org.jboss.byteman.agent.adapter.cfg

Class BBlock

java.lang.Object

org.jboss.byteman.agent.adapter.cfg.BBlock

public class BBlock
extends Object

A Basic Block represents a segment of bytecode in a control flow graph. Basic blocks divide up the code at control flow branch points and hence there is no normal control flow internal to a block. Normal control flow will only transfer control from the end of one basic block to the start of another basic block or to the caller (via a return or throw).

If the block overlaps a try/catch region then exception control flow may transfer control from any instruction lying within the try/catch region to the the start of another basic block which handles the instruction. So, exception control flow may exit a block at a location preceding the block end but may only enter at block start.

Constructor Summary

Constructors

Constructor and Description
BBlock(CFG cfg, org.objectweb.asm.Label start, int blockIdx) construct a new basic block

Method Summary

Methods

Modifier and Type	Method and Description
void	addHandlerStarts(List<TryCatchDetails> details) record details of a try catch block handler which starts in this block
void	addTryEnds(List<TryCatchDetails> details) record details of a try catch block which ends in this block
void	addTryStarts(List<TryCatchDetails> details) record details of a try catch block which starts in this block
int	append(int instruction) add an instruction to the sequence in the block
int	append(int instruction, int operand) add an instruction with one int operand to thhe sequence in the block
int	append(int instruction, int[] operands) add an instruction with an arbitrary number of int operands to thhe sequence in the block
int	append(int instruction, int operand1, int operand2) add an instruction with two int operands to the sequence in the block
int	append(int instruction, int operand1, int operand2, int operand3) add an instruction with three int operands to thhe sequence in the block
void	append(org.objectweb.asm.Label label) install an outgoing normal control flow link
org.objectweb.asm.Label	firstOut() return the label of the first normal control flow link
List<TryCatchDetails>	getActiveTryStarts() retrieve details of all try catch blocks which are capable of generating an exception in this block
int	getBlockIdx() retrieve the index of this block in the block sequence.
CFG	getCFG() obtain the control flow graph to which this block belongs
Iterator<TryCatchDetails>	getHandlerStarts() retrieve details of all try catch block handlers whcih start in this block
int	getInstruction(int index) retirn the instruction at a given index.
int	getInstructionArg(int index, int argIndex) retrieve the integer operand or encoded name associated with a particular instruction
int	getInstructionCount() return the number of instructions in the blocks instructuion sequence equivalent to the index of the next instruction added to the block.
org.objectweb.asm.Label	getLabel() get the primary label which idenitfies tis block.
int	getMonitorEnterCount() retrieve a count of all monitor enter instruction locations occurring in this block
Iterator<CodeLocation>	getMonitorEnters() retrieve a list of all monitor enter instruction locations occurring in this block
int	getMonitorExitCount() retrieve a count of all monitor exit instruction locations occuring in this block
Iterator<CodeLocation>	getMonitorExits() retrieve a list of all monitor exit instruction locations occurring in this block
Iterator<TryCatchDetails>	getTryEnds() retrieve details of all try catch blocks which end in this block
org.objectweb.asm.Label	next() return the label of the next block in line in the block sequence in bytecode order.
int	nOuts() return a count of the normal control flow links from this block.
org.objectweb.asm.Label	nthOut(int n) return the label of the nth normal control flow link
org.objectweb.asm.Label	secondOut() return the label of the second normal control flow link
void	setActiveTryStarts(List<TryCatchDetails> active) set the list of try starts which are active somewhere in this block.
String	toString() return a string represenattion of this block

Methods inherited from class java.lang.Object

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

Constructor Detail

BBlock

public BBlock(CFG cfg,
      org.objectweb.asm.Label start,
      int blockIdx)

construct a new basic block

Parameters:

cfg - the control flow graph it belongs to

start - the label for the start of the block

blockIdx - the index of the block which respects the order of the bytecode segments contained in each block.

Method Detail

getCFG

public CFG getCFG()

obtain the control flow graph to which this block belongs

Returns:

getLabel

public org.objectweb.asm.Label getLabel()

get the primary label which idenitfies tis block. It will be located in the block at offset 0.

Returns:

getBlockIdx

public int getBlockIdx()

retrieve the index of this block in the block sequence.

Returns:

append

public int append(int instruction)

add an instruction to the sequence in the block

Parameters:

instruction - an Opcode

Returns:

the index of the newly added instruction

append

public int append(int instruction,
         int operand)

add an instruction with one int operand to thhe sequence in the block

Parameters:

instruction - an Opcode

operand - an int operand or the code for a String operand lcoated in the cfg name table

Returns:

the index of the newly added instruction

append

public int append(int instruction,
         int operand1,
         int operand2)

add an instruction with two int operands to the sequence in the block

Parameters:

instruction - an Opcode

operand1 - an int operand or the code for a String operand lcoated in the cfg name table

operand2 - an int operand or the code for a String operand lcoated in the cfg name table

Returns:

the index of the newly added instruction

append

public int append(int instruction,
         int operand1,
         int operand2,
         int operand3)

add an instruction with three int operands to thhe sequence in the block

Parameters:

instruction - an Opcode

operand1 - an int operand or the code for a String operand lcoated in the cfg name table

operand2 - an int operand or the code for a String operand lcoated in the cfg name table

operand3 - an int operand or the code for a String operand lcoated in the cfg name table

Returns:

the index of the newly added instruction

append

public int append(int instruction,
         int[] operands)

add an instruction with an arbitrary number of int operands to thhe sequence in the block

Parameters:

instruction - an Opcode

operands - an array containing int operands or codes for String operands lcoated in the cfg name table

Returns:

the index of the newly added instruction

addTryStarts

public void addTryStarts(List<TryCatchDetails> details)

record details of a try catch block which starts in this block

Parameters:

details -

addTryEnds

public void addTryEnds(List<TryCatchDetails> details)

record details of a try catch block which ends in this block

Parameters:

details -

addHandlerStarts

public void addHandlerStarts(List<TryCatchDetails> details)

record details of a try catch block handler which starts in this block

Parameters:

details -

setActiveTryStarts

public void setActiveTryStarts(List<TryCatchDetails> active)

set the list of try starts which are active somewhere in this block.

Parameters:

active -

getTryEnds

public Iterator<TryCatchDetails> getTryEnds()

retrieve details of all try catch blocks which end in this block

Returns:

getHandlerStarts

public Iterator<TryCatchDetails> getHandlerStarts()

retrieve details of all try catch block handlers whcih start in this block

Returns:

getActiveTryStarts

public List<TryCatchDetails> getActiveTryStarts()

retrieve details of all try catch blocks which are capable of generating an exception in this block

Returns:

getMonitorEnters

public Iterator<CodeLocation> getMonitorEnters()

retrieve a list of all monitor enter instruction locations occurring in this block

Returns:

getMonitorExits

public Iterator<CodeLocation> getMonitorExits()

retrieve a list of all monitor exit instruction locations occurring in this block

Returns:

getMonitorEnterCount

public int getMonitorEnterCount()

retrieve a count of all monitor enter instruction locations occurring in this block

Returns:

getMonitorExitCount

public int getMonitorExitCount()

retrieve a count of all monitor exit instruction locations occuring in this block

Returns:

getInstructionCount

public int getInstructionCount()

return the number of instructions in the blocks instructuion sequence equivalent to the index of the next instruction added to the block.

Returns:

getInstruction

public int getInstruction(int index)

retirn the instruction at a given index.

Parameters:

index -

Returns:

getInstructionArg

public int getInstructionArg(int index,
                    int argIndex)

retrieve the integer operand or encoded name associated with a particular instruction

Parameters:

index - the index of the instruction in the block

argIndex - the index of the argument in the sequence of arguments presented when the instruction was inserted intot he block.

Returns:

append

public void append(org.objectweb.asm.Label label)

install an outgoing normal control flow link

Parameters:

label -

next

public org.objectweb.asm.Label next()

return the label of the next block in line in the block sequence in bytecode order.

Returns:

firstOut

public org.objectweb.asm.Label firstOut()

return the label of the first normal control flow link

Returns:

secondOut

public org.objectweb.asm.Label secondOut()

return the label of the second normal control flow link

Returns:

nthOut

public org.objectweb.asm.Label nthOut(int n)

return the label of the nth normal control flow link

Returns:

nOuts

public int nOuts()

return a count of the normal control flow links from this block.

Returns:

the number of outgoingnormalcontrol flow links. n.b. iterations over the links should count from 1 to nOuts() inclusive. this is the size of a 1-based collection

toString

public String toString()

return a string represenattion of this block

Overrides:

toString in class Object

Returns: