[BlobAsync] Disk support for blob storage

storage/browser/blob/blob_slice.h

+// Copyright 2016 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_SLICE_H_
+#define STORAGE_BROWSER_BLOB_BLOB_SLICE_H_
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include <string>
+#include <vector>
+
+#include "base/macros.h"
+#include "storage/browser/blob/internal_blob_data.h"
+#include "storage/browser/blob/shareable_blob_data_item.h"
+
+namespace storage {
+
+struct BlobSlice {
+  BlobSlice(const InternalBlobData& source,
+            uint64_t slice_offset,
+            uint64_t slice_size);
+  ~BlobSlice();
+
+  size_t copying_memory_size = 0;

[michaeln, 2016/07/14 01:44:43]

a comment about what this is would be nice

we can't share a partial data item, so we may have to copy the relevant parts
from the first and last source items

alternatively, we might not need the data member, a method could compute it
based by summing the size of the first and last dest_items (when first_source
and last_source are non-null)

[dmurph, 2016/07/15 02:45:27]

Done.

+
+  // If our first item is a new memory item, where we are a slice of the item
+  // in the original blob. See first_item_slice_offset() and first_item_index().

[michaeln, 2016/07/14 01:44:43]

comment is stale

[dmurph, 2016/07/15 02:45:27]

Done.

+  bool has_sliced_first_memory_item = false;
+  // If our last item is a new memory item, where we are a slice of the item
+  // in the original blob.
+  bool has_sliced_last_memory_item = false;

[michaeln, 2016/07/14 01:44:43]

Since we have the first_source_item and last_source_item data members, i think
the bools are redundant. If i'm reading it right, the refptrs are set only when
we have a respective "sliced" memory item.

[dmurph, 2016/07/15 02:45:27]

Done.

+
+  size_t first_item_slice_offset = 0;
+  scoped_refptr<ShareableBlobDataItem> first_source_item;
+  scoped_refptr<ShareableBlobDataItem> last_source_item;
+
+  std::vector<scoped_refptr<ShareableBlobDataItem>> dest_items;
+};
+
+}  // namespace storage
+#endif  // STORAGE_BROWSER_BLOB_BLOB_SLICE_H_