/* Author: Ruud Harmsen, August 2021.

   Explanation:
   https://rudhar.com/sfreview/siworin/siworin09.htm

   Meant to illustrate this bug:
   https://sourceware.org/bugzilla/show_bug.cgi?id=28277
 */

#include <stdlib.h>
#include <stdio.h>
#include <locale.h>
#include <wchar.h>
#include <ctype.h>
#include <wctype.h>

void timeit (FILE *fp);

int main (void)
{
   FILE *fp;
   int c;
   wint_t wc;
   char *testfile = "../siworin09.htm";
   const int numblks = 4;

   fprintf(stdout, "Default block is %d\n", (int)BUFSIZ);

   setlocale(LC_ALL, "");

   if (!(fp = fopen(testfile, "r")))
      {perror(NULL); exit(1);}
   if (setvbuf(fp, NULL, _IOFBF, 1024 * numblks))
      perror(NULL);

   fprintf(stdout, "File read as character stream\n");
   while (c = getc(fp), c != EOF)
   {
      fprintf(stdout, "c=%c, pos=%4ld ", isprint(c) ? c : '?', ftell(fp));
      timeit(fp);
   }
   fclose(fp);

   if (!(fp = fopen(testfile, "r")))
      {perror(NULL); exit(2);}
   if (setvbuf(fp, NULL, _IOFBF, 1024 * numblks))
      perror(NULL);

   fprintf(stdout, "\nFile read as wide character stream\n");
   while (wc = getwc(fp), wc != WEOF)
   {
      fprintf(stdout, "c=%lc, pos=%4ld ", iswprint(wc) ? wc : L'?', ftell(fp));
      timeit(fp);
   }
   fclose(fp);

   return 0;
}

#include <sys/time.h>
#define HOW_OFTEN 1000
void timeit (FILE *fp)
{
   struct timeval befor, after;
   int i;
   double duration; /* in nanoseconds */

   gettimeofday(&befor, NULL);
   for (i = 0; i < HOW_OFTEN; i++)
   {
      ftell(fp);
   }
   gettimeofday(&after, NULL);

   duration = 1000000.0 * 1000.0 * (after.tv_sec - befor.tv_sec);
   duration += (after.tv_usec - befor.tv_usec) * 1000.0;
   fprintf(stdout, "dura=%5.0f ns\n", duration / HOW_OFTEN);
}