Download resumption - Preliminary

content/browser/download/base_file.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/base_file.h"
 
 #include "base/bind.h"
 #include "base/file_util.h"
 #include "base/format_macros.h"
 #include "base/logging.h"
@@ skipping 497 matching lines @@
 
     // We may be re-opening the file after rename. Always make sure we're
     // writing at the end of the file.
     int64 seek_result = file_stream_->SeekSync(net::FROM_END, 0);
     if (seek_result < 0)
       return ClearStream(LOG_ERROR("Seek", seek_result));
   } else {
     file_stream_->SetBoundNetLogSource(bound_net_log_);
   }
 
+  int64 file_size = file_stream_->SeekSync(net::FROM_END, 0);
+  if (file_size > bytes_so_far_) {
+    // The file is larger than we expected.
+    // This is OK, as long as we don't use the extra.
+    // Truncate the file.
+    int64 truncate_result = file_stream_->Truncate(bytes_so_far_);
+    DCHECK_EQ(bytes_so_far_, truncate_result);
+  } else if (file_size < bytes_so_far_) {
+    // The file is shorter than we expected.  Our hashes won't be valid.
+    // This will map to a generic 'FAIL' interrupt reason.
+    return LOG_ERROR("Seek", 1);  // net::ERR_UNEXPECTED.
+  }
+
   return net::OK;
 }
 
 void BaseFile::Close() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
 
   bound_net_log_.AddEvent(net::NetLog::TYPE_DOWNLOAD_FILE_CLOSED);
 
   if (file_stream_.get()) {
 #if defined(OS_CHROMEOS)
@@ skipping 28 matching lines @@
 int64 BaseFile::CurrentSpeedAtTime(base::TimeTicks current_time) const {
   base::TimeDelta diff = current_time - start_tick_;
   int64 diff_ms = diff.InMilliseconds();
   return diff_ms == 0 ? 0 : bytes_so_far() * 1000 / diff_ms;
 }
 
 int64 BaseFile::CurrentSpeed() const {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
   return CurrentSpeedAtTime(base::TimeTicks::Now());
 }