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