1/*
2 * Copyright (C) 2015 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#ifndef _LINKER_SLEB128_H
18#define _LINKER_SLEB128_H
19
20#include <stdint.h>
21
22// Helper classes for decoding LEB128, used in packed relocation data.
23// http://en.wikipedia.org/wiki/LEB128
24
25class sleb128_decoder {
26 public:
27  sleb128_decoder(const uint8_t* buffer, size_t count)
28      : current_(buffer), end_(buffer+count) { }
29
30  size_t pop_front() {
31    size_t value = 0;
32    static const size_t size = CHAR_BIT * sizeof(value);
33
34    size_t shift = 0;
35    uint8_t byte;
36
37    do {
38      if (current_ >= end_) {
39        __libc_fatal("sleb128_decoder ran out of bounds");
40      }
41      byte = *current_++;
42      value |= (static_cast<size_t>(byte & 127) << shift);
43      shift += 7;
44    } while (byte & 128);
45
46    if (shift < size && (byte & 64)) {
47      value |= -(static_cast<size_t>(1) << shift);
48    }
49
50    return value;
51  }
52
53 private:
54  const uint8_t* current_;
55  const uint8_t* const end_;
56};
57
58#endif // __LINKER_SLEB128_H
59