Wrap large IndexedDB values into Blobs before writing to LevelDB.

third_party/WebKit/Source/modules/indexeddb/IDBRequestQueue.h

+// Copyright 2017 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 IDBRequestQueue_h
+#define IDBRequestQueue_h
+
+#include "platform/heap/Handle.h"
+#include "platform/wtf/PassRefPtr.h"
+#include "platform/wtf/RefPtr.h"
+#include "platform/wtf/Vector.h"
+
+#include <memory>
+
+namespace blink {
+
+class DOMException;
+class IDBKey;
+class IDBRequest;
+class IDBRequestLoader;
+class IDBValue;
+class WebIDBCursor;
+
+// Queues up a transaction's IDBRequest results for orderly delivery.
+//
+// The IndexedDB specification requires that the events corresponding to IDB
+// request results fire in the order in which the requests were issued. The
+// browser-side backend processes requests in order, but the Blink side may need
+// to perform post-processing on the results (e.g., large value unwrapping).

[jsbell, 2017/05/05 00:29:37]

nit: no ,

[pwnall, 2017/05/11 23:54:24]

Done.

+// When a result needs post-processing, this queue captures all results received
+// during the post-processing steps. The events for these results may only fire
+// after the post-processed result's event is fired.
+class IDBRequestQueueItem

[jsbell, 2017/05/05 00:29:37]

Filename should be IDBRequestQueueItem ?

[pwnall, 2017/05/11 23:54:24]

Done.

+    : public GarbageCollectedFinalized<IDBRequestQueueItem> {

[jsbell, 2017/05/05 00:29:37]

Why GC'd? I would imagine this would be owned by the queue.

[pwnall, 2017/05/11 23:54:24]

Done.
I was being lazy and avoiding learning about Persistent<>. I switched to
std::unique_ptr and Persistent<> here and in IDBRequestLoader.

+ public:
+  IDBRequestQueueItem(IDBRequest*, DOMException*);
+  IDBRequestQueueItem(IDBRequest*, IDBKey*);
+  IDBRequestQueueItem(IDBRequest*, PassRefPtr<IDBValue>);
+  IDBRequestQueueItem(IDBRequest*, const Vector<RefPtr<IDBValue>>&);
+  IDBRequestQueueItem(IDBRequest*,
+                      IDBKey*,
+                      IDBKey* primary_key,
+                      PassRefPtr<IDBValue>);
+  IDBRequestQueueItem(IDBRequest*,
+                      std::unique_ptr<WebIDBCursor> backend,
+                      IDBKey*,
+                      IDBKey* primary_key,
+                      PassRefPtr<IDBValue>);
+
+  // False if this result still requires post-processing.
+  inline bool IsReady() { return ready_; }
+
+  // The request whose queued result is tracked by this item.
+  inline IDBRequest* Request() { return request_; }
+
+  // Creates a IDBRequestLoader to post-process the IDBRequest's result.
+  void AttachLoader();
+
+  // Starts post-processing the IDBRequest's result.
+  //
+  // This method must be called after the IDBRequestQueueItem is enqueued into
+  // the appropriate queue, because it is possible for the loading operation to
+  // complete synchronously, in which case IDBtransaction::OnResultReady() will

[jsbell, 2017/05/05 00:29:37]

nit: IDBTransaction

[pwnall, 2017/05/11 23:54:24]

Done.

+  // be called with the (presumably) enqueued IDBRequest before this method
+  // returns.
+  void StartLoading();
+
+  // Calls the correct overload of OnSuccess/OnError on the associated request.
+  //
+  // This should only be called by the request's IDBTransaction.
+  void FireCallback();
+
+  // Marks the result as having being post-processed.
+  //
+  // This method should only be called by the associated IDBRequestLoader.
+  void MarkReady();
+  // Called when an error occurs during result post-processing.
+  //
+  // This method should only be called by the associated IDBRequestLoader.
+  void MarkReady(DOMException* error);
+
+  DECLARE_TRACE();
+
+ private:
+  // The IDBRequest callback that will be called for this result.
+  enum Mode {
+    kError,
+    kBackendKeyPrimaryKeyValue,
+    kKey,
+    kKeyPrimaryKeyValue,
+    kValue,
+    kValueArray,
+  };
+
+  // Performs post-processing on this result.
+  //
+  // nullptr for results that do not require post-processing and for results
+  // whose post-processing has completed.
+  Member<IDBRequestLoader> loader_;
+
+  // The IDBRequest that will receive a callback for this result.
+  Member<IDBRequest> request_;
+
+  // The key argument to the IDBRequest callback.
+  //
+  // Only used if mode_ is kKeyPrimaryKeyValue.
+  Member<IDBKey> key_;
+
+  // The primary_key argument to the IDBRequest callback.
+  //
+  // Only used if mode_ is kKeyPrimaryKeyValue.
+  Member<IDBKey> primary_key_;
+
+  // The error argument to the IDBRequest callback.
+  //
+  // Only used if the mode_ is kError.
+  Member<DOMException> error_;
+
+  // All the values that will be passed back to the IDBRequest.
+  Vector<RefPtr<IDBValue>> values_;
+
+  // The backend argument to the IDBRequest callback.
+  std::unique_ptr<WebIDBCursor> backend_;
+
+  // The IDBRequest callback that will be called for this result.
+  Mode mode_;
+
+  // False if this result still requires post-processing.
+  bool ready_ = true;
+
+#if DCHECK_IS_ON()
+  bool callback_fired_;
+#endif  // DCHECK_IS_ON()
+};
+
+using IDBRequestQueue = HeapDeque<Member<IDBRequestQueueItem>>;
+
+}  // namespace blink
+
+#endif  // IDBRequestQueue_h