linker_sleb128.h revision bcc4da9b752f0def46d63ed7b31f3f49cc2435ad 
1/*
2 * Copyright (C) 2015 The Android Open Source Project
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
7 * are met:
8 *  * Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 *  * Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in
12 *    the documentation and/or other materials provided with the
13 *    distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 */
28
29#ifndef _LINKER_SLEB128_H
30#define _LINKER_SLEB128_H
31
32#include <stdint.h>
33
34#include "linker_debug.h"
35
36// Helper classes for decoding LEB128, used in packed relocation data.
37// http://en.wikipedia.org/wiki/LEB128
38
39class sleb128_decoder {
40 public:
41  sleb128_decoder(const uint8_t* buffer, size_t count)
42      : current_(buffer), end_(buffer+count) { }
43
44  size_t pop_front() {
45    size_t value = 0;
46    static const size_t size = CHAR_BIT * sizeof(value);
47
48    size_t shift = 0;
49    uint8_t byte;
50
51    do {
52      if (current_ >= end_) {
53        __libc_fatal("sleb128_decoder ran out of bounds");
54      }
55      byte = *current_++;
56      value |= (static_cast<size_t>(byte & 127) << shift);
57      shift += 7;
58    } while (byte & 128);
59
60    if (shift < size && (byte & 64)) {
61      value |= -(static_cast<size_t>(1) << shift);
62    }
63
64    return value;
65  }
66
67 private:
68  const uint8_t* current_;
69  const uint8_t* const end_;
70};
71
72#endif // __LINKER_SLEB128_H
73