J. Duke | 319a3b9 | 2007-12-01 00:00:00 +0000 | [diff] [blame^] | 1 | /* |
| 2 | * Copyright 1995-2003 Sun Microsystems, Inc. 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. Sun designates this |
| 8 | * particular file as subject to the "Classpath" exception as provided |
| 9 | * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
| 22 | * CA 95054 USA or visit www.sun.com if you need additional information or |
| 23 | * have any 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 | */ |
| 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 | */ |
| 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 | */ |
| 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 | } |