Glue parallel download job and download file together.

content/browser/download/download_file_impl.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/download/download_file_impl.h"
 
 #include <string>
 #include <utility>
 
 #include "base/bind.h"
@@ skipping 23 matching lines @@
 const int kMaxTimeBlockingFileThreadMs = 1000;
 
 // These constants control the default retry behavior for failing renames. Each
 // retry is performed after a delay that is twice the previous delay. The
 // initial delay is specified by kInitialRenameRetryDelayMs.
 const int kInitialRenameRetryDelayMs = 200;
 
 // Number of times a failing rename is retried before giving up.
 const int kMaxRenameRetries = 3;
 
-DownloadFileImpl::SourceStream::SourceStream(int64_t offset, int64_t length)
-    : offset_(offset), length_(length), bytes_written_(0), finished_(false) {}
+DownloadFileImpl::SourceStream::SourceStream(
+    int64_t offset,
+    int64_t length,
+    std::unique_ptr<ByteStreamReader> stream_reader)
+    : offset_(offset),
+      length_(length),
+      bytes_written_(0),
+      finished_(false),
+      stream_reader_(std::move(stream_reader)) {}
 
 DownloadFileImpl::SourceStream::~SourceStream() = default;
 
-void DownloadFileImpl::SourceStream::SetByteStream(
-    std::unique_ptr<ByteStreamReader> stream_reader) {
-  stream_reader_ = std::move(stream_reader);
-}
-
 void DownloadFileImpl::SourceStream::OnWriteBytesToDisk(int64_t bytes_write) {
   bytes_written_ += bytes_write;
 }
 
 DownloadFileImpl::DownloadFileImpl(
     std::unique_ptr<DownloadSaveInfo> save_info,
     const base::FilePath& default_download_directory,
     std::unique_ptr<ByteStreamReader> stream_reader,
     const std::vector<DownloadItem::ReceivedSlice>& received_slices,
     const net::NetLogWithSource& download_item_net_log,
     bool is_sparse_file,
     base::WeakPtr<DownloadDestinationObserver> observer)
     : net_log_(
           net::NetLogWithSource::Make(download_item_net_log.net_log(),
                                       net::NetLogSourceType::DOWNLOAD_FILE)),
       file_(net_log_),
       save_info_(std::move(save_info)),
       default_download_directory_(default_download_directory),
       is_sparse_file_(is_sparse_file),
       bytes_seen_(0),
       received_slices_(received_slices),
       observer_(observer),
       weak_factory_(this) {
   source_streams_[save_info_->offset] = base::MakeUnique<SourceStream>(
-      save_info_->offset, DownloadSaveInfo::kLengthFullContent);
-  DCHECK(source_streams_.size() == static_cast<size_t>(1));
-  source_streams_[save_info_->offset]->SetByteStream(std::move(stream_reader));
+      save_info_->offset, DownloadSaveInfo::kLengthFullContent,

[qinmin, 2017/03/17 07:54:36]

actually, this is no longer true. For resumption, the length might not be
DownloadSaveInfo::kLengthFullContent.

see
https://cs.chromium.org/chromium/src/content/browser/download/download_item_i....

You either need to remove that line to make the initial request half open, or
set the length here.

[xingliu, 2017/03/17 19:08:25]

Good point, done.

+      std::move(stream_reader));
 
   download_item_net_log.AddEvent(
       net::NetLogEventType::DOWNLOAD_FILE_CREATED,
       net_log_.source().ToEventParametersCallback());
   net_log_.BeginEvent(
       net::NetLogEventType::DOWNLOAD_FILE_ACTIVE,
       download_item_net_log.source().ToEventParametersCallback());
 }
 
 DownloadFileImpl::~DownloadFileImpl() {
@@ skipping 22 matching lines @@
     BrowserThread::PostTask(
         BrowserThread::UI, FROM_HERE, base::Bind(callback, result));
     return;
   }
 
   download_start_ = base::TimeTicks::Now();
 
   // Primarily to make reset to zero in restart visible to owner.
   SendUpdate();
 
-  // Initial pull from the straw.
+  // Initial pull from the straw from all source streams.
   for (auto& source_stream : source_streams_)
     RegisterAndActivateStream(source_stream.second.get());
 
   BrowserThread::PostTask(
       BrowserThread::UI, FROM_HERE, base::Bind(
           callback, DOWNLOAD_INTERRUPT_REASON_NONE));

[asanka, 2017/03/17 17:10:09]

(not for this CL, but since you are in the neighborhood :-) )

Consider moving this before the RegisterAndActivateStream() call. Otherwise any
resulting DestinationUpdates/DestinationErrors will be scheduled ahead of the
DownloadFileInitialized call being scheduled here.

Not a big deal since this is already the case. But it's something that's
counterintuitive to someone reading the code.

[xingliu, 2017/03/17 19:08:25]

Done,

Oh, I see, thanks for this suggestion.

 }
 
 void DownloadFileImpl::AddByteStream(
     std::unique_ptr<ByteStreamReader> stream_reader,
-    int64_t offset) {
+    int64_t offset,
+    int64_t length) {
   DCHECK_CURRENTLY_ON(BrowserThread::FILE);
+  DCHECK(source_streams_.find(offset) == source_streams_.end());
 
-  // The |source_streams_| must have an existing entry for the stream reader.
-  auto current_source_stream = source_streams_.find(offset);
-  DCHECK(current_source_stream != source_streams_.end());
-  SourceStream* stream = current_source_stream->second.get();
-  stream->SetByteStream(std::move(stream_reader));
+  source_streams_[offset] =
+      base::MakeUnique<SourceStream>(offset, length, std::move(stream_reader));
 
-  RegisterAndActivateStream(stream);
+  // If the file is initialized, start to write data, or wait until file opened.
+  if (file_.in_progress())
+    RegisterAndActivateStream(source_streams_[offset].get());
 }
 
 DownloadInterruptReason DownloadFileImpl::WriteDataToFile(int64_t offset,
                                                           const char* data,
                                                           size_t data_len) {
   DCHECK_CURRENTLY_ON(BrowserThread::FILE);
   WillWriteToDisk(data_len);
   return file_.WriteDataToFile(offset, data, data_len);
 }
 
@@ skipping 291 matching lines @@
     const base::FilePath& new_path,
     const RenameCompletionCallback& completion_callback)
     : option(option),
       new_path(new_path),
       retries_left(kMaxRenameRetries),
       completion_callback(completion_callback) {}
 
 DownloadFileImpl::RenameParameters::~RenameParameters() {}
 
 }  // namespace content