1 //
2 // Copyright (C) 2017 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 #include "update_engine/payload_consumer/extent_reader.h"
18
19 #include <algorithm>
20
21 #include <sys/types.h>
22 #include <unistd.h>
23
24 #include "update_engine/common/utils.h"
25 #include "update_engine/payload_consumer/payload_constants.h"
26
27 using google::protobuf::RepeatedPtrField;
28
29 namespace chromeos_update_engine {
30
Init(FileDescriptorPtr fd,const RepeatedPtrField<Extent> & extents,uint32_t block_size)31 bool DirectExtentReader::Init(FileDescriptorPtr fd,
32 const RepeatedPtrField<Extent>& extents,
33 uint32_t block_size) {
34 fd_ = fd;
35 extents_ = extents;
36 block_size_ = block_size;
37 cur_extent_ = extents_.begin();
38
39 extents_upper_bounds_.reserve(extents_.size() + 1);
40 // We add this pad as the first element to not bother with boundary checks
41 // later.
42 extents_upper_bounds_.emplace_back(0);
43 for (const auto& extent : extents_) {
44 total_size_ += extent.num_blocks() * block_size_;
45 extents_upper_bounds_.emplace_back(total_size_);
46 }
47 return true;
48 }
49
Seek(uint64_t offset)50 bool DirectExtentReader::Seek(uint64_t offset) {
51 TEST_AND_RETURN_FALSE(offset <= total_size_);
52 if (offset_ == offset) {
53 return true;
54 }
55 // The first item is zero and upper_bound never returns it because it always
56 // return the item which is greater than the given value.
57 auto extent_idx =
58 std::upper_bound(
59 extents_upper_bounds_.begin(), extents_upper_bounds_.end(), offset) -
60 extents_upper_bounds_.begin() - 1;
61 cur_extent_ = std::next(extents_.begin(), extent_idx);
62 offset_ = offset;
63 cur_extent_bytes_read_ = offset_ - extents_upper_bounds_[extent_idx];
64 return true;
65 }
66
Read(void * buffer,size_t count)67 bool DirectExtentReader::Read(void* buffer, size_t count) {
68 auto bytes = reinterpret_cast<uint8_t*>(buffer);
69 uint64_t bytes_read = 0;
70 while (bytes_read < count) {
71 if (cur_extent_ == extents_.end()) {
72 TEST_AND_RETURN_FALSE(bytes_read == count);
73 }
74 uint64_t cur_extent_bytes_left =
75 cur_extent_->num_blocks() * block_size_ - cur_extent_bytes_read_;
76 uint64_t bytes_to_read =
77 std::min(count - bytes_read, cur_extent_bytes_left);
78
79 ssize_t out_bytes_read;
80 TEST_AND_RETURN_FALSE(utils::ReadAll(
81 fd_,
82 bytes + bytes_read,
83 bytes_to_read,
84 cur_extent_->start_block() * block_size_ + cur_extent_bytes_read_,
85 &out_bytes_read));
86 TEST_AND_RETURN_FALSE(out_bytes_read ==
87 static_cast<ssize_t>(bytes_to_read));
88
89 bytes_read += bytes_to_read;
90 cur_extent_bytes_read_ += bytes_to_read;
91 offset_ += bytes_to_read;
92 if (cur_extent_bytes_read_ == cur_extent_->num_blocks() * block_size_) {
93 // We have to advance the cur_extent_;
94 cur_extent_++;
95 cur_extent_bytes_read_ = 0;
96 }
97 }
98 return true;
99 }
100
101 } // namespace chromeos_update_engine
102