InstructionOffsetMap.java revision d1662b67fecaf835227aff3a136949a2358ccd4e 
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
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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
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13 * in the documentation and/or other materials provided with the
14 * distribution.
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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
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23 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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25 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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30 */
31
32package org.jf.dexlib2.util;
33
34import org.jf.dexlib2.iface.instruction.Instruction;
35import org.jf.util.ExceptionWithContext;
36
37import javax.annotation.Nonnull;
38import java.util.Arrays;
39import java.util.List;
40
41public class InstructionOffsetMap {
42    @Nonnull private final int[] instructionCodeOffsets;
43
44    public InstructionOffsetMap(@Nonnull List<? extends Instruction> instructions) {
45        this.instructionCodeOffsets = new int[instructions.size()];
46
47        int codeOffset = 0;
48        for (int i=0; i<instructions.size(); i++) {
49            instructionCodeOffsets[i] = codeOffset;
50            codeOffset += instructions.get(i).getCodeUnits();
51        }
52    }
53
54    public int getInstructionIndexAtCodeOffset(int codeOffset) {
55        return getInstructionIndexAtCodeOffset(codeOffset, true);
56    }
57
58    public int getInstructionIndexAtCodeOffset(int codeOffset, boolean exact) {
59        int index = Arrays.binarySearch(instructionCodeOffsets, codeOffset);
60        if (index < 0) {
61            if (exact) {
62                throw new ExceptionWithContext("No instruction at offset %d", codeOffset);
63            } else {
64                // This calculation would be incorrect if index was -1 (i.e. insertion point of 0). Luckily, we can
65                // ignore this case, because codeOffset will always be non-negative, and the code offset of the first
66                // instruction will always be 0.
67                return (~index) - 1;
68            }
69        }
70        return index;
71    }
72
73    public int getInstructionCodeOffset(int index) {
74        if (index < 0 || index >= instructionCodeOffsets.length) {
75            throw new ExceptionWithContext("Index out of bounds: %d", index);
76        }
77        return instructionCodeOffsets[index];
78    }
79}
80