Serialization.h

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#ifndef CondCore_CondDB_Serialization_h
#define CondCore_CondDB_Serialization_h
//
// Package:     CondDB
// 
//
// Author:      Giacomo Govi
// Created:     October 2013
//
//

#include "CondCore/CondDB/interface/Binary.h"
#include "CondCore/CondDB/interface/Exception.h" 
#include "CondCore/CondDB/interface/Utils.h" 
//
#include <sstream>
#include <iostream>
//
// temporarely
#include <boost/shared_ptr.hpp>

class TBufferFile;

namespace cond {

  // default payload factory
  template <typename T> T* createPayload( const std::string& payloadTypeName ){
    if( demangledName( typeid(T) )!= payloadTypeName ) 
      throwException(std::string("Type mismatch, target object is type \"")+payloadTypeName+"\"",
             "createPayload" );
    return new T;
  }

  // Archives for the streaming based on ROOT.

  // output
  class RootOutputArchive {
  public:
    explicit RootOutputArchive( std::ostream& destination );

    template <typename T>
    RootOutputArchive& operator<<( const T& instance );
  private:
    // type and ptr of the object to stream
    void write( const std::type_info& sourceType, const void* sourceInstance);
  private:
    // here is where the write function will write on...
    std::ostream& m_buffer;
  };

  template <typename T> inline RootOutputArchive& RootOutputArchive::operator<<( const T& instance ){
    write( typeid(T), &instance );
    return *this;
  }

  // input
  class RootInputArchive {
  public:
    explicit RootInputArchive( std::istream& source );

    virtual ~RootInputArchive();

    template <typename T>
    RootInputArchive& operator>>( T& instance );
  private:
    // type and ptr of the object to restore
    void read( const std::type_info& destinationType, void* destinationInstance);
  private:
    // copy of the input stream. is referenced by the TBufferFile.
    std::string m_buffer;
    TBufferFile* m_streamer = nullptr;
  };

  template <typename T> inline RootInputArchive& RootInputArchive::operator>>( T& instance ){
    read( typeid(T), &instance );
    return *this;
  }

  typedef RootInputArchive CondInputArchive;
  typedef RootOutputArchive CondOutputArchive;

  // call for the serialization. Setting packingOnly = TRUE the data will stay in the original memory layout 
  // ( no serialization in this case ). This option is used by the ORA backend - will be dropped after the changeover
  template <typename T> Binary serialize( const T& payload, bool packingOnly = false ){
    Binary ret;
    if( !packingOnly ){
      // save data to buffer
      std::ostringstream buffer;
      CondOutputArchive oa( buffer );
      oa << payload;
      //TODO: avoid (2!!) copies
      ret.copy( buffer.str() );
    } else {
      ret = Binary( payload );
    }
    return ret;
  }

  // generates an instance of T from the binary serialized data. With unpackingOnly = true the memory is already storing the object in the final 
  // format. Only a cast is required in this case - Used by the ORA backed, will be dropped in the future.
  template <typename T> boost::shared_ptr<T> deserialize( const std::string& payloadType, const Binary& payloadData, bool unpackingOnly = false){
    // for the moment we fail if types don't match... later we will check for base types...
    boost::shared_ptr<T> payload;
    if( !unpackingOnly ){
      std::stringbuf sbuf;
      sbuf.pubsetbuf( static_cast<char*>(const_cast<void*>(payloadData.data())), payloadData.size() );

      std::istream buffer( &sbuf );
      CondInputArchive ia(buffer);
      payload.reset( createPayload<T>(payloadType) );
      ia >> (*payload);
    } else {
      payload = boost::static_pointer_cast<T>(payloadData.share());
    }
    return payload;
  }

}
#endif