1// Copyright 2017 The Chromium OS Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#include "bsdiff/diff_encoder.h"
6
7#include <vector>
8
9#include "bsdiff/logging.h"
10
11namespace {
12
13// The maximum positive number that we should encode. A number larger than this
14// for unsigned fields will be interpreted as a negative value and thus a
15// corrupt patch.
16const uint64_t kMaxEncodedUint64Value = (1ULL << 63) - 1;
17
18}  // namespace
19
20namespace bsdiff {
21
22bool DiffEncoder::Init() {
23  return patch_->Init(new_size_);
24}
25
26bool DiffEncoder::AddControlEntry(const ControlEntry& entry) {
27  if (entry.diff_size > kMaxEncodedUint64Value) {
28    LOG(ERROR) << "Encoding value out of range " << entry.diff_size;
29    return false;
30  }
31
32  if (entry.extra_size > kMaxEncodedUint64Value) {
33    LOG(ERROR) << "Encoding value out of range " << entry.extra_size;
34    return false;
35  }
36
37  // entry.diff_size + entry.extra_size don't overflow in uint64_t since we
38  // checked the kMaxEncodedUint64Value limit before.
39  if (entry.diff_size + entry.extra_size > new_size_ - written_output_) {
40    LOG(ERROR) << "Wrote more output than the declared new_size";
41    return false;
42  }
43
44  if (entry.diff_size > 0 &&
45      (old_pos_ < 0 ||
46       static_cast<uint64_t>(old_pos_) + entry.diff_size > old_size_)) {
47    LOG(ERROR) << "The pointer in the old stream [" << old_pos_ << ", "
48               << (static_cast<uint64_t>(old_pos_) + entry.diff_size)
49               << ") is out of bounds [0, " << old_size_ << ")";
50    return false;
51  }
52
53  // Pass down the control entry.
54  if (!patch_->AddControlEntry(entry))
55    return false;
56
57  // Generate the diff stream.
58  std::vector<uint8_t> diff(entry.diff_size);
59  for (uint64_t i = 0; i < entry.diff_size; ++i) {
60    diff[i] = new_buf_[written_output_ + i] - old_buf_[old_pos_ + i];
61  }
62  if (!patch_->WriteDiffStream(diff.data(), diff.size())) {
63    LOG(ERROR) << "Writing " << diff.size() << " bytes to the diff stream";
64    return false;
65  }
66
67  if (!patch_->WriteExtraStream(new_buf_ + written_output_ + entry.diff_size,
68                                entry.extra_size)) {
69    LOG(ERROR) << "Writing " << entry.extra_size
70               << " bytes to the extra stream";
71    return false;
72  }
73
74  old_pos_ += entry.diff_size + entry.offset_increment;
75  written_output_ += entry.diff_size + entry.extra_size;
76
77  return true;
78}
79
80bool DiffEncoder::Close() {
81  if (written_output_ != new_size_) {
82    LOG(ERROR) << "Close() called but not all the output was written";
83    return false;
84  }
85  return patch_->Close();
86}
87
88}  // namespace bsdiff
89