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      1 /*
      2  * ProGuard -- shrinking, optimization, obfuscation, and preverification
      3  *             of Java bytecode.
      4  *
      5  * Copyright (c) 2002-2009 Eric Lafortune (eric (at) graphics.cornell.edu)
      6  *
      7  * This program is free software; you can redistribute it and/or modify it
      8  * under the terms of the GNU General Public License as published by the Free
      9  * Software Foundation; either version 2 of the License, or (at your option)
     10  * any later version.
     11  *
     12  * This program is distributed in the hope that it will be useful, but WITHOUT
     13  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
     14  * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
     15  * more details.
     16  *
     17  * You should have received a copy of the GNU General Public License along
     18  * with this program; if not, write to the Free Software Foundation, Inc.,
     19  * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
     20  */
     21 package proguard.classfile.attribute.preverification;
     22 
     23 import proguard.classfile.*;
     24 import proguard.classfile.attribute.CodeAttribute;
     25 import proguard.classfile.attribute.preverification.visitor.StackMapFrameVisitor;
     26 
     27 /**
     28  * This abstract class represents a stack map frame. Specific types
     29  * of entries are subclassed from it.
     30  *
     31  * @author Eric Lafortune
     32  */
     33 public abstract class StackMapFrame implements VisitorAccepter
     34 {
     35     public static final int SAME_ZERO_FRAME          =   0;
     36     public static final int SAME_ONE_FRAME           =  64;
     37     public static final int SAME_ONE_FRAME_EXTENDED  = 247;
     38     public static final int LESS_ZERO_FRAME          = 248;
     39     public static final int SAME_ZERO_FRAME_EXTENDED = 251;
     40     public static final int MORE_ZERO_FRAME          = 252;
     41     public static final int FULL_FRAME               = 255;
     42 
     43 
     44     public int u2offsetDelta;
     45 
     46     /**
     47      * An extra field in which visitors can store information.
     48      */
     49     public Object visitorInfo;
     50 
     51 
     52 
     53     /**
     54      * Returns the bytecode offset delta relative to the previous stack map
     55      * frame.
     56      */
     57     public int getOffsetDelta()
     58     {
     59         return u2offsetDelta;
     60     }
     61 
     62 
     63     // Abstract methods to be implemented by extensions.
     64 
     65     /**
     66      * Returns the stack map frame tag that specifies the entry type.
     67      */
     68     public abstract int getTag();
     69 
     70 
     71     /**
     72      * Accepts the given visitor.
     73      */
     74     public abstract void accept(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, StackMapFrameVisitor stackMapFrameVisitor);
     75 
     76 
     77     // Implementations for VisitorAccepter.
     78 
     79     public Object getVisitorInfo()
     80     {
     81         return visitorInfo;
     82     }
     83 
     84     public void setVisitorInfo(Object visitorInfo)
     85     {
     86         this.visitorInfo = visitorInfo;
     87     }
     88 
     89 
     90     // Implementations for Object.
     91 
     92     public boolean equals(Object object)
     93     {
     94         if (object == null ||
     95             this.getClass() != object.getClass())
     96         {
     97             return false;
     98         }
     99 
    100         StackMapFrame other = (StackMapFrame)object;
    101 
    102         return this.u2offsetDelta == other.u2offsetDelta;
    103     }
    104 
    105 
    106     public int hashCode()
    107     {
    108         return getClass().hashCode() ^
    109                u2offsetDelta;
    110     }
    111 
    112 
    113     public String toString()
    114     {
    115         return "[" + u2offsetDelta + "] ";
    116     }
    117 }
    118