Instruction_branch.java example

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/* Soot - a J*va Optimization Framework
 * Copyright (C) 1997 Clark Verbrugge
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

/*
 * Modified by the Sable Research Group and others 1997-1999.  
 * See the 'credits' file distributed with Soot for the complete list of
 * contributors.  (Soot is distributed at http://www.sable.mcgill.ca/soot)
 */







package soot.coffi;
import soot.*;
/** Instruction subclasses are used to represent parsed bytecode; each
 * bytecode operation has a corresponding subclass of Instruction.
 * <p>
 * Each subclass is derived from one of
 * <ul><li>Instruction</li>
 * <li>Instruction_noargs (an Instruction with no embedded arguments)</li>
 * <li>Instruction_byte (an Instruction with a single byte data argument)</li>
 * <li>Instruction_bytevar (a byte argument specifying a local variable)</li>
 * <li>Instruction_byteindex (a byte argument specifying a constant pool index)</li>
 * <li>Instruction_int (an Instruction with a single short data argument)</li>
 * <li>Instruction_intvar (a short argument specifying a local variable)</li>
 * <li>Instruction_intindex (a short argument specifying a constant pool index)</li>
 * <li>Instruction_intbranch (a short argument specifying a code offset)</li>
 * <li>Instruction_longbranch (an int argument specifying a code offset)</li>
 * </ul>
 * @author Clark Verbrugge
 * @see Instruction
 * @see Instruction_noargs
 * @see Instruction_byte
 * @see Instruction_bytevar
 * @see Instruction_byteindex
 * @see Instruction_int
 * @see Instruction_intvar
 * @see Instruction_intindex
 * @see Instruction_intbranch
 * @see Instruction_longbranch
 * @see Instruction_Unknown
 */
abstract class Instruction_branch extends Instruction {
   public int arg_i;
   public Instruction target;         // pointer to target instruction
   public Instruction_branch(byte c) { super(c); branches = true; }

   public String toString(cp_info constant_pool[]) {
      return super.toString(constant_pool) + argsep 
	  + "[label_" + Integer.toString(target.label) + "]";
   }

   public void offsetToPointer(ByteCode bc) {
      target = bc.locateInst(arg_i+label);
      if (target==null) {
         G.v().out.println("Warning: can't locate target of instruction");
         G.v().out.println(" which should be at byte address " + (label+arg_i));
      } else
         target.labelled = true;
   }
   // returns the array of instructions which might be the target of a
   // branch with this instruction, assuming the next instruction is next
   public Instruction[] branchpoints(Instruction next) {
      Instruction i[] = new Instruction[2];
      i[0] = target; i[1] = next;
      return i;
   }

    public String toString()
    {
	return super.toString()+ "\t"+target.label;
    }
}