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Class espresso.classfile.classgen.Instruction 

java.lang.Object
   |
   +----espresso.classfile.classgen.Instruction
public abstract class Instruction
extends Object
implements Constants, Cloneable
This abstract class is the super class for all java byte codes.

Variable Index

o length
o position
o tag

Constructor Index

o Instruction()
Empty constructor needed for the Class.newInstance() statement in Instruction.readInstruction().
o Instruction(short, short)

Method Index

o consumeStack()
o copy()
Use with caution, since `BranchInstruction's have a `target' reference which is not copied correctly (only basic types are).
o dump(DataOutputStream)
Dump instruction as byte code to stream out.
o getLength()
o getPosition()
o getTag()
o initFromFile(ByteSequence, boolean)
Read needed data (e.g.
o produceStack()
o readInstruction(ByteSequence)
Read an instruction from (byte code) input stream and return the appropiate object.
o setPosition(int)
Update position of instruction
o setTag(short)
Needed in readInstruction.
o toString()
o updatePosition(int, int)
Called by InstructionList.setPositions when setting the position for every instruction.

Variables

o position 
 protected int position
o length 
 protected short length
o tag 
 protected short tag

Constructors

o Instruction 
 Instruction()
Empty constructor needed for the Class.newInstance() statement in Instruction.readInstruction(). Not to be used otherwise.

o Instruction 
 public Instruction(short tag,
                    short length)

Methods

o dump 
 public void dump(DataOutputStream out) throws IOException
Dump instruction as byte code to stream out.

Parameters:
out - Output stream
o updatePosition 
 protected int updatePosition(int offset,
                              int max_offset)
Called by InstructionList.setPositions when setting the position for every instruction. In the presence of variable length instructions `setPositions' performs multiple passes over the instruction list to calculate the correct (byte) positions and offsets by calling this function.

Parameters:
offset - additional offset caused by preceding (variable length) instructions
max_offset - the maximum offset that may be caused by these instructions
Returns:
additional offset caused by possible change of this instruction's length
o toString 
 public String toString()
Returns:
mnemonic for instruction
Overrides:
toString in class Object
o copy 
 Instruction copy()
Use with caution, since `BranchInstruction's have a `target' reference which is not copied correctly (only basic types are). This also applies for `Select' instructions with their multiple branch targets. Used by BranchHandle.setTarget()

Returns:
(shallow) copy of an instruction
See Also:
BranchHandle
o initFromFile 
 protected void initFromFile(ByteSequence bytes,
                             boolean wide) throws IOException
Read needed data (e.g. index) from file.

o readInstruction 
 public static final Instruction readInstruction(ByteSequence bytes) throws IOException
Read an instruction from (byte code) input stream and return the appropiate object.

Parameters:
file - file to read from
Returns:
instruction object being read
o consumeStack 
 public int consumeStack()
Returns:
Number of words consumed from stack by this instruction
o produceStack 
 public int produceStack()
Returns:
Number of words produced onto stack by this instruction
o getTag 
 public short getTag()
Returns:
opcode number
o getLength 
 public int getLength()
Returns:
length (in bytes) of instruction
o getPosition 
 public int getPosition()
Returns:
(absolute) position in byte code of this instruction in the current method.
o setPosition 
 public void setPosition(int position)
Update position of instruction

o setTag 
 private void setTag(short tag)
Needed in readInstruction. 

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