/*
* reserved comment block
* DO NOT REMOVE OR ALTER!
*/
package com.sun.org.apache.bcel.internal.generic;
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import java.io.*;
import com.sun.org.apache.bcel.internal.util.ByteSequence;
import com.sun.org.apache.bcel.internal.classfile.Utility;
import com.sun.org.apache.bcel.internal.Constants;
/**
* Abstract super class for instructions dealing with local variables.
*
* @version $Id: LocalVariableInstruction.java,v 1.1.2.1 2005/07/31 23:45:45 jeffsuttor Exp $
* @author <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A>
*/
public abstract class LocalVariableInstruction extends Instruction
implements TypedInstruction, IndexedInstruction {
protected int n = -1; // index of referenced variable
private short c_tag = -1; // compact version, such as ILOAD_0
private short canon_tag = -1; // canonical tag such as ILOAD
private final boolean wide() { return n > Constants.MAX_BYTE; }
/**
* Empty constructor needed for the Class.newInstance() statement in
* Instruction.readInstruction(). Not to be used otherwise.
* tag and length are defined in readInstruction and initFromFile, respectively.
*/
LocalVariableInstruction(short canon_tag, short c_tag) {
super();
this.canon_tag = canon_tag;
this.c_tag = c_tag;
}
/**
* Empty constructor needed for the Class.newInstance() statement in
* Instruction.readInstruction(). Also used by IINC()!
*/
LocalVariableInstruction() {
}
/**
* @param opcode Instruction opcode
* @param c_tag Instruction number for compact version, ALOAD_0, e.g.
* @param n local variable index (unsigned short)
*/
protected LocalVariableInstruction(short opcode, short c_tag, int n) {
super(opcode, (short)2);
this.c_tag = c_tag;
canon_tag = opcode;
setIndex(n);
}
/**
* Dump instruction as byte code to stream out.
* @param out Output stream
*/
public void dump(DataOutputStream out) throws IOException {
if(wide()) // Need WIDE prefix ?
out.writeByte(Constants.WIDE);
out.writeByte(opcode);
if(length > 1) { // Otherwise ILOAD_n, instruction, e.g.
if(wide())
out.writeShort(n);
else
out.writeByte(n);
}
}
/**
* Long output format:
*
* <name of opcode> "["<opcode number>"]"
* "("<length of instruction>")" "<"< local variable index>">"
*
* @param verbose long/short format switch
* @return mnemonic for instruction
*/
public String toString(boolean verbose) {
if(((opcode >= Constants.ILOAD_0) &&
(opcode <= Constants.ALOAD_3)) ||
((opcode >= Constants.ISTORE_0) &&
(opcode <= Constants.ASTORE_3)))
return super.toString(verbose);
else
return super.toString(verbose) + " " + n;
}
/**
* Read needed data (e.g. index) from file.
* PRE: (ILOAD <= tag <= ALOAD_3) || (ISTORE <= tag <= ASTORE_3)
*/
protected void initFromFile(ByteSequence bytes, boolean wide)
throws IOException
{
if(wide) {
n = bytes.readUnsignedShort();
length = 4;
} else if(((opcode >= Constants.ILOAD) &&
(opcode <= Constants.ALOAD)) ||
((opcode >= Constants.ISTORE) &&
(opcode <= Constants.ASTORE))) {
n = bytes.readUnsignedByte();
length = 2;
} else if(opcode <= Constants.ALOAD_3) { // compact load instruction such as ILOAD_2
n = (opcode - Constants.ILOAD_0) % 4;
length = 1;
} else { // Assert ISTORE_0 <= tag <= ASTORE_3
n = (opcode - Constants.ISTORE_0) % 4;
length = 1;
}
}
/**
* @return local variable index referred by this instruction.
*/
public final int getIndex() { return n; }
/**
* Set the local variable index
*/
public void setIndex(int n) {
if((n < 0) || (n > Constants.MAX_SHORT))
throw new ClassGenException("Illegal value: " + n);
this.n = n;
if(n >= 0 && n <= 3) { // Use more compact instruction xLOAD_n
opcode = (short)(c_tag + n);
length = 1;
} else {
opcode = canon_tag;
if(wide()) // Need WIDE prefix ?
length = 4;
else
length = 2;
}
}
/** @return canonical tag for instruction, e.g., ALOAD for ALOAD_0
*/
public short getCanonicalTag() {
return canon_tag;
}
/**
* Returns the type associated with the instruction -
* in case of ALOAD or ASTORE Type.OBJECT is returned.
* This is just a bit incorrect, because ALOAD and ASTORE
* may work on every ReferenceType (including Type.NULL) and
* ASTORE may even work on a ReturnaddressType .
* @return type associated with the instruction
*/
public Type getType(ConstantPoolGen cp) {
switch(canon_tag) {
case Constants.ILOAD: case Constants.ISTORE:
return Type.INT;
case Constants.LLOAD: case Constants.LSTORE:
return Type.LONG;
case Constants.DLOAD: case Constants.DSTORE:
return Type.DOUBLE;
case Constants.FLOAD: case Constants.FSTORE:
return Type.FLOAT;
case Constants.ALOAD: case Constants.ASTORE:
return Type.OBJECT;
default: throw new ClassGenException("Oops: unknown case in switch" + canon_tag);
}
}
}