[Storage] Blob Storage Refactoring pt 1

storage/browser/blob/blob_data_item.h

+// Copyright (c) 2015 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.
+
+#ifndef STORAGE_BROWSER_BLOB_BLOB_DATA_ITEM_H_
+#define STORAGE_BROWSER_BLOB_BLOB_DATA_ITEM_H_
+
+#include "base/basictypes.h"
+#include "base/memory/ref_counted.h"
+#include "storage/browser/blob/shareable_file_reference.h"
+#include "storage/browser/storage_browser_export.h"
+#include "storage/common/data_element.h"
+
+namespace storage {
+class BlobDataBuilder;
+class BlobStorageContext;
+
+// Ref counted blob item.  This class owns the backing data of the blob item.
+// The backing data is immutable, and cannot change after creation.
+// The purpose of this class is to allow the resource to stick around in the
+// snapshot even after the resource was swapped in the blob (either to disk or
+// to memory) by the BlobStorageContext.
+class STORAGE_EXPORT BlobDataItem
+    : public base::RefCountedThreadSafe<BlobDataItem> {

[michaeln, 2015/01/22 02:18:09]

Hmmm, does this class need to be threadsafe? The ShareableFileRef class is not
threadsafe.

Until we have a usecase for iterating the items array on different threads, it
might be good to not declare this as threadsafe to avoid complications for
if/when BlobDataItems become more abstract to accomodate a things like a blobs
backed by data in a ServiceWorker Cache object.

[dmurph, 2015/01/23 00:10:18]

changed, and clarified in BlobDataHandle

+ public:
+  storage::DataElement::Type type() const { return item_->type(); }
+  const char* bytes() const { return item_->bytes(); }
+  const base::FilePath& path() const { return item_->path(); }
+  const GURL& filesystem_url() const { return item_->filesystem_url(); }
+  const std::string& blob_uuid() const { return item_->blob_uuid(); }
+  uint64 offset() const { return item_->offset(); }
+  uint64 length() const { return item_->length(); }
+  const base::Time& expected_modification_time() const {
+    return item_->expected_modification_time();
+  }
+  const DataElement& data_element() const { return *item_; }
+  const DataElement* data_element_ptr() const { return item_.get(); }
+
+ private:
+  friend class BlobDataBuilder;
+  friend class BlobStorageContext;
+  friend class base::RefCountedThreadSafe<BlobDataItem>;
+  BlobDataItem(scoped_ptr<DataElement> item);
+  BlobDataItem(scoped_ptr<DataElement> item,
+               scoped_refptr<ShareableFileReference> file_handle);
+  virtual ~BlobDataItem();
+
+  scoped_ptr<storage::DataElement> item_;
+  scoped_refptr<ShareableFileReference> file_handle_;
+};
+
+#if defined(UNIT_TEST)
+inline bool operator==(const BlobDataItem& a, const BlobDataItem& b) {
+  return a.data_element() == b.data_element();
+}
+
+inline bool operator!=(const BlobDataItem& a, const BlobDataItem& b) {
+  return !(a == b);
+}
+#endif  // defined(UNIT_TEST)
+
+}  // namespace storage
+
+#endif  // STORAGE_BROWSER_BLOB_BLOB_DATA_ITEM_H_