File	Doc	Category	Size	Date	Package
Instruction.java	API Doc	Java SE 5 API	9356	Fri Aug 26 14:55:22 BST 2005	com.sun.org.apache.bcel.internal.generic

Instruction

• java.lang.Object

Fields Summary
protected short	length
protected short	opcode

Constructors Summary
Instruction() Empty constructor needed for the Class.newInstance() statement in Instruction.readInstruction(). Not to be used otherwise. // Opcode number
public Instruction(short opcode, short length) this.length = length; this.opcode = opcode;

Methods Summary
public abstract void	accept(com.sun.org.apache.bcel.internal.generic.Visitor v) Call corresponding visitor method(s). The order is: Call visitor methods of implemented interfaces first, then call methods according to the class hierarchy in descending order, i.e., the most specific visitXXX() call comes last. param v Visitor object
private static final java.lang.String	className(short opcode) String name = Constants.OPCODE_NAMES[opcode].toUpperCase(); /* ICONST_0, etc. will be shortened to ICONST, etc., since ICONST_0 and the like * are not implemented (directly). */ try { int len = name.length(); char ch1 = name.charAt(len - 2), ch2 = name.charAt(len - 1); if((ch1 == '_") && (ch2 >= '0") && (ch2 <= '5")) name = name.substring(0, len - 2); if(name.equals("ICONST_M1")) // Special case name = "ICONST"; } catch(StringIndexOutOfBoundsException e) { System.err.println(e); } return "com.sun.org.apache.bcel.internal.generic." + name;
public int	consumeStack(com.sun.org.apache.bcel.internal.generic.ConstantPoolGen cpg) This method also gives right results for instructions whose effect on the stack depends on the constant pool entry they reference. return Number of words consumed from stack by this instruction, or Constants.UNPREDICTABLE, if this can not be computed statically return Constants.CONSUME_STACK[opcode];
public com.sun.org.apache.bcel.internal.generic.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. see BranchInstruction return (shallow) copy of an instruction Instruction i = null; // "Constant" instruction, no need to duplicate if(InstructionConstants.INSTRUCTIONS[this.getOpcode()] != null) i = this; else { try { i = (Instruction)clone(); } catch(CloneNotSupportedException e) { System.err.println(e); } } return i;
void	dispose() Some instructions may be reused, so don't do anything by default.
public void	dump(java.io.DataOutputStream out) Dump instruction as byte code to stream out. param out Output stream out.writeByte(opcode); // Common for all instructions
public int	getLength() return length (in bytes) of instruction return length;
public short	getOpcode() return this instructions opcode return opcode;
protected void	initFromFile(com.sun.org.apache.bcel.internal.util.ByteSequence bytes, boolean wide) Read needed data (e.g. index) from file. param bytes byte sequence to read from param wide "wide" instruction flag
public int	produceStack(com.sun.org.apache.bcel.internal.generic.ConstantPoolGen cpg) This method also gives right results for instructions whose effect on the stack depends on the constant pool entry they reference. return Number of words produced onto stack by this instruction, or Constants.UNPREDICTABLE, if this can not be computed statically return Constants.PRODUCE_STACK[opcode];
public static final com.sun.org.apache.bcel.internal.generic.Instruction	readInstruction(com.sun.org.apache.bcel.internal.util.ByteSequence bytes) Read an instruction from (byte code) input stream and return the appropiate object. param file file to read from return instruction object being read boolean wide = false; short opcode = (short)bytes.readUnsignedByte(); Instruction obj = null; if(opcode == Constants.WIDE) { // Read next opcode after wide byte wide = true; opcode = (short)bytes.readUnsignedByte(); } if(InstructionConstants.INSTRUCTIONS[opcode] != null) return InstructionConstants.INSTRUCTIONS[opcode]; // Used predefined immutable object, if available /* Find appropiate class, instantiate an (empty) instruction object * and initialize it by hand. */ Class clazz; try { clazz = Class.forName(className(opcode)); } catch (ClassNotFoundException cnfe){ // If a class by that name does not exist, the opcode is illegal. // Note that IMPDEP1, IMPDEP2, BREAKPOINT are also illegal in a sense. throw new ClassGenException("Illegal opcode detected."); } try { obj = (Instruction)clazz.newInstance(); if(wide && !((obj instanceof LocalVariableInstruction) || (obj instanceof IINC) || (obj instanceof RET))) throw new Exception("Illegal opcode after wide: " + opcode); obj.setOpcode(opcode); obj.initFromFile(bytes, wide); // Do further initializations, if any // Byte code offset set in InstructionList } catch(Exception e) { throw new ClassGenException(e.toString()); } return obj;
private void	setOpcode(short opcode) Needed in readInstruction. this.opcode = opcode;
public java.lang.String	toString(boolean verbose) Long output format: <name of opcode> "["<opcode number>"]" "("<length of instruction>")" param verbose long/short format switch return mnemonic for instruction if(verbose) return Constants.OPCODE_NAMES[opcode] + "[" + opcode + "](" + length + ")"; else return Constants.OPCODE_NAMES[opcode];
public java.lang.String	toString() return mnemonic for instruction in verbose format return toString(true);
public java.lang.String	toString(com.sun.org.apache.bcel.internal.classfile.ConstantPool cp) return mnemonic for instruction with sumbolic references resolved return toString(false);