Timing in C

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

typedef uint64_t u64;
static inline u64 T2L()
{
  struct timeval tv;
  gettimeofday(&tv, NULL);
  return 1000000ULL * tv.tv_sec + tv.tv_usec;
}

static u64 _t_start_;
u64 tstart()
{
  _t_start_ = T2L();
  return _t_start_;
}

u64 tdiff()
{
  return T2L() - _t_start_;
}

void ptdiff()
{
  u64 d = T2L() - _t_start_;
  printf("%lu sec %lu usec\n", d/1000000, d%1000000);
}