Handle invalid usage cache file path

webkit/fileapi/file_system_usage_cache.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 "webkit/fileapi/file_system_usage_cache.h"
 
 #include "base/file_path.h"
 #include "base/file_util.h"
 #include "base/pickle.h"
 
@@ skipping 112 matching lines @@
 bool FileSystemUsageCache::Delete(const FilePath& usage_file_path) {
   return file_util::Delete(usage_file_path, true);
 }
 
 // static
 int64 FileSystemUsageCache::Read(const FilePath& usage_file_path,
                                  bool* is_valid,
                                  uint32* dirty) {
   char buffer[kUsageFileSize];
   const char *header;
-  DCHECK(!usage_file_path.empty());
-  if (kUsageFileSize !=
-      file_util::ReadFile(usage_file_path, buffer, kUsageFileSize))
+  if (usage_file_path.empty() ||
+      kUsageFileSize != file_util::ReadFile(usage_file_path,
+                                            buffer, kUsageFileSize))
     return -1;
   Pickle read_pickle(buffer, kUsageFileSize);
   PickleIterator iter(read_pickle);
   int64 fs_usage;
 
   if (!read_pickle.ReadBytes(&iter, &header, kUsageFileHeaderSize) ||
       !read_pickle.ReadBool(&iter, is_valid) ||
       !read_pickle.ReadUInt32(&iter, dirty) ||
       !read_pickle.ReadInt64(&iter, &fs_usage))
     return -1;
@@ skipping 11 matching lines @@
 int FileSystemUsageCache::Write(const FilePath& usage_file_path,
                                 bool is_valid,
                                 uint32 dirty,
                                 int64 fs_usage) {
   Pickle write_pickle;
   write_pickle.WriteBytes(kUsageFileHeader, kUsageFileHeaderSize);
   write_pickle.WriteBool(is_valid);
   write_pickle.WriteUInt32(dirty);
   write_pickle.WriteInt64(fs_usage);
 
-  DCHECK(!usage_file_path.empty());
   FilePath temporary_usage_file_path;
-  if (!file_util::CreateTemporaryFileInDir(usage_file_path.DirName(),
+  if (usage_file_path.empty() ||
+      !file_util::CreateTemporaryFileInDir(usage_file_path.DirName(),
                                            &temporary_usage_file_path)) {
     return -1;
   }
 
   int bytes_written = file_util::WriteFile(temporary_usage_file_path,
                                            (const char *)write_pickle.data(),
                                            write_pickle.size());
   if (bytes_written != kUsageFileSize)
     return -1;
 
   if (file_util::ReplaceFile(temporary_usage_file_path, usage_file_path))
     return bytes_written;
   else
     return -1;
 }
 
 }  // namespace fileapi