1 /* 2 * Copyright (c) 2009, 2018, 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 24 25 package org.graalvm.compiler.bytecode; 26 27 /** 28 * An abstract class that provides the state and methods common to {@link Bytecodes#LOOKUPSWITCH} 29 * and {@link Bytecodes#TABLESWITCH} instructions. 30 */ 31 public abstract class BytecodeSwitch { 32 33 /** 34 * The {@link BytecodeStream} containing the bytecode array. 35 */ 36 protected final BytecodeStream stream; 37 /** 38 * Index of start of switch instruction. 39 */ 40 protected final int bci; 41 /** 42 * Index of the start of the additional data for the switch instruction, aligned to a multiple 43 * of four from the method start. 44 */ 45 protected final int alignedBci; 46 47 /** 48 * Constructor for a {@link BytecodeStream}. 49 * 50 * @param stream the {@code BytecodeStream} containing the switch instruction 51 * @param bci the index in the stream of the switch instruction 52 */ 53 public BytecodeSwitch(BytecodeStream stream, int bci) { 54 this.stream = stream; 55 this.bci = bci; 56 this.alignedBci = (bci + 4) & 0xfffffffc; 57 } 58 59 /** 60 * Gets the current bytecode index. 61 * 62 * @return the current bytecode index 63 */ 64 public int bci() { 65 return bci; 66 } 67 68 /** 69 * Gets the index of the instruction denoted by the {@code i}'th switch target. 70 * 71 * @param i index of the switch target 72 * @return the index of the instruction denoted by the {@code i}'th switch target 73 */ 74 public int targetAt(int i) { 75 return bci + offsetAt(i); 76 } 77 78 /** 79 * Gets the index of the instruction for the default switch target. 80 * 81 * @return the index of the instruction for the default switch target 82 */ 83 public int defaultTarget() { 84 return bci + defaultOffset(); 85 } 86 87 /** 88 * Gets the offset from the start of the switch instruction to the default switch target. 89 * 90 * @return the offset to the default switch target 91 */ 92 public int defaultOffset() { 93 return stream.readInt(alignedBci); 94 } 95 96 /** 97 * Gets the key at {@code i}'th switch target index. 98 * 99 * @param i the switch target index 100 * @return the key at {@code i}'th switch target index 101 */ 102 public abstract int keyAt(int i); 103 104 /** 105 * Gets the offset from the start of the switch instruction for the {@code i}'th switch target. 106 * 107 * @param i the switch target index 108 * @return the offset to the {@code i}'th switch target 109 */ 110 public abstract int offsetAt(int i); 111 112 /** 113 * Gets the number of switch targets. 114 * 115 * @return the number of switch targets 116 */ 117 public abstract int numberOfCases(); 118 119 /** 120 * Gets the total size in bytes of the switch instruction. 121 * 122 * @return the total size in bytes of the switch instruction 123 */ 124 public abstract int size(); 125 126 }