1 /* 2 * Copyright (c) 1995, 2003, 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. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 26 package sun.tools.asm; 27 28 import sun.tools.java.*; 29 import java.io.IOException; 30 import java.io.DataOutputStream; 31 32 /** 33 * This class is used to assemble the local variable table. 34 * 35 * WARNING: The contents of this source file are not part of any 36 * supported API. Code that depends on them does so at its own risk: 37 * they are subject to change or removal without notice. 38 * 39 * @author Arthur van Hoff 40 */ 41 final 42 class LocalVariableTable { 43 LocalVariable locals[] = new LocalVariable[8]; 44 int len; 45 46 /** 47 * Define a new local variable. Merge entries where possible. 48 */ define(MemberDefinition field, int slot, int from, int to)49 void define(MemberDefinition field, int slot, int from, int to) { 50 if (from >= to) { 51 return; 52 } 53 for (int i = 0 ; i < len ; i++) { 54 if ((locals[i].field == field) && (locals[i].slot == slot) && 55 (from <= locals[i].to) && (to >= locals[i].from)) { 56 locals[i].from = Math.min(locals[i].from, from); 57 locals[i].to = Math.max(locals[i].to, to); 58 return; 59 } 60 } 61 if (len == locals.length) { 62 LocalVariable newlocals[] = new LocalVariable[len * 2]; 63 System.arraycopy(locals, 0, newlocals, 0, len); 64 locals = newlocals; 65 } 66 locals[len++] = new LocalVariable(field, slot, from, to); 67 } 68 69 /** 70 * Trim overlapping local ranges. Java forbids shadowing of 71 * locals in nested scopes, but non-nested scopes may still declare 72 * locals with the same name. Because local variable ranges are 73 * computed using flow analysis as part of assembly, it isn't 74 * possible to simply make sure variable ranges end where the 75 * enclosing lexical scope ends. This method makes sure that 76 * variables with the same name don't overlap, giving priority to 77 * fields with higher slot numbers that should have appeared later 78 * in the source. 79 */ trim_ranges()80 private void trim_ranges() { 81 for (int i=0; i<len; i++) { 82 for (int j=i+1; j<len; j++) { 83 if ((locals[i].field.getName()==locals[j].field.getName()) 84 && (locals[i].from <= locals[j].to) 85 && (locals[i].to >= locals[j].from)) { 86 // At this point we know that both ranges are 87 // the same name and there is also overlap or they abut 88 if (locals[i].slot < locals[j].slot) { 89 if (locals[i].from < locals[j].from) { 90 locals[i].to = Math.min(locals[i].to, locals[j].from); 91 } else { 92 // We've detected two local variables with the 93 // same name, and the one with the greater slot 94 // number starts before the other. This order 95 // reversal may happen with locals with the same 96 // name declared in both a try body and an 97 // associated catch clause. This is rare, and 98 // we give up. 99 } 100 } else if (locals[i].slot > locals[j].slot) { 101 if (locals[i].from > locals[j].from) { 102 locals[j].to = Math.min(locals[j].to, locals[i].from); 103 } else { 104 // Same situation as above; just give up. 105 } 106 } else { 107 // This case can happen if there are two variables 108 // with the same name and slot numbers, and ranges 109 // that abut. AFAIK the only way this can occur 110 // is with multiple static initializers. Punt. 111 } 112 } 113 } 114 } 115 } 116 117 /** 118 * Write out the data. 119 */ write(Environment env, DataOutputStream out, ConstantPool tab)120 void write(Environment env, DataOutputStream out, ConstantPool tab) throws IOException { 121 trim_ranges(); 122 out.writeShort(len); 123 for (int i = 0 ; i < len ; i++) { 124 //System.out.println("pc=" + locals[i].from + ", len=" + (locals[i].to - locals[i].from) + ", nm=" + locals[i].field.getName() + ", slot=" + locals[i].slot); 125 out.writeShort(locals[i].from); 126 out.writeShort(locals[i].to - locals[i].from); 127 out.writeShort(tab.index(locals[i].field.getName().toString())); 128 out.writeShort(tab.index(locals[i].field.getType().getTypeSignature())); 129 out.writeShort(locals[i].slot); 130 } 131 } 132 } 133