1 /*
 2  * Copyright (c) 2024, 2025, 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 package jdk.incubator.code.bytecode.impl;
26 
27 import java.lang.classfile.CodeBuilder;
28 import java.lang.classfile.CodeElement;
29 import java.lang.classfile.CodeTransform;
30 import java.lang.classfile.instruction.ExceptionCatch;
31 
32 /**
33  * ExceptionTableCompactor defragments exception table.
34  */
35 public final class ExceptionTableCompactor implements CodeTransform {
36 
37     ExceptionCatch last = null;
38 
39     @Override
40     public void accept(CodeBuilder cob, CodeElement coe) {
41         if (coe instanceof ExceptionCatch ec) {
42             if (ec.tryStart() != ec.tryEnd()) {
43                 if (last != null) {
44                     if (last.handler() == ec.handler() && last.catchType().equals(ec.catchType())) {
45                         if (last.tryStart() == ec.tryEnd()) {
46                             last = ExceptionCatch.of(last.handler(), ec.tryStart(), last.tryEnd(), last.catchType());
47                             return;
48                         } else if (last.tryEnd() == ec.tryStart()) {
49                             last = ExceptionCatch.of(last.handler(), last.tryStart(), ec.tryEnd(), last.catchType());
50                             return;
51                         }
52                     }
53                     cob.with(last);
54                 }
55                 last = ec;
56             }
57         } else {
58             cob.with(coe);
59         }
60     }
61 
62     @Override
63     public void atEnd(CodeBuilder cob) {
64         if (last != null) {
65             cob.with(last);
66             last = null;
67         }
68     }
69 }