference getReturnType()

Handed through to the IMethod / MethodReference

getNumberOfParameters

public int getNumberOfParameters()

Number of parameters _excluding_ implicit this

dump

public String dump()

Extensive output for debugging purposes.

toString

public String toString()

Overrides:

toString in class Object