#include <stdint.h>
#include <sys/time.h>
#include <stdlib.h>
#include <string.h>

#include <iostream>
#include <fstream>
#include <string>
using namespace std;


uint32_t BUFF_SIZE=1000*4; // chunk size to read in bytes

void Usage(string maess="");
void ParseCommandLineArguments(int narg, char *argv[]);

//----------------------------
// Usage
//----------------------------
void Usage(string mess)
{
	cout << endl;
	cout << "Usage:" <<endl;
	cout << "    ramspeed_reader [options]" << endl;
	cout << endl;
	cout << "This utility will simply copy memory as fast as possible" << endl;
	cout << "reporting the rate to the screen once a second. This will" << endl;
	cout << "continue until you hit ctl-C to kill the program." << endl;
	cout << "This is meant to test the read speed from RAM using memcpy." << endl;
	cout << "n.b. It was observed here and web research confirmed that" << endl;
	cout << "much larger rates can be obtained for buffer sizes of 2kB-4kB" << endl;
	cout << "Larger buffer sizes actually result in slower rates." << endl;
	cout << endl;
	cout << "  options:" <<endl;
	cout << "    -h, --help      print this usage statement" << endl;
	cout << "    -b buffsize     size of buffer in bytes" << endl;
	cout << endl;
	
	cout << mess << endl;
	
	exit(0);
}

//----------------------------
// ParseCommandLineArguments
//----------------------------
void ParseCommandLineArguments(int narg, char *argv[])
{
	for(int i=1; i<narg; i++){
		string arg = argv[i];
		bool has_next = (i+1)<narg;
		string next = has_next ? argv[i+1]:"";
		
		if(arg[0]=='-'){
			if(arg=="-h" || arg=="--help") Usage();
			if(arg=="-b"){
				if( !has_next )Usage("-b requires an argument!");
					
				BUFF_SIZE = atoi(next.c_str());
				i++;
			}
		
		}
	}
}

//----------------------------
// main
//----------------------------
int main(int narg, char *argv[])
{
	ParseCommandLineArguments(narg, argv);
	
	cout << endl;
	cout << "=================================" << endl;
	cout << "buffer size: "<< BUFF_SIZE << " bytes (=" << BUFF_SIZE/1024/1024 << " MB)" << endl;
	cout << endl;
	
	// Allocate buffers
	char *buff1 = new char[BUFF_SIZE];
	char *buff2 = new char[BUFF_SIZE];
	if( (!buff1) || (!buff2) ){
		cout << "Unable to allocate buffer of size " << BUFF_SIZE << " bytes" << endl;
		return -1;
	}
	
	// Setup hi-res timer
	struct itimerval tval={{0,0},{1000000,0}};
	setitimer(ITIMER_REAL, &tval, NULL);
	
	uint64_t Nread_total = 0;
	double last_tval_sec = (double)tval.it_value.tv_sec + 1.0E-6*(double)tval.it_value.tv_usec;;
	double tdiff_total = 0;
	
	// Loop continuously
	while(true){
	
		// Copy buff1 to buff2
		memcpy(buff2, buff1, BUFF_SIZE);
		uint64_t Nread = BUFF_SIZE;

		// Copy buff2 to buff1
		memcpy(buff1, buff2, BUFF_SIZE);
		Nread += BUFF_SIZE;

		// Get current timer
		struct itimerval tval;
		getitimer(ITIMER_REAL, &tval);
		double tval_sec = (double)tval.it_value.tv_sec + 1.0E-6*(double)tval.it_value.tv_usec;
		double tdiff = last_tval_sec - tval_sec;
		last_tval_sec = tval_sec;

		tdiff_total += tdiff;
		Nread_total += Nread;

		if(tdiff_total>1){
			double rate = (double)Nread_total/tdiff_total;
			rate /= 1024.0*1024.0;

			cout << "  " << rate << " MB/sec                 \r";
			cout.flush();

			Nread_total = 0;
			tdiff_total = 0;
		}
			
	}

	return 0;
}