DexBackedTryBlock.java revision 380ca70a2ccb583d391e4b965dcb29eb2c6f386b 
1/*
2 * Copyright 2012, Google Inc.
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions are
7 * met:
8 *
9 *     * Redistributions of source code must retain the above copyright
10 * notice, this list of conditions and the following disclaimer.
11 *     * Redistributions in binary form must reproduce the above
12 * copyright notice, this list of conditions and the following disclaimer
13 * in the documentation and/or other materials provided with the
14 * distribution.
15 *     * Neither the name of Google Inc. nor the names of its
16 * contributors may be used to endorse or promote products derived from
17 * this software without specific prior written permission.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
20 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
21 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
22 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
23 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
24 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
25 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
26 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
27 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
28 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
29 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
30 */
31
32package org.jf.dexlib2.dexbacked;
33
34import org.jf.dexlib2.dexbacked.util.InstructionOffsetMap;
35import org.jf.dexlib2.iface.ExceptionHandler;
36import org.jf.dexlib2.iface.TryBlock;
37import org.jf.dexlib2.dexbacked.util.VariableSizeList;
38
39import javax.annotation.Nonnull;
40import java.util.List;
41
42public class DexBackedTryBlock implements TryBlock {
43    public final DexBuffer dexBuf;
44    private final InstructionOffsetMap instructionOffsetMap;
45
46    public final int startIndex;
47    public final int instructionCount;
48
49    private final int exceptionHandlersOffset;
50
51    private static final int START_ADDRESS_OFFSET = 0;
52    private static final int CODE_UNIT_COUNT_OFFSET = 4;
53    private static final int HANDLER_OFFSET_OFFSET = 6;
54
55    public DexBackedTryBlock(DexBuffer dexBuf,
56                             int tryItemOffset,
57                             int handlersStartOffset,
58                             InstructionOffsetMap instructionOffsetMap) {
59        this.dexBuf = dexBuf;
60        this.instructionOffsetMap = instructionOffsetMap;
61
62        int startOffset = dexBuf.readSmallUint(tryItemOffset + START_ADDRESS_OFFSET);
63        // map the code unit offset to the instruction index
64        this.startIndex = instructionOffsetMap.getInstructionIndexAtOffsetExact(startOffset);
65
66        int codeUnitCount = dexBuf.readUshort(tryItemOffset + CODE_UNIT_COUNT_OFFSET);
67        // TODO: check if dalivk accepts insns_size = 0
68        if (codeUnitCount == 0) {
69            this.instructionCount = 0;
70        } else {
71            int lastIndex = instructionOffsetMap.getInstructionIndexAtOffset(startOffset + codeUnitCount - 1);
72            this.instructionCount = lastIndex - startIndex + 1;
73        }
74
75        this.exceptionHandlersOffset = handlersStartOffset + dexBuf.readUshort(tryItemOffset + HANDLER_OFFSET_OFFSET);
76    }
77
78    @Override public int getStartIndex() { return startIndex; }
79    @Override public int getInstructionCount() { return instructionCount; }
80
81    @Nonnull
82    @Override
83    public List<? extends ExceptionHandler> getExceptionHandlers() {
84        DexReader reader = dexBuf.readerAt(exceptionHandlersOffset);
85        final int encodedSize = reader.readSleb128();
86
87        if (encodedSize > 0) {
88            //no catch-all
89            return new VariableSizeList<ExceptionHandler>(dexBuf, reader.getOffset()) {
90                @Nonnull
91                @Override
92                protected ExceptionHandler readItem(DexReader reader, int index) {
93                    return new DexBackedExceptionHandler(reader, instructionOffsetMap);
94                }
95
96                @Override
97                protected void skipItem(DexReader dexReader, int index) {
98                    DexBackedExceptionHandler.skipFrom(dexReader);
99                }
100
101                @Override public int size() { return encodedSize; }
102            };
103        } else {
104            //with catch-all
105            final int sizeWithCatchAll = (-1 * encodedSize) + 1;
106            return new VariableSizeList<ExceptionHandler>(dexBuf, reader.getOffset()) {
107                @Nonnull
108                @Override
109                protected ExceptionHandler readItem(DexReader dexReader, int index) {
110                    if (index == sizeWithCatchAll-1) {
111                        return new DexBackedCatchAllExceptionHandler(dexReader, instructionOffsetMap);
112                    } else {
113                        return new DexBackedExceptionHandler(dexReader, instructionOffsetMap);
114                    }
115                }
116
117                @Override
118                protected void skipItem(DexReader dexReader, int index) {
119                    if (index == sizeWithCatchAll-1) {
120                        DexBackedCatchAllExceptionHandler.skipFrom(dexReader);
121                    } else {
122                        DexBackedExceptionHandler.skipFrom(dexReader);
123                    }
124
125                }
126
127                @Override public int size() { return sizeWithCatchAll; }
128            };
129        }
130    }
131}
132