sysModel.classFile.code
Class InstructionList

java.lang.Object
  sysModel.classFile.code.InstructionList

public class InstructionList
extends java.lang.Object

Represents a list of Java instructions.

Author:

Mathias Ricken

Field Summary

protected short	_index
(package private) java.util.LinkedList<AInstruction>	_instructionList
(package private) LineNumberTable	_lnt

Constructor Summary

InstructionList(byte[] code)
Constructor.

InstructionList(byte[] code, short index)
Constructor.

InstructionList(InstructionList original)
Copy constructor.

Method Summary

boolean	advanceIndex() Advance the program index to the next instruction.
boolean	advanceIndex(int count) Advance the program index by multiple instructions.
boolean	deleteInstr(CodeAttributeInfo codeAttribute) This method deletes the instruction at the program index.
boolean	equals(java.lang.Object o) Return true if this instruction list and the other object are equal.
boolean	findInstruction(AInstruction instr) Finds the next instruction that matches the specified instruction completely and moves the program counter there.
boolean	findOpcode(byte opcode) Finds the next instruction with the specified opcode and moves the program counter there.
byte[]	getCode() Accessor for the bytecode.
short	getIndex() Accessor for the program index.
AInstruction	getInstr() Return the instruction at the program index.
short	getLength() Get the length of the instruction list.
byte	getOpcode() Return the opcode at the program index.
short	getPCFromIndex(short index) Calculate the PC for an index.
int	hashCode() Return hash code.
void	insertBeforeInstr(AInstruction instr, CodeAttributeInfo codeAttribute) This method inserts the instruction before the program counter.
void	insertInstr(AInstruction instr, CodeAttributeInfo codeAttribute) This method inserts the instruction at the program counter.
protected void	relocateBranches(AInstruction relocInstr, int ip) Relocate branches in the instruction.
boolean	rewindIndex() Rewind the program index to the previous instruction.
boolean	rewindIndex(int count) Rewind the program index by multiple instructions.
void	setCode(byte[] code) Mutator for the bytecode.
void	setIndex(int index) Mutator for the program index.
java.lang.String	toString() Return a human-readable version of the code.
java.lang.String	toString(boolean lineNumbers, boolean PCs) Return a human-readable version of the code.

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

_instructionList

java.util.LinkedList<AInstruction> _instructionList

_index

protected short _index

_lnt

LineNumberTable _lnt

Constructor Detail

InstructionList

public InstructionList(byte[] code)

Constructor.

Parameters:

code - bytecode

InstructionList

public InstructionList(InstructionList original)

Copy constructor.

Parameters:

original - original

InstructionList

public InstructionList(byte[] code,
                       short index)
                throws java.lang.IndexOutOfBoundsException

Constructor.

Parameters:

code - bytecode

index - program index.

Throws:

java.lang.IndexOutOfBoundsException

Method Detail

toString

public java.lang.String toString()

Return a human-readable version of the code.

Overrides:

toString in class java.lang.Object

Returns:

mnemonics

toString

public java.lang.String toString(boolean lineNumbers,
                                 boolean PCs)

Return a human-readable version of the code.

Parameters:

lineNumbers - print line numbers

PCs - print PC values

Returns:

mnemonics

getCode

public byte[] getCode()
               throws java.lang.IllegalStateException

Accessor for the bytecode.

Returns:

bytecode

Throws:

java.lang.IllegalStateException

setCode

public void setCode(byte[] code)

Mutator for the bytecode. This also resets the program counter to 0.

Parameters:

code - bytecode

getIndex

public short getIndex()

Accessor for the program index.

Returns:

program index

getPCFromIndex

public short getPCFromIndex(short index)

Calculate the PC for an index.

Parameters:

index - index

Returns:

PC

getLength

public short getLength()

Get the length of the instruction list.

Returns:

length

setIndex

public void setIndex(int index)
              throws java.lang.IndexOutOfBoundsException,
                     java.lang.IllegalArgumentException

Mutator for the program index.

Parameters:

index - new program index

Throws:

java.lang.IndexOutOfBoundsException

java.lang.IllegalArgumentException

advanceIndex

public boolean advanceIndex(int count)

Advance the program index by multiple instructions.

Parameters:

count - number of instructions

Returns:

true while the end of the instruction list has not been reached

advanceIndex

public boolean advanceIndex()

Advance the program index to the next instruction.

Returns:

true while the end of the instruction list has not been reached

rewindIndex

public boolean rewindIndex(int count)

Rewind the program index by multiple instructions.

Parameters:

count - number of instructions

Returns:

true while the beginning of the instruction list has not been reached

rewindIndex

public boolean rewindIndex()

Rewind the program index to the previous instruction.

Returns:

true while the beginning of the instruction list has not been reached

getOpcode

public byte getOpcode()

Return the opcode at the program index.

Returns:

opcode at program index

getInstr

public AInstruction getInstr()

Return the instruction at the program index. This includes the code and the operands.

Returns:

instruction at program index

deleteInstr

public boolean deleteInstr(CodeAttributeInfo codeAttribute)

This method deletes the instruction at the program index. It also relocates all jumps. All jumps to places after the deletion point will be changed so that they still point to the same instruction. Jumps to the deletion point or to places before it are not changed. The index will remain unchanged. In case the program counter is past the end of the code block, false will be returned. If codeAttribute is non-null, the PCs in the CodeAttribute will be adjusted.

Parameters:

codeAttribute - CodeAttribute that contains this code block, or null if none

Returns:

true while the end of the code block has not been reached

insertInstr

public void insertInstr(AInstruction instr,
                        CodeAttributeInfo codeAttribute)

This method inserts the instruction at the program counter. The instruction currently at the program counter will be pushed towards the end of the bytecode array. It also relocates all jumps. Jumps to the insertion point or to places before it are not changed. Jumps to all other places will be changed so that they still point to the same instruction. That means that jumps to the instruction previously at the insertion point will now jump to the newly inserted instruction. If codeAttribute is non-null, the PCs in the CodeAttribute will be adjusted. The program counter will remain unchanged. If the inserted instruction itself contains jump targets, these will be relocated as well. Notice, though, that if the instruction contains a jump exactly to the insertion point, this jump will be relocated so that it points to the old instruction (this is the behavior of insertBeforeInstr).

Assume the following code: 1. a 2. b 3. c 4. goto 1 // jump to place before insertion point 5. goto 2 // jump to insertion point 6. goto 3 // junp to place after insertion point The program counter is currently at 2, and the instruction x is inserted using insertInstr. The result is: 1. a 2. x // inserted 3. b 4. c 5. goto 1 // not changed 6. goto 2 // not changed 7. goto 4 // changed

Relocation of branches in the instruction inserted. Type : jump to place before insertion point Action : not changed Example; goto 1 --> goto 1 Type : jump to insertion point Action : changed Example; goto 2 --> goto 3 Type : jump to place after instruction point Action : changed Example; goto 3 --> goto 4

Parameters:

codeAttribute - CodeAttribute that contains this code block, or null if none

instr - instruction to be inserted

relocateBranches

protected void relocateBranches(AInstruction relocInstr,
                                int ip)

Relocate branches in the instruction. If a branch target is to somewhere past the insertion point, it is increased by one.

Parameters:

relocInstr - instruction whose branches should be relocated

ip - insertion point

insertBeforeInstr

public void insertBeforeInstr(AInstruction instr,
                              CodeAttributeInfo codeAttribute)

This method inserts the instruction before the program counter. The instruction currently at the program counter will be pushed towards the end of the bytecode array. It also relocates all jumps. Jumps to places before the insertion point are not changed. Jumps to all other places will be changed so that they still point to the same instruction. That means that jumps to the instruction previously at the insertion point will still jump to the old instruction. If codeAttribute is non-null, the PCs in the CodeAttribute will be adjusted. The program counter will remain unchanged. If the inserted instruction itself contains jump targets, these will be relocated as well.

Assume the following code: 1. a 2. b 3. c 4. goto 1 // jump to place before insertion point 5. goto 2 // jump to insertion point 6. goto 3 // junp to place after insertion point The program counter is currently at 2, and the instruction x is inserted using insertBeforeInstr. The result is: 1. a 2. x // inserted 3. b 4. c 5. goto 1 // not changed 6. goto 3 // changed 7. goto 4 // changed

Relocation of branches in the instruction inserted. Type : jump to place before insertion point Action : not changed Example; goto 1 --> goto 1 Type : jump to insertion point Action : changed Example; goto 2 --> goto 3 Type : jump to place after instruction point Action : changed Example; goto 3 --> goto 4

Parameters:

codeAttribute - CodeAttribute that contains this code block, or null if none

instr - instruction to be inserted

findOpcode

public boolean findOpcode(byte opcode)

Finds the next instruction with the specified opcode and moves the program counter there. If the current instruction matches the opcode, the program counter will not be changed. This means that the caller is responsible for advancing the program counter after a match has been found!

Parameters:

opcode - opcode to find

Returns:

true while the end of the code block has not been reached

findInstruction

public boolean findInstruction(AInstruction instr)

Finds the next instruction that matches the specified instruction completely and moves the program counter there. A complete match requires that both the opcode and all the operands are identical. If the current instruction matches already, the program counter will not be changed. This means that the caller is responsible for advancing the program counter after a match has been found!

Parameters:

instr - instruction to find

Returns:

true while the end of the code block has not been reached

equals

public boolean equals(java.lang.Object o)

Return true if this instruction list and the other object are equal.

Overrides:

equals in class java.lang.Object

Parameters:

o - other object

Returns:

true if equal

hashCode

public int hashCode()

Return hash code.

Overrides:

hashCode in class java.lang.Object

Returns:

hash code