Android P update_engine分析--升级核心DeltaPerformer的分析
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前面几篇分析了update_engine的启动，update_engine_client的使用，boot_control的AB切换，以及update_engine的4个Action，但始终没有看到核心的部分，如何将payload.bin如何下载到目标分区的。之前一直以为是在PostinstallRunnerAction的做的，后面发现错了，升级包里根本没有Postinstall脚本。重新分析之后发现，核心的升级操作都在DownloadAction 里做的，从而牵扯出一个核心的升级类DeltaPerformer。那我们还是从我们之前分析漏了的DownloadAction内容里开始。
Writer的初始化和使用
在DownloadAction的StartDonwloading中，已经初始化了Delta_performer_和wrter_。
void DownloadAction::StartDownloading()
...
if (writer_ && writer_ != delta_performer_.get())
LOG(INFO) << "Using writer for test.";
else
//初始化delta_performer_ 和 writer_
delta_performer_.reset(new DeltaPerformer(prefs_,
boot_control_,
hardware_,
delegate_,
&install_plan_,
payload_,
is_interactive_));
writer_ = delta_performer_.get();
...
//开始下载
http_fetcher_->BeginTransfer(install_plan_.download_url);
void UpdateAttempterandroid::BuildUpdateActions(const string& url)
...
//初始化HtttpFetcher，使用FileFetcher 还是LibcurlHttpFetcher
HttpFetcher* download_fetcher = nullptr;
if (FileFetcher::SupportedUrl(url))
DLOG(INFO) << "Using FileFetcher for file URL.";
download_fetcher = new FileFetcher();
else
#ifdef _UE_SIDELOAD
LOG(FATAL) << "Unsupported sideload URI: " << url;
#else
LibcurlHttpFetcher* libcurl_fetcher =
new LibcurlHttpFetcher(&proxy_resolver_, hardware_);
libcurl_fetcher->set_server_to_check(ServerToCheck::kDownload);
download_fetcher = libcurl_fetcher;
#endif // _UE_SIDELOAD
shared_ptr<DownloadAction> download_action(
new DownloadAction(prefs_,
boot_control_,
hardware_,
nullptr, // system_state, not used.
download_fetcher, // passes ownership
true /* is_interactive */));
...
bool FileFetcher::SupportedUrl(const string& url)
// check url是不是以file:///开头
return base::StartsWith(
url, "file:///", base::CompareCase::INSENSITIVE_ASCII);
因为我们升级更多的是将升级包下载后，使用U盘或SD卡在安装，调用的方式一般使用file:///开头的，所以download_fetcher使用的是FileFetcher类。同步download_action的初始化也是用FileFetcher初始化，那我们继续分析FileFetcher.BeginTransfer(…)。
FileFetcher传输
// Begins the transfer, which must not have already been started.
void FileFetcher::BeginTransfer(const string& url)
CHECK(!transfer_in_progress_);
//再次确认是不是以file:///开头的
if (!SupportedUrl(url))
LOG(ERROR) << "Unsupported file URL: " << url;
// No HTTP error code when the URL is not supported.
http_response_code_ = 0;
CleanUp();
if (delegate_)
delegate_->TransferComplete(this, false);
return;
//从指定路径使用文件流以只读的方式打开
string file_path = url.substr(strlen("file://"));
stream_ =
brillo::FileStream::Open(base::FilePath(file_path),
brillo::Stream::AccessMode::READ,
brillo::FileStream::Disposition::OPEN_EXISTING,
nullptr);
if (!stream_)
LOG(ERROR) << "Couldn't open " << file_path;
http_response_code_ = kHttpResponseNotFound;
CleanUp();
if (delegate_)
delegate_->TransferComplete(this, false);
return;
http_response_code_ = kHttpResponseOk;
//如果有设置offset，就从指定offset开始
if (offset_)
stream_->SetPosition(offset_, nullptr);
bytes_copied_ = 0;
transfer_in_progress_ = true;
ScheduleRead();
void FileFetcher::ScheduleRead()
//检查状态
if (transfer_paused_ || ongoing_read_ || !transfer_in_progress_)
return;
//设置此次buffer读取的大小，默认为16K
buffer_.resize(kReadBufferSize);
size_t bytes_to_read = buffer_.size();
if (data_length_ >= 0)
bytes_to_read = std::min(static_cast<uint64_t>(bytes_to_read),
data_length_ - bytes_copied_);
//检查bytes_to_read是否合法
if (!bytes_to_read)
OnReadDoneCallback(0);
return;
//从文件流中开始读取bytes_to_read字节，同时设置读取完成回调和读取出错回调
ongoing_read_ = stream_->ReadAsync(
buffer_.data(),
bytes_to_read,
base::Bind(&FileFetcher::OnReadDoneCallback, base::Unretained(this)),
base::Bind(&FileFetcher::OnReadErrorCallback, base::Unretained(this)),
nullptr);
if (!ongoing_read_)
LOG(ERROR) << "Unable to schedule an asynchronous read from the stream.";
CleanUp();
if (delegate_)
delegate_->TransferComplete(this, false);
使用文件流的方式打开升级包文件，使用buffer作为下载的接收缓存，然后开始下载，每次默认下载16K，下载完成之后就会回调onReadDoneCallback。
void FileFetcher::OnReadDoneCallback(size_t bytes_read)
ongoing_read_ = false;
//如果读取数据为0，清除下载现场，同时完成传输
if (bytes_read == 0)
CleanUp();
if (delegate_)
delegate_->TransferComplete(this, true);
else
//如果有设置delegate回调，就使用回调，调用ReceivedBytes处理buffer数据
bytes_copied_ += bytes_read;
if (delegate_)
delegate_->ReceivedBytes(this, buffer_.data(), bytes_read);
ScheduleRead();
void DownloadAction::PerformAction()
http_fetcher_->set_delegate(this);
...
在DownloadAction的PerformAction中，已经设置了delegate回调，将DownloadAction对象本身做为回调delegate设置给FileFetcher。上面的ReceivedBytes调用就是调用DownloadAction的ReceivedBytes
void DownloadAction::ReceivedBytes(HttpFetcher* fetcher,
const void* bytes,
size_t length)
// Note that bytes_received_ is the current offset.
if (!p2p_file_id_.empty())
WriteToP2PFile(bytes, length, bytes_received_);
bytes_received_ += length;
uint64_t bytes_downloaded_total =
bytes_received_previous_payloads_ + bytes_received_;
//updateAttermpterAndroid也设置了downloadAction的delegate_，同时也会回调updateAttermpterAndroid的BytesReceived
if (delegate_ && download_active_)
delegate_->BytesReceived(length, bytes_downloaded_total, bytes_total_);
//调用DeltaPerformer的Write，这个是重点
if (writer_ && !writer_->Write(bytes, length, &code_))
if (code_ != ErrorCode::kSuccess)
LOG(ERROR) << "Error " << utils::ErrorCodeToString(code_) << " (" << code_
<< ") in DeltaPerformer's Write method when "
<< "processing the received payload -- Terminating processing";
....
//DownloadAction 回调UpdateAttermpterAndroid的BytesReceived，上报进度
void UpdateAttempterAndroid::BytesReceived(uint64_t bytes_progressed,
uint64_t bytes_received,
uint64_t total)
double progress = 0;
if (total)
progress = static_cast<double>(bytes_received) / static_cast<double>(total);
if (status_ != UpdateStatus::DOWNLOADING || bytes_received == total)
download_progress_ = progress;
SetStatusAndNotify(UpdateStatus::DOWNLOADING);
else
//更新进度，同时将进度上报给上层调用者
ProgressUpdate(progress);
// 更新进度到sharePerferences的文件中
int64_t current_bytes_downloaded =
metrics_utils::GetPersistedValue(kPrefsCurrentBytesDownloaded, prefs_);
int64_t total_bytes_downloaded =
metrics_utils::GetPersistedValue(kPrefsTotalBytesDownloaded, prefs_);
prefs_->SetInt64(kPrefsCurrentBytesDownloaded,
current_bytes_downloaded + bytes_progressed);
prefs_->SetInt64(kPrefsTotalBytesDownloaded,
total_bytes_downloaded + bytes_progressed);
DownloadAction的BytesReceived 一方面回调给UpdateAttempterAndroid的BytesReceived，将升级进度上报给上层调用者，同时将数据传给DeltaPerformer的write。 那这个函数是不是实际的升级动作呢，我们继续往下分析：
// Wrapper around write. Returns true if all requested bytes
// were written, or false on any error, regardless of progress
// and stores an action exit code in |error|.
bool DeltaPerformer::Write(const void* bytes, size_t count, ErrorCode *error)
*error = ErrorCode::kSuccess;
const char* c_bytes = reinterpret_cast<const char*>(bytes);
//更新下载的总数
total_bytes_received_ += count;
UpdateOverallProgress(false, "Completed ");
//当manifest_vaild 为false，即无效时，如果manifest和metadata 还没有下载，就先下载manifest和metadata数据
while (!manifest_valid_)
// Read data up to the needed limit; this is either maximium payload header
// size, or the full metadata size (once it becomes known).
const bool do_read_header = !IsHeaderParsed();
//拷贝数据到Buffer中去
CopyDataToBuffer(&c_bytes, &count,
(do_read_header ? kMaxPayloadHeaderSize :
metadata_size_ + metadata_signature_size_));
//解析metadata,并并检查是否有错
MetadataParseResult result = ParsePayloadMetadata(buffer_, error);
if (result == MetadataParseResult::kError)
return false;
if (result == MetadataParseResult::kInsufficientData)
// If we just processed the header, make an attempt on the manifest.
if (do_read_header && IsHeaderParsed())
continue;
return true;
// 检查Manifest是否有效
if ((*error = ValidateManifest()) != ErrorCode::kSuccess)
return false;
manifest_valid_ = true;
//清除buffer数据
DiscardBuffer(false, metadata_size_);
// This populates |partitions_| and the |install_plan.partitions| with the
// list of partitions from the manifest.
if (!ParseManifestPartitions(error))
return false;
// |install_plan.partitions| was filled in, nothing need to be done here if
// the payload was already applied, returns false to terminate http fetcher,
// but keep |error| as ErrorCode::kSuccess.
if (payload_->already_applied)
return false;
num_total_operations_ = 0;
for (const auto& partition : partitions_)
num_total_operations_ += partition.operations_size();
acc_num_operations_.push_back(num_total_operations_);
LOG_IF(WARNING, !prefs_->SetInt64(kPrefsManifestMetadataSize,
metadata_size_))
<< "Unable to save the manifest metadata size.";
LOG_IF(WARNING, !prefs_->SetInt64(kPrefsManifestSignatureSize,
metadata_signature_size_))
<< "Unable to save the manifest signature size.";
if (!PrimeUpdateState())
*error = ErrorCode::kDownloadStateInitializationError;
LOG(ERROR) << "Unable to prime the update state.";
return false;
if (!OpenCurrentPartition())
*error = ErrorCode::kInstallDeviceOpenError;
return false;
if (next_operation_num_ > 0)
UpdateOverallProgress(true, "Resuming after ");
LOG(INFO) << "Starting to apply update payload operations";
//开始真实下载分区里的数据
while (next_operation_num_ < num_total_operations_)
// 检查是否应该退出下载
if (download_delegate_ && download_delegate_->ShouldCancel(error))
return false;
//检查是否超过当前分区大小限制.
while (next_operation_num_ >= acc_num_operations_[current_partition_])
CloseCurrentPartition();
current_partition_++;
if (!OpenCurrentPartition())
*error = ErrorCode::kInstallDeviceOpenError;
return false;
//计算当前需要操作的分区的块数
const size_t partition_operation_num = next_operation_num_ - (
current_partition_ ? acc_num_operations_[current_partition_ - 1] : 0);
//将当前需要操作的分区块的参数封装到installOperation中
const InstallOperation& op =
partitions_[current_partition_].operations(partition_operation_num);
//将需要下载的数据拷贝到buffet_中
CopyDataToBuffer(&c_bytes, &count, op.data_length());
// 检查是否接收到了下次操作的全部数据
if (!CanPerformInstallOperation(op))
return true;
// 检查metadata的签名是否为空，如果是空，则无效
if (!payload_->metadata_signature.empty())
// Note: Validate must be called only if CanPerformInstallOperation is
// called. Otherwise, we might be failing operations before even if there
// isn't sufficient data to compute the proper hash.
*error = ValidateOperationHash(op);
if (*error != ErrorCode::kSuccess)
if (install_plan_->hash_checks_mandatory)
LOG(ERROR) << "Mandatory operation hash check failed";
return false;
// For non-mandatory cases, just send a UMA stat.
LOG(WARNING) << "Ignoring operation validation errors";
*error = ErrorCode::kSuccess;
// Makes sure we unblock exit when this operation completes.
ScopedTerminatorExitUnblocker exit_unblocker =
ScopedTerminatorExitUnblocker(); // Avoids a compiler unused var bug.
base::TimeTicks op_start_time = base::TimeTicks::Now();
bool op_result;
//根据操作的不同类型做不同的操作处理，我们使用比较多得多的是升级替代
switch (op.type())
case InstallOperation::REPLACE:
case InstallOperation::REPLACE_BZ:
case InstallOperation::REPLACE_XZ:
//执行替代的相关操作
op_result = PerformReplaceOperation(op);
OP_DURATION_HISTOGRAM("REPLACE", op_start_time);
break;
case InstallOperation::ZERO:
case InstallOperation::DISCARD:
op_result = PerformZeroOrDiscardOperation(op);
OP_DURATION_HISTOGRAM("ZERO_OR_DISCARD", op_start_time);
break;
case InstallOperation::MOVE:
op_result = PerformMoveOperation(op);
OP_DURATION_HISTOGRAM("MOVE", op_start_time);
break;
case InstallOperation::BSDIFF:
op_result = PerformBsdiffOperation(op);
OP_DURATION_HISTOGRAM("BSDIFF", op_start_time);
break;
case InstallOperation::SOURCE_COPY:
op_result = PerformSourceCopyOperation(op, error);
OP_DURATION_HISTOGRAM("SOURCE_COPY", op_start_time);
break;
case InstallOperation::SOURCE_BSDIFF:
case InstallOperation::BROTLI_BSDIFF:
op_result = PerformSourceBsdiffOperation(op, error);
OP_DURATION_HISTOGRAM("SOURCE_BSDIFF", op_start_time);
break;
case InstallOperation::PUFFDIFF:
op_result = PerformPuffDiffOperation(op, error);
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