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