DynamicFCN.h

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#ifndef AMPGEN_DYNAMICFCN_H
#define AMPGEN_DYNAMICFCN_H
 
#include "AmpGen/MsgService.h"
#include <dlfcn.h>
#include <iostream>
 
namespace AmpGen
{
 
  template <class RETURN_TYPE, class ...IN_TYPES> 
  class DynamicFCN; 
 
  template <class RETURN_TYPE, class ...IN_TYPES>
  class DynamicFCN<RETURN_TYPE( IN_TYPES... )>
  {
  private:
    struct LibHandle {
      void* handle={nullptr}; 
      LibHandle(void* handle) : handle(handle) {};
      ~LibHandle(){ if( handle !=nullptr) dlclose(handle); }
      operator void*(){ return handle; }
    };
 
    std::shared_ptr<LibHandle> m_handle   = {nullptr};
    RETURN_TYPE ( *m_fcn )( IN_TYPES... ) = {nullptr};
 
  public:
    DynamicFCN() = default; 
    DynamicFCN( const std::string& lib, const std::string& name ) : 
      m_handle(std::make_shared<LibHandle>(dlopen( lib.c_str(), RTLD_NOW ))) {
      set(*m_handle,name);
    }
    DynamicFCN( void* handle, const std::string& name ) : m_handle(std::make_shared<LibHandle>(handle)) { set( handle, name ); }
    ~DynamicFCN(){ }
 
    bool set( const std::string& lib, const std::string& name )
    {
      DEBUG("Linking handle: " << lib << ":" << name );
      m_handle = std::make_shared<LibHandle>( dlopen( lib.c_str(), RTLD_NOW ) );
      if( !m_handle ){
        DEBUG( dlerror() );
        return false;
      }
      return set(*m_handle,name);
    }
    bool set( void* handle, const std::string& name, bool isFatal = false)
    {
      m_fcn = (RETURN_TYPE( * )( IN_TYPES... ))dlsym( handle, name.c_str() );
      if ( m_fcn == nullptr ) {
        if( !isFatal ) ERROR( "Failed to link: " << name << " error: " << dlerror() );
        else FATAL("Failed to link: " << name << " error: " << dlerror() );
        return false;
      }
      return true;
    }
    RETURN_TYPE operator()( IN_TYPES... input ) const { return ( *m_fcn )( input... ); }
    bool isLinked() const { return m_fcn != nullptr; }
  };
} // namespace AmpGen
 
#endif