org.apache.bcel.verifier.structurals

Class Subroutines


public class Subroutines
extends java.lang.Object

Instances of this class contain information about the subroutines found in a code array of a method. This implementation considers the top-level (the instructions reachable without a JSR or JSR_W starting off from the first instruction in a code array of a method) being a special subroutine; see getTopLevel() for that. Please note that the definition of subroutines in the Java Virtual Machine Specification, Second Edition is somewhat incomplete. Therefore, JustIce uses an own, more rigid notion. Basically, a subroutine is a piece of code that starts at the target of a JSR of JSR_W instruction and ends at a corresponding RET instruction. Note also that the control flow of a subroutine may be complex and non-linear; and that subroutines may be nested. JustIce also mandates subroutines not to be protected by exception handling code (for the sake of control flow predictability). To understand JustIce's notion of subroutines, please read TODO: refer to the paper.
Version:
$Id: Subroutines.java 386056 2006-03-15 11:31:56Z tcurdt $
Author:
Enver Haase
See Also:
getTopLevel()

Nested Class Summary

private class
Subroutines.SubroutineImpl
This inner class implements the Subroutine interface.

Field Summary

private static Integer
BLACK
private static Integer
GRAY
Subroutine
TOPLEVEL
This is referring to a special subroutine, namely the top level.
private static Integer
WHITE
private Hashtable
subroutines
The Hashtable containing the subroutines found.

Constructor Summary

Subroutines(MethodGen mg)
Constructor.

Method Summary

Subroutine
getSubroutine(InstructionHandle leader)
Returns the Subroutine object associated with the given leader (that is, the first instruction of the subroutine).
private static InstructionHandle[]
getSuccessors(InstructionHandle instruction)
A utility method that calculates the successors of a given InstructionHandle in the same subroutine.
Subroutine
getTopLevel()
For easy handling, the piece of code that is not a subroutine, the top-level, is also modeled as a Subroutine object.
private void
noRecursiveCalls(Subroutine sub, Set set)
This (recursive) utility method makes sure that no subroutine is calling a subroutine that uses the same local variable for the RET as themselves (recursively).
Subroutine
subroutineOf(InstructionHandle any)
Returns the subroutine object associated with the given instruction.
String
toString()
Returns a String representation of this object; merely for debugging puposes.

Field Details

BLACK

private static final Integer BLACK

GRAY

private static final Integer GRAY

TOPLEVEL

public final Subroutine TOPLEVEL
This is referring to a special subroutine, namely the top level. This is not really a subroutine but we use it to distinguish between top level instructions and unreachable instructions.

WHITE

private static final Integer WHITE

subroutines

private Hashtable subroutines
The Hashtable containing the subroutines found. Key: InstructionHandle of the leader of the subroutine. Elements: SubroutineImpl objects.

Constructor Details

Subroutines

public Subroutines(MethodGen mg)
Constructor.
Parameters:
mg - A MethodGen object representing method to create the Subroutine objects of.

Method Details

getSubroutine

public Subroutine getSubroutine(InstructionHandle leader)
Returns the Subroutine object associated with the given leader (that is, the first instruction of the subroutine). You must not use this to get the top-level instructions modeled as a Subroutine object.
See Also:
getTopLevel()

getSuccessors

private static InstructionHandle[] getSuccessors(InstructionHandle instruction)
A utility method that calculates the successors of a given InstructionHandle in the same subroutine. That means, a RET does not have any successors as defined here. A JsrInstruction has its physical successor as its successor (opposed to its target) as defined here.

getTopLevel

public Subroutine getTopLevel()
For easy handling, the piece of code that is not a subroutine, the top-level, is also modeled as a Subroutine object. It is a special Subroutine object where you must not invoke getEnteringJsrInstructions() or getLeavingRET().

noRecursiveCalls

private void noRecursiveCalls(Subroutine sub,
                              Set set)
This (recursive) utility method makes sure that no subroutine is calling a subroutine that uses the same local variable for the RET as themselves (recursively). This includes that subroutines may not call themselves recursively, even not through intermediate calls to other subroutines.

subroutineOf

public Subroutine subroutineOf(InstructionHandle any)
Returns the subroutine object associated with the given instruction. This is a costly operation, you should consider using getSubroutine(InstructionHandle). Returns 'null' if the given InstructionHandle lies in so-called 'dead code', i.e. code that can never be executed.

toString

public String toString()
Returns a String representation of this object; merely for debugging puposes.