001: /*
002: * Copyright 1995-2003 Sun Microsystems, Inc. All Rights Reserved.
003: * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
004: *
005: * This code is free software; you can redistribute it and/or modify it
006: * under the terms of the GNU General Public License version 2 only, as
007: * published by the Free Software Foundation. Sun designates this
008: * particular file as subject to the "Classpath" exception as provided
009: * by Sun in the LICENSE file that accompanied this code.
010: *
011: * This code is distributed in the hope that it will be useful, but WITHOUT
012: * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
013: * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
014: * version 2 for more details (a copy is included in the LICENSE file that
015: * accompanied this code).
016: *
017: * You should have received a copy of the GNU General Public License version
018: * 2 along with this work; if not, write to the Free Software Foundation,
019: * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
020: *
021: * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
022: * CA 95054 USA or visit www.sun.com if you need additional information or
023: * have any questions.
024: */
025:
026: package sun.tools.asm;
027:
028: import sun.tools.java.*;
029: import java.io.IOException;
030: import java.io.DataOutputStream;
031:
032: /**
033: * This class is used to assemble the local variable table.
034: *
035: * WARNING: The contents of this source file are not part of any
036: * supported API. Code that depends on them does so at its own risk:
037: * they are subject to change or removal without notice.
038: *
039: * @author Arthur van Hoff
040: * @version 1.26, 05/05/07
041: */
042: final class LocalVariableTable {
043: LocalVariable locals[] = new LocalVariable[8];
044: int len;
045:
046: /**
047: * Define a new local variable. Merge entries where possible.
048: */
049: void define(MemberDefinition field, int slot, int from, int to) {
050: if (from >= to) {
051: return;
052: }
053: for (int i = 0; i < len; i++) {
054: if ((locals[i].field == field) && (locals[i].slot == slot)
055: && (from <= locals[i].to) && (to >= locals[i].from)) {
056: locals[i].from = Math.min(locals[i].from, from);
057: locals[i].to = Math.max(locals[i].to, to);
058: return;
059: }
060: }
061: if (len == locals.length) {
062: LocalVariable newlocals[] = new LocalVariable[len * 2];
063: System.arraycopy(locals, 0, newlocals, 0, len);
064: locals = newlocals;
065: }
066: locals[len++] = new LocalVariable(field, slot, from, to);
067: }
068:
069: /**
070: * Trim overlapping local ranges. Java forbids shadowing of
071: * locals in nested scopes, but non-nested scopes may still declare
072: * locals with the same name. Because local variable ranges are
073: * computed using flow analysis as part of assembly, it isn't
074: * possible to simply make sure variable ranges end where the
075: * enclosing lexical scope ends. This method makes sure that
076: * variables with the same name don't overlap, giving priority to
077: * fields with higher slot numbers that should have appeared later
078: * in the source.
079: */
080: private void trim_ranges() {
081: for (int i = 0; i < len; i++) {
082: for (int j = i + 1; j < len; j++) {
083: if ((locals[i].field.getName() == locals[j].field
084: .getName())
085: && (locals[i].from <= locals[j].to)
086: && (locals[i].to >= locals[j].from)) {
087: // At this point we know that both ranges are
088: // the same name and there is also overlap or they abut
089: if (locals[i].slot < locals[j].slot) {
090: if (locals[i].from < locals[j].from) {
091: locals[i].to = Math.min(locals[i].to,
092: locals[j].from);
093: } else {
094: // We've detected two local variables with the
095: // same name, and the one with the greater slot
096: // number starts before the other. This order
097: // reversal may happen with locals with the same
098: // name declared in both a try body and an
099: // associated catch clause. This is rare, and
100: // we give up.
101: }
102: } else if (locals[i].slot > locals[j].slot) {
103: if (locals[i].from > locals[j].from) {
104: locals[j].to = Math.min(locals[j].to,
105: locals[i].from);
106: } else {
107: // Same situation as above; just give up.
108: }
109: } else {
110: // This case can happen if there are two variables
111: // with the same name and slot numbers, and ranges
112: // that abut. AFAIK the only way this can occur
113: // is with multiple static initializers. Punt.
114: }
115: }
116: }
117: }
118: }
119:
120: /**
121: * Write out the data.
122: */
123: void write(Environment env, DataOutputStream out, ConstantPool tab)
124: throws IOException {
125: trim_ranges();
126: out.writeShort(len);
127: for (int i = 0; i < len; i++) {
128: //System.out.println("pc=" + locals[i].from + ", len=" + (locals[i].to - locals[i].from) + ", nm=" + locals[i].field.getName() + ", slot=" + locals[i].slot);
129: out.writeShort(locals[i].from);
130: out.writeShort(locals[i].to - locals[i].from);
131: out.writeShort(tab.index(locals[i].field.getName()
132: .toString()));
133: out.writeShort(tab.index(locals[i].field.getType()
134: .getTypeSignature()));
135: out.writeShort(locals[i].slot);
136: }
137: }
138: }
|