[BlobAsync] Disk support for blob storage

storage/browser/blob/blob_flattener.h

Index: storage/browser/blob/blob_flattener.h
diff --git a/storage/browser/blob/blob_flattener.h b/storage/browser/blob/blob_flattener.h
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+// 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_FLATTENER_H_
+#define STORAGE_BROWSER_BLOB_BLOB_FLATTENER_H_
+
+#include <map>
+#include <string>
+#include <utility>
+
+#include "base/macros.h"
+#include "base/numerics/safe_math.h"
+#include "storage/browser/blob/blob_storage_registry.h"
+#include "storage/browser/blob/internal_blob_data.h"
+#include "storage/browser/storage_browser_export.h"
+
+namespace storage {
+class BlobDataBuilder;
+
+// The class takes an input BlobDataBuilder and turns it into our
+// InternalBlobData representation. This includes 'flattening' out blob
+// references by extracting the ShareableBlobDataItem slice from the reference
+// and including those items instead. The resulting flattened blob (both regular
+// items and items from other blobs) is put into the |output_blob|. We keep
+// track of edge cases like partial slicing on data or pending file entries,
+// and calculate the total & required memory for this blob.
+struct STORAGE_EXPORT BlobFlattener {
+  BlobFlattener(const BlobDataBuilder& input_builder,
+                InternalBlobData* output_blob,
+                BlobStorageRegistry* registry);
+  ~BlobFlattener();
+
+  // This can be:
+  // * DONE if we're successful,
+  // * PENDING_DATA_POPULATION if there's pending data that the user needs to
+  //   populate,
+  // * INVALID_CONSTRUCTION_ARGUMENTS if we have invalid input, or
+  // * REFERENCED_BLOB_BROKEN if one of the referenced blobs is broken or we
+  //   reference ourself.
+  BlobStatus status = BlobStatus::ERR_INVALID_CONSTRUCTION_ARGUMENTS;
+
+  // This is the total size of the blob, including all memory, files, etc.
+  base::CheckedNumeric<uint64_t> total_size;
+  // This is the new memory needed to construct the blob, including both memory
+  // items as well as copies from other blobs.
+  base::CheckedNumeric<uint64_t> memory_needed;
+
+  // This contains all blobs referenced.
+  std::vector<std::pair<std::string, InternalBlobData*>> dependent_blobs;
+
+  // These record all future copies we'll need to do from referenced blobs. This
+  // happens when we do a partial slice from a pending data or file item.
+  std::vector<InternalBlobData::ItemCopyEntry> copies;
+};
+
+}  // namespace storage
+#endif  // STORAGE_BROWSER_BLOB_BLOB_FLATTENER_H_