Blimp: Add BlobChannelSender implementation

blimp/net/blob_channel/blob_channel_sender.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_SENDER_H_
+#define BLIMP_NET_BLOB_CHANNEL_BLOB_CHANNEL_SENDER_H_
+
+#include <memory>
+#include <set>
+#include <string>
+
+#include "base/macros.h"
+#include "base/threading/thread_checker.h"
+#include "blimp/common/blob_cache/blob_cache.h"
+#include "blimp/net/blimp_net_export.h"
+
+namespace blimp {
+
+// Sends blobs to a remote receiver.
+// The transport-specific details are provided by the caller using the Delegate
+// subclass.
+class BLIMP_NET_EXPORT BlobChannelSender {
+ public:
+  // Delegate interface for transport-specific implementations of blob transfer
+  // commands.
+  class Delegate {
+   public:
+    virtual ~Delegate() {}
+
+    // Send blob |id| with payload |data| to the receiver.
+    virtual void DeliverBlob(const BlobId& id, BlobDataPtr data) = 0;
+  };
+
+  BlobChannelSender(std::unique_ptr<BlobCache> cache,
+                    std::unique_ptr<Delegate> delegate);
+  ~BlobChannelSender();
+
+  // Puts a blob in the local BlobChannel. The blob can then be pushed to the
+  // remote receiver via "DeliverBlob()".
+  // Does nothing if there is already a blob |id| in the channel.
+  void Put(const BlobId& id, BlobDataPtr data);

[Wez, 2016/05/03 22:11:05]

nit: PutBlob, to match DeliverBlob below?

+
+  // Sends the blob |id| to the remote side, if the remote side doesn't already
+  // have the blob.
+  void DeliverBlob(const BlobId& id);
+
+ private:
+  std::unique_ptr<BlobCache> cache_;
+  std::unique_ptr<Delegate> delegate_;
+
+  // A set of the cache item IDs in the receiver's cache.

[Wez, 2016/05/03 22:11:05]

nit: I'd suggest:

"Used to track the item Ids in the receiver's cache. This may differ from the
set of Ids in |cache_|, for instance if an Id hasn't yet been delivered, or has
been evicted at the receiver.

[Kevin M, 2016/05/03 22:42:57]

Good suggestion, thx

+  // Allows the sender to determine if a cache item should be sent to the
+  // receiver.
+  std::set<BlobId> receiver_cache_contents_;
+
+  DISALLOW_COPY_AND_ASSIGN(BlobChannelSender);
+};
+
+}  // namespace blimp
+
+#endif  // BLIMP_NET_BLOB_CHANNEL_BLOB_CHANNEL_SENDER_H_