100 lines
3.0 KiB
C++
100 lines
3.0 KiB
C++
//
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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/cached_file_descriptor.h"
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#include <unistd.h>
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#include <algorithm>
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#include <base/logging.h>
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#include "update_engine/common/utils.h"
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namespace chromeos_update_engine {
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off64_t CachedFileDescriptorBase::Seek(off64_t offset, int whence) {
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// Only support SEEK_SET and SEEK_CUR. I think these two would be enough. If
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// we want to support SEEK_END then we have to figure out the size of the
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// underlying file descriptor each time and it may not be a very good idea.
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CHECK(whence == SEEK_SET || whence == SEEK_CUR);
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off64_t next_offset = whence == SEEK_SET ? offset : offset_ + offset;
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if (next_offset != offset_) {
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// We sought somewhere other than what we are now. So we have to flush and
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// move to the new offset.
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if (!FlushCache()) {
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return -1;
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}
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// Then we have to seek there.
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if (GetFd()->Seek(next_offset, SEEK_SET) < 0) {
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return -1;
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}
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offset_ = next_offset;
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}
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return offset_;
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}
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ssize_t CachedFileDescriptorBase::Write(const void* buf, size_t count) {
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auto bytes = static_cast<const uint8_t*>(buf);
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size_t total_bytes_wrote = 0;
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while (total_bytes_wrote < count) {
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auto bytes_to_cache =
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std::min(count - total_bytes_wrote, cache_.size() - bytes_cached_);
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if (bytes_to_cache > 0) { // Which means |cache_| is still have some space.
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memcpy(cache_.data() + bytes_cached_,
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bytes + total_bytes_wrote,
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bytes_to_cache);
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total_bytes_wrote += bytes_to_cache;
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bytes_cached_ += bytes_to_cache;
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}
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if (bytes_cached_ == cache_.size()) {
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// Cache is full; write it to the |fd_| as long as you can.
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if (!FlushCache()) {
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return -1;
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}
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}
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}
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offset_ += total_bytes_wrote;
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return total_bytes_wrote;
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}
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bool CachedFileDescriptorBase::Flush() {
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return FlushCache() && GetFd()->Flush();
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}
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bool CachedFileDescriptorBase::Close() {
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offset_ = 0;
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return FlushCache() && GetFd()->Close();
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}
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bool CachedFileDescriptorBase::FlushCache() {
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size_t begin = 0;
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while (begin < bytes_cached_) {
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auto bytes_wrote =
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GetFd()->Write(cache_.data() + begin, bytes_cached_ - begin);
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if (bytes_wrote < 0) {
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PLOG(ERROR) << "Failed to flush cached data!";
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return false;
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}
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begin += bytes_wrote;
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}
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bytes_cached_ = 0;
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return true;
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}
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} // namespace chromeos_update_engine
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