[BlobAsync] Asynchronous Blob Construction Final Patch

storage/browser/blob/blob_data_handle.h

 // Copyright (c) 2013 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_HANDLE_H_
 #define STORAGE_BROWSER_BLOB_BLOB_DATA_HANDLE_H_
 
 #include <string>
 
+#include "base/callback_forward.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "base/supports_user_data.h"
 #include "storage/browser/storage_browser_export.h"
 
 namespace base {
 class SequencedTaskRunner;
 }
@@ skipping 13 matching lines @@
 // is not intended to be persisted, and serves to ensure that the backing
 // resources remain around for the duration of reading the blob.  This snapshot
 // can be read on any thread, but it must be destructed on the IO thread.
 // This object has delete semantics and may be deleted on any thread.
 class STORAGE_EXPORT BlobDataHandle
     : public base::SupportsUserData::Data {
  public:
   BlobDataHandle(const BlobDataHandle& other);  // May be copied on any thread.
   ~BlobDataHandle() override;                   // May be deleted on any thread.
 
+  // Returns if this blob is still constructing. If so, one can use the
+  // RunOnConstructionComplete to wait.
+  // Must be called on IO thread.
+  bool IsBeingBuilt() const;
+
+  // Returns if this blob is broken, and there is no data associated with it.
+  // Must be called on IO thread.
+  bool IsBroken() const;
+
+  // The callback will be run on the IO thread when construction of the blob
+  // is complete. If construction is already complete, then the task is run
+  // immediately on the current message loop (i.e. IO thread).
+  // Must be called on IO thread.  Returns if construction successful.
+  // Calling this multiple times results in registering multiple
+  // completion callbacks.
+  void RunOnConstructionComplete(const base::Callback<void(bool)>& done);
+
   // A BlobReader is used to read the data from the blob.  This object is
   // intended to be transient and should not be stored for any extended period
   // of time.
   scoped_ptr<BlobReader> CreateReader(
       FileSystemContext* file_system_context,
       base::SequencedTaskRunner* file_task_runner) const;
 
   // May be accessed on any thread.
   const std::string& uuid() const;
   // May be accessed on any thread.
   const std::string& content_type() const;
   // May be accessed on any thread.
   const std::string& content_disposition() const;
 
   // This call and the destruction of the returned snapshot must be called
-  // on the IO thread.
+  // on the IO thread. If the blob is broken, then we return a nullptr here.
+  // Please do not call this, and use CreateReader instead. It appropriately
+  // waits until the blob is built before having a size (see CalculateSize).
   // TODO(dmurph): Make this protected, where only the BlobReader can call it.
   scoped_ptr<BlobDataSnapshot> CreateSnapshot() const;
 
  private:
   // Internal class whose destructor is guarenteed to be called on the IO
   // thread.
   class BlobDataHandleShared
       : public base::RefCountedThreadSafe<BlobDataHandleShared> {
    public:
     BlobDataHandleShared(const std::string& uuid,
                          const std::string& content_type,
                          const std::string& content_disposition,
                          BlobStorageContext* context);
 
+    void RunOnConstructionComplete(const base::Callback<void(bool)>& done);
+
     scoped_ptr<BlobDataSnapshot> CreateSnapshot() const;
 
    private:
     friend class base::DeleteHelper<BlobDataHandleShared>;
     friend class base::RefCountedThreadSafe<BlobDataHandleShared>;
     friend class BlobDataHandle;
 
     virtual ~BlobDataHandleShared();
 
     const std::string uuid_;
@@ skipping 11 matching lines @@
                  BlobStorageContext* context,
                  base::SequencedTaskRunner* io_task_runner);
 
   scoped_refptr<base::SequencedTaskRunner> io_task_runner_;
   scoped_refptr<BlobDataHandleShared> shared_;
 };
 
 }  // namespace storage
 
 #endif  // STORAGE_BROWSER_BLOB_BLOB_DATA_HANDLE_H_