Blimp: Add BlobChannelReceiver and bindings interface.

blimp/net/blob_channel/blob_channel_receiver.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 BLIMP_NET_BLOB_CHANNEL_BLOB_CHANNEL_RECEIVER_H_
+#define BLIMP_NET_BLOB_CHANNEL_BLOB_CHANNEL_RECEIVER_H_
+
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "base/synchronization/lock.h"
+#include "blimp/common/blob_cache/blob_cache.h"
+#include "blimp/net/blimp_message_processor.h"
+#include "blimp/net/blimp_net_export.h"
+
+namespace blimp {
+
+class BlobCache;
+
+// Receives blobs from a remote sender.
+// Can be accessed concurrently from any thread.

[Wez, 2016/04/21 22:52:50]

That's a very strong statement for a not-ref-counted class.  

I think you meant to put this comment on Get(), with a stern warning about the
caller being responsible for making sure that the instance is not deleted while
any threads might want to call Get() on it.

[Kevin M, 2016/04/22 00:21:24]

Done.

+class BLIMP_NET_EXPORT BlobChannelReceiver {
+ public:
+  class Delegate {
+   public:
+    Delegate();
+    virtual ~Delegate();
+
+   protected:
+    // Forwards incoming blob data to |receiver_|.
+    void OnBlobReceived(const BlobId& id, BlobDataPtr data);
+
+   private:
+    friend class BlobChannelReceiver;
+
+    // Sets the Receiver object which will take incoming blobs.
+    void SetReceiver(BlobChannelReceiver* receiver);
+
+    BlobChannelReceiver* receiver_ = nullptr;
+
+    DISALLOW_COPY_AND_ASSIGN(Delegate);
+  };
+
+  BlobChannelReceiver(std::unique_ptr<BlobCache> cache,
+                      std::unique_ptr<Delegate> delegate);
+  ~BlobChannelReceiver();
+
+  // Gets a blob from the BlobChannel.
+  // Returns nullptr if the blob is not available in the channel.
+  BlobDataPtr Get(const BlobId& id);
+
+ private:
+  friend class Delegate;
+
+  // Called by Delegate::OnBlobReceived() when a blob arrives over the channel.
+  void OnBlobReceived(const BlobId& id, BlobDataPtr data);
+
+  std::unique_ptr<BlobCache> cache_;
+  std::unique_ptr<Delegate> delegate_;
+
+  // Guards against concurrent access to |cache_|.
+  base::Lock lock_;
+
+  DISALLOW_COPY_AND_ASSIGN(BlobChannelReceiver);
+};
+
+}  // namespace blimp
+
+#endif  // BLIMP_NET_BLOB_CHANNEL_BLOB_CHANNEL_RECEIVER_H_