[BlobAsync] Disk support for blob storage

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 <limits>
 #include <memory>
 #include <string>
 
 #include "base/callback_forward.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
 #include "base/supports_user_data.h"
 #include "storage/browser/storage_browser_export.h"
 #include "storage/common/blob_storage/blob_storage_constants.h"
@@ skipping 14 matching lines @@
 // that needs to keep a blob alive needs to store this handle.
 // When the blob data itself is needed, clients must call the CreateSnapshot()
 // method on the IO thread to create a snapshot of the blob data.  This snapshot
 // 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:
+  static constexpr uint64_t kUnknownSize = std::numeric_limits<uint64_t>::max();
+
   // True means the blob was constructed successfully, and false means that
   // there was an error, which is reported in the second argument.
   using BlobConstructedCallback =
       base::Callback<void(bool, IPCBlobCreationCancelCode)>;
 
   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.
@@ skipping 18 matching lines @@
   std::unique_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;
+  // May be accessed on any thread. In rare cases where the blob is created
+  // as a file from javascript, this will be kUnknownSize.
+  uint64_t size() const;
 
   // This call and the destruction of the returned snapshot must be called
   // 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.
   std::unique_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,
+                         uint64_t size,
                          BlobStorageContext* context);
 
    private:
     friend class base::DeleteHelper<BlobDataHandleShared>;
     friend class base::RefCountedThreadSafe<BlobDataHandleShared>;
     friend class BlobDataHandle;
 
     virtual ~BlobDataHandleShared();
 
     const std::string uuid_;
     const std::string content_type_;
     const std::string content_disposition_;
+    const uint64_t size_;
     base::WeakPtr<BlobStorageContext> context_;
 
     DISALLOW_COPY_AND_ASSIGN(BlobDataHandleShared);
   };
 
   friend class BlobStorageContext;
   BlobDataHandle(const std::string& uuid,
                  const std::string& content_type,
                  const std::string& content_disposition,
+                 uint64_t size,
                  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_