#include <iostream>
#include <stdio.h>
#include <string>
#include <stddef.h>
#include <sys/time.h>

#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <libaio.h>
#include <time.h>
#include <stdio.h>
#include <errno.h>



using namespace std;

int main (int argc, char *argv[])
{
  if (argc<5){
	cout << "usage  <device name>  <size to write in kb> <offset in kb > <loop>" << endl;
	return 0;
  }

  char* dev_name = argv[1];

  int fd = open(dev_name, O_LARGEFILE | O_DIRECT | O_WRONLY , 777 );
  if (fd<0){
	perror("open ");
	return (-1);
  }

  long long write_sz_bytes = ( (long long)atoi(argv[2]))<<10;
  long long offset_sz_bytes   = atoi(argv[3])<<10;
  int   loops = atoi(argv[4]); 

  char* buffer = (char*)valloc(write_sz_bytes);
  if (!buffer) {
	perror("alloc : ");
	return -1;
  }

  memset(buffer,0x00,write_sz_bytes);

  while( (--loops)>0 ){
    
    int ret = pwrite64(fd,buffer,write_sz_bytes,offset_sz_bytes);
    if (ret<0) {
      perror("failed to write: ");
      printf("read_sz_kb=%d offset_sz_kb=%d\n",write_sz_bytes,offset_sz_bytes);
      return -1;
    }

    offset_sz_bytes += write_sz_bytes;
    printf("writing %lld bytes at offset %lld\n",write_sz_bytes,offset_sz_bytes);
  }
  
  return(0);
}