1 /* 2 * reserved comment block 3 * DO NOT REMOVE OR ALTER! 4 */ 5 /* 6 * Licensed to the Apache Software Foundation (ASF) under one or more 7 * contributor license agreements. See the NOTICE file distributed with 8 * this work for additional information regarding copyright ownership. 9 * The ASF licenses this file to You under the Apache License, Version 2.0 10 * (the "License"); you may not use this file except in compliance with 11 * the License. You may obtain a copy of the License at 12 * 13 * http://www.apache.org/licenses/LICENSE-2.0 14 * 15 * Unless required by applicable law or agreed to in writing, software 16 * distributed under the License is distributed on an "AS IS" BASIS, 17 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 18 * See the License for the specific language governing permissions and 19 * limitations under the License. 20 */ 21 22 package com.sun.org.apache.bcel.internal.generic; 23 24 25 /** 26 * SWITCH - Branch depending on int value, generates either LOOKUPSWITCH or 27 * TABLESWITCH instruction, depending on whether the match values (int[]) can be 28 * sorted with no gaps between the numbers. 29 * 30 * @author <A HREF="mailto:markus.dahm@berlin.de">M. Dahm</A> 31 */ 32 public final class SWITCH implements CompoundInstruction { 33 private int[] match; 34 private InstructionHandle[] targets; 35 private Select instruction; 36 private int match_length; 37 38 /** 39 * Template for switch() constructs. If the match array can be 40 * sorted in ascending order with gaps no larger than max_gap 41 * between the numbers, a TABLESWITCH instruction is generated, and 42 * a LOOKUPSWITCH otherwise. The former may be more efficient, but 43 * needs more space. 44 * 45 * Note, that the key array always will be sorted, though we leave 46 * the original arrays unaltered. 47 * 48 * @param match array of match values (case 2: ... case 7: ..., etc.) 49 * @param targets the instructions to be branched to for each case 50 * @param target the default target 51 * @param max_gap maximum gap that may between case branches 52 */ 53 public SWITCH(int[] match, InstructionHandle[] targets, 54 InstructionHandle target, int max_gap) { 55 this.match = (int[])match.clone(); 56 this.targets = (InstructionHandle[])targets.clone(); 57 58 if((match_length = match.length) < 2) // (almost) empty switch, or just default 59 instruction = new TABLESWITCH(match, targets, target); 60 else { 61 sort(0, match_length - 1); 62 63 if(matchIsOrdered(max_gap)) { 64 fillup(max_gap, target); 65 66 instruction = new TABLESWITCH(this.match, this.targets, target); 67 } 68 else 69 instruction = new LOOKUPSWITCH(this.match, this.targets, target); 70 } 71 } 72 73 public SWITCH(int[] match, InstructionHandle[] targets, 74 InstructionHandle target) { 75 this(match, targets, target, 1); 76 } 77 78 private final void fillup(int max_gap, InstructionHandle target) { 79 int max_size = match_length + match_length * max_gap; 80 int[] m_vec = new int[max_size]; 81 InstructionHandle[] t_vec = new InstructionHandle[max_size]; 82 int count = 1; 83 84 m_vec[0] = match[0]; 85 t_vec[0] = targets[0]; 86 87 for(int i=1; i < match_length; i++) { 88 int prev = match[i-1]; 89 int gap = match[i] - prev; 90 91 for(int j=1; j < gap; j++) { 92 m_vec[count] = prev + j; 93 t_vec[count] = target; 94 count++; 95 } 96 97 m_vec[count] = match[i]; 98 t_vec[count] = targets[i]; 99 count++; 100 } 101 102 match = new int[count]; 103 targets = new InstructionHandle[count]; 104 105 System.arraycopy(m_vec, 0, match, 0, count); 106 System.arraycopy(t_vec, 0, targets, 0, count); 107 } 108 109 /** 110 * Sort match and targets array with QuickSort. 111 */ 112 private final void sort(int l, int r) { 113 int i = l, j = r; 114 int h, m = match[(l + r) / 2]; 115 InstructionHandle h2; 116 117 do { 118 while(match[i] < m) i++; 119 while(m < match[j]) j--; 120 121 if(i <= j) { 122 h=match[i]; match[i]=match[j]; match[j]=h; // Swap elements 123 h2=targets[i]; targets[i]=targets[j]; targets[j]=h2; // Swap instructions, too 124 i++; j--; 125 } 126 } while(i <= j); 127 128 if(l < j) sort(l, j); 129 if(i < r) sort(i, r); 130 } 131 132 /** 133 * @return match is sorted in ascending order with no gap bigger than max_gap? 134 */ 135 private final boolean matchIsOrdered(int max_gap) { 136 for(int i=1; i < match_length; i++) 137 if(match[i] - match[i-1] > max_gap) 138 return false; 139 140 return true; 141 } 142 143 public final InstructionList getInstructionList() { 144 return new InstructionList(instruction); 145 } 146 147 public final Instruction getInstruction() { 148 return instruction; 149 } 150 }