ExceptionHandlerFilter.java revision db267bc191f906f55eaef21a27110cce2ec57fdf 
1/*
2 * ProGuard -- shrinking, optimization, obfuscation, and preverification
3 *             of Java bytecode.
4 *
5 * Copyright (c) 2002-2009 Eric Lafortune (eric@graphics.cornell.edu)
6 *
7 * This program is free software; you can redistribute it and/or modify it
8 * under the terms of the GNU General Public License as published by the Free
9 * Software Foundation; either version 2 of the License, or (at your option)
10 * any later version.
11 *
12 * This program is distributed in the hope that it will be useful, but WITHOUT
13 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
15 * more details.
16 *
17 * You should have received a copy of the GNU General Public License along
18 * with this program; if not, write to the Free Software Foundation, Inc.,
19 * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
20 */
21package proguard.classfile.visitor;
22
23import proguard.classfile.*;
24import proguard.classfile.attribute.*;
25import proguard.classfile.attribute.visitor.ExceptionInfoVisitor;
26
27/**
28 * This <code>ExceptionInfoVisitor</code> delegates its visits to another given
29 * <code>ExceptionInfoVisitor</code>, but only when the visited exception
30 * targets an instruction in the given range of offsets.
31 *
32 * @author Eric Lafortune
33 */
34public class ExceptionHandlerFilter
35implements   ExceptionInfoVisitor
36{
37    private final int                  startOffset;
38    private final int                  endOffset;
39    private final ExceptionInfoVisitor exceptionInfoVisitor;
40
41
42    /**
43     * Creates a new ExceptionHandlerFilter.
44     * @param startOffset          the start of the instruction offset range.
45     * @param endOffset            the end of the instruction offset range.
46     * @param exceptionInfoVisitor the ExceptionInfoVisitor to which visits
47     *                             will be delegated.
48     */
49    public ExceptionHandlerFilter(int                  startOffset,
50                                  int                  endOffset,
51                                  ExceptionInfoVisitor exceptionInfoVisitor)
52    {
53        this.startOffset          = startOffset;
54        this.endOffset            = endOffset;
55        this.exceptionInfoVisitor = exceptionInfoVisitor;
56    }
57
58
59    // Implementations for ExceptionInfoVisitor.
60
61    public void visitExceptionInfo(Clazz clazz, Method method, CodeAttribute codeAttribute, ExceptionInfo exceptionInfo)
62    {
63        int handlerPC = exceptionInfo.u2handlerPC;
64        if (handlerPC >= startOffset &&
65            handlerPC <  endOffset)
66        {
67            exceptionInfoVisitor.visitExceptionInfo(clazz, method, codeAttribute, exceptionInfo);
68        }
69    }
70}