Arduino interrupt template magic thing

interrupts.h

#ifndef __INCLUDE_INTERRUPTS_H__
#define __INCLUDE_INTERRUPTS_H__


#include "Arduino.h"
#include <algorithm>


typedef void (*ISRFunctionPtr)();


template <class C, int N>
class InterruptHandlers;


class InterruptHandler
{
  private:
    
  public:

    static ISRFunctionPtr GetISR(int n);
    
    static void HandleInterrupt(int pin)
    {
      Serial.print("Interrupt on pin ");
      Serial.print(pin);
      Serial.println();
    }
};


template <class C, int N>
class InterruptHandlers
{
  public:
    InterruptHandlers()
    {
      memset(&_interruptHandlers, sizeof(_interruptHandlers), 0);
      Init(int_<N>());
    }

    ISRFunctionPtr GetISR(int n)
    {
       return _interruptHandlers[n];
    }
  private:
    template<int offset>
    static void ICACHE_RAM_ATTR isr()
    {
        InterruptHandler::HandleInterrupt(offset);
    }

    void (*_interruptHandlers[N])();
  
    template <int M>
    struct int_ {};
    
    template <int M>
    void Init(int_<M>)
    {
      Init(int_<M - 1>());
      _interruptHandlers[M - 1] = &InterruptHandlers<C, N>::template isr<M>;
      Serial.print("Initializing ISR");
      Serial.print(M - 1);
      Serial.println("...\n");
    }

    void Init(int_<0>) {}
};


static InterruptHandlers<int, 32> GlobalInterruptHandlers;


ISRFunctionPtr InterruptHandler::GetISR(int n)
{
  return GlobalInterruptHandlers.GetISR(n);
}


#endif