Add a utility function to calculate the next slice to download

content/browser/download/download_item_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.
 
 // File method ordering: Methods in this file are in the same order as
 // in download_item_impl.h, with the following exception: The public
 // interface Start is placed in chronological order with the other
 // (private) routines that together define a DownloadItem's state
 // transitions as the download progresses.  See "Download progression
 // cascade" later in this file.
@@ skipping 27 matching lines @@
 #include "base/strings/utf_string_conversions.h"
 #include "content/browser/download/download_create_info.h"
 #include "content/browser/download/download_file.h"
 #include "content/browser/download/download_interrupt_reasons_impl.h"
 #include "content/browser/download/download_item_impl_delegate.h"
 #include "content/browser/download/download_job_factory.h"
 #include "content/browser/download/download_job_impl.h"
 #include "content/browser/download/download_net_log_parameters.h"
 #include "content/browser/download/download_request_handle.h"
 #include "content/browser/download/download_stats.h"
+#include "content/browser/download/parallel_download_utils.h"
 #include "content/browser/renderer_host/render_view_host_impl.h"
 #include "content/browser/web_contents/web_contents_impl.h"
 #include "content/public/browser/browser_context.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/content_browser_client.h"
 #include "content/public/browser/download_danger_type.h"
 #include "content/public/browser/download_interrupt_reasons.h"
 #include "content/public/browser/download_url_parameters.h"
 #include "content/public/browser/storage_partition.h"
 #include "content/public/common/content_features.h"
@@ skipping 1879 matching lines @@
                                                  site_url_);
 
   // Avoid using the WebContents even if it's still around. Resumption requests
   // are consistently routed through the no-renderer code paths so that the
   // request will not be dropped if the WebContents (and by extension, the
   // associated renderer) goes away before a response is received.
   std::unique_ptr<DownloadUrlParameters> download_params(
       new DownloadUrlParameters(GetURL(),
                                 storage_partition->GetURLRequestContext()));
   download_params->set_file_path(GetFullPath());
-  download_params->set_offset(GetReceivedBytes());
+  if (received_slices_.size() > 0) {
+    ReceivedSlice next_slice = FindNextSliceToDownload(received_slices_);
+    download_params->set_offset(next_slice.offset);
+    download_params->set_length(next_slice.received_bytes);
+  } else {
+    download_params->set_offset(GetReceivedBytes());
+  }
   download_params->set_last_modified(GetLastModifiedTime());
   download_params->set_etag(GetETag());
   download_params->set_hash_of_partial_file(hash_);
   download_params->set_hash_state(std::move(hash_state_));
 
   // Note that resumed downloads disallow redirects. Hence the referrer URL
   // (which is the contents of the Referer header for the last download request)
   // will only be sent to the URL returned by GetURL().
   download_params->set_referrer(
       Referrer(GetReferrerUrl(), blink::WebReferrerPolicyAlways));
@@ skipping 178 matching lines @@
     case RESUME_MODE_USER_CONTINUE:
       return "USER_CONTINUE";
     case RESUME_MODE_USER_RESTART:
       return "USER_RESTART";
   }
   NOTREACHED() << "Unknown resume mode " << mode;
   return "unknown";
 }
 
 }  // namespace content