Preliminary work on resuming downloads whose connections have expired.

base/file_util_win.cc

 // Copyright (c) 2010 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 "base/file_util.h"
 
 #include <windows.h>
 #include <propvarutil.h>
 #include <psapi.h>
 #include <shellapi.h>
@@ skipping 182 matching lines @@
       0,
       FILE_SHARE_READ | FILE_SHARE_WRITE,
       NULL,
       CREATE_NEW,
       FILE_ATTRIBUTE_NORMAL,
       NULL);
   if (target_file != INVALID_HANDLE_VALUE)
     ::CloseHandle(target_file);
   // When writing to a network share, we may not be able to change the ACLs.
   // Ignore ACL errors then (REPLACEFILE_IGNORE_MERGE_ERRORS).
-  return ::ReplaceFile(to_path.value().c_str(),
+  BOOL replaced = ::ReplaceFile(to_path.value().c_str(),
       from_path.value().c_str(), NULL,
-      REPLACEFILE_IGNORE_MERGE_ERRORS, NULL, NULL) ? true : false;
+      REPLACEFILE_IGNORE_MERGE_ERRORS, NULL, NULL);
+
+  if (!replaced) {
+    DWORD replace_error = ::GetLastError();
+    DLOG(WARNING) << "Unable to replace file \"" << from_path.value()
+                  << "\" with \"" << to_path.value()
+                  << "\", error = " << replace_error
+                  << " (" << win_util::FormatMessage(replace_error) << ")";
+  }
+  return replaced ? true : false;
 }
 
 bool CopyFile(const FilePath& from_path, const FilePath& to_path) {
   // NOTE: I suspect we could support longer paths, but that would involve
   // analyzing all our usage of files.
   if (from_path.value().length() >= MAX_PATH ||
       to_path.value().length() >= MAX_PATH) {
     return false;
   }
   return (::CopyFile(from_path.value().c_str(), to_path.value().c_str(),
@@ skipping 878 matching lines @@
       uint8 unused = *(touch + offset);
       offset += step_size;
     }
     FreeLibrary(dll_module);
   }
 
   return true;
 }
 
 }  // namespace file_util