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102 lines
3.3 KiB
102 lines
3.3 KiB
//
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// Copyright (C) 2017 The Android Open Source Project
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//
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#include "update_engine/payload_consumer/extent_reader.h"
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#include <algorithm>
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#include <sys/types.h>
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#include <unistd.h>
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#include "update_engine/common/utils.h"
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#include "update_engine/payload_consumer/payload_constants.h"
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using google::protobuf::RepeatedPtrField;
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namespace chromeos_update_engine {
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bool DirectExtentReader::Init(FileDescriptorPtr fd,
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const RepeatedPtrField<Extent>& extents,
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uint32_t block_size) {
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fd_ = fd;
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extents_ = extents;
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block_size_ = block_size;
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cur_extent_ = extents_.begin();
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extents_upper_bounds_.reserve(extents_.size() + 1);
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// We add this pad as the first element to not bother with boundary checks
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// later.
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extents_upper_bounds_.emplace_back(0);
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for (const auto& extent : extents_) {
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total_size_ += extent.num_blocks() * block_size_;
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extents_upper_bounds_.emplace_back(total_size_);
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}
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return true;
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}
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bool DirectExtentReader::Seek(uint64_t offset) {
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TEST_AND_RETURN_FALSE(offset <= total_size_);
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if (offset_ == offset) {
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return true;
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}
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// The first item is zero and upper_bound never returns it because it always
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// return the item which is greater than the given value.
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auto extent_idx =
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std::upper_bound(
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extents_upper_bounds_.begin(), extents_upper_bounds_.end(), offset) -
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extents_upper_bounds_.begin() - 1;
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cur_extent_ = std::next(extents_.begin(), extent_idx);
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offset_ = offset;
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cur_extent_bytes_read_ = offset_ - extents_upper_bounds_[extent_idx];
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return true;
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}
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bool DirectExtentReader::Read(void* buffer, size_t count) {
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auto bytes = reinterpret_cast<uint8_t*>(buffer);
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uint64_t bytes_read = 0;
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while (bytes_read < count) {
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if (cur_extent_ == extents_.end()) {
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TEST_AND_RETURN_FALSE(bytes_read == count);
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}
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uint64_t cur_extent_bytes_left =
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cur_extent_->num_blocks() * block_size_ - cur_extent_bytes_read_;
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uint64_t bytes_to_read =
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std::min(count - bytes_read, cur_extent_bytes_left);
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ssize_t out_bytes_read;
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TEST_AND_RETURN_FALSE(utils::ReadAll(
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fd_,
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bytes + bytes_read,
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bytes_to_read,
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cur_extent_->start_block() * block_size_ + cur_extent_bytes_read_,
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&out_bytes_read));
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TEST_AND_RETURN_FALSE(out_bytes_read ==
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static_cast<ssize_t>(bytes_to_read));
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bytes_read += bytes_to_read;
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cur_extent_bytes_read_ += bytes_to_read;
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offset_ += bytes_to_read;
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if (cur_extent_bytes_read_ == cur_extent_->num_blocks() * block_size_) {
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// We have to advance the cur_extent_;
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cur_extent_++;
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cur_extent_bytes_read_ = 0;
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}
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}
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return true;
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}
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} // namespace chromeos_update_engine
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