add primitive esp8266 counter

#ifndef COUNTER_H

#define COUNTER_H

extern "C" {

#include "osapi.h"

#include "user_interface.h"

}

#include "c_types.h"

class Counter {

	private:

		Counter(const Counter &copy);

		uint32_t start_cycles;

	public:

		Counter() : start_cycles(0) {}

		uint32_t overflowed;

		inline void start() {

			asm volatile ("esync; rsr %0,ccount":"=a" (start_cycles));

		}

		inline uint32_t stop() {

			uint32_t stop_cycles;

			asm volatile ("esync; rsr %0,ccount":"=a" (stop_cycles));

			if (stop_cycles > start_cycles) {

				return stop_cycles - start_cycles;

			} else {

				return 0;

			}

		}

};

extern Counter counter;

#endif

#include "driver/counter.h"

Counter counter;