#include <stdio.h>
#include <string.h>
#include <stddef.h>
#include <stdint.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/time.h>
#include <signal.h>
#include <unistd.h>

char * volatile src, * volatile dst;

#define CHECK(x) do{                                    \
    errno=0;                                            \
    if(!(x)) {                                          \
      fprintf(stderr,"%s:%d: %s failed -- %s\n",        \
              __FILE__, __LINE__, #x, strerror(errno)); \
      abort(); } }while(0)

double now (void) {
  struct timeval tv;
  gettimeofday(&tv,0);
  return tv.tv_sec + 1e-6 * tv.tv_usec;
}

extern void memcpy_gcc (char * restrict d, const char * restrict s, size_t n);
extern void memcpy_clang (char * restrict d, const char * restrict s, size_t n);

static inline void movsb(void *d, const void *s, size_t n) {
  asm volatile ("rep movsb"
                : "=D" (d),
                  "=S" (s),
                  "=c" (n)
                : "0" (d),
                  "1" (s),
                  "2" (n)
                : "memory");
}

char *fmt_uint (unsigned long long x, char *buf) {
  char tmp[80];                 /* sic! */
  size_t i, j, n;
  snprintf(tmp,sizeof(tmp)-1,"%llu",x);
  n = strlen(tmp);
  j = 0;
  for(i = 0; i < n; i++) {
    if (i && (n-i)%3 == 0) buf[j++]=',';
    buf[j++] = tmp[i];
  }
  buf[j]=0;
  return buf;
}

char *meth_name[] = { "for loop", "for loop", "rep movsb", "memcpy" };
char *meth_name2[] = { "gcc", "clang", "", "" };
#define N_METH ((sizeof(meth_name)/sizeof(meth_name[0]))-1)

volatile int had_alarm;

void alarm_handler (int ignore) {
  (void)ignore;
  had_alarm = 1;
}

double bench_1 (int meth, size_t sz) {
  double t1;
  int rep = 10;

  CHECK (src = malloc(sz)); 
  CHECK (dst = malloc(sz));
  memset(src,1,sz);
  memset(dst,2,sz);

  signal(SIGALRM,alarm_handler);
  had_alarm = 0;
  alarm(1);
  rep = 0;
  t1 = now();
  switch (meth) {
  case 0:
    while(!had_alarm) { memcpy_gcc(dst,src,sz); rep++; }
    break;
  case 1:
    while(!had_alarm) { memcpy_clang(dst,src,sz); rep++; }
    break;
  case 2:
    while(!had_alarm) { movsb(dst,src,sz); rep++; }
    break;
  case 3:
    while(!had_alarm) { memcpy(dst,src,sz); rep++; }
    break;
  }
  t1 = now() - t1;

  CHECK(0 == memcmp(dst,src,sz));

  free(src);
  free(dst);
  return t1 / rep;
}

void bench (size_t sz)
{
  char b1[80], b2[80];
  double ti [N_METH];
  int i;

  sz = 64 * ((sz+63)/64);         /* Hmm */

  for (i = 0; i < N_METH; i++) ti[i] = bench_1(i, sz);

  int winner = 0;
  for (i = 0; i < N_METH; i++) if (ti[i] < ti[winner]) winner = i;

  printf("%16s octets ", fmt_uint(sz,b1));
  for (i = 0; i < N_METH; i++)
    printf ("%11s MB/s %s", fmt_uint(((sz)/ti[i])/1024/1024, b2),
            (i==winner)?"*":" ");
  printf("\n");
  fflush(stdout);
}

size_t e12_series [] = { 10, 12, 15, 18, 22, 27, 33, 39, 47, 56, 68, 82 };

size_t e12 (int x) {
  if (x >= 12)
    return 10 * e12(x-12);
  else
    return e12_series[x];
}

int main (void) {
  int i;
  printf("%16s        ","");
  for (i = 0; i < N_METH; i++)
    printf("%16s  ", meth_name[i]);
  printf("\n");
  printf("%16s        ","");
  for (i = 0; i < N_METH; i++)
    printf("%16s  ", meth_name2[i]);
  printf("\n");
  for(i=0;i < 79;i++)printf("-");
  printf("\n");
  for (i = 1*12; i < 7*12; i+=1)
    bench (e12(i));
  printf("\n'*' marks the fastest.\n");
  return 0;
}