[xrd_ssi_pb] OStreamBuffer serializes Protocol Buffer objects onto the stream

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xroot_ssi_pb/XrdSsiPbOStreamBuffer.hpp

+/*!
+ * @project        The CERN Tape Archive (CTA)
+ * @brief          Output stream to send a stream of protocol buffers from server to client
+ * @copyright      Copyright 2017 CERN
+ * @license        This program is free software: you can redistribute it and/or modify
+ *                 it under the terms of the GNU General Public License as published by
+ *                 the Free Software Foundation, either version 3 of the License, or
+ *                 (at your option) any later version.
+ *
+ *                 This program is distributed in the hope that it will be useful,
+ *                 but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *                 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *                 GNU General Public License for more details.
+ *
+ *                 You should have received a copy of the GNU General Public License
+ *                 along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#pragma once
+
+#include <arpa/inet.h>
+#include <XrdSsi/XrdSsiStream.hh>
+
+namespace XrdSsiPb {
+
+/*!
+ * Stream Buffer.
+ *
+ * This class binds XrdSsiStream::Buffer to the stream interface.
+ *
+ * This is a naïve implementation, where memory is allocated and deallocated on every use.
+ *
+ * A more performant implementation could be implemented using a buffer pool, using the Recycle()
+ * method to return buffers to the pool.
+ */
+class OStreamBuffer : public XrdSsiStream::Buffer
+{
+public:
+   OStreamBuffer() : XrdSsiStream::Buffer(nullptr) {
+#ifdef XRDSSI_DEBUG
+      std::cerr << "[DEBUG] StreamBuffer() constructor" << std::endl;
+#endif
+   }
+
+   ~OStreamBuffer() {
+#ifdef XRDSSI_DEBUG
+      std::cerr << "[DEBUG] StreamBuffer() destructor" << std::endl;
+#endif
+      // data is a public member of XrdSsiStream::Buffer. It is an unmanaged char* pointer.
+      delete[] data;
+   }
+
+   //! Serialize a Protocol Buffer into the Stream Buffer and return its size
+   template<typename ProtoBuf>
+   int serialize(const ProtoBuf &pb) {
+      // Drop any existing data. A more sophisticated implementation could chain new objects onto the buffer,
+      // using XrdSsiStream::Buffer::Next
+      delete[] data;
+
+      uint32_t bytesize = pb.ByteSize();
+      data = new char[bytesize + sizeof(uint32_t)];
+
+      // Write the size into the buffer in network order
+      *reinterpret_cast<uint32_t*>(data) = htonl(bytesize);
+
+      // Serialize the Protocol Buffer
+      pb.SerializeToArray(data + sizeof(uint32_t), bytesize);
+
+      // Return the total size of the buffer including bytesize
+      return bytesize + sizeof(uint32_t);
+   }
+
+private:
+   //! Called by the XrdSsi framework when it is finished with the object
+   virtual void Recycle() {
+      std::cerr << "[DEBUG] StreamBuffer::Recycle()" << std::endl;
+      delete this;
+   }
+};
+
+} // namespace XrdSsiPb
+