Stackable file_util for FileAPIs. Sample code for discussion. Incomplete. Cannot be compiled.

webkit/fileapi/quota_file_util.cc

+// Copyright (c) 2011 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_file_util_base.h"
+#include "webkit/fileapi/file_system_operation_context.h"
+
+#include "base/file_util.h"
+
+namespace fileapi {
+
+// static
+QuotaFileUtil* QuotaFileUtil::GetInstance() {
+  QuotaFileUtil* self = Singleton<QuotaFileUtil>::get();
+  self->next_file_util_to_quota = FileSystemFileUtilBase::GetInstance();
+  return self;
+}
+
+base::PlatformFileError QuotaFileUtil::Copy(
+    const FileSystemOperationContext& fs_context,
+    const FilePath& src_file_path,
+    const FilePath& dest_file_path) {
+  int allowed_growth = fs_context.GetAllowedGrowth();
+
+  if (allowed_growth < SIZE_MAX) {
+    const char* path_str = src_file_path.value().c_str();
+    stat_wrapper_t file_info;
+    int test = CallStat(path_str, &file_info);
+    if (test != 0)
+      return base::PLATFORM_FILE_ERROR_FAILED;
+    if (file_info.st_size > allowed_growth)
+      return base::PLATFORM_FILE_ERROR_NO_SPACE;
+  }
+
+  return next_file_util_to_quota->Copy(
+      fs_context, src_file_path, dest_file_path);
+}
+
+}  // namespace fileapi