net/disk_cache/simple/simple_util_win.cc

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "net/disk_cache/simple/simple_util.h"
   6
   7 #include <windows.h>
   8
   9 #include "base/files/file_util.h"
  10 #include "base/format_macros.h"
  11 #include "base/rand_util.h"
  12 #include "base/strings/stringprintf.h"
  13 #include "net/disk_cache/cache_util.h"
  14
  15 namespace disk_cache {
  16 namespace simple_util {
  17
  18 bool SimpleCacheDeleteFile(const base::FilePath& path) {
  19   // Even if a file was opened with FLAG_SHARE_DELETE, it is not possible to
  20   // create a new file with the same name until the original file is actually
  21   // deleted. To allow new files to be created with the new name right away,
  22   // the file is renamed before it is deleted.
  23
  24   // Why a random name? Because if the name was derived from our original name,
  25   // then churn on a particular cache entry could cause flakey behaviour.
  26
  27   // TODO(gavinp): Ensure these "todelete_" files are cleaned up on periodic
  28   // directory sweeps.
  29   const base::FilePath rename_target =
  30       path.DirName().AppendASCII(base::StringPrintf("todelete_%016" PRIx64,
  31                                                     base::RandUint64()));
  32
  33   bool rename_succeeded = !!MoveFile(path.value().c_str(),
  34                                      rename_target.value().c_str());
  35   if (rename_succeeded)
  36     return DeleteCacheFile(rename_target);
  37
  38   // The rename did not succeed. The fallback behaviour is to delete the file in
  39   // place, which might cause some flake.
  40   return DeleteCacheFile(path);
  41 }
  42
  43 }  // namespace simple_util
  44 }  // namespace disk_cache