[BlobAsync] Disk support for blob storage

storage/browser/blob/blob_flattener.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_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;
+class InternalBlobData;
+class ShareableBlobDataItem;
+
+// 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.
+//
+// This class is only used once while building a blob, and is ephemeral in the
+// blob construction (the data is immediately consumed and then it gets
+// destructed).
+struct STORAGE_EXPORT BlobFlattener {
+  BlobFlattener(const BlobDataBuilder& input_builder,
+                InternalBlobData* output_blob,
+                BlobStorageRegistry* registry);
+  ~BlobFlattener();
+
+  // This can be:
+  // * DONE if we're populated and don't need quota.
+  // * PENDING if there's pending data that the user needs to
+  //   populate. This also means we need to request quota.
+  // * 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 contains all blobs referenced.
+  std::vector<std::pair<std::string, InternalBlobData*>> dependent_blobs;
+
+  // This is the total amount of quota space needed transporting this blob.
+  base::CheckedNumeric<uint64_t> transport_quota_needed;
+  std::vector<ShareableBlobDataItem*> transport_pending_items;
+
+  // Total amount of space needed for copying depending blob items.
+  base::CheckedNumeric<uint64_t> copy_quota_needed;
+  std::vector<ShareableBlobDataItem*> copy_pending_items;
+
+  // 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;
+};
+
+// This class handles the cases where the slice partially intersects with
+// either a data item (which we want to copy instead of share when it's partial
+// intersection) or a 'future file item', which isn't populated yet in the
+// source blob so we need to copy it over later when it's completed.
+struct STORAGE_EXPORT BlobSlice {
+  BlobSlice(const InternalBlobData& source,
+            uint64_t slice_offset,
+            uint64_t slice_size);
+  ~BlobSlice();
+
+  // The is the amount of memory we'll be copying from the source blob, as we
+  // can't share a partial data item. This can happen on the first and/or last
+  // item our slice is intersecting.
+  size_t copying_memory_size = 0;
+
+  size_t first_item_slice_offset = 0;
+  // Populated if our first slice item is a temporary item that we'll copy to
+  // later from this |first_source_item|, at offset |first_item_slice_offset|.
+  scoped_refptr<ShareableBlobDataItem> first_source_item;
+  // Populated if our last slice item is a temporary item that we'll copy to
+  // later from this |last_source_item|.
+  scoped_refptr<ShareableBlobDataItem> last_source_item;
+
+  std::vector<scoped_refptr<ShareableBlobDataItem>> dest_items;
+};
+
+}  // namespace storage
+#endif  // STORAGE_BROWSER_BLOB_BLOB_FLATTENER_H_