1 /*
   2  * Copyright (c) 2009, 2011, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  */
  23 package org.graalvm.compiler.bytecode;
  24 
  25 /**
  26  * An abstract class that provides the state and methods common to {@link Bytecodes#LOOKUPSWITCH}
  27  * and {@link Bytecodes#TABLESWITCH} instructions.
  28  */
  29 public abstract class BytecodeSwitch {
  30 
  31     /**
  32      * The {@link BytecodeStream} containing the bytecode array.
  33      */
  34     protected final BytecodeStream stream;
  35     /**
  36      * Index of start of switch instruction.
  37      */
  38     protected final int bci;
  39     /**
  40      * Index of the start of the additional data for the switch instruction, aligned to a multiple
  41      * of four from the method start.
  42      */
  43     protected final int alignedBci;
  44 
  45     /**
  46      * Constructor for a {@link BytecodeStream}.
  47      *
  48      * @param stream the {@code BytecodeStream} containing the switch instruction
  49      * @param bci the index in the stream of the switch instruction
  50      */
  51     public BytecodeSwitch(BytecodeStream stream, int bci) {
  52         this.stream = stream;
  53         this.bci = bci;
  54         this.alignedBci = (bci + 4) & 0xfffffffc;
  55     }
  56 
  57     /**
  58      * Gets the current bytecode index.
  59      *
  60      * @return the current bytecode index
  61      */
  62     public int bci() {
  63         return bci;
  64     }
  65 
  66     /**
  67      * Gets the index of the instruction denoted by the {@code i}'th switch target.
  68      *
  69      * @param i index of the switch target
  70      * @return the index of the instruction denoted by the {@code i}'th switch target
  71      */
  72     public int targetAt(int i) {
  73         return bci + offsetAt(i);
  74     }
  75 
  76     /**
  77      * Gets the index of the instruction for the default switch target.
  78      *
  79      * @return the index of the instruction for the default switch target
  80      */
  81     public int defaultTarget() {
  82         return bci + defaultOffset();
  83     }
  84 
  85     /**
  86      * Gets the offset from the start of the switch instruction to the default switch target.
  87      *
  88      * @return the offset to the default switch target
  89      */
  90     public int defaultOffset() {
  91         return stream.readInt(alignedBci);
  92     }
  93 
  94     /**
  95      * Gets the key at {@code i}'th switch target index.
  96      *
  97      * @param i the switch target index
  98      * @return the key at {@code i}'th switch target index
  99      */
 100     public abstract int keyAt(int i);
 101 
 102     /**
 103      * Gets the offset from the start of the switch instruction for the {@code i}'th switch target.
 104      *
 105      * @param i the switch target index
 106      * @return the offset to the {@code i}'th switch target
 107      */
 108     public abstract int offsetAt(int i);
 109 
 110     /**
 111      * Gets the number of switch targets.
 112      *
 113      * @return the number of switch targets
 114      */
 115     public abstract int numberOfCases();
 116 
 117     /**
 118      * Gets the total size in bytes of the switch instruction.
 119      *
 120      * @return the total size in bytes of the switch instruction
 121      */
 122     public abstract int size();
 123 
 124 }